UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 20172019

ORor

Commission File Numberfile number 001-38266

SPERO THERAPEUTICS, INC.

(Exact name of registrant as specified in its Charter)charter)

Registrant’s telephone number, including area code:code (857) 242-1600

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. YESYes ☐ NONo ☒

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. YESYes ☐ NONo ☒

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. YESYes ☒ NONo ☐

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). YESYes ☒ NONo ☐

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§229.405) is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. ☒

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☒

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    YESYes ☐    NONo ☒

AsThe aggregate market value of Common Stock held by non-affiliates of the registrant computed by reference to the price of the registrant’s Common Stock as of June 30, 2017,28, 2019, the last business day of the registrant’s most recently completed second fiscal quarter, there was no established public market forapproximately $150.5 million (based on the registrant’s common stock. The registrant therefore cannot calculatelast reported sale price on the aggregate market value of its voting and non-voting common equity held by non-affiliatesNasdaq Global Market as of such date. The registrant’s common stock began trading on the The Nasdaq Global Select Market on November 2, 2017.

date). As of March 28, 2018, the registrant had 14,369,1829, 2020, there were 20,328,340 shares of common stock,the registrant’s Common Stock, $0.001 par value per share, outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

The registrant intends to file a definitive proxy statement pursuant to Regulation 14A relating to the 2018 Annual Meeting of Stockholders within 120 days of the end of the registrant’s fiscal year ended December 31, 2017. Portions of such definitive proxy statement are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein.None.

Table of Contents

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PART I

Forward-Looking Information

This Annual Report on Form 10-K contains forward-looking statements that involve risks and uncertainties. We make such forward-looking statements pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 and other federal securities laws. All statements other than statements of historical facts contained in this Annual Report on Form 10-K are forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as “may,” “will,” “should,” “expects,” “intends,” “plans,” “anticipates,” “believes,” “estimates,” “predicts,” “potential,” “continue” or the negative of these terms or other comparable terminology. These forward-looking statements include, but are not limited to, statements about:

Any forward-looking statements in this Annual Report on Form 10-K reflect our current views with respect to future events or to our future financial performance and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Factors that may cause actual results to differ materially from current expectations include, among other things, those listed under Part III Item 1A. “Risk Factors” and elsewhere in this Annual Report on Form 10-K. Given these uncertainties, you should not place undue reliance on these forward-looking statements. Except as required by law, we assume no obligation to update or revise these forward-looking statements for any reason, even if new information becomes available in the future.

This Annual Report on Form 10-K also contains estimates, projections and other information concerning our industry, our business, and the markets for certain diseases, including data regarding the estimated size of those markets, and the incidence and prevalence of certain medical conditions. Information that is based on estimates, forecasts, projections, market research or similar methodologies is inherently subject to uncertainties and actual events or circumstances may differ materially from events and circumstances reflected in this information. Unless otherwise expressly stated, we obtained this industry, business, market and other data from reports, research surveys, studies and similar data prepared by market research firms and other third parties, industry, medical and general publications, government data and similar sources.

Item 1. Business.Business.

Overview

We are a multi-asset, clinical-stage biopharmaceutical company focused on identifying, developing and commercializing novel treatments forin high unmet need areas involving multi-drug resistant, or MDR, bacterial infections.infections and rare diseases. Our most advanced product candidate, SPR994,Tebipenem Pivoxil Hydrobromide, or tebipenem HBr (previously SPR994), is designed to be the

first broad-spectrum oral carbapenem-class antibiotic for use in adults to treat MDR Gram-negative infections. Treatment with effective orally administrable antibiotics may prevent hospitalizations for serious infections and enable earlier, more convenient and cost-effective treatment of patients after hospitalization. We are also developing SPR720, a novel oral antibiotic designed for the treatment of a rare, orphan disease caused by pulmonary non-tuberculous mycobacterial infections, or NTM disease. In addition, we have a platform technology known as our Potentiator Platform, that we believe will enable us to develop drugs that will expand the spectrum and potency of existing antibiotics, including formerly inactive antibiotics, against Gram-negative bacteria. Our leadincludes an IV-administered product candidates generated from our Potentiator Platform are two intravenous, or IV,-administered agents, SPR741 andcandidate, SPR206, designedbeing developed to treat MDR Gram-negative infections in the hospital setting. In addition, we are developing SPR720, an oral antibiotic designed for the treatment of an orphan disease called pulmonary non-tuberculous mycobacterial infections, or NTM.hospital. We believe that our novel product candidates, if successfully developed and approved, would have a meaningful patient impact and significant commercial applications for the treatment of MDR infections in both the community and hospital settings.

Antibiotic-resistant bacteria are one of the largest threats to global health, and their prevalence is increasing. While the majority of life-threatening infections historically resulting from antibiotic-resistant bacteria are acquired in the hospital setting, there is an increasing incidence of MDR pathogens in the community setting. Antibiotics used currently for first-line empiric treatment of MDR bacterial infections suffer from significant limitations and risks, including narrow spectrums of coverage and safety and tolerability concerns, and they can be associated with serious adverse effects. In addition, there are no oral antibiotics commercially available that can reliably be used in adults with MDR Gram-negative bacterial infections. This limits the ability of physicians to prevent hospitalizations and transition patients to their home from the hospital after receiving IV-administered therapy. The increasing prevalence of drug resistance and MDR Gram-negative bacteria, as well as the limitations of existing therapies and traditional drug development approaches, highlightshighlight the critical need for novel therapies, and in particular orally administrable agents, that are capable of overcoming these obstacles to effective patient treatment.

To address the foregoing, we are developing a portfolio of novel product candidates, including:

Based on Following the FDA’s acceptance of our pre-investigationalinvestigational new drug, or IND, application meeting,for tebipenem HBr treatment of complicated urinary tract infections, or pre-IND meeting, withcUTI, we initiated the U.S. Food and Drug Administration, or FDA, and subject to our receiving favorable results from our Phase 1 clinical trial of SPR994 acceptable to the FDA, we believe we will be able to progress directly to asingle pivotal Phase 3 clinical trial, which is entitled ADAPT-PO, that is required for approval of SPR994 fortebipenem HBr to treat cUTI, and which continues to enroll patients.  The ADAPT-PO trial is designed as a double-blind, double-dummy trial to compare oral tebipenem HBr with an existing standard of care intravenous, or IV, antibiotic, ertapenem, in approximately 1,200 patients with cUTI or acute pyelonephritis, randomized 1:1 in each arm. In October 2019, an independent review committee issued a positive recommendation to continue the treatmenttrial using the protocol-defined dose without modification following its analysis of cUTI. We filed a Clinical Trial Notification, or CTN, in Australia in September 2017 and initiated in October 2017 a Phase 1 dose-selection clinical trial of SPR994. A CTN enables conduct of clinical trials in Australia similar to an investigational new drug application, or IND,interim pharmacokinetic data from the first 33 patients dosed with tebipenem HBr in the United States. Wetrial. The trial is enrolling well and we expect to report top-line data from this trial in mid-2018. We intend to request a meeting with the FDA to discuss the clinical trial protocol during the second half of 2018. Following our discussions with the FDA, we expect to initiate a pivotal Phase 3 clinical trial in the third quarter of SPR9942020. In March 2019, the FDA granted Fast Track Designation for tebipenem HBr for the treatment of cUTI around year-end 2018and acute pyelonephritis, a designation that provides opportunities for more frequent interaction with the FDA review team to expedite development and review as well as the potential for rolling review of the NDA upon request and agreement with the FDA. In addition to cUTI, we believe that tebipenem HBr has the potential to treat other serious and life-threatening infections, including community acquired bacterial pneumonia, or CABP, for which we could receive funding support from the Biomedical Advanced Research and Development Authority, or BARDA, subject to BARDA exercising its future option under our BARDA award, as further described in support of a new drug application, or NDA.this section.

Prior Safety and Efficacy Experience with Tebipenem Pivoxil in Japan

Our clinical strategy is supported by extensive safety data underlying tebipenem’stebipenem pivoxil’s regulatory approval in Japan and long-standing use in Japan for common pediatric infections. Approximately 1,1001,200 subjects, including approximately 741 adults, have been dosed with tebipenem pivoxil at a range of doses in clinical and pharmacologic studies. We have rights to use all clinical data generated byIn addition, Meiji has completed a post-market study including 3,540 patients following the safety and tolerability of tebipenem pivoxil at the approved dose. In addition, two exploratory Phase 2 trials that were conducted in Japan in patients with cUTI, the first indication in which we intend to study SPR994. Further,tebipenem HBr. We have the rights to all data from the registration and post-marketing studies conducted by Meiji.

In addition, we have received Qualified Infectious Disease Product, or QIDP, designation from the FDA for SPR994tebipenem HBr for the treatment of cUTI, community-acquired bacterial pneumonia, or CABP, and moderate to severe diabetic foot infections, or DFI, which providesDFI. The QIDP designation was created by the Generating Antibiotic Incentives Now, or GAIN, Act and creates incentives for the development of certain antibiotics that treat serious or life-threatening infections. QIDP designation entitles us to priority review of SPR994tebipenem HBr for regulatory approval by the FDA. The QIDP designation for SPR994,tebipenem HBr, however, does not guarantee a faster development process or ensure FDA approval.

We have global commercialization rights to SPR994,tebipenem HBr, except in certain contractually specified Asian countries.countries which are licensed to Meiji. We believe that our intellectual property portfolio will provide SPR994us global protection globally,for tebipenem HBr, including in the United States and Europe, through 2038.

We have two Potentiator Platform product candidates – SPR741, our combination IV-administered agent that has demonstrated in vitro the ability to expand the spectrum and increase the potency of a co-administered antibiotic; and SPR206, our direct acting IV-administered agent that has demonstrated in vitro activity alone. Both have demonstrated potency against Gram-negative bacteria, including organisms identified by the Centers for Disease Control and Prevention, or the CDC, and the World Health Organization, or the WHO, as urgent and serious threats to human health.

SPR741 has demonstrated an ability to potentiate over two dozen existing antibiotics by expanding their activity against Gram-negative pathogens. While previous attempts by others to develop agents that interact with the bacteria’s outer membrane using the mechanism of action employed by SPR741 have, to our knowledge, failed in preclinical testing and Phase 1 clinical trials due to safety concerns, data from our Phase 1 single-ascending dose, or SAD, and multiple-ascending dose, or MAD, clinical trial of SPR741 demonstrate it was generally well tolerated at single doses up to and including 800 mg and at doses up to and including 600 mg every 8 hours for 14 days.

In late November 2017, we initiated our Phase 1b drug-drug interaction clinical trial of SPR741 in the United Kingdom. The Phase 1b trial enrolled 27 healthy volunteers to evaluate SPR741 as a single dose in combination with compounds from the beta-lactam class of antibiotics, including cephalosporins ( ceftazidime), monobactams (aztreonam) and beta-lactams/beta-lactamase inhibitors (piperacillin/tazobactam). The trial was designed to assess the impact, if any, on the standalone pharmacokinetics of SPR741 or the standalone pharmacokinetics of the beta-lactam combination drug when the two are dosed together as a single dose. We anticipate top-line data from this Phase 1b trial during the second quarter of 2018.

In addition, we continue to progress the development of our direct-acting Potentiator Platform molecules, exemplified by our product candidate SPR206. SPR206 is designed to also have antibiotic activity as a single agent against MDR and extremely drug resistant, or XDR, bacterial strains, including variants isolated in Pseudomonas aeruginosa, Acinetobacter baumannii and carbapenem-resistant Enterobacteriaceae. We are currently testing SPR206 in a good laboratory practice, or GLP, preclinical toxicology study.  Recent data from this study suggest a potency and safety profile for SPR206 that may be superior to SPR741, as well as a potentially faster path to market than SPR741 because SPR206 can be developed as a single agent.

We believe that our intellectual property portfolio for SPR741 will provide SPR741 protection globally, including in the United States and Europe, through 2038. Additionally, we have multiple patent applications pending for SPR206 that we believe will provide SPR206 protection globally, including in the United States and Europe, through 2035.

SPR720 is currently in preclinical development.

We are conducting 28-day and 31-day toxicity studies in rats and non-human primates in accordance with GLP regulations. We have also observed activity as good as or better than positive controls in in vitro and in vivo studies, including in an acute murine pneumonia model of infection caused by Mycobacterium abscessus. We are currently testing SPR720 in animal studies to assess activity across other pathogens of interest. Pending positive results from our additional toxicity studies, we plan to initiateinitiated a Phase 1 clinical trial of SPR720 in January 2019, designed as a double-blind, placebo-controlled, single and multiple ascending dose, multi-cohort study in healthy subjects, and reported preliminary findings from the trial in December 2019. Analysis of the blinded data from this trial supports further development of the compound as an oral agent for the treatment of NTM disease. Specifically, there were no serious adverse events reported and all participants completed the trial. Although the data remain blinded, an analysis of preliminary data indicates that SPR720 was generally well-tolerated at doses up to 1000 mg over the maximum studied duration of 14 days. Preliminary analyses of pharmacokinetic, or PK, data across the cohorts show no significant impact of either advanced age or administration with food on PK variables. At doses of 500 mg or higher, the mean plasma drug exposures of SPR719, the active metabolite of SPR720, are consistent with those suggested by in vitro and in vivo models of SPR720 to be necessary for clinical efficacy against target NTM pathogens.

We plan to meet with the FDA in the first half of 2019.2020, submit an IND to the FDA in the second half of 2020 and, subject to FDA acceptance of the IND, initiate a Phase 2a clinical trial evaluating SPR720 in patients with NTM pulmonary disease due to Mycobacterium avium complex in the second half of 2020. In March 2020, the FDA granted orphan drug designation for SPR720, a designation that is given to drugs intended to treat a rare disease or condition that affects fewer than 200,000 persons in the United States. An orphan drug designation can provide specific benefits including up to seven years of market exclusivity in the United States upon regulatory approval.  In February 2019, we received QIDP designation for SPR720 for the treatment of lung infections caused by nontuberculous mycobacteria and for the treatment of lung infections caused by Mycobacterium tuberculosis. QIDP designation entitles us to priority review of SPR720 for regulatory approval by the FDA. Neither the QIDP nor orphan drug designation, however, guarantee a faster development process or ensure FDA approval.

We believe that our intellectual property portfolio for SPR720 will provide protection globally, including in the United States and Europe, through 2033.

SPR206 is a direct acting IV-administered agent that has demonstrated single-agent antibacterial activity in preclinical studies against Gram-negative bacteria, including organisms identified by the Centers for Disease Control and Prevention, or CDC, and the World Health Organization, or WHO, as urgent and serious threats to human health, including Acinetobacter baumannii and Pseudomonas aeruginosa. We have completed a preclinical toxicology study of SPR206 in accordance with good laboratory practice, or GLP, requirements. In May 2018, we announced preclinical toxicology and efficacy data that we believe support advancing SPR206 into clinical development. In December 2018, we initiated a Phase 1 clinical trial of SPR206, designed as a double-blind, placebo-controlled, ascending dose, multi-cohort study in healthy subjects and in January 2020 we reported a preliminary analysis of the results from the trial. Analysis of preliminary, blinded Phase 1 data suggests that SPR206 is well-tolerated at doses that are likely to be within a therapeutic range for target MDR Gram-negative bacterial infections and has a safety profile that we believe supports the further development of SPR206. The decision to continue development of SPR206 is also supported by data from nonclinical studies in which SPR206 demonstrated activity as a single agent against MDR and extensively drug resistant, or XDR, bacterial strains, including isolates of Pseudomonas aeruginosa, Acinetobacter baumannii and carbapenem-resistant Enterobacteriaceae, in both in vitro and in vivo models of infection.

Following an evaluation of the Potentiator Platform product candidates, we have determined to discontinue development of SPR741, effective January 1, 2020, and to move forward with SPR206 as our lead product candidate within the Potentiator Platform. We believe that the collective data from the recent Phase 1 and preclinical studies of SPR206 suggest a potency and safety profile that may be superior to SPR741. Further, we believe SPR206 may have a potentially faster path to pivotal clinical trials when compared with SPR741 because SPR206 is being developed as a single agent. As a result of this decision, we have terminated our license agreement with Northern Antibiotics Oy (Ltd.) relating to SPR741. Effective January 1, 2020, the intellectual property rights associated with SPR741 have entirely reverted to Northern Antibiotics and we no longer have any rights with respect thereto and we no longer have any obligations for the cost of maintaining such intellectual property.  

Our Pipeline

– Multiple Near-term Catalysts Across the Rare and Infectious Disease Portfolio

The following table sets forth our product candidates, their status and certain anticipated milestones for our product candidates.

Portfolio Prioritization

After we receive results from the Phase 1b clinical trial of SPR741 and our ongoing preclinical toxicology study of SPR206, we intend to prioritize our product candidates for further clinical development. Our decision will be based on which program we believe represents the best opportunity for us within an optimal timeframe, factoring in the choices we must make to prioritize the opportunities within our portfolio and to best deploy our capital resources. Accordingly, for the balance of 2018, our internal operational plans and budget and our estimate of our cash runway being sufficient to fund our operating expenses and capital expenditure requirements into the second quarter of 2019 are based on us funding the development of SPR994 and SPR720 and either SPR206 or SPR741 during that period. We may seek partnering opportunities or other non-dilutive funding for further clinical development of the potentiator candidate we elect to deprioritize.

Our Strategy

Our goal is to identify, develop and commercialize novel treatments for MDR bacterial infections, focusing on areas of high unmet medical need for safe and effective antibiotic treatments. Key elements of our strategy are as follows:

The Problem:  Antibiotics and Drug ResistanceIncreasingly Limited Antibiotic Options for Severe Infections

Antibiotic Background

Antibiotics are drugs used to treat infections that are caused by bacteria. Prior to the introduction of the first antibiotics in the 1930s and 1940s, bacterial infections were often fatal. Today, antibiotics are used routinely to treat and prevent infections. There are two main varieties of bacteria, Gram-negative bacteria and Gram-positive bacteria, which are distinguished by structural differences in their cell envelope. Gram-positive bacteria are surrounded by a single lipid membrane and a thick cell wall, while Gram-negative bacteria are encircled by two lipid membranes, an inner membrane and an outer membrane, with a thinner cell wall in between, as shown in the illustration below.

Antibiotics that target Gram-negative bacteria must be specifically designed to cross both the inner and outer membranes to enter the bacteria. The outer membrane, with its LPS-containing outer leaflet, represents a significant barrier to the entry into the bacteria by antibiotics and is a significant contributor toward reduced potency of many agents in treating Gram-negative bacterial infections. ARecent studies have found that Gram-negative bacteria in certain patient types, such as those with sepsis and Interstitial Lung Disease, are associated with higher mortality and increased intensive care unit, or ICU, admission. Moreover, a study of 13,796 patients in intensive care units around the world reported in 2009 that 51% of patients experienced bacterial infections, and of these patients 62% were infected by Gram-negative organisms.

Antibiotics are evaluated according to several criteria, including:

Growing Antibiotic Resistance in the Hospital and Community Settings

Antibiotic resistance is one of the largest threats to global health, and resistance rates are increasing. Antibiotic resistance can affect anyone, of any age and in any country. According to the CDC, each year in the United States at least 2 million peoplehospitalized patients become infected with bacteria that are resistant to antibiotics, and at least 23,000 people die each year as a direct result of these infections. Approximately 70% of the pathogens that cause these infections are resistant to at least one drug, meaningdrug. Likewise, resistance rates are climbing among community-acquired infections as well. According to van Duin and colleagues in 2016: “Some MDR bacteria have become quite prevalent causes of community-acquired infections. The spread of MDR bacteria into the community is a crucial development, and is associated with increased morbidity, mortality, healthcare costs and antibiotic use.” The incidence rate of serious infections is increasing and the proportion of the infections caused by MDR pathogens is increasingly seen as an emerging threat to world health. The CDC estimates that the excess annual cost resulting from these infections in the United States is as high as $20 billion.

According to the CDC, among all of the bacterial resistance problems, Gram-negative pathogens, which cause a majority of all bacterial infections, are particularly worrisome because they are becoming resistant to nearly all drugs that would be considered for treatment. In February 2017, the WHO published a list of Gram-negativeGram- negative bacteria based on the urgency of need for new antibiotics and highlighted a critical group of MDR Gram-negative bacteria that pose a particular threat to human health, including Acinetobacter, Pseudomonas and various multiple Enterobacteriaceae (including Klebsiella spsp.., E. coli, Serratia and Proteus). These pathogens are associated with significant mortality because the increased incidence of antibiotic resistance has limited the number of effective treatment options.

There is an acute need for new antibiotics to treat MDR bacterial infections, as few new antibiotics capable of addressing such infections have been approved recently for commercialization or are in clinical development. Further, the majority of MDR bacterial infections historically have been acquired in the hospital setting, where they have been treated using IV-administered antibiotics. However, increasingly such infections are being acquired in the community setting, emphasizing the need for orally administrable antibiotics that can effectively treat such infections.

Chronic Bacterial Infection without a Viable Cure

NTM infections represent a growing global health concern and major unmet medical need because of the lack of new medications being developed to combat these bacteria. NTM infections are ubiquitous environmental pathogens that can cause progressive lung damage and respiratory failure, particularly in patients with compromised immune systems or underlying pulmonary disorders.

Although rare, the incidence of pulmonary NTM disease is increasing worldwide. It is estimated that approximately 130,000 patients suffer from NTM disease in the U.S. and Europe, a figure that is growing at a rate of 8% annually. In addition, many patients go undiagnosed and could benefit from treatment with additional testing. The elderly and people with compromised immune or lung function are at greatest risk, as are patients with bronchiectasis for whom it is estimated that up to 50% may also have active lung infection caused by NTM. Treatment of pulmonary NTM disease requires prolonged therapy (continuing for approximately 12 to 24 months) with a combination regimen and is frequently complicated by tolerability and/or toxicity issues. Additionally, there are currently no oral antibiotics specifically approved for use to treat pulmonary NTM disease.

The most common treatment for NTM infections is combination therapy with drugs traditionally used for tuberculosis (TB) which have limited efficacy and high toxicity. NTM infection is also associated with high healthcare costs and high mortality. In 2014, the annual cost in the United States of treating NTM infections alone was estimated at $1.7 billion.

Our Product Candidates Have the Potential to Overcome Limitations of Available Treatment Options

Solution  

Antibiotics currently used for first-line empiric treatment of MDR acute bacterial infections and NTM infection suffer from significant limitations. We believe that our product candidates will overcome these limitations, as described below:

Our Product Candidates

SPR994 (Tebipenem Pivoxil Extended Release)

Tebipenem HBr (tebipenem pivoxil hydrobromide)

Our lead product candidate, SPR994,tebipenem HBr, is designed to be a broad-spectrum oral carbapenem intended for use in adults to treat MDR Gram-negative infections. Currently, there are no commercially availableA pivotal Phase 3 clinical trial of tebipenem HBr for the treatment of cUTI entitled ADAPT-PO continues to enroll patients. This Phase 3 clinical trial compares an all oral carbapenems for useregimen of tebipenem HBr with an existing standard of care IV antibiotic, ertapenem, in adults,approximately 1,200 patients with cUTI or acute pyelonephritis, randomized 1:1 in each arm. In October 2019, an independent review committee issued a positive recommendation to continue the trial using the protocol-defined dose without modification following its analysis of interim pharmacokinetic data from the first 33 patients dosed with tebipenem HBr in the trial. The trial is enrolling well and we believe SPR994 hascontinue to expect to report top-line data from the potential to address this unmet need.Phase 3 clinical trial in the third quarter of 2020. Carbapenems have been utilized for over 30 years and are considered the standard of care for many serious MDR Gram-negative bacterial infections, but to date they have only been available as IV-administered formulations. SPR994Currently, there are no commercially available oral carbapenems for use in adults, and we believe tebipenem HBr has the potential to address this unmet need. Tebipenem HBr is an oral extended-release tablet formulation of tebipenem. Tebipenem was approved in 2009 in Japan for sale under the name Orapenem for pediatric use into treat common infections including pneumonia, otitis media and sinusitis. It has been sold by Meiji in Japan as a granule presentation for children, and is combined with food and dosed twice per day.pediatric patients. To accelerate our clinical development of SPR994,tebipenem HBr, in June 2017 we exclusively licensedsigned an exclusive license to certain data and know-how from Meiji and a global pharmaceutical company, to which we refer to as Global Pharma, which we intend to use to support our clinical development of SPR994. tebipenem HBr. We have global commercialization rights to tebipenem HBr, except in certain contractually specified Asian countries.

The FDA has designated SPR994tebipenem HBr as a QIDP for the treatment of cUTI, CABP and DFI under the Generating Antibiotics Incentives Now Act, or the GAIN Act, which enables priority review for regulatory approval by the FDA. The QIDP designation for SPR994, however, does not guarantee a faster development process or ensure FDA approval. We believe, if approved, that SPR994, which incorporates our proprietary formulation technology and benefits from know-how and data we have licensed from Meiji, has the potential to further increase the clinical demand for the carbapenem class of antibiotics.

We have global commercialization rights to SPR994, except in certain contractually specified Asian countries. If SPR994tebipenem HBr is approved for treatment of cUTI, CABP or DFI, the QIDP designation for SPR994tebipenem HBr will extend by an additional five years any non-patent exclusivity period awarded for SPR994tebipenem HBr in the United States, such as a five-year New Chemical Entity, or NCE, exclusivity granted under the Drug Price Competition and Patent Term Restoration Act of 1984, or the Hatch-Waxman Act, for a total of 10 years. In Europe, exclusivity for NCEs is 10 years (eight years for data exclusivity and an additional two years for market exclusivity), with the possibility of a one-year extension if the chemical entity is approved for use in an additional indication. Additionally, we believe that our intellectual property portfolio for SPR994,tebipenem HBr, which includes multiple patent applications pending, will provide SPR994tebipenem HBr protection globally, including in the United States and Europe, through 2038.2039.

Potential Advantages of SPR994tebipenem HBr

Key attributes of tebipenem HBr, as well as pharmacokinetic data following enrollment of the first 33 patients in our on-going ADAPT-PO pivotal Phase 3 clinical trial, support our confidence in tebipenem HBr’s commercial potential, if tebipenem HBr receives regulatory approval. We believe that the following key attributes differentiate SPR994 from other antibiotics targeting MDR Gram-negative infections. We believe these attributes havetebipenem HBr has the potential to make SPR994be a safe and effective treatment for cUTI and other serious and life-threatening infections for which we may develop SPR994.tebipenem HBr.

We believe the foregoing advantages of SPR994tebipenem HBr also significantly differentiate SPR994tebipenem HBr from fluoroquinolones. Fluoroquinolones are the most widely used antibiotic class in treating community and hospital Gram-negative infections, but they have encountered increasing resistance among MDR Gram-negative bacteria and are associated with significant adverse effects. The table below reflects resistance rates in the United States in the community and hospital settings.

Currently, fluoroquinolones are the most frequently selected antibiotic for empirical urinary tract infection, or UTI, treatment in the community and hospital settings. Current UTI treatment guidelines published by the Infectious Diseases Society of America identify fluoroquinolones as an appropriate empirical therapy option. This recommendation, however, is contingent on local resistance rates being less than 10%. The endemicity (high rates) of fluoroquinolone-resistant E. coli found in the United States today in the community and hospital settings based on the table above would suggest that fluoroquinolones should not be used empirically for cUTI patients.

The following table highlights the observed in vitro potency differences between SPR994tebipenem HBr and levofloxacin, the most widely used fluoroquinolone. As shown below, SPR994tebipenem HBr has a MIC90 value of 0.03 µg/mL, which compares favorably (i.e., at or below) to the potency value obtained by levofloxacin.

In addition, the FDA has issued several warnings against the use of fluoroquinolones in certain patients. In particular, an FDA Advisory Committee stated in November 2015 that the risk of serious side effects caused by fluoroquinolones generally outweighs the benefits for patients with acute bacterial sinusitis, acute exacerbation of chronic bronchitis and uncomplicated UTIs. The FDA has determined that fluoroquinolones should be reserved for use in patients with these conditions who have no alternative treatment options. In Japan, Orapenem (tebipenem pivoxil) does not have a black box warning and has been studied in approximately 1,100 subjects. We believe SPR994tebipenem HBr could become a potential alternative to oral fluoroquinolones based on its safety and efficacy profile.

Significant Market Opportunity for SPR994

tebipenem HBr

Given the observed activity of SPR994tebipenem HBr against different bacteria, we view the market opportunity for SPR994,tebipenem HBr, if approved, to be substantial, including for the following uses:

UTIs are among the most common bacterial diseases worldwide, with significant clinical and economic burden. QuintilesIMSIQVIA (formerly QuintilesIMS) estimates that between 33 and 34 million patients either visit their physician or are hospitalized for a UTI or otherwise suspected of experiencing a UTI in the United States annually. While drugs such as trimethoprim/sulfamethoxazole (Bactrim/Septra) and fluoroquinolones (levofloxacin, ciprofloxacin) have been the primary oral options for treatment of UTIs caused by Gram-negative organisms, nearly 30% to 35% of UTIs are resistant, which has led to increased use of IV-administered therapeutics such as carbapenems.

QuintilesIMSIQVIA completed a market assessment in August 2017 in the community and hospital settings in which it estimated that there were 11 to 12 million patients annually who presented in the community physician’s office with a UTI and 3.5 to 4.5 million patients annually in the hospital with a UTI in the United States alone. Of these UTIs, 10 to 11 million are suspected to be caused by Gram-negative bacteria, and 4 to 5 million of these patients had an infection that is resistant to or failed first-line therapy, such as the fluoroquinolone class, or require IV therapy due to the severity of infection. Physicians in the survey reported high concern with growing fluoroquinolone resistance and lack of oral options for MDR Gram-negative infections. We believe SPR994tebipenem HBr is well positioned to meet the unmet need for an oral therapy for community-acquired UTI and may offer physicians an option for treating MDR UTIs while avoiding patient hospitalization. In addition, we believe SPR994tebipenem HBr has the potential to accelerate hospital discharge and obviate the need for continued IV-administered therapy at home by transitioning discharged patients to an at-home oral therapy. Our initial studyADAPT-PO, our ongoing pivotal Phase 3 clinical trial for SPR994 will focustebipenem HBr, is focused on patients who suffer from a subset of UTIs called cUTIs, which affect approximately 4.9 million patients in the United States annually. A significant majority of UTIs, including cUTIs, are caused by a group of MDR Gram-negative bacteria called Enterobacteriaceae.

Tebipenem HBr Clinical Development Program

Additional use may be seen in treating patients hospitalized with complicated Gram-negative infections, such as complicated intra-abdominal infections, or cIAI, hospital-acquired, or nosocomial, pneumonia and blood stream infections as they are discharged from the hospital.Single Pivotal Phase 3 Clinical Trial (ADAPT-PO)

SPR994 Clinical Development Program

We initiated a Phase 1 dose-selection clinical trial of tebipenem HBr in healthy volunteers in Australia in October 2017. In September 2018, we announced positive results from the final analysis of this study and identified a dose of 600 mg TID for our planned single pivotal Phase 3 clinical trial of tebipenem HBr in cUTI. Based on our pre-IND, pre-Phase 3 meeting with the FDA, we initiatedbelieve that positive results from a single pivotal Phase 1 pharmacokinetics and safety3 clinical trial of tebipenem HBr in AustraliacUTI demonstrating a 10% non-inferiority margin would support the approval of SPR994tebipenem HBr for the treatment of cUTI. As a result of the meeting, we submitted an IND application for tebipenem HBr in cUTI with the FDA and received FDA acceptance of the IND application in February 2019. We then initiated the single pivotal Phase 3 clinical trial required for approval of tebipenem HBr in cUTI entitled ADAPT-PO. We opened clinical trial sites in April 2019 for the Phase 3 trial and are actively enrolling patients. The pivotal Phase 3 clinical trial is designed as a double-blind, double-dummy trial to compare oral tebipenem HBr with an existing standard of care IV antibiotic, ertapenem, in approximately 1,200 patients with cUTI or acute pyelonephritis, randomized 1:1 in each arm. In October 2017,2019, an independent review committee issued a positive recommendation to continue the trial using the protocol-defined dose without modification following its analysis of interim pharmacokinetic data from the first 33 patients dosed with tebipenem HBr in the trial. The trial is enrolling well and we expect to report top-line data from this trial in mid-2018. Following completion of this trial to select a dose for pivotal trials, we intend to request a pre-Phase 3 meeting with the FDA to confirm that no additional clinical trials or preclinical studies are required prior to initiating a Phase 3 clinical trial. Subject to feedbacktrial in the third quarter of 2020. Following receipt of top-line data from the FDA, and using know-how we have licensed from Meiji, we plan to obtain agreement on the clinical trial protocol in late 2018 and expect to initiate the  pivotal

our ADAPT-PO Phase 3 clinical trial of SPR994tebipenem HBr, if favorable, together with requisite safety data, drug-drug interaction studies and other studies, we intend to submit to the FDA an NDA for the treatment oftebipenem HBr to treat cUTI, around year-end 2018 under an IND. We anticipate that theincluding acute pyelonephritis. These data, from this study will form the basis for the clinical trial data package that willif positive, may also support an NDA.marketing applications in other global regions.

QIDP Designation

The FDA has designated SPR994tebipenem HBr as a QIDP for the treatment of cUTI, CABP and DFI under the GAIN Act, which enables priority review for regulatory approval by the FDA. The QIDP designation for SPR994,tebipenem HBr, however, does not guarantee a faster development process or ensure FDA approval. Further, if SPR994tebipenem HBr is successfully developed and approved for the treatment of cUTI, CABP or DFI, the FDA’s QIDP designation for SPR994tebipenem HBr should extend any non-patent exclusivity period awarded to SPR994tebipenem HBr in the United States for five years, such as a five-year New Chemical Entity data exclusivity granted under The Drug Price Competition and Patent Term Restoration Act of 1984, or the Hatch-Waxman Act.

SPR994 Phase 1 Clinical Trial Results

We filed a CTN in Australia in September 2017 and initiated in October 2017 aOur completed Phase 1 SAD and MAD clinical trial in Australia of SPR994 in approximately 60 healthy volunteers. A CTN enables conducttebipenem HBr assessed the safety, tolerability and pharmacokinetics of a clinical trial in Australia similar to the manner that an IND enables such a study in the United States.orally administered tebipenem HBr. The Phase 1 clinical trial is evaluating several oral tablet formulations of SPR994 designed to optimize exposure. The trial consists ofenrolled 124 healthy adult volunteers into 14 SAD cohorts with tebipenem HBr given orally as single doses ranging from 100 mg to 900 mg daily and multipletwo MAD cohorts with tebipenem HBr given orally at doses of 300 mg and 600 mg every 8 hours (TID administration) for 14 days. Repeated dose cohorts. The objectiveadministration of both 300 mg and 600 mg of tebipenem HBr TID was well tolerated, with a safety profile consistent with the trial is primarilycarbapenem class of antibiotics. Final results demonstrated a linear and proportional increase in plasma exposure over the dose selectionrange tested, with no accumulation over 14 days of repeated dosing. Furthermore, the administration of tebipenem HBr in the fed or fasting state did not substantially alter the plasma drug exposure, indicating that tebipenem HBr can likely be administered without regard to meals. Consistent with the predominantly renal elimination of tebipenem HBr, peak urine concentrations were approximately 50 to 100-fold higher than maximum concentrations in plasma, as shown in the charts below, supporting tebipenem HBr’s potential utility as a treatment for our plannedpatients with cUTI.

Free Plasma Concentrations of tebipenem HBr

Urine Concentration of tebipenem HBr after a Single Dose

We also plan to conduct routine ancillary clinical pharmacology studies in parallel with the Phase 3 trial as required by the FDA for the approval of tebipenem HBr, including a renal insufficiency study, a thorough QT prolongation study and includes determination of pharmacokinetics, safety and tolerability for up to 14 days and food effect. a drug-drug interaction study.

In particular, the focus of the SAD cohort is to assess the safety and probability of target attainment (killing of target pathogens). The focus of the MAD cohorts is on dose and schedule, specifically, determining how dose drives bacterial clearance over time. We expect to use data from the trial to refine a pharmacokinetic/pharmacodynamic model to establish anvitro Activity Against MDR Enterobacteriaceae

Tebipenem HBr has shown activity in preclinical in vitro/in vivovitro relationship to support dosestudies against a wide variety of ESBL-producing E. coli and schedule administration for our planned pivotal Phase 3 clinical trial based on drug concentration and inter-patient variability. We expect to report top-line data from the Phase 1 clinical trial in mid-2018.  

Planned Pivotal SPR994 Phase 3 Clinical Trial

Based on our pre-IND meeting with the FDA, we believe that results from our Phase 1 clinical trial of SPR994, together with nonclinical studies, PK/PD, and other supporting data, will be acceptable to FDA to allow us to commence a pivotal Phase 3 clinical trial of SPR994 under a U.S. IND. After we report top-line data from our Phase 1 clinical trial, we plan to request a pre-Phase 3 meeting with the FDA to confirm that no additional clinical trials or preclinical studies are required prior to initiating our Phase 3 clinical trial. Subject to feedback from the FDA, we plan to submit an IND and agree upon the clinical trial protocol in late 2018 and expect to initiate the pivotal Phase 3 clinical trial of SPR994 for the treatment of cUTI and acute pyelonephritis around year-end 2018. Clinical trial applications will also be submitted in Europe and other regions, as needed, to support study enrollment. Our planned pivotal Phase 3 clinical trial of the efficacy and safety of SPR994 is currently designed as a double-blind, double-dummy trial to compare SPR994 with an existing standard of care antibiotic in approximately 1,100 patients randomized 1:1 in each arm.ESBL-producing K. pneumoniae strains. We believe thatthese data show the primary endpointability of the trial will be non-inferiority versus a standard of care antibiotic, with a 10% non-inferiority margin. We intendorally available tebipenem HBr to commence our pivotal Phase 3 clinical trial with a lead-in cohort with intensive pharmacokinetics sampling in orderdeliver similar activity to analyze exposure prior to enrolling the majority of the Phase 3 clinical trial cohort. In this Phase 3 trial, the primary efficacy endpoint is clinical cure and microbiological eradication in the microbiological intent-to-treat population per U.S. FDA guidance for cUTI trials. We will also assess the trial for the primary efficacy endpoint of microbiological eradiation in the microbiologically evaluable population per the European regulatory requirements, under a separate statistical analysis plan of the same datasets.  comparative IV-administered agents.

Following receipt of top-line data from this pivotal Phase 3 clinical trial, with requisite safety data, drug-drug interaction studies and other studies, we intend to submit to the FDA an NDA for SPR994 to treat cUTI including acute pyelonephritis. These data, if positive, may also support marketing applications in other global regions. We also intend to reach an agreement with the FDA on a Pediatric Study Plan and initiate development of SPR994 in pediatrics for cUTI upon receipt of top-line data in adult patients.

Data Supporting the Use of SPR994 for the Treatment of cUTI

We have tested SPR994 in vitro and in animal models. We believe that nonclinical assays are generally predictive of clinical efficacy for antibiotics, particularly in the case of a well-understood class such as carbapenems. In addition, approximately 1,100Approximately 1,200 subjects have been dosed with tebipenem pivoxil in clinical and pharmacologic studies during the development of this drug by Meiji in Japan. The data set from these studies includes 741 adults, including 88 patients with cUTIs, the initial indication for which we plan to develop SPR994.tebipenem HBr. In addition, there are post-marketing outcomes data reporting the safety and efficacy of tebipenem in 3,540 pediatric patients with pneumonia, otitis media, or sinusitis. These data are consistent with the safety profile of tebipenem as established in the clinical trial.

We have also tested tebipenem HBr in vitro and in animal models. We believe that nonclinical assays are generally predictive of clinical efficacy for antibiotics, particularly in the case of a well-understood class such as carbapenems.

In vitro Activity Against MDR Enterobacteriaceae

Results from multiple susceptibility testing studies against MDR Enterobacteriaceae demonstrate that SPR994 remained potent against strains resistant to several other classes of antibiotics, including aminoglycosides and fluoroquinolones. In these studies, we measured the potency, or MIC, of each drug by determining the concentration of drug required to inhibit the growth of 50% and 90% of the isolate set (i.e., the MIC₅₀ or MIC₉₀). The graph below depicts the in vitro activity of SPR994 compared to two commercially available intravenously delivered antibiotics commonly used to treat cUTI against a large number of clinical isolates, namely Invanz (ertapenem, or ETP) from Merck and generically available imipenem, or IMI.

SPR994 Activity Against Contemporary Isolates of E. coli

SPR994 has showed MIC₅₀ and MIC₉₀ values of less than or equal to 0.015 µg/mL and 0.03 µg/mL, which compare favorably (i.e., at or below) to the values obtained by competitive agents ertapenem and imipenem.

Regarding a more resistant set of E. coli isolates, including fluoroquinolone-resistant strains, SPR994 again showed in vitro activity similar to commercially available intravenously delivered drugs such as Merrem (meropenem, or MEM), and better than levofloxacin, or LVX, as shown in the graph below.

SPR994 is Active Against E. coli, Including Fluoroquinolone-Resistant Isolates

SPR994 has also shown activity in preclinical in vitro studies against a wide variety of ESBL-producing E. coli and ESBL-producing K. pneumoniae strains, as highlighted in the table below.

SPR994 Has Potent Activity Against A Variety of ESBL Enzymes

In vitro Activity of SPR994 and Comparator Antibiotics against Clinical Isolates

We believe these data show the ability of orally available SPR994 to deliver similar activity to comparative IV-administered agents.

Tebipenem Phase 1 Clinical Trial Data Support Development of SPR994 for the Treatment of cUTI

Tebipenem was also tested by Meiji in healthy volunteers to determine urinary concentrations as a predictor of efficacy in the cUTI population. Results from this single-ascending dose study are shown in the graph below.

Single-Ascending Dose Calculated Urine Levels of Tebipenem

In early clinical studies in Japan, healthy volunteers received doses up to 600 mg/day. At each dose level, and in a dose dependent manner, the urine concentration of tebipenem exceeded the MIC90 for E. coli of 0.03 µg/ml (defined as the level that is expected to inhibit 90% of E. coli isolates).

A food-effect clinical study was performed to evaluate the impact of meals or dairy products on tebipenem-pivoxil granule pharmacokinetics. The study showed comparable plasma AUC (a measure of drug exposure over time) and urinary excretion rates of tebipenem pivoxil among the study’s subjects in both the fed and fasted states. The effect of a meal or dairy products on tebipenem absorption was observed to be limited, and no adverse safety or tolerability effects were observed in dosing in the fed state.

Meiji Phase 2 Clinical Trial Data of Tebipenem in cUTI

Meiji and Global Pharmaits partner conducted two exploratory, dose-ranging Phase 2 clinical trials of tebipenem in patients with cUTI including patients with acute pyelonephritis. These trials were conducted in Japan between 2001 and 2004. Study L-084 04 (report date 2003), a multicenter open-label study to evaluate the efficacy (clinical and microbiological) and safety (adverse events and laboratory tests) of tebipenem pivoxil at doses of 100 mg administered three times daily, or TID (Group A), 150 mg administered BID (Group B), and 150 mg administered TID (Group C), for seven days in patients with cUTI. There were 51 adult patients, aged 20-74 years inclusive, enrolled with 40 being evaluable for efficacy (14 in Group A; 17 in Group B; 9 in Group C). Study ME1211 (report date 2004), a multicenter, open-label study to evaluate efficacy (early and late assessments) and safety (adverse events and laboratory tests) of tebipenem pivoxil at doses of 250 mg administered BID (500 mg Group) and 300 mg administered TID (900 mg Group) for seven days in patients with cUTI.UTI. There were 37 adult patients, aged 20 to 74 years inclusive, enrolled with all being evaluable for efficacy (19 in 500-mg Group; 18 in 900-mg Group).

In these studies, dosing three times per day showed the greatest effect as compared with other dosing regimens, consistent with the interim results from our Phase 1 clinical trial.

Although the design of the Phase 2 clinical trials in Japan was different from what is recommended in FDA guidance for clinical trials in patients with cUTI, including acute pyelonephritis, we believe these results provide support for our plan to develop SPR994 inplanned single pivotal Phase 3 clinical trial of tebipenem HBr at a dose of 600 mg TID for the treatment of cUTI. With respect to these results, which are summarized in the chart below, the efficacy rate refers to the proportion of subjects judged to have experienced a “markedly effective” or “effective” tebipenem dosage versus the total number of subjects tested, and the negative conversion rate refers to the proportion of subjects with negative urine cultures versus the total number of subjects tested.

Observed Efficacy of Tebipenem Pivoxil in Meiji Phase 2 Trials in cUTIUTI

In these two Phase 2 cUTI trials, 83-84% of patients had complicated lower tract UTIs (complicated cystitis). Taken together, the Meiji Phase 2 trials assessed the clinical and microbiological response to doses of tebipenem pivoxil ranging from 300 mg to 900 mg per day administered as two (BID) or three (TID) split doses. Clinical and microbiological responses at end of therapy, or EOT, were high for all regimens tested; however, the microbiological eradication rates at test of cure, or TOC, were highest in patients  receiving tebipenem 150 mg or 300 mg TID. Of note, the microbiological eradication rates at the TOC in these dosing groups was similar to that reported for the subsets of patients with complicated cystitis in recent cUTI clinical trials utilizing intravenously administered antibiotics. Of note, the AUC exposure observed with 600 mg oral TID of tebipenem HBr in in our single- and multiple-ascending dose study was comparable to that demonstrated to be effective in the Meiji cUTI trials. The appropriateness of the proposed therapeutic dose of tebipenem HBr is supported by a pharmacokinetic/pharmacodynamic analysis based on three preclinical pharmacodynamic models (murine neutropenic thigh, hollow fiber, and one compartment pharmacodynamic model) and a clinical population pharmacokinetic model, which indicates that 600 mg of tebipenem HBr administered TID is likely to achieve high target attainment over the MIC range of the most prevalent Enterobacteriaceae causing cUTI.

Japanese Data Supporting Safety of Tebipenem

Tebipenem pivoxil is a prodrug that is metabolized to tebipenem, its therapeutically active form. We view the clinical safety profile of tebipenem pivoxil established by Meiji as relevant and supportive of SPR994tebipenem HBr because both metabolize to the active metabolite, tebipenem, in plasma. Our formulation development efforts are designed to improve target concentration while maintaining the exposure per dose.

Tebipenem pivoxil is an orally administered carbapenem, which is a sub-group of the beta-lactam class of antibiotics. The safety of tebipenem pivoxil was evaluated in approximately 1,1001,200 subjects supporting the application for approval in Japan. In this safety data set, there are 741 adult subjects across 17 trials and 440 pediatric subjects across six trials. These 23 trials in total, included one double-blind, comparator-controlled trial in children, five open-label trials in children, five trials enrolling adult patients (including two open-label cUTI trials), and 12 Phase 1 clinical pharmacology trials. Among the pharmacology trials, tebipenem pivoxil was studied for an effect on QT interval, and for the known effect of the pivoxil prodrug on serumplasma carnitine concentrations.

In these studies, tebipenem pivoxil was generally safe and well tolerated, with an adverse event, or AE, profile comparable to common, approved oral beta lactam antibiotics and IV-administered carbapenems. The most common AEs were gastrointestinal (e.g., diarrhea, loose stools) in both children and adults, and in the Phase 3 clinical trial of otitis media, the incidence was similar to that reported for the comparator, cefditoren (also a pivoxil, prodrug), an oral cephalosporin antibiotic. No effect of the administration of tebipenem pivoxil on the prolongation of the QT interval was observed, and the effect on serumplasma carnitine concentrations was reversed post treatment and not associated with AEs. A side effect seen with beta-lactam antibiotics is seizures; however, there have been no reports of inducement of seizures due to the administration of tebipenem pivoxil in clinical trials. In addition, there are

Meiji has reported post-marketing outcomes data reporting the safety and efficacy of tebipenemOrapenem Fine Granules 10% for Pediatric Use (tebipenem pivoxil) in 3,540 pediatric patients with pneumonia, otitis media, or sinusitis. These data are consistent with the safety profile of tebipenem as established in the clinical trial.

A total of 3,547 cases were enrolled into the observational study, and the analysis was conducted using 3,540 cases for which it was possible to recover the questionnaires. Of these 3,540 cases, a

A total of 3,331348 instances of adverse drug reactions were observed in 334 cases wereamongst the 3,337 cases (including 6 adult cases) used in the safety analysis, 2,844 cases were used inanalyses, and the efficacy analysis, 2,769 cases were used in the clinical efficacy analysis, and 461 cases were used in the bacteriological efficacy analysis. The incidence of adverse drug reactions was 9.97% (332/3,33110.01% (334 cases/3,337 cases), and the primary. The adverse drug reactions were “gastrointestinal disorders” suchreaction that occurred most frequently was “diarrhea” (9.5%, 318 instances/3,337 cases). One serious drug reaction was observed of “multi-organ failure”. These data are consistent with the safety profile of tebipenem as diarrhea, which occurredestablished in 317 cases (9.52%). “Diarrhea” occurredthe pediatric clinical trials and reflected in 313 cases (316 instances).  All of these events were non-serious, and 94.9% (297/313 cases) showed recovery or remission.

the Orapenem product labeling in Japan.

A clinical studytrial evaluating the effect of tebipenem pivoxil dosing over one week on intestinal flora was also performed. Total aerobic and anaerobic bacterial counts were evaluated. Total bacterial count was reduced by day 7 of the study in both the 100 and 200 mg TID groups. However, no additional change in bacterial count was observed on subsequent examination days. Neither fecal C. difficile nor its toxin was detected in any of the subjects during or following completion of the 7-day dosing period.

Funded Label Expansion Opportunity

In addition to cUTI, we believe that tebipenem HBr has the potential to treat other serious and life-threatening infections, including CABP. Our Potentiator Platform (SPR741 and SPR206)

We have two product candidates in our Potentiator Platform, SPR741 and SPR206. Both product candidates are IV-administered derivatives of Polymyxin B, or PMB. Both have demonstrated in vitro activity against Gram-negative bacteria, including organisms identified by the CDC and the WHO as urgent and serious threats to human health. There are two primary differences between these two product candidates. SPR741 has minimal antibacterial activity as a single agent and requires combination therapy with a companion antibiotic to demonstrate antimicrobial potency. SPR741 also has demonstrated activity primarily against MDR Gram Negative organisms such as Enterbacteriaceae and against some strains of Acinetobacter baumanii depending on its combination partner. SPR206 is active as a single agent and exerts potency with and without a partner. SPR206 also has a broad spectrum of activity including all the strains SPR741 covers, as well as expanded coverage of carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant Acinetobacter baumanii and carbapenem-resistant Enterobacteriaceae.

We have completed aBARDA award provides funding for Phase 1 two part, randomized, double-blind, placebo-controlled, dose-escalation trial of SPR741. We initiated ourand Phase 1b drug-drug interaction clinical trial of SPR741 in the United Kingdom during the fourth quarter of 2017. The Phase 1b trial enrolled 27 healthy volunteers to evaluate SPR741 as2 trials supporting a single dose in combination with compounds from the beta-lactam class of antibiotics, including cephalosporins (ceftazidime), monobactams (aztreonam) and beta-lactam/beta-lactamase inhibitors (piperacillin/tazobactam). The trial was designed to assess the impact, if any, on the standalone pharmacokinetics of SPR741 or the standalone pharmacokinetics of the beta-lactam combination drug when the two are dosed together as a single dose. We anticipate top-line data from this Phase 1b trial during the second quarter of 2018.

potential CABP indication for tebipenem HBr.

We believe that our intellectual property portfolio for SPR741, which includes multiple issued patents and patent applications pending, will provide SPR741 protection globally, including in the United States and Europe, through 2038. Additionally, we have multiple patent applications pending for SPR206 that we believe will provide SPR206 protection globally, including in the United States and Europe, through 2035.

How Our Potentiator Platform Molecules Are Designed to Work

Gram-positive and Gram-negative bacteria are classified by the lab staining test known as the “Gram stain”, but their nature is due to structural differences in their cell envelope, with Gram-positive bacteria surrounded by a single lipid membrane and a thick cell wall and Gram-negative bacteria encircled by two lipid membranes, an inner membrane and an outer membrane, with a thinner cell wall in between. The outer membrane, with its LPS-containing outer leaflet, represents a significant barrier to the entry into the bacteria by antibiotics and is a significant contributor to reduced potency of many agents in treating Gram-negative bacterial infections. Each membrane in Gram-negative bacteria excludes different types of chemical entities, requiring Gram-negative active antibiotics to be specifically designed to permeate both membranes. Gram-negative bacteria include Pseudomonas aeruginosa, Acinetobacter baumannii, and the Enterobacteriaceae, a family of related organisms that includes E. coli, Klebsiella pneumoniae, Enterobacter, Salmonella, and Shigella species.

Advantages of our Potentiator Platform

We believe that the following key attributes of our Potentiator Platform generally have the potential to support the clinical utility and commercial value of our Potentiator Platform for the safe and effective treatment of serious infections:

Significant Market Opportunity for SPR741 and SPR206, including Gram-Negative IV Market

The need for new antibiotics to treat CRE, CRAB and MDR PA is particularly acute, as together these represent among the top global threats in infectious disease. In February 2017, the WHO published a list of Gram-negative bacteria based on the urgency of need for new antibiotics: critical, high and medium priority. The most critical group includes MDR bacteria that pose a particular threat including Acinetobacter, Pseudomonas and various Enterobacteriaceae (including Klebsiella, E. coli, Serratia, and Proteus). These bacteria can cause severe and often deadly infections. As such, there is an acute need for new drugs to treat MDR Gram-negative bacteria. Currently approved products are increasingly ineffective against Gram-negative bacteria due to increasing resistance, resulting in limited treatment options for patients with MDR infections. Few new therapeutic agents have been approved or are in clinical development to treat infections caused by Gram-negative bacteria.

Acinetobacter baumannii is an opportunistic bacterial pathogen primarily associated with hospital-acquired infections. The recent increase in incidence, largely associated with infected combat troops returning from conflict zones, coupled with a dramatic increase in the incidence of MDR strains, has significantly raised the profile of this emerging opportunistic pathogen. It is estimated between 50,000 to 80,000 infections annually in the United States and approximately 63% of isolates are MDR. Mortality rates for patients with Acinetobacter baumannii have been reported as high as 43%. Currently the only drugs to treat these resistant organisms are polymyxins such as colistin, polymixyn B, or PMB, and tigecycline, or TIG, both of which have significant safety and tolerability issues. SPR206 would provide a much needed addition to the treatment of these very serious infections.

Pseudomonas is one of the most common Gram-negative organisms in the hospital setting. Incidence ranges from 13% in UTIs and as high as 25% in respiratory tract infections. Resistance to commonly used agents such as cephalosporins, piperacillin/tazobactam and quinolones ranges from 10% in the non-ICU setting to upwards of 35% in the ICU. Even more problematic is the increase in resistance to carbapenems, which is reported to be as high as 19% in the ICU. Pseudomonas is a serious cause of infection with morbidity and mortality rates of 18% to 61%. In preclinical studies to date, SPR206 has demonstrated potent activity across a broad range of resistant strains of Pseudomonas aeruginosa. There are limited treatment options available today to treat these resistant organisms.

CRE infections are associated with significant mortality, with up to 50% mortality observed in patients with bloodstream infections. With limited treatment options available for CRE infections, physicians have resorted to older drugs such as colistin or more recently drugs such as tigecycline and ceftazidime/avibactam. However, there is evidence that these antibiotics are failing patients. For example, in bloodstream infections due to carbapenemase-producing Klebsiella pneumoniae, all-cause mortality for treatment with colistin, tigecycline, or combinations of antibiotics that do not include a carbapenem active in vitro against the infecting isolate was reported to be 46%, 47%, and 37%, respectively. Recently, resistance to even these last-resort treatments has begun to be reported, further increasing the urgency for new therapeutic options.

SPR741—Phase 1 Clinical Trial and Clinical Development

Data from our Phase 1 SAD and MAD clinical trial show SPR741 administered intravenously in single doses up to and including 800 mg and multiple daily doses up to and including 600 mg every 8 hours for 14 days was generally well tolerated in healthy adult subjects. There were no deaths or serious adverse events. All subjects completed the study. As shown in the chart below, the pharmacokinetics observed in the SAD portion of the trial were dose linear and dose proportional with a half-life of between two and four hours, consistent with expectations from preclinical modeling. Similarly, the pharmacokinetics observed in the MAD portion of the trial were dose linear and dose proportional, with only minor accumulation noted in the top dose cohort (600 mg every 8 hours).

We initiated our Phase 1b drug-drug interaction clinical trial of SPR741 in the United Kingdom during the fourth quarter of 2017. The Phase 1b trial enrolled 27 healthy volunteers to evaluate SPR741 as a single dose in combination with compounds from the beta-lactam class of antibiotics, including cephalosporins (ceftazidime), monobactams (aztreonam) and beta-lactams/beta-lactamase inhibitors (piperacillin/tazobactum). The trial was designed to assess the impact, if any, on the standalone pharmacokinetics of SPR741 or the standalone pharmacokinetics of the beta-lactam combination drug when the two are dosed together as a single dose. We anticipate top-line data from this Phase 1b trial during the second quarter of 2018.

Our Potentiator Platform is funded in part with non-dilutive funding from the DoD and CARB-X, consisting of $1.9 million through March 31, 2018. We have global commercialization rights to SPR741, which has global patent protection extending through 2038.

In Vitro Activity of SPR741 Against MDR Gram-Negative Bacteria

Results from multiple susceptibility testing studies against suggest that SPR741 is capable of potentiating the activity of several classes of antibiotics, including some beta-lactams and macrolides. We ascertained the potential clinical profile of combinations of SPR741 against MDR Enterobacteriaceae encountered in the hospital setting by testing the combinations against a large number of clinical isolates collected from unique patients with different types of infections from hospitals around the world. In one such study,

we measured the ability of SPR741 to enhance the activity of ceftazidime, or CAZ, or piperacillin-tazobactam (Zosyn, or TZP) against a large collection of clinical isolates expressing the drug-resistant phenotype ESBL. In each case, as shown in the graph and summarized in the table below, SPR741 potentiated the activity of the antibiotics resulting in an MIC₉₀ shift from 256 to 8 for CAZ and from 256 to 1 for TZP. We believe that this data demonstrates SPR741’s ability to restore the combined antibiotic’s therapeutic activity against a resistant strain of bacteria.

Potency of Piperacillin-Tazobactam and Ceftazidime with and without SPR741

in Global Set of Clinical Isolates Classified as ESBL Producers

MIC₉₀ and % of Bacteria Susceptible to Piperacillin-Tazobactam and Ceftazidime

with and without SPR741 in Global Set of Clinical Isolates Classified as ESBL Producers

SPR206—Development Plan

In Vitro Activity of SPR206 Against MDR Gram-Negative Bacteria

Results from multiple susceptibility testing studies against MDR Enterobacteriaceae suggests that SPR206 is capable potent activity against MDR Enterobacteriaceae, carbapenem resistant Pseudomonas aeruginosa and carbapenem resistant Acinetobacter baumanii.

In vivo Activity of SPR206 against Carbapenem-Resistant Acinetobacter baumannii

The activity of SPR206 against a carbapenem resistant strain of Acinetobacter baumannii exceeded the activity of polymyxin B (PMB) and tigecycline (TIG) in a mouse lung infection model as shown below.

Activity of SPR206 vs. Comparators in a Mouse Lung Infection Model

Orphan disease,SPR720 Pulmonary Non-Tuberculous Mycobacterial Infection(NTM) Disease Program

A thirdsecond area of our focus is anti-infective orphanrare infectious diseases, specifically non-tuberculous mycobacterial disease. We are developing SPR720, a therapeutic candidate with a novel mechanism of action therapeutic candidate for the treatment of NTM infection.disease. NTM causes chronic and serious lung disease with debilitating symptoms that leads to a decline in lung function. It can have a significant physical and emotional impact on patients. SPR720 is designed to be the first novel, oral candidate to treat pulmonary NTM infection.disease. SPR720 represents a novel class of antibacterial agents that target enzymes essential for bacterial DNA replication.

SPR720 has several key attributes including:

SPR720 has shown potent activity against most common NTM infection species, such as M. avium, M. abscessus and M. kansasii. As shown in the exhibit below, SPR720 showsshowed dose responsive efficacyactivity against difficult to treat multidrug resistantMDR pathogens, with better activity as compared to amikacin or AMK,(AMK) considered one of the positive controlcontrols in this experiment.

Lung Infections in Multidrug Resistant Abscessus Strains

Non-tuberculous mycobacteria are typically found in water and soil. NTM infections cause a rare infection of the lung that is acquired through inhalation of this microbe. There are approximately 150 types of mycobacteria, with Mycobacterium avium complex, or MAC and Mycobacterium abscessus the most common cause of NTM infections, together comprising almost 90% of all NTM infections.

NTM infections occurdisease occurs in many different types of patients. NTM infectionsdisease often occuroccurs in people with compromised immune systems, such as those with HIV, or those with respiratory conditions such as cystic fibrosis, chronic obstructive pulmonary disease, asthma or bronchiectasis. According to Strollo et al. and Adjemian et al., the diagnosed patient population is approximately 86,000 in the United States. The annual prevalence of NTM infectiondisease is increasing at an estimated rate of 8% per year. While people of any age can be infected by NTM, it mostly affects middle-aged to elderly adults, and is increasing among patients over 65, a population expected to nearly double by 2030. While relatively rare compared to other infectious diseases, the prevalence of NTM infectiondisease has more than doubled since 1997.1997 and unfortunately, infections caused by NTM are often undiagnosed, masquerading as another respiratory condition such as COPD or asthma. By comparison, the prevalence of tuberculosis in North America has declined.

There are currently no oral FDA-approved therapeutics indicatedspecifically approved for use to treat NTM infections.disease. Given the unmet medical need, there are regulatory incentives available to encourage drug development to address NTM infection.disease. These include orphan drug designation, potential for breakthrough therapy status and QIDP designation. The current treatmentTreatment of NTM disease requires prolonged therapy (continuing for NTM infectionapproximately 12 to 24 months) with a combination regimen and is lengthy and involves combination therapy, often including three frequently complicated by tolerability and/or more drugs including an injectable.toxicity issues. Treatment failure is common and is often due to poor compliance or inability to tolerate the regimen. Many patients experience progressive lung disease and mortality is high. We believe there is a need for new, potent, orally available therapies for NTM infection.disease. While there are competitive compounds in late-stage development for NTM infection,disease, these therapies are not effective in all patients and are not orally available.

We believe that our intellectual property portfolio for SPR720, which includes multiple issued patents and patent applications pending, will provide SPR720 protection globally, including in the United States and Europe, through 2033.

Our SPR720 Development Plan

Our strategy is to develop SPR720 to become the first oral treatment FDA-indicated for NTM infection,disease, and to enable refractory patients to regain a better quality of life. SPR720 is currently in preclinicalclinical development. We have conducted 28-day GLP toxicity studiesinitiated a Phase 1 clinical trial of SPR720 in rats and non-human primates, andJanuary 2019, designed as a double-blind, placebo-controlled, ascending dose, multi-cohort study in healthy subjects. Preliminary analysis of blinded data from this Phase 1 trial suggests that SPR720 is generally well-tolerated, with a PK profile that we are waitingbelieve supports the further development of SPR720 as an oral agent for the treatment of NTM pulmonary disease. We expect to present final resultsdata from the SPR720 Phase 1 SAD/MAD clinical trial in 2020 at a medical meeting. We plan to request a meeting with the FDA in the first half of these studies. We have also observed activity2020, submit an IND to the FDA in the second half of 2020 and, following IND acceptance, initiate a dose-ranging Phase 2a clinical trial evaluating SPR720 in patients with NTM disease due to Mycobacterium avium complex, or MAC, in the second half of 2020.

The Phase 1 clinical trial of SPR720 evaluated the safety, tolerability and PK of orally administered SPR720 at single doses ranging from 100 mg to 2000 mg and repeat total daily doses ranging from 500 mg to 1500 mg for up to 7 to 14 days. Across seven SAD and five MAD cohorts, a total of 96 healthy volunteers (including a cohort of healthy elderly (age ≥ 65 years) volunteers) were randomized to receive SPR720 or placebo. There were no serious adverse events reported and all participants completed the trial. An analysis of preliminary blinded data indicates that SPR720 was generally well-tolerated at doses up to 1000 mg over the maximum studied duration of 14 days. Preliminary analyses of PK data across the cohorts show no significant impact of either advanced age or administration with food on PK variables. At doses of 500 mg or higher, the mean plasma drug exposures of SPR719, the active metabolite of SPR720, are consistent with those suggested by in vivo models of SPR720 to be necessary for clinical efficacy against target NTM pathogens.

Our IV Potentiator Product Candidate SPR206

SPR206 is a product candidate from our IV Potentiator Platform in development as good as or better than positive controlsan innovative option to treat Gram-negative infections in the hospital setting. SPR206 has exhibited in vitro and in vivo testing,activity against Gram-negative bacteria, including organisms identified by the CDC and the WHO as urgent and serious threats to human health. Specifically, in an infection model caused bynonclinical studies SPR206 demonstrated activity as a single agent against MDR and XDR bacterial strains, including isolates of Mycobacterium abscessusPseudomonas aeruginosa, Acinetobacter baumannii and Mycobacterium aviumcarbapenem-resistant Enterobacteriaceae. Pending further evidence of, in both in vitro and in vivo activity and positive results from our additional toxicity studies,models of infection.

In December 2018, we plan to initiateinitiated a Phase 1 SAD/MADclinical trial of SPR206, designed as a double-blind, placebo-controlled, ascending dose, multi-cohort study in healthy subjects, and we reported positive preliminary data from the trial in January 2020. The analysis of preliminary, blinded data from the Phase 1 double-blind, placebo-controlled single ascending dose (SAD) and multiple ascending dose (MAD) clinical trial in healthy adult volunteers suggests that SPR206 is well-tolerated at doses that are likely to be within a therapeutic range for target MDR Gram-negative bacterial infections and has a safety profile that we believe supports continuing development of the product candidate. A total of 96 healthy volunteers were randomized to receive SPR206 or placebo. All reported adverse events were mild to moderate and there were no reported severe or serious adverse events. No evidence of nephrotoxicity was observed and there were no subjects with clinically significant changes in laboratory tests during the firststudy. Although the data remain blinded, an analysis of preliminary data indicates that SPR206 was well-tolerated at doses up to 100 mg administered three-times a day, a total of 300 mg daily, for 14 consecutive days. Preliminary analyses of pharmacokinetic data across the cohorts indicates dose linearity and dose proportionality as well as mean plasma drug exposures of SPR206 that are concordant with preclinical models predictive for clinical efficacy against target Gram-negative pathogens.

We plan to conduct a Phase 1 bronchoalveolar lavage (BAL) clinical trial assessing the penetration of SPR206 into the pulmonary compartment as well as initiate a renal impairment study of SPR206 in the second half of 2019.2020.

SPR206 has been granted QIDP designation by the FDA for the treatment of cUTI and hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (HABP/VABP). We have multiple patent applications pending for SPR206 that we believe will provide SPR206 protection globally, including in the United States and Europe, through 2039.

Following an evaluation of the IV Potentiator Platform product candidates, we have determined to discontinue development of SPR741, effective January 1, 2020, and to move forward with SPR206 as our lead product candidate within the Potentiator Platform. We believe that the collective data from the recent Phase 1 and preclinical studies of SPR206 suggest a potency and safety profile that may be superior to SPR741. Further, we believe SPR206 may have a potentially faster path to pivotal clinical trials when compared with SPR741 because SPR206 is being developed as a single agent. As a result of this decision, we have terminated our license agreement with Northern Antibiotics Oy (Ltd.) relating to SPR741. Effective January 1, 2020, the intellectual property rights associated with SPR741 have entirely reverted to Northern Antibiotics and we no longer have any rights with respect thereto and we no longer have any obligations for the cost of maintaining such intellectual property.

SPR206 Advantages

We believe that the following key attributes of SPR206, an agent from our Potentiator Platform, generally has the potential to support the clinical utility and commercial value of our Potentiator Platform for the safe and effective treatment of serious Gram-negative infections:

SPR206—Development Plan

Positive Phase 1 Preliminary data for SPR206

In December 2018, we initiated a Phase 1 trial of SPR206, designed as a double-blind, placebo-controlled, ascending dose, multi-cohort study in healthy subjects. The trial evaluated the safety, tolerability and pharmacokinetics of intravenously administered SPR206 at single doses ranging from 10 mg to 400 mg in seven SAD cohorts and repeat total daily doses ranging from 75 mg to 450 mg for seven consecutive days and 300 mg for 14 consecutive days across five MAD cohorts. A total of 96 healthy volunteers were randomized to receive SPR206 or placebo. Preliminary data of the blinded data in January 2020 indicated that SPR206 was well-tolerated at doses up to 100 mg administered three-times a day, a total of 300 mg daily, for 14 consecutive days. All reported adverse events were mild to moderate and there were no reported severe or serious adverse events. No evidence of nephrotoxicity was observed and there were no subjects with clinically significant changes in laboratory tests during the study. Preliminary analyses of pharmacokinetic data across the cohorts indicates dose linearity and dose proportionality as well as mean plasma drug exposures of SPR206 that are concordant with preclinical models predictive for clinical efficacy against target Gram-negative pathogens.

In Vitro Activity of SPR206 against MDR Gram-Negative Bacteria

Results from multiple susceptibility studies against contemporary clinical isolates suggest that SPR206 possesses potent activity against MDR Enterobacteriaceae, carbapenem resistant Pseudomonas aeruginosa and carbapenem resistant Acinetobacter baumannii.

Collaboration and License Agreements

In addition to our own patents and patent applications, we have acquired or licensed patents, patent applications and know-how from various third parties to access intellectual property covering product candidates that we are exploring and developing. We have certain obligations under these acquisitionacquisitions or licensing agreements, including diligence obligations and payments, thatwhich are contingent upon achieving various development, regulatory and commercial milestones. Also, pursuant to the terms of some of these license agreements, when and if commercial sales of a product commence, we may be obligated to pay royalties to such third parties on net sales of the respective products. Some of our license agreements include sublicenses of rights owned by third-party head licensors.

In addition, we have entered into a license agreement (described below) pursuant to which we have granted certain development, manufacturing and commercialization rights with respect our Potentiator product candidates.

Meiji Agreements

To support our development of SPR994,tebipenem HBr, in June 2017 we entered into an exclusive License Agreement with Meiji Seika Pharma Co., Ltd., or the Meiji License. Pursuant to the Meiji License, we obtained know-how, data and regulatory documents that will support the development of SPR994.

tebipenem HBr.

We retain exclusive rights to commercialize SPR994tebipenem HBr throughout the world, except in Japan, Bangladesh, Brunei, Cambodia, China, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, South Korea, Taiwan, Thailand and Vietnam, where Meiji will have exclusive rights to commercialize SPR994.tebipenem HBr. With Meiji, we have established a joint development committee for the management of the development of SPR994,tebipenem HBr, including any joint, cross-territory studies that may be undertaken by the parties, if any. In addition, the parties will establish a joint commercialization committee to coordinate information sharing relative to commercialization of the new formulation.

Meiji and we have granted each other exclusive cross licenses to our respective tebipenem intellectual property, including know-how and regulatory documentation. The license granted to us by Meiji includes certain know-how that Meiji received from Global Pharma, as described below. As such, our rights to the Global Pharma know-how component are non-exclusive.

Under the Meiji License, we have paid Meiji a one-time nonrefundable upfront fee of $0.6 million and are obligated to pay Meiji future clinical and regulatory milestone payments up to an aggregate of $3.0 million and royalties of a low single-digit percentage based on net sales of SPR994.tebipenem HBr. In October 2017, we paid a $1.0 million milestone payment to Meiji upon the enrollment of the first patient in the Company’sour Phase 1 clinical trial of SPR994.tebipenem HBr. Additionally, we are obligated to pay Meiji a percentage of certain amounts received from any sublicensees, up to an aggregate of $7.5 million.

Some of the know-how that we received under the Meiji License to support SPR994tebipenem HBr development was originally obtained by Meiji through a license from Global Pharma, which we refer to as the head license. Prior to entering into the Meiji License with us, Meiji received written approval from Global Pharma permitting Meiji to enter into the Meiji License with us. Specifically, in a letter agreement between Global Pharma and Meiji entered into in January 2017, Global Pharma consented to Meiji assisting us with the transfer or license of the Global Pharma know-how and Meiji know-how on a non-exclusive basis outside of those Asian countries identified above, as well as certain related matters. This letter agreement does not contemplate us having any right to sublicense the Global Pharma know-how. Global Pharma retains rights to its know-how outside of those Asian countries identified above.

The Meiji License continues in effect until the expiration of all payment obligations thereunder (including royalty payments and licensee revenue) on a product-by-product and country-by-country basis, unless earlier terminated by the parties. Pursuant to the terms of the Meiji License, in addition to each party’s right to terminate the agreement upon the other party’s material breach (if not cured within a specified period after receipt of notice) or insolvency, we also have unilateral termination rights (i) in the event that we abandon the development and commercialization of SPR994tebipenem HBr for efficacy, safety, legal or business factors, and (ii) under certain circumstances arising out of the head license with Global Pharma.

IV Potentiator Platform Agreements

Northern License Agreement

In February 2015,January 2020, we terminated our subsidiary, Spero Potentiator, Inc., or Spero Potentiator, entered into a license agreement or the 2015 Northern License Agreement, with Northern Antibiotics Oy (Ltd.) of Finland pursuantrelating to whichSPR741. Effective January 1, 2020, the intellectual property rights associated with SPR741 have entirely reverted to Northern granted to Spero Potentiator an exclusive, worldwide, perpetualAntibiotics and irrevocable license to developwe no longer have any rights with respect thereto and commercialize certain licensed compounds under certain patents, patent applications and know-how of Northern. In exchange for such exclusive license, Spero Potentiator issued an equity interest in Spero Potentiator and entered into a subscription agreement and shareholders agreement with Northern. In June 2017, we repurchased Northern’s minority equity interest in Spero Potentiator in exchange for a one-time nonrefundable upfront fee of $1.0 million immediately and agreed to pay Northern $0.1 million within five days of the consummation of our initial public offering, or IPO, which event occurred and which amount was paid in November 2017. We also amended and restated the 2015 Northern License Agreement, which, as amended, we refer to as the 2017 Northern License Agreement, to include certain contingent cash payments as described below. The 2017 Northern License Agreement has a perpetual term and no express termination rights.

Under the 2017 Northern License Agreement, Northern granted to Spero Potentiator an exclusive, perpetual, irrevocable, worldwide license to develop and commercialize certain licensed compounds under certain Northern patents, patent applications and know-how in consideration for one or more near-term milestone payments up to an aggregate of $2.5 million based on either clinical milestones or the completion of our IPO, which event occurred and which amount was paid in November 2017, and in consideration for up to an aggregate of $4.5 million upon receipt of marketing approval of SPR741 or other compounds licensed from Northern which, in either case, is approved to be co-administered with a different antibiotic agent. With Northern, welonger have established a joint development committeeany obligations for the exchangecost of information and ideas regarding development of the licensed compounds, to monitor conduct of activities and to provide and receive updates regarding new inventions. In addition, we provide periodic reports to Northern describing the development and commercialization of the licensed compounds, including SPR741.

maintaining such intellectual property.

Cantab Agreements

In June 2016, we entered into a stock purchase agreement, or the Cantab Agreement, with Pro Bono Bio PLC, a corporation organized under the laws of England, and its affiliates, including PBB Distributions Limited, or PBB, Cantab Anti-Infectives Ltd., or CAI and New Pharma License Holdings Limited, or NPLH, in order to acquire NPLH and its intellectual property rights and assets relating to our Potentiator Platform, and our next-generation potentiating agents in particular. The intellectual property portfolio we acquired includes patents which cover SPR206 as well as other novel potentiating agents, polymyxin derivatives and other LPS or outer-membrane bacterial disrupting agents. In exchange for the acquisition of NPLH, we paid PBB upfront consideration in the amount of $0.3 million and also agreed to pay a totalmake milestone payments of up to $5.8 million upon the achievement of specified clinical and regulatory milestones and to paya payment of £5.0 million ($6.76.6 million as of December 31, 2017)2019) upon the achievement of a specified commercial milestone. We also agreed to pay royalties of a low single-digit percentage based on net sales of products licensed under the agreement. In addition, Spero Cantab issued an equity interest in Spero Cantab and entered into a subscription agreement and shareholders agreement with PBB. In July 2017, we repurchased PBB’s minority equity interest in Spero Cantab in exchange for a one-time nonrefundable upfront fee of approximately $0.2 million and we also amended the Cantab Agreement to increase the contingent milestone payments to PBB by an aggregate of $0.1 million. The Cantab Agreement continues indefinitely, with royalty payment obligations thereunder continuing on a product-by-product and country-by-country basis until the later of ten years after the first commercial sale of such product in such country or the expiration in such country of the last to expire valid claim of any of the applicable patents.

During the three months ended December 31, 2018, we recorded $0.2 million in expense related to the achievement of regulatory milestones for SPR206.

In addition, Spero holdswe hold a NIAID contract that partially funds the next-generation potentiating agent development program. That contract was novated from CAI to Sperous in December 2017. IfUnder the contract we pay PBB a percentage of funds received from NIAID exercises future contract optionsup to a maximum of $1.3 million, of which $0.3 million was paid upfront to PBB as part of this agreement. During the years ended December 31, 2019 and 2018, we recorded approximately $0.3 million and $0.4 million in expense related to amounts payable to PBB under this agreement.

Everest Medicines License Agreement

On January 4, 2019, we, through NPLH, entered into a license agreement, or the Everest License Agreement, with Everest Medicines II Limited, which Everest License Agreement also includes an option granted by our wholly owned subsidiary, Spero Potentiator, Inc., a Delaware corporation, or Potentiator. Under the terms of the Everest License Agreement, we granted Everest an exclusive license to develop, manufacture and commercialize SPR206 or products that contain SPR206, or Licensed Products, in Greater China (which includes Mainland China, Hong Kong and Macau), South Korea and certain Southeast Asian countries, collectively referred to as the Territory. We retained development, manufacturing and commercialization rights with respect to SPR206 and Licensed Products in the rest of the world and also retained the right to develop or manufacture SPR206 and Licensed Products in the Territory for use outside the Territory. In addition to the license grant to SPR206, we granted Everest a 12-month exclusive option to negotiate with us for an exclusive license to develop, manufacture and commercialize SPR741 in the Territory. For the reasons discussed above, following an evaluation of the Potentiator Platform product candidates, we determined to discontinue development of SPR741, effective January 1, 2020, and to move forward with SPR206 as our lead product candidate within the Potentiator Platform. In addition, on October 29, 2019, Everest notified us that it did not intend to exercise its option with respect to SPR741 under the Everest License Agreement. Accordingly, effective January 1, 2020, we no longer have any intellectual property rights with respect to SPR741 and we receive further funding from NIAID, then we will pay a portionno longer have any obligations for the cost of maintaining such intellectual property.

Under the terms of the proceedsEverest License Agreement, we received an upfront payment of $3.0 million. We may also receive up to PBB pursuantan additional $59.5 million in milestone payments upon Everest’s achievement of certain developmental, regulatory and sales milestone events related to SPR206, which achievement cannot be guaranteed. We are also entitled to receive high single-digit to low double-digit royalties on net sales, if any, of Licensed Products in the Cantab Agreement.Territory following regulatory approval of SPR206. Everest has the right to sublicense to affiliates and third parties in the Territory.

Everest is responsible for all costs related to developing, obtaining regulatory approval of and commercializing SPR206 and Licensed Products in the Territory, and is obligated to use commercially reasonable efforts to develop, manufacture and commercialize Licensed Products, including to achieve certain specified diligence milestones within agreed-upon periods. A joint development committee will be established between us and Everest to coordinate and review the development, manufacturing and commercialization plans with respect to Licensed Products in the Territory.

Unless earlier terminated due to certain material breaches of the contract, or otherwise, the Everest License Agreement will expire on a jurisdiction-by-jurisdiction and Licensed Product-by-Licensed Product basis until the latest to occur of expiration of the last valid claim under a licensed patent in such jurisdiction, the expiration of regulatory exclusivity in such jurisdiction or ten years after the first commercial sale of such Licensed Product in such jurisdiction. The Everest License Agreement may be terminated in its entirety by Everest upon 90 or 180 days’ prior written notice, depending on the stage of development of the initial Licensed Product.

Other License and Collaboration Agreements

Gates MRI Collaboration

In June 2019, we entered into a collaboration with the Bill & Melinda Gates Medical Research Institute, or the Gates MRI, a nonprofit research institution wholly owned by the Bill and Melinda Gates Foundation, to develop SPR720 for the treatment of lung infections caused by Mycobacterium tuberculosis, or Mtb. In furtherance of the Gates MRI’s charitable purposes, we also granted the Gates MRI a no cost, exclusive license to develop, manufacture and commercialize SPR720 for the treatment of tuberculosis, or TB, in low- and middle- income countries. Gates MRI will conduct and fund preclinical and clinical studies for the development of SPR720 against TB as well as certain collaborative research activities performed by us.

Vertex Assignment and License Agreement

In May 2016, we entered into an agreement with Vertex Pharmaceuticals Incorporated, or Vertex, pursuant to which Vertex assigned to us rights to patents relating to SPR720 and SPR719 (an active metabolite). The acquired patent portfolio includes protection for composition of matter, method of use, and specific key intermediates used in the manufacture of SPR719 and SPR720. We also obtained certain know-how and a license to research, develop, manufacture and sell products for a proprietary compound, as well as a transfer of materials as part of the transaction. In return, we granted Vertex an exclusive license to the assigned patents and know-how for use outside of the diagnosis, treatment or prevention of bacterial infections. In exchange for the assigned patents, we paid Vertex an upfront, one-time, non-refundable, non-creditable fee of $0.5 million, which was recognized as research and development expense, and we also agreed to pay Vertex future clinical, regulatory and commercial milestones up to $81.1 million in the aggregate and a royalty on the net sales of licensed products ranging from mid-single digits to low double digits. During the three months ended December 31, 2018, we recorded $0.2 million in expense related to the achievement of regulatory milestones for SPR720. The agreement continues in effect until the expiration of all payment obligations thereunder, with royalty payment obligations continuing on a

product-by-product and country-by-country basis until the later of ten years after the first commercial sale of such product in such country or the date of expiration in such country of the last to expire applicable patent. Further, Vertex has the right to terminate the agreement if provided with notification from us of our intent to cease all development or if no material development or commercialization efforts occur for a period of 12 consecutive months.

Government Awards

WeAs described below, through December 31, 2019, we have commitmentscommitted funding support of up to an aggregate of $10.1$49.7 million in non-dilutivenon- dilutive funding from BARDA, NIAID, the DoD and CARB-X.CARB-X, with the potential to receive a total of up to $63.0 million (inclusive of amounts we have already received) if certain options are exercised. These awards are structured in the following manner:

Intellectual Property

We strive to protect the proprietary technology that we believe is important to our business, including seeking and maintaining patents intended to cover our product candidates and compositions, their methods of use and processes for their manufacture and any other inventions that are commercially important to the development of our business. We also rely on trade secrets to protect aspects of our business that are not amenable to, or that we do not consider appropriate for, patent protection.

Our success will significantly depend on our ability to obtain and maintain patent and other proprietary protection for commercially important technology and inventions and know-how related to our business, defend and enforce our patents, preserve the confidentiality of our trade secrets and operate without infringing the valid and enforceable patents and proprietary rights of third parties. We also rely on know-how and continuing technological innovation to develop and maintain our proprietary position.

Spero-Owned Intellectual Property Relating to SPR994tebipenem HBr and Other Compounds Under Development

We have patent applications directed to the composition of matter, formulation and/or use of SPR994,tebipenem HBr, SPR741, SPR206 and SPR720 pending in the United States, Europe, Japan and other countries.

Tebipenem HBr Oral Carbapenem (SPR994)

(Previously SPR994 – tebipenem pivoxil hydrobromide)

Our SPR994tebipenem HBr program contains one pending U.S. provisional patent application, two pending U.S. provisionalpatent applications, and one20 pending foreign patent cooperation treaty, or PCT, applicationapplications covering novel preparations of tebipenem pivoxil hydrobromide as of December 31, 2017,2019, all wholly owned by us. The provisional patent applications willapplication must be converted to Patent Cooperation Treaty, or PCT applications within one year of theirits May 2019 filing dates.date. The foreign patent applications are pending in Australia, Brazil, Canada, China, Colombia, the Eurasian Patent Office, the European Patent Office, Egypt, Indonesia, Israel, India, Japan, South Korea, Mexico, New Zealand, the Philippines, Singapore, Thailand, Vietnam, and South Africa.  U.S. and foreign patents issuing fromcovering our tebipenem pivoxil patent applicationshydrobromide preparations will have statutory expiration dates of December 2037, February 2038, and February 2038.May 2039. Patent term adjustments or patent term extensions could result in later expiration dates.

Potentiator Platform (Including SPR741)

The intellectual property portfolio for our Potentiator Platform contains patent applications and issued patents directed to composition of matter for SPR741 and analogs thereof, composition of matter with different structural features, combinations of SPR741 or other potentiators with other anti-bacterial compounds, and methods of use for these novel compounds and compositions. As of December 31, 2017, we owned or were exclusively licensed eight U.S. patents and one U.S. provisional application; 94 foreign patents and nine pending foreign patent applications in a number of jurisdictions, including Australia, Brazil, Canada, China, the European Union member states, Israel, India, Indonesia, Japan, South Korea, Mexico, New Zealand, Russia, Singapore, South Africa, and Taiwan; four pending PCT applications; and two pending U.S. provisional patent applications directed to our Potentiator Platform. Issued U.S. or foreign patents and any patents issuing any pending U.S., foreign or PCT applications covering SPR741 will have a statutory expiration date of August 2027, February 2029, April 2037, May 2037, May 2038 and July 2038. Patent term adjustments or patent term extensions could result in later expiration dates.

Next-Generation Potentiator Platform Program (Including SPR206)

The intellectual property portfolio for our next-generation polymyxin program contains patent applications and issued patents directed to composition of matter for polymyxin-like compounds with different structural features, pharmaceutical compositions comprising the same, and methods of use for these novel compounds and compositions. As of December 31, 2017,2019, we owned one U.S. patent, threetwo pending U.S. applications, fiveone PCT application, three foreign patentspatent, and 4131 pending foreign patent applications in a number of jurisdictions including Argentina, Australia, Brazil, Canada, China, Colombia, Eurasia, the European Union, Hong Kong, Israel, Indonesia, Japan, South Korea, Mexico, Russia, Singapore, South Africa, Taiwan, and Vietnam.Venezuela. Issued U.S. or foreign patents and any patents issuing anyfrom pending U.S., or foreign, or PCT applications covering our next-generation polymyxin program will have a statutory expiration date of November 2032, May 2034, March 2035, and November 2035.2035, or June 2039. Patent term adjustments or patent term extensions could result in later expiration dates.

Orphan NTM InfectionDisease Program (SPR720)

Our intellectual property portfolio for our DNA Gyrase Inhibitor program includes issued patents and pending patent applications directed to composition of matter for SPR720, and its close analogs and prodrugs, novel solid forms of SPR720 and its prodrugs, methods of manufacture, and methods of treatment using SPR720 alone and in combination with other antibiotic compounds. All patents and patent applications in the portfolio are wholly owned by us. As of December 31, 2017,2019, we owned teneleven issued U.S. patents, one pending U.S. patent application, 6287 issued foreign patents, and 278 pending foreign patent applications. The issued and foreign patents are in a number of jurisdictions including the European Union and its member states, Argentina, Australia, Brazil, Canada, China, Hong Kong, Indonesia, Israel, India, Japan, South Korea, Mexico, New Zealand, the Philippines, Russia, Singapore, South Africa, and Taiwan. Issued U.S. and foreign patents, and patents issuing from pending U.S. and foreign applications will have statutory expiration dates of January 2032, June 2032 and July 2033. Patent term adjustments or patent term extensions could result in later expiration dates.

Patent Term and Patent Term Extensions

The term of individual patents depends upon the legal term for patents in the countries in which they are obtained. In most countries, including the United States, the patent term is 20 years from the earliest filing date of a non-provisional patent application. In the United States, a patent’s term may be lengthened by patent term adjustment, which compensates a patentee for administrative delays by the U.S. Patent and Trademark Office in examining and granting a patent, or may be shortened if a patent is terminally disclaimed over an earlier filed patent. The term of a patent that covers a drug, biological product or medical device approved pursuant to a pre-market approval may also be eligible for patent term extension when FDA approval is granted, provided statutory and regulatory requirements are met. The length of the patent term extension is related to the length of time the drug is under regulatory review while the patent is in force. The Drug Price Competition and Patent Term Restoration Act of 1984, or the Hatch-Waxman Act, permits a patent term extension of up to five years beyond the expiration date set for the patent. Patent extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval, only one patent applicable to each regulatory review period may be granted an extension and only those claims reading on the approved drug are extended. Similar provisions are available in Europe and other foreign jurisdictions to extend the term of a patent that covers an approved drug.

Trade Secrets

We rely, in some circumstances, on trade secrets to protect our unpatented technology. However, trade secrets can be difficult to protect. We seek to protect our trade secrets and proprietary technology and processes, in part, by confidentiality agreements with our employees, consultants, scientific advisors and contractors. We also seek to preserve the integrity and confidentiality of our data and trade secrets by maintaining physical security of our premises and physical and electronic security of our information technology systems. While we have confidence in these individuals, organizations and systems, agreements or security measures may be breached. We may not have adequate remedies for any breach and could lose our trade secrets through such a breach. In addition, our trade secrets may otherwise become known or be independently discovered by competitors. To the extent that our consultants, contractors or collaborators use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting trade secrets, know-how and inventions.

Competition

The biopharmaceutical industry is characterized by intense competition and rapid innovation. Our potential competitors include large pharmaceutical and biotechnology companies, specialty pharmaceutical companies and generic drug companies. Many of our potential competitors have greater financial, technical human resources than we do, as well as greater experience in the discovery and development of product candidates, obtaining FDA and other regulatory approvals of products and the commercialization of those products. Accordingly, our potential competitors may be more successful than us in obtaining FDA approval drugs and achieving widespread market acceptance. We anticipate that we will face intense and increasing competition as new drugs enter the market and advanced technologies become available. Finally, the development of new treatment methods for the diseases we are targeting could render our product candidates non-competitive or obsolete.

We believe the key competitive factors that will affect the development and commercial success of most advanced product candidate, SPR994,tebipenem HBr, if approved, will be efficacy, coverage of drug-resistant strains bacteria, safety and tolerability profile, reliability, convenience of oral dosing, price, availability of reimbursement from governmental and other third-party payers and susceptibility to drug resistance.

We are developing SPR994tebipenem HBr as an oral antibiotic for use as a monotherapy for the treatment of resistant and MDR infections. If approved, SPR994tebipenem HBr would compete with several antibiotics currently in clinical development, including C-Scapeceftibuten/clavulanate (“C-Scape”) from Achaogen, Inc., and sulopenem from Iterum Therapeutics Limited, eravacycline from Tetraphase Pharmaceuticals, Inc. and omadacycline from Paratek Pharmaceuticals, Inc.

Limited. We also expect that SPR994,tebipenem HBr, if approved, would compete with future and current generic versions of marketed antibiotics.

If approved, we believe that SPR994tebipenem HBr would compete effectively against these compounds on the basis of SPR994’stebipenem HBr’s potential:

We are also developing SPR206 from our Potentiator Platform SPR741 and SPR206, as an innovative IV-administered agentsagent for Gram-negative infections in the hospital. If approved, SPR741 or our single-agent candidate SPR206 would compete with several IV-administered product candidatesproducts marketed for the treatment of Gram-negative infections, including Avycazceftazidime-avibactam (“Avycaz”) from Allergan plc and Pfizer Inc. and Zerbaxa, ceftolozane-tazobactam (“Zerbaxa”) from Merck & Co., plazomicin (“Zemdri”) from Cipla Therapeutics, Inc., eravacycline (“Xerava”) from Tetraphase Pharmaceuticals, Inc., and meropenem-vaborbactam (“Vabomere”) from Melinta Therapeutics, Inc. There are also a number of IV-administered product candidates in late-stage clinical development that are intended to treat resistant Gram-negative infections, including plazomicin from Achaogen Inc., meropenem-vaborbactam from The Medicines Company, cefiderocol from Shionogi & Co. Ltd., eravacycline IV from Tetraphase Pharmaceuticals Inc. and relabactamimipenem-relebactam from Merck & Co. Each of these products and product candidates employs a mechanism of action that differs from the mechanism of action employed by SPR741.

We are developing SPR720 asto be the first approved oral treatment for NTM infection.disease. There are currently no oral agents approved agents to treat NTM infection.  Current SOC is a combination of generically available options.  There isdisease. Only one drug in late-stage development,is approved to treat NTM infection that would potentially compete with SPR720 called Arikayce from Insmed.  It isInsmed, an inhaled version of a commonly used drug in the hospital setting called amikacin. If approved, it would potentially compete with SPR720.  It should be noted that combination therapy is recommended for treating this condition.

Government Regulation and Product Approval

Government authorities in the United States, at the federal, state and local level, and in other countries, extensively regulate, among other things, the research, development, clinical trials, testing, manufacture, including any manufacturing changes, authorization, pharmacovigilance, adverse event reporting, recalls, packaging, storage, recordkeeping, labeling, advertising, promotion, distribution, marketing, import and export of pharmaceutical products and product candidates such as those we are developing. The processes for obtaining regulatory approvals in the United States and in foreign countries, along with subsequent compliance with applicable statutes and regulations, require the expenditure of substantial time and financial resources.

Recent Changes in the Regulatory Landscape

The FDA’s Division of Anti-Infective Products, or DAIP, has undergone evolution in recent years, primarily driven by concerns that increasingly less effective antibiotics may have been approved in the last 10 to 15 years and a desire to bring what DAIP perceives to be greater statistical rigor to their analyses. The impact of this was a rethinking of how antibiotic efficacy is measured in clinical trials, and a review of the statistical tools used to analyze the data. In February 2015, the FDA published guidance documents for industry entitled “Complicated Urinary Tract Infections: Developing Drugs for Treatment” and guidance entitled “Complicated Intra-Abdominal Infections: Developing Drugs for Treatment.” The purpose of these guidance documents is to address considerations surrounding the clinical development of drugs for cUTI and cIAI indications, including clinical trial design and efficacy. Additionally, in August 2017, the FDA published a guidance document entitled “Antibacterial Therapies for Patients With an Unmet Medical Need for the Treatment of Serious Bacterial Diseases,” setting forth its current thinking with respect to development programs and clinical trial designs for antibacterial drugs to treat serious bacterial diseases.

On December 13, 2016, President Obama signed into law the Cures Act, which is intended to accelerate medical product development. Section 3042 of the Cures Act establishes the limited population pathway for certain antibacterial or antifungal drugs intended to treat targeted groups of patients suffering from serious or life-threatening infections where unmet need exists. Approvals of these limited population drugs are expected to rely on data from smaller clinical trials than would ordinarily be required by the FDA. To date, the FDA has not approved any drugs utilizing the limited population pathway. For drugs approved through this pathway, the statement “Limited Population” will appear prominently next to the drug’s name in labeling, which is intended to provide notice to healthcare providers that the drug is indicated for use in a limited and specific population of patients.

U.S. Government Regulation

In the United States, the FDA regulates drugs under the Federal Food, Drug, and Cosmetic Act, or FDCA, and implementing regulations. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal, state, local and foreign statutes and regulations requires the expenditure of substantial time and financial resources. Failure to comply with the applicable U.S. requirements at any time during the product development process, approval process or after approval, may subject an applicant to a variety of administrative or judicial sanctions, such as the FDA’s refusal to approve pending NDAs, withdrawal of an approval, imposition of a clinical hold, issuance of warning letters, product recalls, product seizures, total or partial suspension of production or distribution, injunctions, fines, refusals of government contracts, restitution, disgorgement or civil and/or criminal penalties.

The process required by the FDA before a drug may be marketed in the United States generally involves the following:

Preclinical Studies

Preclinical studies include laboratory evaluation of product chemistry, toxicity and formulation, as well as animal studies to assess potential safety and efficacy. Preclinical tests intended for submission to the FDA to support the safety of a product candidate must be conducted in compliance with GLP regulations and the United States Department of Agriculture’s Animal Welfare Act. A drug sponsor must submit the results of the preclinical tests, together with manufacturing information, analytical data and any available clinical data or literature, among other things, to the FDA as part of an IND. Some nonclinical testing may continue even

after the IND is submitted. An IND automatically becomes effective 30 days after receipt by the FDA, unless before that time the FDA raises concerns or questions related to one or more proposed clinical trials and places the clinical trial on a clinical hold. In such a case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin. As a result, submission of an IND may not result in the FDA allowing clinical trials to commence.

Clinical Trials

Clinical trials involve the administration of the investigational new drug to human subjects under the supervision of qualified investigators in accordance with GCP requirements, which include the requirement that all research subjects provide their informed consent in writing for their participation in any clinical trial along with the requirement to ensure that the data and results reported from the clinical trials are credible and accurate. Clinical trials are conducted under protocols detailing, among other things, the objectives of the trial, the criteria for determining subject eligibility, the dosing plan, the parameters to be used in monitoring safety, the procedure for timely reporting of adverse events, and the effectiveness criteria to be evaluated. A protocol for each clinical trial and any subsequent protocol amendments must be submitted to the FDA as part of the IND. In addition, an IRB at each institution participating in the clinical trial must review and approve the plan for any clinical trial before it commences at that institution. Information about certain clinical trials must be submitted within specific timeframes to the NIH for public dissemination on its www.clinicaltrials.gov website.

Human clinical trials are typically conducted in three sequential phases, which may overlap or be combined:

Phase 1: The drug is initially introduced into healthy human subjects or patients with the target disease or condition and tested for safety, dosage tolerance, absorption, metabolism, distribution, excretion and, if possible, to gain an early indication of its effectiveness. During Phase 1 clinical trials, sufficient information about the investigational drug’s or biological product’s pharmacokinetics and pharmacological effects may be obtained to permit the design of well-controlled and scientifically valid Phase 2 clinical trials.

Phase 2: The drug is administered to a larger, but still limited patient population to identify possible adverse effects and safety risks, to preliminarily evaluate the efficacy of the product for specific targeted indications and to determine dosage tolerance and optimal dosage. Phase 2 clinical trials are typically well-controlled and closely monitored.

Phase 3: The drug is administered to an expanded patient population, generally at geographically dispersed clinical trial sites, in well-controlled clinical trials to generate enough data to statistically evaluate the efficacy and safety of the product for approval, to establish the overall risk-benefit profile of the product, and to provide adequate information for the labeling of the product. Phase 3 clinical trials usually involve a larger number of participants than a Phase 2 clinical trial.

Progress reports detailing the results of the clinical trials must be submitted at least annually to the FDA and more frequently if serious adverse events occur. Phase 1, Phase 2 and Phase 3 clinical trials may not be completed successfully within any specified period, or at all. Results from one trial may not be predictive of results from subsequent trials. Furthermore, the FDA or the sponsor may suspend or terminate a clinical trial at any time on various grounds, including a finding that the research subjects are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the IRB’s requirements or if the drug has been associated with unexpected serious harm to patients.

Marketing Approval

Assuming successful completion of the required clinical testing, the results of the nonclinical studies and clinical trials, together with detailed information relating to the product’s chemistry, manufacture, controls and proposed labeling, among other things, are submitted to the FDA as part of an NDA requesting approval to market the product for one or more indications. In most cases, the submission of an NDA is subject to a substantial application user fee. Under the Prescription Drug User Fee Act, or PDUFA, guidelines that are currently in effect, the FDA has a goal of ten months from the date of “filing” of a standard NDA for a new molecular entity to review and act on the submission. This review typically takes twelve months from the date the NDA is submitted to FDA because the FDA has approximately two months to make a “filing” decision. Furthermore, the FDA is not required to complete its review within the established ten-month timeframe and may extend the review process by issuing requests for additional information or clarification.

The FDA conducts a preliminary review of all NDAs within the first 60 days after submission, before accepting them for filing, to determine whether they are sufficiently complete to permit substantive review. The FDA may request additional information rather than accept an NDA for filing. In this event, the application must be resubmitted with the additional information. The resubmitted application is also subject to review before the FDA accepts it for filing. Once the submission is accepted for filing, the FDA begins an in-depth substantive review. The FDA reviews an NDA to determine, among other things, whether the drug is safe and effective and whether the facilities in which it is manufactured, processed, packaged or held meet standards designed to assure the product’s continued safety, quality and purity.

In addition, under the Pediatric Research Equity Act of 2003, as amended and reauthorized, certain NDAs or supplements to an NDA must contain data that are adequate to assess the safety and effectiveness of the drug for the claimed indications in all relevant pediatric subpopulations, and to support dosing and administration for each pediatric subpopulation for which the product is safe and effective. The FDA may, on its own initiative or at the request of the applicant, grant deferrals for submission of some or all pediatric data until after approval of the product for use in adults or full or partial waivers from the pediatric data requirements.

Unless otherwise required by regulation, the pediatric data requirements do not apply to products with orphan designation.

The FDA also may require submission of a risk evaluation and mitigation strategy, or REMS, plan to mitigate any identified or suspected serious risks. The REMS plan could include medication guides, physician communication plans, assessment plans, and elements to assure safe use, such as restricted distribution methods, patient registries, or other risk minimization tools.

The FDA may refer an application for a novel drug to an advisory committee. An advisory committee is a panel of independent experts, including clinicians and other scientific experts, that reviews, evaluates and provides a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions.

Before approving an NDA, the FDA typically will inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications. Additionally, before approving an NDA, the FDA will typically inspect one or more clinical trial sites to assure compliance with GCP.

The FDA generally accepts data from foreign clinical trials in support of an NDA if the trials were conducted under an IND. If a foreign clinical trial is not conducted under an IND, the FDA nevertheless may accept the data in support of an NDA if the study was conducted in accordance with GCPs and the FDA is able to validate the data through an on-site inspection, if deemed necessary. Although the FDA generally requests that marketing applications be supported by some data from domestic clinical trials, the FDA may accept foreign data as the sole basis for marketing approval if (1) the foreign data are applicable to the U.S. population and U.S. medical practice, (2) the studies were performed by clinical investigators with recognized competence, and (3) the data may be considered valid without the need for an on-site inspection or, if the FDA considers the inspection to be necessary, the FDA is able to validate the data through an on-site inspection or other appropriate means.

The testing and approval process for an NDA requires substantial time, effort and financial resources, and each may take several years to complete. Data obtained from preclinical and clinical testing are not always conclusive and may be susceptible to varying interpretations, which could delay, limit or prevent regulatory approval. The FDA may not grant approval on a timely basis, or at all.

After evaluating the NDA and all related information, including the advisory committee recommendation, if any, and inspection reports regarding the manufacturing facilities and clinical trial sites, the FDA may issue an approval letter, or, in some cases, a complete response letter. A complete response letter generally contains a statement of specific conditions that must be met in order to secure final approval of the NDA and may require additional clinical or preclinical testing in order for FDA to reconsider the application. Even with submission of this additional information, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval. If and when those conditions have been met to the FDA’s satisfaction, the FDA will typically issue an approval letter. An approval letter authorizes commercial marketing of the drug with specific prescribing information for specific indications.

Even if the FDA approves a product, it may limit the approved indications for use of the product, require that contraindications, warnings or precautions be included in the product labeling , require that post-approval studies, including Phase 4 clinical trials, be conducted to further assess a drug’s safety after approval, require testing and surveillance programs to monitor the product after commercialization, or impose other conditions, including distribution and use restrictions or other risk management mechanisms under a REMS which can materially affect the potential market and profitability of the product. The FDA may prevent or limit further marketing of a product based on the results of post-marketing studies or surveillance programs. After approval, some types of changes to the approved product, such as adding new indications, manufacturing changes, and additional labeling claims, are subject to further testing requirements and FDA review and approval.

Special FDA Expedited Review and Approval Programs

The FDA has various programs, including fast track designation, accelerated approval and priority review, that are intended to expedite or simplify the process for the development and FDA review of drugs that are intended for the treatment of serious or life threatening diseases or conditions and demonstrate the potential to address unmet medical needs. The purpose of these programs is to provide important new drugs to patients earlier than under standard FDA review procedures.

To be eligible for a fast track designation, the FDA must determine, based on the request of a sponsor, that a product is intended to treat a serious or life threatening disease or condition and demonstrates the potential to address an unmet medical need, or if the drug qualifies as a QIDP under the GAIN Act. The FDA will determine that a product will fill an unmet medical need if it will provide a therapy where none exists or provide a therapy that may be potentially superior to existing therapy based on efficacy or safety factors. Fast track designation provides additional opportunities for interaction with the FDA’s review team and may allow for rolling review of NDA components before the completed application is submitted, if the sponsor provides a schedule for the submission of the sections of the NDA, the FDA agrees to accept sections of the NDA and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the NDA. The FDA may decide to rescind the fast track designation if it determines that the qualifying criteria no longer apply.

The FDA may give a priority review designation to drugs that offer major advances in treatment for a serious condition, or provide a treatment where no adequate therapy exists. Most products that are eligible for fast track designation are also likely to be considered appropriate to receive a priority review. A priority review means that the goal for the FDA to review an application is six months, rather than the standard review of ten months under current PDUFA guidelines. Under the current PDUFA agreement, these six and ten month review periods are measured from the “filing” date rather than the receipt date for NDAs for new molecular entities, which typically adds approximately two months to the timeline for review and decision from the date of submission.

In addition, products studied for their safety and effectiveness in treating serious or life-threatening illnesses and that provide meaningful therapeutic benefit over existing treatments may receive accelerated approval, meaning that it may be approved on (i) the basis of adequate and well-controlled clinical trials establishing that the drug product has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or (ii) on an intermediate clinical endpoint that can be measured earlier than irreversible morbidity or mortality and that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity or prevalence of the condition and the availability or lack of alternative treatments. As a condition of approval, the FDA may require a sponsor of a drug receiving accelerated approval to perform post-marketing studies to verify and describe the predicted effect on irreversible morbidity or mortality or other clinical endpoint, and the drug may be subject to accelerated withdrawal procedures.

Moreover, under the provisions of the Food and Drug Administration Safety and Innovation Act, or FDASIA, enacted in 2012, a sponsor can request designation of a product candidate as a “breakthrough therapy.” A breakthrough therapy is defined as a drug that is intended, alone or in combination with one or more other drugs, to treat a serious or life-threatening disease or condition, and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. Drugs designated as breakthrough therapies are also eligible for accelerated approval. The FDA must take certain actions, such as holding timely meetings and providing advice, intended to expedite the development and review of an application for approval of a breakthrough therapy.

Even if a product qualifies for one or more of these programs, the FDA may later decide that the product no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened.

Post-Approval Requirements

Drugs manufactured or distributed pursuant to FDA approvals are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to recordkeeping, periodic reporting, product sampling and distribution, advertising and promotion and reporting of adverse experiences with the product. After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval. There also are continuing, annual user fee requirements for any marketed products and the establishments at which such products are manufactured, as well as new application fees for supplemental applications with clinical data.

The FDA may impose a number of post-approval requirements as a condition of approval of an NDA. For example, the FDA may require post-marketing testing, including Phase 4 clinical trials, and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization.

In addition, drug manufacturers and other entities involved in the manufacture and distribution of approved drugs are required to register their establishments with the FDA and some state agencies, and are subject to periodic unannounced inspections by the FDA for compliance with cGMP requirements. Changes to the manufacturing process are strictly regulated and often require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting and documentation requirements upon the sponsor and any third-party manufacturers. Accordingly, manufacturers must continue to expend time, money, and effort in the area of production and quality control to maintain cGMP compliance.

The FDA strictly regulates the marketing, labeling, advertising and promotion of drug products that are placed on the market. A product cannot be commercially promoted before it is approved, and approved drugs may generally be promoted only for their approved indications. Promotional claims must also be consistent with the product’s FDA-approved label, including claims related to safety and effectiveness. The FDA and other federal agencies also closely regulate the promotion of drugs in specific contexts such as direct-to-consumer advertising, industry-sponsored scientific and education activities, and promotional activities involving the Internet and social media.

Once an approval is granted, the FDA may withdraw the approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market.

Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in mandatory revisions to the approved labeling to add new safety information; imposition of post-market studies or clinical trials to assess new safety risks; or imposition of distribution or other restrictions under a REMS program. Other potential consequences of regulatory non-compliance include, among other things:

In addition, the distribution of prescription pharmaceutical products is subject to the Prescription Drug Marketing Act, or PDMA, which regulates the distribution of drugs and drug samples at the federal level, and sets minimum standards for the registration and regulation of drug distributors by the states. Both the PDMA and state laws limit the distribution of prescription pharmaceutical product samples and impose requirements to ensure accountability in distribution.

Exclusivity and Approval of Competing Products

Hatch-Waxman Exclusivity

Market and data exclusivity provisions under the FDCA can delay the submission or the approval of certain applications for competing products. The FDCA provides a five-year period of non-patent data exclusivity within the United States to the first applicant to gain approval of an NDA for a new chemical entity. A drug is a new chemical entity if the FDA has not previously approved any other new drug containing the same active moiety, which is the molecule or ion responsible for the activity of the drug substance. We believe that our product candidates are new chemical entities. During the exclusivity period, the FDA may not accept for review an abbreviated new drug application, or ANDA, or a 505(b)(2) NDA submitted by another company that references the previously approved drug. However, an ANDA or 505(b)(2) NDA may be submitted after four years if it contains a certification of patent invalidity or non-infringement. The FDCA also provides three years of marketing exclusivity for an NDA, 505(b)(2) NDA, or supplement to an existing NDA or 505(b)(2) NDA if new clinical investigations, other than bioavailability studies, that were conducted or sponsored by the applicant, are deemed by the FDA to be essential to the approval of the application or supplement. Three-year exclusivity may be awarded for changes to a previously approved drug product, such as new indications, dosages, strengths or dosage forms of an existing drug. This three-year exclusivity covers only the conditions of use associated with the new clinical investigations and, as a general matter, does not prohibit the FDA from approving ANDAs or 505(b)(2) NDAs for generic versions of the original, unmodified drug product. Five-year and three-year exclusivity will not delay the submission or approval of a full NDA; however, an applicant submitting a full NDA would be required to conduct or obtain a right of reference to all of the

preclinical studies and adequate and well-controlled clinical trials necessary to demonstrate safety and effectiveness. For drug products that contain an “antibiotic” ingredient approved prior to 1997, the statute imposes certain limitations on the award of non-patent exclusivity. However, we do not believe these limitations would apply to SPR994tebipenem HBr or any of our other investigational antibiotics.

Qualified Infectious Disease Product Exclusivity

Under the GAIN Act provisions of FDASIA, which was signed into law in July 2012, the FDA may designate a product as a qualified infectious disease product, or QIDP. In order to receive this designation, a drug must qualify as an antibiotic or antifungal drug for human use intended to treat serious or life-threatening infections, including those caused by either (i) an antibiotic or antifungal resistant pathogen, including novel or emerging infectious pathogens, or (ii) a so-called “qualifying pathogen” found on a list of potentially dangerous, drug-resistant organisms to be established and maintained by the FDA under the new law. A sponsor must request such designation before submitting a marketing application. We obtained a QIDP designation for the oral formulation of SPR994tebipenem HBr for cUTI in November 2016 and CABP and DFI in April 2017,2017. We were granted QIDP designation by the FDA for SPR206 in October 2018 for the treatment of cUTI and expect to requesthospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (HABP/VABP). We were granted QIDP designationsdesignation for our other product candidates prior to submitting a marketing applicationSPR720 capsule for such product candidates, as appropriate.oral use for the treatment of lung infections caused by nontuberculous mycobacteria and for the treatment of lung infections caused by Mycobacterium tuberculosis.

Upon approving an application for a qualified infectious disease product, the FDA will extend by an additional five years any non-patent marketing exclusivity period awarded, such as a five-year exclusivity period awarded for a new molecular entity. ThisFor example, this extension is in addition to any pediatric exclusivity extension awarded, and the extension will be awarded only to a drug first approved on or after the date of enactment.

awarded.

The GAIN Act provisions prohibit the grant of an exclusivity extension where the application is a supplement to an application for which an extension is in effect or has expired, is a subsequent application for a specified change to an approved product, or is an application for a product that does not meet the definition of qualified infectious disease product based on the uses for which it is ultimately approved.

Orphan Drug Designation and Exclusivity

In March 2020, the FDA granted orphan drug designation for SPR720. Under the Orphan Drug Act, the FDA may grant orphan drug designation to a drug intended to treat a rare disease or condition, which is generally a disease or condition that affects fewer than 200,000 individuals in the U.S., or more than 200,000 individuals in the U.S. and for which there is no reasonable expectation that the cost of developing and making available in the U.S. a drug for this type of disease or condition will be recovered from sales in the U.S. for that drug. Orphan drug designation must be requested before submitting an NDA. After the FDA grants orphan drug designation, the identity of the therapeutic agent and its potential orphan use will be disclosed publicly by the FDA; the posting will also indicate whether a drug is no longer designated as an orphan drug. More than one product candidate may receive an orphan drug designation for the same indication. Orphan drug designation does not convey any advantage in or shorten the duration of the regulatory review and approval process.

If a product that has orphan drug designation subsequently receives the first FDA approval for the disease for which it has such designation, the product is entitled to seven years of orphan product exclusivity, except in very limited circumstances. The FDA issued a final rule intended to clarify what constitutes some of those limited circumstances. For example, the FDA will not recognize orphan drug exclusive approval if a sponsor fails to demonstrate upon approval that the drug is clinically superior to a previously approved drug, regardless of whether or not the approved drug was designated an orphan drug or had orphan drug exclusivity. Thus, orphan drug exclusivity also could block the approval of one of our products for seven years if a competitor obtains approval of the same drug as defined by the FDA and we are not able to show the clinical superiority of our drug or if our product candidate is determined to be contained within the competitor’s product for the same indication or disease. The FDA continues to periodically provide additional clarification, and in July 2018 published a final guidance entitled, “Clarification of Orphan Designation of Drugs and Biologics for Pediatric Subpopulations of Common Diseases,”  

Foreign Regulation

In addition to regulations in the United States, we will be subject to a variety of foreign regulations governing clinical trials and commercial sales and distribution of our products. Whether or not we obtain FDA approval for a product, we must obtain approval by the comparable regulatory authorities of foreign countries or economic areas, such as the European Union and Australia, before we may commence clinical trials or market products in those countries or areas. The approval process and requirements governing the conduct of clinical trials, product authorization, pricing and reimbursement vary greatly from place to place, and the time may be longer or shorter than that required for FDA approval.

Before clinical trials may be conducted in any EU Member State, a sponsor must submit a clinical trial authorization application, or CTA, which must be approved in each country in which the sponsor intends to perform a clinical trial. The procedure for submitting a CTA was set forth in an existing EU Clinical Trial Directive. However, the way clinical trials are conducted in the EU will undergo a major change when the Clinical Trial Regulation becomes effective in 2019. The Regulation harmonizes the assessment and supervision processes for clinical trials throughout the EU, via an EU portal and database. The European Medicines Agency, or the EMA, will set up and maintain the portal and database, in collaboration with the Member States and the European Commission.

The goal of Clinical Trial Regulation is to create an environment that is favorable to conducting clinical trials in the EU, with the highest standards of safety for participants and increased transparency of trial information. The Regulation will require consistent rules for conducting clinical trials throughout the EU and information on the authorization, conduct and results of each clinical trial carried out in the EU to be publicly available.

When the Regulation becomes applicable, it will replace the existing EU Clinical Trial Directive and national legislation that was put in place to implement the Directive. It will also apply to trials authorized under the previous legislation if they are still ongoing three years after the Regulation becomes effective. The authorization and oversight of clinical trials will remain the responsibility of Member States, with EMA managing the database and supervising content publication on the public website.

Under European Union regulatory systems, a company may submit marketing authorization applications either under a centralized or decentralized procedure. The centralized procedure is compulsory for medicinal products produced by biotechnology or those medicinal products containing new active substances for specific indications such as the treatment of AIDS, cancer, neurodegenerative disorders, diabetes, viral diseases and designated orphan medicines, and optional for other medicines which are highly innovative. Under the centralized procedure, a marketing application is submitted to the European Medicines Agency where it will be evaluated by the Committee for Medicinal Products for Human Use and a favorable opinion typically results in the grant by the European Commission of a single marketing authorization that is valid for all European Union member states within 67 days of receipt of the opinion. The initial marketing authorization is valid for five years, but once renewed is usually valid for an unlimited period.

The decentralized procedure provides for approval by one or more “concerned” member states based on an assessment of an application performed by one member state, known as the “reference” member state. Under the decentralized approval procedure, an applicant submits an application, or dossier, and related materials to the reference member state and concerned member states. The reference member state prepares a draft assessment and drafts of the related materials within 120 days after receipt of a valid application. Within 90 days of receiving the reference member state’s assessment report, each concerned member state must decide whether to approve the assessment report and related materials. If a member state does not recognize the marketing authorization, the disputed points are eventually referred to the European Commission, whose decision is binding on all member states.

Pharmaceutical Coverage and Reimbursement

Sales of our products will depend, in part, on the availability and extent of coverage and reimbursement by third-party payors, such as government health programs, including Medicare and Medicaid, commercial insurance and managed healthcare organizations. These third-party payors are increasingly challenging the price and limiting the coverage and reimbursement amounts for medical products and services.

The containment of healthcare costs has become a priority for federal and state governments, and the prices of drugs have been a focus in this effort. The U.S. government, state legislatures and foreign governments have shown significant interest in implementing cost-containment programs, including price controls, restrictions on coverage and reimbursement, and requirements for substitution of generic products. Adoption of price controls and cost-containment measures, and adoption of more restrictive policies in jurisdictions with existing controls and measures, could further limit our net revenue and results. Decreases in third-party reimbursement for our product candidates or a decision by a third-party payor to not cover our product candidates could reduce physician usage of the product candidate and have a material adverse effect on our sales, results of operations and financial condition.

In the United States, the federal government provides health insurance for people who are 65 or older, and certain people with disabilities or certain conditions irrespective of their age, through the Medicare program, which is administered by the Centers for Medicare & Medicaid Services, or CMS. Coverage and reimbursement for products and services under Medicare are determined in accordance with the Social Security Act and pursuant to regulations promulgated by CMS, as well as the agency’s coverage and reimbursement guidance and determinations. Drugs and other products that are utilized within the hospital in-patient setting are typically reimbursed under a prospective payment system, or a predetermined payment amount that is based on diagnosis related groups, or DRGs for Medicare patients and under a bundled payment for commercially insured patients. These payment amounts differ by type of diagnoses, procedures performed and the severity of the patient’s condition, among other things. A drug that is used in a treatment or procedure under a specific DRG or bundled payment is generally not eligible for any separate payment. For catastrophic cases where costs greatly exceed the bundled payment amount, the hospital may be eligible for an outlier payment that is intended to cover part of the expense above the standard payment.

Medicaid is a health insurance program for low-income children, families, pregnant women, and people with disabilities that is jointly funded by the federal and state governments, but administered by the states. In general, state Medicaid programs are required to cover drugs and biologicals of manufacturers that have entered into a Medicaid Drug Rebate Agreement, although such drugs and biologicals may be subject to prior authorization or other utilization controls.

The U.S. Congress and state legislatures from time to time propose and adopt initiatives aimed at cost containment, which could impact our ability to sell our products profitably. For example, the federal Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act of 2010, known collectively as the ACA, among other things, contains provisions that may reduce the profitability of drug products through increased rebates for drugs reimbursed by Medicaid programs, extension of Medicaid rebates to Medicaid managed care plans, mandatory discounts for certain Medicare Part D beneficiaries and annual fees based on pharmaceutical companies’ share of sales to federal health care programs. Adoption of general controls and measures, coupled with the tightening of restrictive policies in jurisdictions with existing controls and measures, could limit payments for pharmaceutical drugs. The Medicaid Drug Rebate Program requires pharmaceutical manufacturers to enter into and have in effect a national rebate agreement with the Secretary of the Department of Health and Human Services as a condition for states to receive federal matching funds for manufacturers’ outpatient drugs furnished to Medicaid patients. The ACA also expanded the universe of Medicaid utilization subject to drug rebates by requiring pharmaceutical manufacturers to pay rebates on Medicaid managed care utilization and by enlarging the population potentially eligible for Medicaid drug benefits.

Since its enactment, there have been judicial and Congressional challenges to certain aspects of the ACA. Both Congress and President Trump have expressed their intention to repeal or repeal and replace the ACA, and as a result certain sections of the ACA have not been fully implemented or effectively repealed. The uncertainty around the future of the ACA, and in particular the impact to reimbursement levels, may lead to uncertainty or delay in the purchasing decisions of our customers, which may in turn negatively impact our product sales. If there are not adequate reimbursement levels, our business and results of operations could be adversely affected.

In addition, in some foreign countries, the proposed pricing for a drug must be approved before it may be lawfully marketed. The requirements governing drug pricing vary widely from country to country. For example, in the EU, the sole legal instrument at the EU level governing the pricing and reimbursement of medicinal products is Council Directive 89/105/EEC, or the Price Transparency Directive. The aim of this Directive is to ensure that pricing and reimbursement mechanisms established in the EU Member States are transparent and objective, do not hinder the free movement of and trade in medicinal products in the EU, and do not hinder, prevent or distort competition on the market. The Price Transparency Directive does not provide any guidance concerning the specific criteria on the basis of which pricing and reimbursement decisions are to be made in individual EU Member States, nor does it have any direct consequence for pricing or reimbursement levels in individual EU Member States. The EU Member States are free to restrict the range of medicinal products for which their national health insurance systems provide reimbursement, and to control the prices and/or reimbursement levels of medicinal products for human use. An EU Member State may approve a specific price or level of reimbursement for the medicinal product, or alternatively adopt a system of direct or indirect controls on the profitability of the company responsible for placing the medicinal product on the market, including volume-based arrangements, caps and reference pricing mechanisms.

Health Technology Assessment, or HTA, of medicinal products is becoming an increasingly common part of the pricing and reimbursement procedures in some EU Member States, including the United Kingdom, France, Germany, Ireland, Italy and Sweden. The HTA process in the EU Member States is governed by the national laws of these countries. HTA is the procedure according to which the assessment of the public health impact, therapeutic impact, and the economic and societal impact of use of a given medicinal product in the national healthcare systems of the individual country is conducted. HTA generally focuses on the clinical efficacy and effectiveness, safety, cost, and cost-effectiveness of individual medicinal products as well as their potential implications for the healthcare system. Those elements of medicinal products are compared with other treatment options available on the market. The outcome of HTA regarding specific medicinal products will often influence the pricing and reimbursement status granted to these medicinal products by the competent authorities of individual EU Member States. The extent to which pricing and reimbursement decisions are influenced by the HTA of the specific medicinal product vary between EU Member States. A negative HTA of one of our products by a leading and recognized HTA body, such as the National Institute for Health and Care Excellence in the United Kingdom, could not only undermine our ability to obtain reimbursement for such product in the EU Member State in which such negative assessment was issued, but also in other EU Member States. For example, EU Member States that have not yet developed HTA mechanisms could rely to some extent on the HTA performed in countries with a developed HTA framework, such as the United Kingdom, when adopting decisions concerning the pricing and reimbursement of a specific medicinal product.

Other Healthcare Laws

Although we currently do not have any products on the market, if our product candidates are approved and we begin commercialization, we may be subject to additional healthcare regulation and enforcement by the federal government and by authorities in the states and foreign jurisdictions in which we conduct our business. Such laws include, without limitation, state and federal anti-kickback, fraud and abuse, false claims, privacy and security and physician sunshine laws and regulations. If our operations are found to be in violation of any of such laws or any other governmental regulations that apply to us, we may be subject to penalties, including, without limitation, civil and criminal penalties, damages, fines, the curtailment or restructuring of our operations, exclusion from participation in federal and state healthcare programs and imprisonment, any of which could adversely affect our ability to operate our business and our financial results.

Manufacturing

We do not own or operate manufacturing facilities for the production of any of our product candidates, nor do we have plans to develop our own manufacturing operations in the foreseeable future. We currently rely on a limited number of third-party contract manufacturers for all of our required raw materials, drug substance, and finished drug product for our preclinical research and clinical trials. We currently employ internal resources to manage our manufacturing. We intend to have two suppliers for SPR994’stebipenem HBr’s active pharmaceutical ingredient. Each supplier would be capable of producing kilogram quantities for commercial scale and would be able to produce over 10kg of active pharmaceutical ingredient under cGMP conditions.

Employees

As of December 31, 2017,2019, we had 3557 full-time employees, including a total of 1214 employees with M.D. or Ph.D. degrees. 2237 employees were primarily engaged in research and development activities, with the rest providing administrative, business and operations support. None of our employees are represented by labor unions or covered by collective bargaining agreements. We consider our employee relations to be good.

Our Corporate Information

We were formed as Spero Therapeutics, LLC in December 2013 under the laws of the State of Delaware. On June 30, 2017, through a series of transactions, Spero Therapeutics, LLC merged with and into Spero Therapeutics, Inc. (formerly known as Spero OpCo, Inc.), a Delaware corporation. Our principal executive offices are located at 675 Massachusetts Avenue, Cambridge, Massachusetts 02139, and our telephone number is (857) 242-1600. Our website address is www.sperotherapeutics.com.

Available Information

Financial and other information about us is available on our website. We make available on our website, free of charge, copies of our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, current reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act as soon as reasonably practicable after we electronically file such material with, or furnish it to, the U.S. Securities and Exchange Commission, or the SEC. In addition, we have previously filed registration statements and other documents with the SEC. Any document we file may be inspected, without charge, at the SEC’s public reference room at 100 F Street NE, Washington, DC 20549, or at the SEC’s internet address at www.sec.gov. These website addresses are not intended to function as hyperlinks, and theThe information contained in our website and in the SEC’s website is not intended to be a part of this filing. Information related to the operation of the SEC’s public reference room may be obtained by calling the SEC at 800-SEC-0330.

Item 1A. Risk Factors.

Careful consideration should be given to the following risk factors, in addition to the other information set forth in this Annual Report on Form 10-K, including the section of this Annual Report on Form 100-K10-K titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and related notes, and in other documents that we file with the SEC, in evaluating our company and our business. Investing in our common stock involves a high degree of risk. If any of the events described in the following risk factors and the risks described elsewhere in this Annual Report on Form 10-K occurs, our business, financial condition, results of operations and future growth prospects could be materially and adversely affected and the trading price of our common stock could decline. Our actual results could differ materially from those anticipated in the forward-looking statements as a result of factors that are described below and elsewhere in this Annual Report on Form 10-K.

Risks Related to Our Financial Position and Need for Additional Capital

We have incurred netnot generated any revenue from the sale of our products, have a history of losses in each year since our inception and anticipate that we will continueexpect to incur significant losses for the foreseeablesubstantial future andlosses. The report of our auditor on our consolidated financial statements expresses substantial doubt about our ability to continue as a going concern; if we are unable to achieveobtain additional capital, we may not be able to continue our operations on the scope or scale as currently conducted, and sustain profitability, the market valuethat could have a material adverse effect on our business, results of our common stock will likely decline.operations and financial condition.

We are a clinical-stage biopharmaceutical company with a limited operating history. We have not generated any revenue from the sale of our products and have incurred losses in each year since our inception in 2013. Our net loss was $39.9losses were $60.9 million and $32.6$41.7 million forduring the years ended December 31, 20172019 and 2016,2018, respectively. All of our product candidates are in development, none have been approved for sale and we may never have a product candidate approved for commercialization. We have financed

In accordance with Accounting Standards Update (“ASU”) 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), we are required to evaluate whether there are conditions and events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern from the issuance date of our financial statements. Based on our current plans, we believe that our existing cash, cash equivalents and marketable securities as of December 31, 2019, together with committed funding from our BARDA contract and other non-dilutive funding commitments, together with the net proceeds from our rights offering completed in early March 2020, will not be sufficient to fund our operating expenses and capital expenditure requirements, as currently planned, for more than one year. Specifically we believe these funds will enable us to fund our operating expenses and capital expenditure requirements into the first quarter of 2021, including through the filing of an NDA for tebipenem HBr. Because these funds will not sufficient to fund our operations primarily through private placementsas currently planned for more than one year beyond the filing date of this Annual Report on Form 10-K, we have determined that there is substantial doubt regarding our preferredability to continue as a going concern. Our consolidated financial statements as of December 31, 2019 were prepared under the assumption that we will continue as a going concern for the next twelve months. As a result, the opinion from our independent registered public accounting firm with respect to our annual financial statements contains an explanatory paragraph about such substantial doubt about our ability to continue as a going concern. Our ability to continue as a going concern is dependent upon our ability to obtain additional equity or debt financing, attain further operating efficiencies, reduce expenditures, and, ultimately, to generate revenue. The financial statements do not include any adjustments that might result from the outcome of this uncertainty. The substantial doubt about our ability to continue as a going concern may adversely affect our stock collaborationsprice and governmentour ability to raise capital.  There is no assurance that we will be successful in obtaining sufficient funding for researchon acceptable terms, if at all, and development. We have devoted substantiallywe could be forced to delay, reduce or eliminate some or all of our financial resources and efforts to research and development including preclinical and clinical development.programs, product portfolio expansion or commercialization efforts, which could materially adversely affect our business prospects or our ability to continue operations.

We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future; if we are unable to achieve commercialization, revenue from product sales, and, ultimately, profitability, the market value of our common stock will likely decline.

We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future as we continue to advance our product candidates through preclinical and clinical development and seek marketing approval for such candidates if clinical trials are successful. Our expenses will also increase substantially if and as we:

If our product candidates fail to demonstrate safety and efficacy in clinical trials, do not gain regulatory approval, or do not achieve market acceptance following regulatory approval and commercialization, we may never become profitable. Even if we achieve profitability in the future, we may not be able to sustain profitability in subsequent periods. Our prior losses, combined with expected future losses, have had and will continue to have an adverse effect on our stockholders’ equity and working capital. If we are unable to achieve and sustain profitability, the market value of our common stock will likely decline.

Because of the numerous risks and uncertainties associated with developing biopharmaceutical products, we are unable to predict the extent of any future losses or when, if ever, we will become profitable. Our expenses could increase if we are required by the FDA, or any comparable foreign regulatory authority to perform studies in addition to those currently expected, or if there are any delays in completing our clinical trials or the development of any of our product candidates.

We expect that we will need substantial additional funding. If we are unable to raise capital when needed, or do not receive payment under our government awards, we could be forced to delay, reduce or eliminate our product development programs or commercialization efforts.

Developing pharmaceutical products, including conducting preclinical studies and clinical trials, is a time-consuming, expensive and uncertain process that takes years to complete. We expect that our expenses will increase substantially as we commence and advance our ongoing and planned clinical trials and other studies of SPR994,tebipenem HBr, SPR720 and SPR206, seek marketing approval for SPR994tebipenem HBr if clinical trials are successful, and evaluate the advancement of our other product candidates, including SPR741, SPR206 and SPR720.candidates. If we obtain marketing approval for SPR994tebipenem HBr or any other product candidate, we expect to incur significant commercialization expenses related to product sales, marketing, distribution and manufacturing. Some of these expenses may be incurred in advance of marketing approval, and could be substantial. Accordingly, we will be required to obtain further funding through public or private equity offerings, debt financings, collaborations, licensing arrangements, government funding or other sources. Adequate additional financing may not be available to us on acceptable terms, or at all. Our failure to raise capital as and when needed would have a negative effect on our financial condition and our ability to pursue our business strategy.

We believe that our existing cash, and cash equivalents and marketable securities as of December 31, 20172019, together with committed funding from our BARDA contract and other non-dilutive funding commitments, together with the net proceeds from our rights offering completed in early March 2020, will enable us to fund our operating expenses and capital expenditure requirements into the secondfirst quarter of 2019.2021, including through the filing of an NDA for tebipenem HBr. Our cash forecasts are based on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we currently expect. Changing circumstances could cause us to consume capital significantly faster than we currently anticipate, and we may need to spend more than currently expected because of circumstances beyond our control. Our future funding requirements, both short-term and long-term, will depend on many factors, including:

As of December 31, 2017,2019, our non-dilutive sources of funding consisted of an award from BARDA for tebipenem HBr, an award from NIAID under its Small Business Innovation Research program or SBIR, for our SPR720 program, an award from NIAID for SPR206, awards from CARB-X and the DoD that provide partial funding for the development of our Potentiator Platform product candidates including SPR741, and an award from NIAID,the DoD Congressionally Directed Medical Research Programs (“CDMRP”) Joint Warfighter Medical Research Program for our SPR720 program. Our DoD cooperative agreementSPR206.

The BARDA award provides total reimbursement to us of $46.8 million for qualified expenses for tebipenem HBr development over a five-year period through November 2021. The award initially committed funding of $15.7 million over a three-year base period from July 2018 to June 2021 for cUTI development activities. In May 2019, the contract was modified to include additional funding of $2.5 million for tebipenem HBr, increasing the amount of initial committed funding from $15.7 million to $18.1 million. In February 2020, BARDA exercised its first option under the contract, committing $15.9 million for tebipenem HBr through November 2021. Total committed funding under the BARDA award to date is structured as$34.1 million, including the first option exercised in 2020. There is a single, two-year $1.5 million award. We are eligiblesecond option exercisable by BARDA for the fullremaining $12.7 million of funding, subject to specified milestones being achieved under the award agreement. As part of our tebipenem HBr collaboration with BARDA described above, there will be studies assessing the efficacy of tebipenem HBr in treatment of infections caused by biodefense threats such as anthrax, plague, and melioidosis, including a clinical trial in pneumonia patients. The Defense Threat Reduction Agency, or DTRA, will provide up to $10.0 million in addition to the total potential $46.8 million from BARDA, to cover the DoDcost of the nonclinical biodefense aspects of the collaboration program. While such funding would be for the purpose of developing tebipenem HBr in these areas, we will not receive any funds from DTRA. Upon these achievements, BARDA may exercise its second option to fund a bronchoalveolar lavage study to demonstrate safety and there are no optionslung exposure sufficient to be exercised atsupport a later date. clinical trial in pneumonia patients to demonstrate safety and data suggestive of efficacy.

The NIAID contract for SPR206 provides for total development funding of up to $6.5 million over a base period and three option periods. To date, funding for the base period and the first two option periods totaling $5.9 million have been committed. The NIAID SBIR award is structured as a base period followed by a single option. For the base period of March 1, 2017 through February 28, 2018, NIAID committed funding of approximately $0.6 million for the SPR720 program. In February 2018 NIAID exercised the approximately $0.4 million option, which will havehad an initial a period of performance from March 1, 2018 through February 28, 2019. In January 2019, the period of performance for this award was extended for an additional 12-month period. Our DoD cooperative agreement is structured as a single, two-year $1.5 million award. We are eligible for the full funding from the DoD and there are no options to be exercised at a later date. The CARB-X award is structured as a base period followed by two sequential options. In March 2017, CARB-X committed funds of $1.5 million to support SPR741 development efforts for the period from April 1, 2017 to March 31, 2018. On March 12, 2018, CARB-X committed an additional $0.4 million related to the first option for a period from December 1, 2017 to March 31, 2018. There will be no additional options exercised under the CARB-X award. The NIAID and CARB-X awards areaward is subject to termination for convenience at any time by NIAID. NIAID and CARB-X. Neither organization is not obligated to provide funding to Sperous beyond the base period amounts from Congressionally approved annual appropriations. The DoD CDMRP award commits funding of $5.9 million over a four-year period to cover the costs of select Phase 1 pharmacology studies, 28-day GLP non-human primate toxicology study and microbiological surveillance studies that would be required for a potential NDA submission with the FDA for SPR206.

Raising additional capital may cause dilution to our stockholders, restrict our operations or require us to relinquish rights to our technologies or product candidates.

Unless and until we can generate a substantial amount of revenue from our product candidates, we expect to finance our future cash needs through public or private equity offerings, debt financings, or collaborations, licensing arrangements and government funding arrangements. In addition, we may seek additional capital due to favorable market conditions or strategic considerations, even if we believe that we have sufficient funds for our current or future operating plans. We filed a universal shelf registration statement on Form S-3 (Registration No. 333-228661) with the SEC, which was declared effective on December 11, 2018 and pursuant to which we registered for sale up to $200.0 million of any combination of our common stock, preferred stock, debt securities, warrants, rights and/or units from time to time and at prices and on terms that we may determine, including up to $50.0 million of our common stock available for issuance pursuant to an at-the-market offering program sales agreement that we entered into with Cantor Fitzgerald & Co., or Cantor. Under the sales agreement, Cantor may sell shares of our common stock by any method permitted by law deemed to be an “at the market” offering as defined in Rule 415 of the Securities Act, subject to the terms of the sales agreement.

On June 12, 2019, we entered into a securities purchase agreement with Novo Holdings A/S (“Novo”) to sell up to an aggregate of $10.0 million of our common stock in two closings pursuant to our effective registration statement on Form S-3 (Registration No. 333-228661). The initial closing occurred on June 14, 2019 and consisted of 465,983 shares of common stock sold at a price of $10.73 per share for gross proceeds of approximately $5.0 million, prior to deducting offering expenses. The second closing occurred on October 18, 2019 and consisted of 465,116 shares of common stock sold at a price of $10.75 per share for gross proceeds of approximately $5.0 million, prior to deducting offering expenses.

We may seek to raise additional capital at any time. To the extent that we raise additional capital through the sale of common stock, convertible securities or other equity securities, the ownership interest of our then existing stockholders may be materially diluted, and the terms of these securities could include liquidation or other preferences and anti-dilution protections that could adversely affect the rights of our stockholders. In addition, debt financing, if available, would result in increased fixed payment obligations and may involve agreements that include restrictive covenants that limit our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends, which could adversely affect our ability to conduct our business. In addition, securing additional financing would require a substantial amount of time and attention from our management and may divert a disproportionate amount of their attention away from day-to-day activities, which may adversely affect our management’s ability to oversee the development of our product candidates.

If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams or product candidates or grant licenses on terms that may not be favorable to us.

Our independent registered public accounting firm has included in its report on our audited consolidated financial statements for the fiscal year ended December 31, 2016 an explanatory paragraph relating to our ability to continue as a going concern.

The report from our independent registered public accounting firm for the year ended December 31, 2016 includes an explanatory paragraph stating that our recurring losses from operations since inception and required additional funding to finance our operations raise substantial doubt about our ability to continue as a going concern. If we are unable to obtain sufficient funding, our

business, prospects, financial condition and results of operations will be materially and adversely affected and we may be unable to continue as a going concern. If we are unable to continue as a going concern, we may have to liquidate our assets and may receive less than the value at which those assets are carried on our audited financial statements, and it is likely that investors will lose all or a part of their investment. Future reports from our independent registered public accounting firm may also contain statements expressing substantial doubt about our ability to continue as a going concern. If we seek additional financing to fund our business activities in the future and there remains substantial doubt about our ability to continue as a going concern, investors or other financing sources may be unwilling to provide additional funding to us on commercially reasonable terms or at all.

Our ability to use our net operating loss carryforwards may be limited.

As of December 31, 2017,2019, we had U.S. federal, state and foreign net operating loss carryforwards, or NOLs, of $76.4$156.8 million, $76.0$157.8 million and $4.3$7.7 million, respectively.  OurThe federal NOLs of $73.0 million will expire at various dates from 2033 to 2037 and approximately $83.8 million can be carried forward indefinitely.  The state NOLs begin to expire in 2033.2033 and will expire at various dates through 2039.  The foreign NOLs do not expire. Utilization of these NOLs depends on many factors, including our future income, which cannot be assured. These NOLs could expire unused and be unavailable to offset our future income tax liabilities. In addition, under Section 382 of the Internal Revenue Code of 1986, as amended, or the Code, and corresponding provisions of state law, if a corporation undergoes an “ownership change,” which is generally defined as a greater than 50% change, by value, in its equity ownership by 5% stockholders over a three-year period, the corporation’s ability to use its pre-change NOLs and other pre-change tax attributes to offset its post-change income may be limited. We have not determined if we have experienced Section 382 ownership changes in the past and if a portion of our NOLs is subject to an annual limitation under Section 382. In addition, we may experience ownership changes in the future as a result of subsequent changes in our stock ownership, some of which may be outside of our control. If we determine that an ownership change has occurred and our ability to use our historical NOLs is materially limited, it would harm our future operating results by effectively increasing our future tax obligations.

Under recently enacted U.S. federal tax legislation, although the treatment of net operating loss carryforwards arising in tax years beginning on or before December 31, 2017 has generally not changed, net operating loss carryforwards arising in tax years beginning after December 31, 2017 may be used to offset only 80% of taxable income. In addition, net operating losses arising in tax years beginning after December 31, 2017 may be carried forward indefinitely, as opposed to the 20-year carryforward under prior law.

We have a limited operating history and no history of commercializing pharmaceutical products, which may make it difficult to evaluate the prospects for our future viability.

We were established in 2013 and began operations in 2014. Our operations to date have been limited to financing and staffing our company, developing our technology and developing SPR994tebipenem HBr and our other product candidates. We have not yet demonstrated an ability to successfully complete a large-scale, pivotal clinical trial, obtain marketing approval, manufacture a commercial scale product, or arrange for a third party to do so on our behalf, or conduct sales and marketing activities necessary for successful product commercialization. Consequently, predictions about our future success or viability may not be as accurate as they could be if we had a longer operating history or a history of successfully developing and commercializing pharmaceutical products.

We will need to transition from a development-focused company to a company with commercial activities, and we may experience difficulties in managing this transition, which could disrupt our operations.

We may encounter unforeseen expenses, difficulties, complications, delays and other known or unknown factors in achieving our business objectives. We will eventually need to transition from a company with a development focus to a company capable of supporting commercial activities. We may not be successful in such a transition.

We expect our financial condition and operating results to continue to fluctuate significantly from quarter to quarter and year to year due to a variety of factors, many of which are beyond our control. Accordingly, stockholders should not rely upon the results of any quarterly or annual periods as indications of future operating performance.

Risks Related to Product Development and Commercialization

We are heavily dependent on the success of SPR994,tebipenem HBr, which is still under development, and our ability to develop, obtain marketing approval for and successfully commercialize SPR994.tebipenem HBr. If we are unable to develop, obtain marketing approval for and successfully commercialize SPR994,tebipenem HBr, or if we experience significant delays in doing so, our business could be materially harmed.

We currently have no products approved for sale and have invested a significant portion of our efforts and financial resources in the development of SPR994tebipenem HBr as a product candidate for the treatment of MDR bacterial infections. Our near-term prospects are substantially dependent on our ability to develop, obtain marketing approval for and successfully commercialize SPR994.tebipenem HBr. The success of SPR994tebipenem HBr will depend on several factors, including the following:

Successful development of SPR994tebipenem HBr for any additional indications would be subject to these same risks.

Many of these factors are beyond our control, including clinical development, the regulatory submission process, potential threats to our intellectual property rights and the manufacturing, marketing and sales efforts of any future collaborator. If we are unable to develop, receive marketing approval for, or successfully commercialize SPR994,tebipenem HBr, or if we experience delays as a result of any of these factors or otherwise, our business could be materially harmed. Even if we successfully obtain regulatory approvals to manufacture and market tebipenem HBr, our revenues will be dependent, in part, upon the size of the markets in the territories for which we gain regulatory approval and have commercial rights. If the markets for patient subsets that we are targeting are not as significant as we estimate, we may not generate significant revenues from sales of such product, if approved.

We have no experience as a company in obtaining regulatory approval for a drug.

As a company, we have never obtained regulatory approval for, or commercialized, a drug. It is possible that the FDA may refuse to accept any or all of our planned new drug applications, or NDAs, for substantive review or may conclude after review of our data that our application is insufficient to obtain regulatory approval for any current or future product candidates. If the FDA does not approve any of our planned NDAs, it may require that we conduct additional costly clinical, nonclinical or manufacturing validation studies before it will reconsider our applications. Depending on the extent of these or any other FDA-required studies, approval of any NDA or other application that we submit may be significantly delayed, possibly for several years, or may require us to expend more resources than we have available. Any failure or delay in obtaining regulatory approvals would prevent us from commercializing SPR994tebipenem HBr or any of our other product candidates for which we may seek regulatory approval, generating revenues and achieving and sustaining profitability. It is also possible that additional studies, if performed and completed, may not be considered sufficient by the FDA to approve any NDA or other application that we submit. If any of these outcomes occur, we may be forced to abandon the development of our product candidates, which would materially adversely affect our business and could potentially cause us to cease operations. We face similar risks for our applications in foreign jurisdictions.

If clinical trials of SPR994tebipenem HBr or any other product candidate that we may advance to clinical trials fail to demonstrate safety and efficacy to the satisfaction of the FDA or comparable foreign regulatory authorities or do not otherwise produce favorable results, we may incur additional costs or experience delays in completing, or ultimately be unable to complete, the development and commercialization of SPR994tebipenem HBr or any other product candidate.

We may not commercialize, market, promote or sell any product candidate in the United States without obtaining marketing approval from the FDA or in other countries without obtaining approvals from comparable foreign regulatory authorities, such as the European Medicines Agency, or EMA, and we may never receive such approvals. We must complete extensive preclinical development and clinical trials to demonstrate the safety and efficacy of our product candidates in humans before we will be able to obtain these approvals. Clinical testing is expensive, difficult to design and implement, can take many years to complete and is inherently uncertain as to outcome. We have not previously submitted an NDA to the FDA or similar applications to comparable foreign regulatory authorities for any of our product candidates.

The clinical development of SPR994tebipenem HBr and any of our other product candidates is susceptible to the risk of failure inherent at any stage of drug development, including failure to demonstrate efficacy in a trial or across a broad population of patients, the occurrence of severe adverse events, failure to comply with protocols or applicable regulatory requirements, and determination by the FDA or any comparable foreign regulatory authority that a drug product is not approvable. A number of companies in the pharmaceutical industry, including biotechnology companies, have suffered significant setbacks in clinical trials, even after promising results in earlier nonclinical studies or clinical trials. The results of preclinical and other nonclinical studies and/or early clinical trials of our product candidates may not be predictive of the results of later-stage clinical trials. Notwithstanding any promising results in early nonclinical studies or clinical trials, we cannot be certain that we will not face similar setbacks. For example, although SPR994tebipenem HBr is a new formulation of the active pharmaceutical ingredient tebipenem that exhibited a favorable safety and efficacy profile during Phase 2 clinical trials conducted by Meiji and a global pharmaceutical company, which we refer to as Global Pharma, in Japan, we may nonetheless fail to achieve success in our clinical trials. Even if our clinical trials are completed, the results may not be sufficient to obtain regulatory approval for our product candidates.

In addition, preclinical and clinical data are often susceptible to varying interpretations and analyses. Many companies that believed their product candidates performed satisfactorily in preclinical studies and clinical trials have nonetheless failed to obtain marketing approval for the product candidates. Even if we believe that the results of our clinical trials warrant marketing approval, the FDA or comparable foreign regulatory authorities may disagree and may not grant marketing approval of our product candidates.

In some instances, there can be significant variability in safety and/or efficacy results between different trials of the same product candidate due to numerous factors, including changes in trial procedures set forth in protocols, differences in the size and type of the patient populations, adherence to the dosing regimen and other trial protocols and the rate of dropout among clinical trial participants, among others. It is possible that even if one or more of our product candidates has a beneficial effect, that effect will not be detected during clinical evaluation as a result of one of the factors listed or otherwise. Conversely, as a result of the same factors, our clinical trials may indicate an apparent positive effect of a product candidate that is greater than the actual positive effect, if any. Similarly, in our clinical trials, we may fail to detect toxicity of or intolerability of our product candidates or may determine that our product candidates are toxic or not well tolerated when that is not in fact the case. In the case of our clinical trials, results may differ on the basis of the type of bacteria with which patients are infected. We cannot make assurances that any Phase 2, Phase 3 or other clinical trials that we may conduct will demonstrate consistent or adequate efficacy and safety to obtain regulatory approval to market our product candidates.

We may encounter unforeseen events prior to, during, or as a result of, clinical trials that could delay or prevent us from obtaining regulatory approval for SPR994tebipenem HBr or any of our other product candidates, including: