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KALA Kala Pharmaceuticals

Document and Entity Information

Document and Entity Information - shares3 Months Ended
Mar. 31, 2021May 04, 2021
Document and Entity Information
Entity Registrant NameKALA PHARMACEUTICALS, INC.
Entity Central Index Key0001479419
Document Type10-Q
Document Quarterly Reporttrue
Document Period End DateMar. 31,
2021
Document Transition Reportfalse
Amendment Flagfalse
Current Fiscal Year End Date--12-31
Entity File Number001-38150
Entity Incorporation, State or Country CodeDE
Entity Tax Identification Number27-0604595
Entity Address, Address Line One490 Arsenal Way, Suite 120
Entity Address, City or TownWatertown
Entity Address, State or ProvinceMA
Entity Address, Postal Zip Code02472
City Area Code781
Local Phone Number996-5252
Title of 12(b) SecurityCommon Stock, $0.001 par value per share
Trading SymbolKALA
Security Exchange NameNASDAQ
Entity Interactive Data CurrentYes
Entity Current Reporting StatusYes
Entity Filer CategoryNon-accelerated Filer
Entity Small Businesstrue
Entity Emerging Growth Companytrue
Entity Ex Transition Periodtrue
Entity Common Stock, Shares Outstanding64,642,365
Entity Shell Companyfalse
Document Fiscal Year Focus2021
Document Fiscal Period FocusQ1

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in ThousandsMar. 31, 2021Dec. 31, 2020
Current assets:
Cash and cash equivalents $ 127,970 $ 77,264
Short-term investments28,015 76,276
Accounts receivable, net12,206 9,604
Inventory8,241 5,229
Prepaid expenses and other current assets2,633 3,006
Total current assets179,065 171,379
Non-current assets:
Property and equipment, net3,042 3,166
Long-term inventory6,200 6,219
Right-of-use assets28,542 27,853
Restricted cash and other long-term assets12,978 12,989
Total assets229,827 221,606
Current liabilities:
Accounts payable2,855 1,724
Accrued expenses and other current liabilities15,149 18,971
Current portion of lease liabilities1,985 1,530
Total current liabilities19,989 22,225
Long-term liabilities:
Long-term lease liabilities27,525 27,143
Long-term debt72,521 72,243
Total long-term liabilities100,046 99,386
Total liabilities120,035 121,611
Commitments and Contingencies (Note 14)
Stockholders' equity:
Common stock, $0.001 par value; 120,000,000 shares authorized as of March 31, 2021 and December 31, 2020; 63,805,108 and 58,915,375 shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively64 59
Additional paid-in capital539,920 499,715
Accumulated other comprehensive income3 4
Accumulated deficit(430,195)(399,783)
Total stockholders' equity109,792 99,995
Total liabilities and stockholders' equity $ 229,827 $ 221,606

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / sharesMar. 31, 2021Dec. 31, 2020
CONDENSED CONSOLIDATED BALANCE SHEETS
Common stock, par value $ 0.001 $ 0.001
Common stock, authorized120,000,000 120,000,000
Common stock, shares issued63,805,108 58,915,375
Common stock, shares outstanding63,805,108 58,915,375

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands3 Months Ended
Mar. 31, 2021Mar. 31, 2020
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Product revenues, net $ 3,266 $ 1,071
Costs and expenses:
Cost of product revenues755 354
Selling, general and administrative27,699 15,408
Research and development3,126 5,434
Total costs and expenses31,580 21,196
Loss from operations(28,314)(20,125)
Other income (expense):
Interest and other income43 298
Interest and other expense(2,141)(2,128)
Total interest and other expense(2,098)(1,830)
Net loss $ (30,412) $ (21,955)
Net loss per share-basic and diluted $ (0.49) $ (0.54)
Weighted average shares outstanding-basic and diluted61,655,867 40,761,984
Statement of Comprehensive Loss
Net loss $ (30,412) $ (21,955)
Other comprehensive loss:
Change in unrealized gains on investments(1)
Total other comprehensive loss(1)
Total comprehensive loss $ (30,413) $ (21,955)

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in ThousandsCommon StockAdditional Paid-In CapitalAccumulated Other Comprehensive IncomeAccumulated DeficitTotal
Balance as of beginning of period at Dec. 31, 2019 $ 36 $ 325,112 $ (295,456) $ 29,692
Balance as of beginning of period (in shares) at Dec. 31, 201936,086,254
Stockholders' Equity
At the market offering, net of sales agent commission $ 3 12,543 12,546
At the market offering, net of sales agent commission (in shares)2,352,671
Exercise of stock options167 167
Exercise of stock options (in shares)61,158
Issuance under employee stock purchase plan269 269
Issuance under employee stock purchase plan (in shares)85,553
Common stock offering, net of offering costs $ 16 118,191 118,207
Common stock offering, net of offering costs (in shares)16,000,000
Stock-based compensation expense2,584 2,584
Net loss(21,955)(21,955)
Balance as of end of period at Mar. 31, 2020 $ 55 458,866 (317,411)141,510
Balance as of end of period (in shares) at Mar. 31, 202054,585,636
Balance as of beginning of period at Dec. 31, 2020 $ 59 499,715 $ 4 (399,783)99,995
Balance as of beginning of period (in shares) at Dec. 31, 202058,915,375
Stockholders' Equity
At the market offering, net of sales agent commission $ 5 34,704 34,709
At the market offering, net of sales agent commission (in shares)4,746,072
Exercise of stock options184 184
Exercise of stock options (in shares)68,814
Issuance under employee stock purchase plan431 431
Issuance under employee stock purchase plan (in shares)74,847
Stock-based compensation expense4,886 4,886
Change in fair value of investments(1)(1)
Net loss(30,412)(30,412)
Balance as of end of period at Mar. 31, 2021 $ 64 $ 539,920 $ 3 $ (430,195) $ 109,792
Balance as of end of period (in shares) at Mar. 31, 202163,805,108

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - (Parenthetical) - USD ($) $ in Thousands3 Months Ended
Mar. 31, 2021Mar. 31, 2020
CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY
Sales agent commission $ 991 $ 388
Offering costs $ 8,011

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands3 Months Ended
Mar. 31, 2021Mar. 31, 2020
Cash flows from operating activities:
Net loss $ (30,412) $ (21,955)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization248 230
Non-cash operating lease cost529 473
Amortization of debt discount and other non-cash interest278 253
Stock-based compensation4,702 2,497
Amortization of discount on available-for-sale securities10
Change in operating assets and liabilities:
Accounts receivable(2,602)6,769
Prepaid expenses and other current assets373 99
Inventory(2,809)(579)
Accounts payable1,237 (1,332)
Accrued expenses and other current liabilities(3,822)(6,023)
Lease liabilities and other long-term liabilities(372)(312)
Net cash used in operating activities(32,640)(19,880)
Cash flows from investing activities:
Purchases of property and equipment and other assets(219)(292)
Proceeds from sales or maturities of short-term investments48,250
Net cash provided by (used in) investing activities48,031 (292)
Cash flows from financing activities:
Proceeds from common stock offerings, net of offering costs34,709 130,754
Payment of principal on finance lease(9)(8)
Proceeds from exercise of stock options and issuance of common stock under employee stock purchase plan615 435
Net cash provided by financing activities35,315 131,181
Net increase in cash, cash equivalents and restricted cash:50,706 111,009
Cash, cash equivalents and restricted cash at beginning of period89,756 98,031
Cash, cash equivalents and restricted cash at end of period140,462 209,040
Reconciliation of cash, cash equivalents and restricted cash:
Cash, cash equivalents, and restricted cash at end of period140,462 209,040
Cash and cash equivalents at end of period127,970 196,456
Non-cash investing and financing activities:
Purchases of property and equipment in accounts payable24
Supplemental disclosure:
Cash paid for interest1,851 $ 1,875
Right-of-use assets obtained in exchange of operating lease obligations $ 1,218

NATURE OF BUSINESS AND BASIS OF

NATURE OF BUSINESS AND BASIS OF PRESENTATION3 Months Ended
Mar. 31, 2021
NATURE OF BUSINESS AND BASIS OF PRESENTATION
NATURE OF BUSINESS AND BASIS OF PRESENTATION1. NATURE OF BUSINESS AND BASIS OF PRESENTATION Nature of Business ® ® ® In January 2019, the Company launched its first commercial product, INVELTYS, in the United States and began shipping its second commercial product, EYSUVIS, to wholesalers in the United States in late December 2020 with the full promotional launch commencing in early January 2021. The Company is engaged in the commercialization of EYSUVIS and INVELTYS, research and development activities, raising capital and recruiting skilled personnel. The Company is subject to a number of risks similar to those of other companies conducting high-risk, research and development of pharmaceutical product candidates and launching products for the first time. Principal among these risks are dependence on key individuals and intellectual property, competition from other products and companies and the technical risks associated with the successful research, development and marketing of its product candidates. The Company’s success is dependent upon its ability to successfully commercialize its products, the success of its research and development efforts, its ability to obtain regulatory approval of its product candidates, its ability to raise additional capital when needed and, ultimately, attain profitable operations. The Company is also progressing its pipeline of proprietary preclinical development programs targeted to address front and back of the eye diseases. These preclinical development programs, all of which are new chemical entities, include its receptor Tyrosine Kinase Inhibitor program, that is designed to inhibit the vascular endothelial growth factor pathway, for the treatment of retinal diseases, including wet age-related macular degeneration; its selective glucocorticoid receptor modulators, which are a novel class of therapies designed to modify the downstream activity of the receptors to exhibit the anti-inflammatory and immunomodulatory properties of the corticosteroid class of therapies without their associated side effects; and its novel surface targeting steroid designed to target the ocular surface and thus have the potential to have fewer side effects compared to traditional topical steroids. The Company owns all intellectual property and worldwide rights to these pipeline preclinical development programs. Liquidity The Company expects that its cash, cash equivalents and short-term investments as of March 31, 2021, together with anticipated net revenue from sales of EYSUVIS and INVELTYS, will enable it to fund its operating expenses, debt service obligations and capital expenditure requirements for at least twelve months from the date these condensed consolidated financial statements were issued. This evaluation is based on relevant conditions and events that are known and reasonably knowable at the date that the condensed consolidated financial statements are issued. As a result, the Company could deplete its available capital resources sooner than it currently expects. COVID-19 – all office-based personnel have been instructed to work from home, and the Company’s laboratory facilities that support its early-stage research activities are being utilized as necessary. In addition, The Company’s sales force has since resumed substantially all in-person interactions in the field, but if the Company suspends all or some in-person interactions with physicians in the future, or to the extent physicians limit in-person interactions, the Company may be limited to conducting educational and promotional activities virtually, which may continue to hamper its ability to market INVELTYS. The effects of the COVID-19 pandemic may also disrupt the full promotional launch and commercialization of EYSUVIS. In addition, government restrictions have at times led to moratoria on elective ocular surgeries in many jurisdictions, which has significantly reduced, and may in the future continue to significantly reduce, the demand for INVELTYS, which is indicated for the treatment of post-operative inflammation and pain following ocular surgery. commercialization efforts of EYSUVIS and INVELTYS and its Use of Estimates Net Loss per Share The weighted average number of common shares included in the computation of diluted net loss gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, warrants and unvested RSUs and PSUs. Common stock equivalent shares are excluded from the computation of diluted net loss per share if their effect is antidilutive. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for each of the three months ended March 31, 2021 and 2020. As of March 31, 2021 and 2020, potentially dilutive securities excluded from the calculation of diluted net loss per share because including such securities would have an anti-dilutive effect consisted of outstanding options to purchase 10,120,453 and 8,817,943 shares of the Company’s common stock, respectively, an aggregate of 1,365,592 unvested RSUs and PSUs as of March 31, 2021 and an aggregate of 248,505 and 297,988 unexercised warrants as of March 31, 2021 and 2020, respectively. Unaudited Interim Financial Information The unaudited condensed consolidated financial statements include the accounts of Kala Pharmaceuticals, Inc. and its wholly owned subsidiary, Kala Pharmaceuticals Security Corporation. All intercompany transactions and balances have been eliminated in consolidation.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES3 Months Ended
Mar. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES The Company’s significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies,” to the consolidated financial statements included in the Annual Report. There have been no material changes to the significant accounting policies during the three months ended March 31, 2021. Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Financial Instruments - Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) ,

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS3 Months Ended
Mar. 31, 2021
FAIR VALUE OF FINANCIAL INSTRUMENTS
FAIR VALUE OF FINANCIAL INSTRUMENTS3. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company has short-term investments which are considered financial instruments that are measured on a recurring basis. ASC 820, Fair Value Measurements and Disclosures, ● Level 1—Quoted prices in active markets for identical assets or liabilities. ● Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ● Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s financial instruments consist primarily of cash equivalents and short-term investments in money market funds and short-term securities. Cash equivalents and short-term investments are reported at their respective fair values on the Company’s condensed consolidated balance sheets. See Note 4, “Investments” for additional information. The following tables sets forth the fair value of the Company’s financial assets by level within the fair value hierarchy as of March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ Fair Value ​ Level 1 ​ Level 2 ​ Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents ​ $ 112,071 ​ $ 112,071 ​ $ — ​ $ — Short-term investments ​ ​ 28,015 ​ ​ 28,015 ​ ​ — ​ ​ — Total Assets ​ $ 140,086 ​ $ 140,086 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ Fair Value ​ Level 1 ​ Level 2 ​ Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents ​ $ 63,811 ​ $ 63,811 ​ $ — ​ $ — Short-term investments ​ ​ 76,276 ​ ​ 76,276 ​ ​ — ​ ​ — Total Assets ​ $ 140,087 ​ $ 140,087 ​ $ — ​ $ — ​ During the three months ended March 31, 2021 and the year ended December 31, 2020, there were no transfers between Level 1, Level 2, and Level 3.

INVESTMENTS

INVESTMENTS3 Months Ended
Mar. 31, 2021
INVESTMENTS
INVESTMENTS4. INVESTMENTS Investments by security type consisted of the following as of March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ ​ Gross ​ Gross ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost ​ Gains ​ Losses ​ Value U.S. treasury securities $ 9,700 ​ $ 1 ​ $ — ​ $ 9,701 U.S. government agencies securities ​ 18,312 ​ ​ 2 ​ ​ — ​ ​ 18,314 Total $ 28,012 ​ $ 3 ​ $ — ​ $ 28,015 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ Gross ​ Gross ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost ​ Gains ​ Losses ​ Value U.S. treasury securities $ 26,744 ​ $ 2 ​ $ — ​ $ 26,746 U.S. government agencies securities ​ 49,528 ​ ​ 2 ​ ​ — ​ ​ 49,530 Total $ 76,272 ​ $ 4 ​ $ — ​ $ 76,276 ​ As of March 31, 2021 and December 31, 2020, all of the Company’s investments had a contractual maturity within one year. The fair value of all of the Company’s investments are classified as short-term on its condensed consolidated balance sheets.

REVENUE & ACCOUNTS RECEIVABLE,

REVENUE & ACCOUNTS RECEIVABLE, NET3 Months Ended
Mar. 31, 2021
REVENUE & ACCOUNTS RECEIVABLE, NET
REVENUE & ACCOUNTS RECEIVABLE, NET5. REVENUE & ACCOUNTS RECEIVABLE, NET The Company accounts for revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers Product revenues, net The Company sells EYSUVIS and INVELTYS primarily to wholesalers in the United States (collectively, “Customers”). These Customers subsequently resell the Company’s products to specialty and other retail pharmacies. In addition to agreements with Customers, the Company enters into arrangements with third-party payors that provide for government-mandated and/or privately-negotiated rebates, chargebacks and discounts for the purchase of the Company’s products. The Company also holds inventory at a third-party pharmacy on a consignment basis and records revenue when control of the product transfers to the customer upon sale to the end user. The amount of inventory held on a consignment basis as of March 31, 2021 and December 31, 2020 was immaterial. The goods promised in the Company’s product sales contracts represent a single performance obligation. The Company recognizes revenue from product sales at the point the Customer obtains control of the product, which occurs upon delivery. The transaction price (“net sales price”) that is recognized as revenue for product sales includes the selling price to the Customer and an estimate of variable consideration. Components of variable consideration include prompt pay and other discounts, product returns, government rebates, third-party payor rebates, coverage gap rebates, incentives such as patient co-pay assistance, and other fees paid to Customers and other third-party payors where a distinct good or service is not received. Variable consideration is recorded on the condensed consolidated balance sheet as either a reduction of accounts receivable, if payable to a Customer, or as a current liability, if payable to a third-party other than a Customer. The Company considers all relevant information when estimating variable consideration such as assessment of its current and anticipated sales and demand forecasts, actual payment history, information from third parties regarding the payor mix for products, information from third parties regarding the units remaining in the distribution channel, specific known market events and trends, industry data and current contractual and statutory requirements that are reasonably available. The Company includes estimated amounts for variable consideration in the net sales price to the extent it is determined probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Payment terms with Customers do not exceed one year and, therefore, the Company does not account for a significant financing component in its arrangements. The Company expenses incremental cost of obtaining a contract with a Customer when incurred as the period of benefit is generally less than one year. Reserves for Variable Consideration Trade Discounts and Allowances The Company provides its Customers with certain trade discounts and allowances including discounts for prompt payments and other discounts and fees paid for distribution, data and administrative services. These discounts and fees are based on contractually-determined percentages and are recorded as a reduction of revenue and accounts receivable in the period in which the related product revenue is recognized. Chargebacks Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These components of variable consideration are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Reserves for chargebacks consist of credits the Company expects to issue for units that remain in the distribution channel at the end of each reporting period and that the Company expects will be sold to qualified healthcare providers, as well as chargebacks that Customers have claimed, but for which the Company has not yet issued a credit. Product Returns Consistent with industry practice, the Company has a product returns policy that provides Customers right of return for product purchased within a specified period prior to and subsequent to the product’s expiration date. The Company estimates the amount of its products that may be returned and presents this amount as a reduction of revenue in the period the related product revenue is recognized, in addition to establishing a liability. The Company’s estimates for product returns are based upon available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel as well as historical returns, which develop over time. Commercial Payor and Medicare Part D Rebates The Company contracts with certain third-party payors, primarily pharmacy benefit managers (“PBMs”) and health plans (“Plans”), for the payment of rebates with respect to utilization of its product. These rebates are based on contractual percentages applied to the amount of product prescribed to patients who are covered by the PBMs or the Plans with which it contracts. The Company estimates the rebates for commercial and Medicare Part D payors based on the contractual discount percentage, the various payor mix for EYSUVIS and INVELTYS as well as future rebates that will be made for product that has been recognized as revenue but remains in the distribution channel at the end of each reporting period. The Company also estimates the number of patients in the prescription drug coverage gap for whom it will owe an additional liability under the Medicare Part D program. Such estimates are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. Government Rebates The Company is subject to discount obligations under Medicaid and other government programs. For Medicaid, reserves are based on actual payment history, and estimates of future Medicaid beneficiary utilization applied to the Medicaid unit rebate formula established by the Centers for Medicaid and Medicare Services. The Company’s liability for these rebates consists of estimates of claims for the current period and estimated future claims that will be made for product that has been recognized as revenue but remains in the distribution channel at the end of each reporting period. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. Co-pay Assistance Program The Company offers a co-pay assistance program (the “co-pay program”), which is intended to provide financial assistance to patients who may or may not be covered by commercial insurance or who opt out of Medicare Part D programs. The calculation of accruals for the co-pay program is based on actual claims processed during the period as well as an estimate of the number and cost per claim that the Company expects to receive associated with product that has been recognized as revenue but remains in the distribution channel at the end of each reporting period. Allowances for estimated co-pay claims are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. The following tables summarize activity in each of the Company’s product revenue provision and allowance categories for the three months ended March 31, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trade Discounts, ​ ​ ​ ​ ​ ​ ​ ​ Allowances and ​ ​ ​ ​ Rebates and ​ ​ Chargebacks (1) Product Returns (2) Incentives (3) Balance as of December 31, 2020 ​ $ 1,157 ​ $ 600 ​ $ 4,904 Provision related to current period sales ​ ​ 2,201 ​ ​ 245 ​ ​ 10,216 Changes in estimate related to prior period sales ​ ​ 3 ​ ​ 30 ​ ​ (26) Credit/payments made ​ ​ (1,823) ​ ​ (419) ​ ​ (7,880) Balance as of March 31, 2021 ​ $ 1,538 ​ $ 456 ​ $ 7,214 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trade Discounts, ​ ​ ​ ​ ​ ​ ​ ​ Allowances and ​ ​ ​ ​ Rebates and ​ ​ Chargebacks (1) Product Returns (2) Incentives (3) Balance as of December 31, 2019 ​ $ 1,783 ​ $ 180 ​ $ 10,044 Provision related to current period sales ​ ​ 725 ​ ​ — ​ ​ 4,576 Changes in estimate related to prior period sales ​ ​ 2 ​ ​ (66) ​ ​ 93 Credit/payments made ​ ​ (1,114) ​ ​ — ​ ​ (8,090) Balance as of March 31, 2020 ​ $ 1,396 ​ $ 114 ​ $ 6,623 (1) Trade discounts, allowances and chargebacks include fees for distribution service fees, prompt pay and other discounts, and chargebacks. Estimated trade discounts, allowances and chargebacks are deducted from gross revenue at the time revenues are recognized and are recorded as a reduction to accounts receivable on the Company’s condensed consolidated balance sheets. (2) Estimated provisions for product returns are deducted from gross revenues at the time revenues are recognized and are included in accrued expenses and other current liabilities on the Company’s condensed consolidated balance sheets. (3) Rebates and incentives include managed care rebates, government rebates, co-pay program incentives, and sales incentives and allowances. Estimated provisions for rebates and discounts are deducted from gross revenues at the time revenues are recognized and are included in accrued expenses and other current liabilities on the Company’s condensed consolidated balance sheets. ​ Accounts Receivable, net Accounts receivable are reported on the condensed consolidated balance sheets at outstanding amounts due from Customers for product sales. The Company deducts sales discounts for prompt payments and other discounts, contractual fees for service arrangements and chargebacks from accounts receivable. The Company evaluates the collectability of accounts receivable on a regular basis, by reviewing the financial condition and payment history of Customers, an overall review of collections experience on other accounts, and economic factors or events expected to affect future collections experience. An allowance for doubtful accounts is recorded when a receivable is deemed to be uncollectible. The Company recorded no allowance for doubtful accounts as of March 31, 2021 or March 31, 2020. The Company recorded an allowance of $1,538 and $1,396 for expected sales discounts, related to prompt pay discounts and other discounts, contractual fee for service arrangements and chargebacks, to wholesalers and distributors as of March 31, 2021 and March 31, 2020, respectively.

INVENTORY

INVENTORY3 Months Ended
Mar. 31, 2021
INVENTORY
INVENTORY6. Inventory consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Raw materials ​ $ 995 ​ $ 801 Work in progress ​ ​ 9,303 ​ ​ 6,437 Finished goods ​ ​ 4,143 ​ ​ 4,210 Total inventory ​ $ 14,441 ​ $ 11,448 ​ As of March 31, 2021, the Company had $8,241 of current inventory and $6,200 of long-term inventory. As of December 31, 2020, the Company had $5,229 of current inventory and $6,219 of long-term inventory.

ACCRUED EXPENSES

ACCRUED EXPENSES3 Months Ended
Mar. 31, 2021
ACCRUED EXPENSES
ACCRUED EXPENSES7. ACCRUED EXPENSES Accrued expenses consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Compensation and benefits ​ $ 5,550 ​ $ 9,676 Accrued revenue reserves (1) ​ ​ 6,345 ​ ​ 5,224 Commercial costs ​ ​ 949 ​ ​ 2,103 Professional services ​ ​ 750 ​ ​ 926 Contract manufacturing ​ ​ 826 ​ ​ 336 Development costs ​ ​ 206 ​ ​ 154 Other ​ ​ 523 ​ ​ 552 Accrued expenses ​ $ 15,149 ​ $ 18,971 (1) There were additional revenue reserves included in accounts payable of $1,325 and $280, as of March 31, 2021 and December 31, 2020, respectively.

LEASES

LEASES3 Months Ended
Mar. 31, 2021
LEASES
LEASES8. LEASES Operating leases In connection with the lease of the Company’s corporate headquarters (the “Watertown Lease”), the Company issued a letter of credit to the landlord for $2,042. The Company secured the letter of credit for the full amount of the letter with cash on deposit, which is reported as restricted cash on the condensed consolidated balance sheets as of March 31, 2021 and December 31, 2020. For the three months ended March 31, 2021and 2020, the variable lease expense for the Watertown Lease, which includes common area maintenance and real estate taxes, was $363 and $348 respectively. The remaining lease term was 10.6 years as of March 31, 2021. Vehicle Fleet lease During the year ended December 31, 2019, the Company entered into a master fleet lease agreement (the “Vehicle Fleet Lease”), pursuant to which it leased 65 vehicles. In connection with the Vehicle Fleet Lease, the Company issued a letter of credit for $450, which was reported as restricted cash on the condensed consolidated balance sheets as of March 31, 2021 and December 31, 2020. The lease has an expected term of three years, which commenced upon the delivery of the vehicles in March 2019. ​ During the three months ended March 31, 2021, the Company modified the Vehicle Fleet Lease to add 54 additional vehicles to the fleet. The new component of the lease has an expected term of approximately three years, which commenced upon the delivery of the additional vehicles in March 2021. ​ The components of lease expense and related cash flows were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ 2021 2020 Lease cost ​ ​ Operating lease cost ​ $ 1,216 ​ $ 1,185 Variable lease cost ​ ​ 509 ​ ​ 410 Total lease cost ​ $ 1,725 ​ $ 1,595 ​ ​ ​ ​ ​ ​ ​ Operating cash outflows from operating leases ​ $ 1,584 ​ $ 1,444 ​ The weighted average remaining lease term and weighted average discount rate of operating leases are as follows: ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Weighted average remaining lease term 10.1 years ​ 10.3 years Weighted average discount rate 9.6% ​ 9.8% ​

DEBT

DEBT3 Months Ended
Mar. 31, 2021
DEBT
DEBT9. DEBT Athyrium Credit Facility On October 1, 2018, the Company entered into a credit agreement (the “Athyrium Credit Facility”) with Athyrium Opportunities III Acquisition LP (“Athyrium”) for up to $110,000. The Athyrium Credit Facility provided for a Term Loan A in the aggregate principal amount of $75,000 (the “Term Loan A”), and a Term Loan B in the aggregate principal amount of $35,000 (the “Term Loan B”). On October 1, 2018, the Company borrowed the entire principal amount of the Term Loan A. The maturity date of the Athyrium Credit Facility is October 1, 2024, the six-year anniversary of the close. The Term Loan A bears interest at a rate of 9.875% per annum, with quarterly, interest-only payments until the fourth anniversary of the Term Loan A. The unpaid principal amount of the Term Loan A is due and payable in quarterly installments starting on October 1, 2022. The Company may make voluntary prepayments, in whole or in part, and subject to certain exceptions, is required to make mandatory prepayments upon the occurrence of certain events of default as defined in the agreement, including but not limited to, the occurrence of a change of control. In addition, upon payment or repayment of any outstanding balance under the Athyrium Credit Facility, the Company will have to pay a 1% exit fee of the total principal payments (whether mandatory, voluntary, or at maturity) made throughout the term. The exit fee of $750 based on the $75,000 principal amount outstanding, will be accreted to the carrying amount of the debt using the effective interest method over the term of the loan. All mandatory and voluntary prepayments of the Athyrium Credit Facility are subject to the payment of prepayment premiums as follows: (i) if prepayment occurs prior to the second anniversary of the applicable date of issuance, an amount equal to the amount by which (a) the present value of 105% of the principal prepaid plus all interest that would have accrued on such principal through such second anniversary exceeds (b) the amount of principal prepaid, (ii) if prepayment occurs on or after the second anniversary of the applicable date of issuance but prior to the third anniversary of such issuance, an amount equal to 3% of the principal prepaid, and (iii) if prepayment occurs on or after the third anniversary of the applicable date of issuance but prior to the fourth anniversary of such issuance, an amount equal to 2% of the principal prepaid. No prepayment premium is due on any principal prepaid after the fourth anniversary of the applicable date of issuance. The Athyrium Credit Facility includes features requiring (1) additional interest rate upon an event of default accrued at an additional 3% , or a total interest rate of 12.875% , and (2) the lender’s right to declare all outstanding principal and interest immediately payable upon an event of default. These two features were analyzed and determined to be embedded derivatives to be valued as separate financial instruments. These embedded derivatives were bundled and valued as one compound derivative in accordance with the applicable accounting guidance for derivatives and hedging transactions. The Company determined that, due to the unlikely event of default, the embedded derivatives have a de minimis value as of March 31, 2021. The derivative liability will be remeasured at fair value at each reporting date, with changes in fair value being recorded as other income (expense) in the condensed consolidated statements of operations and comprehensive loss. The Athyrium Credit Facility is secured by a pledge of substantially all of the Company’s assets and contains affirmative and negative covenants customary for financings of this type, including limitations on the Company’s and its subsidiaries’ ability to, among other things, incur and prepay additional debt, grant or permit additional liens, make investments and acquisitions, merge or consolidate with others, dispose of assets, change in the nature of business, enter into sale and leaseback transactions, make distributions, and enter into affiliate transactions, in each case, subject to certain exceptions. In addition, the Athyrium Credit Facility also contains a financial covenant requiring the Company to maintain at least $10,000 of cash and cash equivalents. As a result of this financial covenant, the Company has recorded $10,000 as restricted cash on the condensed consolidated balance sheets as of March 31, 2021 and December 31, 2020. In connection with the Athyrium Credit Facility, the Company issued a warrant (“Warrant”), to purchase up to 270,835 shares of the Company’s common stock, at an exercise price per share of $12.18456. The Warrant is immediately exercisable as to 184,660 shares. The remaining 86,175 shares under the Warrant were exercisable only upon the Company’s draw of the Term Loan B and, as a result, the remaining 86,175 shares under the Warrant are no longer exercisable. The Warrant is exercisable through October 1, 2025 and is classified as an equity instrument. The Company allocated the proceeds from the Term Loan A to the Warrant using the relative fair value method. The fair value of the Warrant of $1,900 was recognized as equity with a corresponding debt discount of $1,980. In addition, the Company paid certain fees to Athyrium and other third-party service providers. These fees paid to Athyrium were recorded as a debt discount while the fees paid to other third-party service providers were recorded as debt issuance cost. These costs, along with the fair value of the Warrant of $1,900 are being amortized using the effective interest method over the term of the Athyrium Credit Facility. The amortization of debt discount and debt issuance cost is included in interest expense within the condensed consolidated statements of operations and comprehensive loss. As of March 31, 2021 and March 31, 2020, the effective interest rate was 11.63%, which takes into consideration the non-cash accretion of the exit fee and the amortization of the debt discount and issuance costs. During the three months ended March 31, 2021, the Company recognized interest expense of $2,092, which consisted of amortization of the debt discount of $241, and the contractual coupon interest expense of $1,851. During the three months ended March 31, 2020, the Company recognized interest expense of $2,089, which consisted of amortization of the debt discount of $217, and the contractual coupon interest expense of $1,872. The components of the carrying value of the debt as of March 31, 2021 and December 31, 2020 are detailed below: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Principal loan balance ​ $ 75,000 ​ $ 75,000 Unamortized debt discount and issuance cost ​ ​ (2,848) ​ ​ (3,088) Cumulative accretion of exit fee ​ ​ 369 ​ ​ 331 Long-term debt, net ​ $ 72,521 ​ $ 72,243 ​ The annual principal payments due under the Athyrium Credit Facility as of March 31, 2021 were as follows: ​ ​ ​ ​ Years Ending December 31, ​ ​ 2021 (remaining nine months) ​ $ — 2022 ​ ​ 16,665 2023 ​ ​ 33,330 2024 ​ ​ 25,005 Total ​ $ 75,000 ​

WARRANTS

WARRANTS3 Months Ended
Mar. 31, 2021
WARRANTS
WARRANTS10. WARRANTS The following table summarizes the common stock warrants outstanding as of March 31, 2021 and December 31, 2020, each exercisable into the number of shares of common stock set forth below as of the specified dates: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shares Exercisable at ​ ​ Exercise Expiration Exercisable March 31, December 31, Issued Price ​ Date ​ From ​ 2021 ​ 2020 2013 ​ $ 7.50 ​ April 2021 ​ July 2017 ​ 33,333 ​ 33,333 2014 ​ $ 7.50 November 2024 July 2017 ​ 16,000 ​ 16,000 2016 ​ $ 8.27 October 2026 September 2017 ​ 14,512 ​ 14,512 2018 ​ $ 12.18 ​ October 2025 ​ October 2018 ​ 184,660 ​ 184,660 ​ ​ ​ ​ ​ ​ ​ ​ ​ 248,505 ​ 248,505 ​

EQUITY FINANCINGS

EQUITY FINANCINGS3 Months Ended
Mar. 31, 2021
EQUITY FINANCINGS
EQUITY FINANCINGS11. EQUITY FINANCINGS On August 9, 2018, the Company filed a shelf registration statement on Form S-3 with the SEC, which was declared effective on August 27, 2018 (the “2018 Shelf Registration”). Under the 2018 Shelf Registration, the Company could initially offer and sell up to $250,000 of a variety of securities including common stock, preferred stock, warrants, depositary shares, debt securities, purchase contracts, purchase units or any combination of such securities during the three-year period that commenced upon the 2018 Shelf Registration becoming effective. In connection with the filing of the 2018 Shelf Registration, the Company entered into a sales agreement (the “2018 Sales Agreement”) with Jefferies, LLC (“Jefferies”) pursuant to which the Company may issue and sell, from time to time, up to an aggregate of $50,000 of its common stock in an at-the-market equity offering (“ATM Offering”) through Jefferies, as sales agent. Through the first quarter of 2020, the Company issued an aggregate of 4,945,605 shares of its common stock under the ATM Offering, resulting in net proceeds to the Company of $25,605 . On March 10, 2020 , the Company notified Jefferies that it was suspending and terminating the prospectus related to the 2018 Sales Agreement. On March 11, 2020, the Company sold 16,000,000 shares of its common stock (the “2020 Offering Shares”) in an underwritten offering (the “2020 Offering”), pursuant to the 2018 Shelf Registration, at a public offering price of $7.89 per share, resulting in net proceeds of $118,207 , after underwriting discounts, commissions, and offering expenses. In addition, the underwriters of the 2020 Offering were granted the option for a period of 30 days to purchase up to an additional 2,400,000 shares of common stock offered in the public offering at the public offering price, less underwriting discounts, commissions and offering expenses. On April 3, 2020, the underwriters exercised their option and purchased an additional 979,371 shares of common stock at $7.89 per share, resulting in net proceeds to the Company of $7,216 , after underwriting discounts, commissions, and offering expenses. The total number of shares sold by the Company in the 2020 Offering was 16,979,371 , resulting in total net proceeds to the Company, after underwriting discounts, commissions, and offering expenses, of $125,423 . was $18,334 of securities available to be issued under the 2018 Shelf Registration as of March 31, 2021. On May 7, 2020, the Company filed a shelf registration statement on Form S-3 with the SEC, which was declared effective on May 19, 2020 (the “2020 Shelf Registration”). Under the 2020 Shelf Registration, the Company may offer and sell up to $350,000 of a variety of securities including common stock, preferred stock, warrants, depositary shares, debt securities or units during the three-year period that commenced upon the 2020 Shelf Registration becoming effective. In connection with the filing of the 2020 Shelf Registration, the Company entered into an amended and restated sales agreement with Jefferies pursuant to which

STOCKBASED COMPENSATION

STOCKBASED COMPENSATION3 Months Ended
Mar. 31, 2021
STOCKBASED COMPENSATION
STOCK-BASED COMPENSATION12. STOCK‑BASED COMPENSATION During the three months ended March 31, 2021, the Company granted options for the purchase of 1,512,964 shares of common stock including 56,700 non-statutory stock options granted to new employees and 431,333 restricted stock units. In January 2021, employees of the Company purchased an aggregate of 74,847 shares under the ESPP. The assumptions used in determining fair value of the stock options granted during the three months ended March 31, 2021 are as follows: ​ ​ ​ ​ ​ ​ Three Months Ended March 31, 2021 Expected volatility 73.0% – 73.7% Risk-free interest rate 0.50% – 1.07% Expected dividend yield ​ 0% ​ Expected term (in years) 6.03 – 6.08 ​ During the three months ended March 31, 2021 the weighted average grant-date fair value of options granted was $4.42. In June 2020, the Company issued 693,537 PSUs to certain executives and other employees tied to certain performance criteria, which will vest, if at all, as to 50% on the first anniversary of satisfying the performance criteria and the remaining 50% vesting upon the second anniversary of satisfying the performance criteria. The Company has determined that the performance criteria for these awards has been achieved but the awards have not vested as of March 31, 2021. As of March 31, 2021, a total of 1,365,592 RSUs and PSUs were unvested and outstanding. Stock-based compensation expense was classified in the condensed consolidated statements of operations and comprehensive loss as follows for the three months ended March 31, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ 2021 2020 Cost of product revenues ​ $ 34 ​ $ 20 Research and development ​ ​ 966 ​ ​ 723 Selling, general and administrative ​ ​ 3,702 ​ ​ 1,754 Total ​ $ 4,702 ​ $ 2,497 ​

INCOME TAXES

INCOME TAXES3 Months Ended
Mar. 31, 2021
INCOME TAXES
INCOME TAXES13. INCOME TAXES The Company did not record a provision or benefit for income taxes during the three months ended March 31, 2021 and 2020. The Company continues to maintain a full valuation allowance for its U.S. federal and state deferred tax assets. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its generation of limited revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Management reevaluates the positive and negative evidence at each reporting period. Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the net operating loss carryforward period. Under the provisions of Section 382 of the Internal Revenue Code of 1986, as amended, certain substantial changes in the Company’s ownership, including a sale of the Company, or significant changes in ownership due to sales of equity, may have limited, or may limit in the future, the amount of net operating loss carryforwards, which could be used annually to offset future taxable income. The Company previously completed an analysis and determined that an ownership change has materially limited the net operating loss carryforwards and research and development tax credits available to offset future tax liabilities. The Company may be further limited by any changes that may have occurred or may occur subsequent to December 31, 2020. The Company files its corporate income tax returns in the United States and various states. All tax years since the date of incorporation remain open to examination by the major taxing jurisdictions (state and federal) to which the Company is subject, as carryforward attributes generated in years past may still be adjusted upon examination by the Internal Revenue Service (“IRS”) or other authorities if they have or will be used in a future period. The Company is not currently under examination by the IRS or any other jurisdictions for any tax year. As of March 31, 2021and 2020, the Company had no uncertain tax positions. The Company’s policy is to recognize interest and penalties related to income tax matters as a component of income tax expense, of which no interest or penalties were recorded for the three months ended March 31, 2021 and 2020.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES3 Months Ended
Mar. 31, 2021
COMMITMENTS AND CONTINGENCIES.
COMMITMENTS AND CONTINGENCIES.14. COMMITMENTS AND CONTINGENCIES License Agreement After 2016 and until the first commercial sale of product, which occurred in January 2019, the minimum annual payment was $38. Upon the first commercial sale of INVELTYS, the annual minimum payment increased to $113. The Company is obligated to pay JHU low single-digit running royalties based upon a percentage of net sales of the licensed products, which is applied to the annual minimum payment. The Company also has an obligation to pay JHU certain one-time development and commercial milestone payments. During the three months ended March 31, 2021 and 2020, the Company paid JHU $22 and $12, respectively, in royalty payments associated with the sales of EYSUVIS and INVELTYS. The Company paid JHU a $150 milestone payment during the three months ended March 31, 2021, which was triggered by the first commercial sale of EYSUVIS in the United States in December 2020. The Company recorded a credit for other expenses related to the JHU agreement of $51 during the three months ended March 31, 2021 and other expenses of $46 for the three months ended March 31, 2020. Litigation Other Commitments The Company has the following minimum purchase obligations for EYSUVIS and INVELTYS as of March 31, 2021: ​ ​ ​ ​ ​ Years Ending December 31, ​ ​ 2021 (remaining nine months) ​ $ 2,295 2022 ​ ​ 5,390 2023 ​ ​ 6,285 2024 ​ ​ 7,875 2025 ​ ​ 8,199 Thereafter ​ ​ 17,925 Total minimum purchase commitments ​ $ 47,969 ​

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS3 Months Ended
Mar. 31, 2021
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS​ 15. SUBSEQUENT EVENTS ​ Entry into Loan and Security Agreement ​ On May 4, 2021 (the “Closing Date”), the Company entered into a Loan and Security Agreement with Oxford Finance LLC, in its capacity as lender (in such capacity, the “Lender”), and in its capacity as collateral agent (in such capacity, the “Agent”), pursuant to which a term loan of up to an aggregate principal amount of $125,000 is available to the Company, consisting of (i) a tranche A term loan that was disbursed on the Closing Date in the aggregate principal amount of $80,000; (ii) a contingent tranche B term loan in the aggregate principal amount of $20,000 available to the Company through June 30, 2023 and within 90 days of the Company achieving trailing 6-month 6-month ​ The term loans bear interest at a floating rate equal to the greater of 30-day LIBOR and 0.11%, plus 7.89%. The Loan Agreement provides for interest-only payments until December 1, 2024 if neither the tranche B term loan nor the tranche C term loan are made, and until June 1, 2025 if either the tranche B term loan or the tranche C term loan is made (the “Amortization Date”). The aggregate outstanding principal balance of the term loans are required to be repaid in monthly installments starting on the Amortization Date based on a repayment schedule equal to (i) 18 months if neither the tranche B term loan nor the tranche C term loan is made and (ii) 12 months if either the tranche B term loan or the tranche C term loan is made. All unpaid principal and accrued and unpaid interest with respect to each term loan is due and payable in full on May 1, 2026 (the “Maturity Date”). ​ The Company paid a facility fee of $400 on the Closing Date and has agreed to pay a facility fee of $100 upon closing of the tranche B term loan and a $125 facility fee upon the closing of the tranche C term loan. The Company will be required to make a final payment fee of 7.00% of the original principal amount of any funded term loan payable on the earlier of (i) the prepayment of the term loan in full or (ii) the Maturity Date. At the Company’s option, the Company may elect to prepay all, but not less than all, of the outstanding loans, subject to a prepayment fee equal to the following percentage of the principal amount being prepaid: 3.00% if an advance is prepaid during the first 12 months following the applicable advance date, 2.00% if an advance is prepaid after 12 months but prior to 24 months following the applicable advance date, and 1.00% if an advance is prepaid any time after 24 months following the applicable advance date but prior to the Maturity Date. ​ In connection with its entry into the Loan Agreement, the Company granted the Agent a security interest in substantially all of the Company’s personal property owned or later acquired, including intellectual property. The Loan Agreement also contains customary representations and warranties and affirmative and negative covenants, as well as customary events of default. Certain of the customary negative covenants limit the ability of the Company and certain of its subsidiaries, among other things, to incur future debt, grant liens, make investments, make acquisitions, distribute dividends, make certain restricted payments and sell assets, subject in each case to certain exceptions. ​ Termination of Athyrium Credit Facility ​ On May 4, 2021, concurrently with the closing of the Loan Agreement and the initial borrowing of the tranche A loan, the Company utilized substantially all of the proceeds from the tranche A loan to repay in full all outstanding amounts owed under the Athyrium Credit Facility, and terminated all commitments by Athyrium to extend further credit thereunder and all guarantees and security interests granted by the Company to the lenders thereunder. In connection with the termination of the Athyrium Credit Facility, the Company paid to the lenders a prepayment premium of $2,250 and an exit fee of $750. ​

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)3 Months Ended
Mar. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Recent Accounting PronouncementsRecent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Financial Instruments - Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) ,

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)3 Months Ended
Mar. 31, 2021
FAIR VALUE OF FINANCIAL INSTRUMENTS
Schedule of assets and liabilities measured at fair value on a recurring basis​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ Fair Value ​ Level 1 ​ Level 2 ​ Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents ​ $ 112,071 ​ $ 112,071 ​ $ — ​ $ — Short-term investments ​ ​ 28,015 ​ ​ 28,015 ​ ​ — ​ ​ — Total Assets ​ $ 140,086 ​ $ 140,086 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ Fair Value ​ Level 1 ​ Level 2 ​ Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents ​ $ 63,811 ​ $ 63,811 ​ $ — ​ $ — Short-term investments ​ ​ 76,276 ​ ​ 76,276 ​ ​ — ​ ​ — Total Assets ​ $ 140,087 ​ $ 140,087 ​ $ — ​ $ —

INVESTMENTS (Tables)

INVESTMENTS (Tables)3 Months Ended
Mar. 31, 2021
INVESTMENTS
Schedule of investments by security type​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ ​ Gross ​ Gross ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost ​ Gains ​ Losses ​ Value U.S. treasury securities $ 9,700 ​ $ 1 ​ $ — ​ $ 9,701 U.S. government agencies securities ​ 18,312 ​ ​ 2 ​ ​ — ​ ​ 18,314 Total $ 28,012 ​ $ 3 ​ $ — ​ $ 28,015 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ Gross ​ Gross ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost ​ Gains ​ Losses ​ Value U.S. treasury securities $ 26,744 ​ $ 2 ​ $ — ​ $ 26,746 U.S. government agencies securities ​ 49,528 ​ ​ 2 ​ ​ — ​ ​ 49,530 Total $ 76,272 ​ $ 4 ​ $ — ​ $ 76,276

REVENUE & ACCOUNTS RECEIVABLE_2

REVENUE & ACCOUNTS RECEIVABLE, NET (Tables)3 Months Ended
Mar. 31, 2021
REVENUE & ACCOUNTS RECEIVABLE, NET
Schedule of co-pay assistance program​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trade Discounts, ​ ​ ​ ​ ​ ​ ​ ​ Allowances and ​ ​ ​ ​ Rebates and ​ ​ Chargebacks (1) Product Returns (2) Incentives (3) Balance as of December 31, 2020 ​ $ 1,157 ​ $ 600 ​ $ 4,904 Provision related to current period sales ​ ​ 2,201 ​ ​ 245 ​ ​ 10,216 Changes in estimate related to prior period sales ​ ​ 3 ​ ​ 30 ​ ​ (26) Credit/payments made ​ ​ (1,823) ​ ​ (419) ​ ​ (7,880) Balance as of March 31, 2021 ​ $ 1,538 ​ $ 456 ​ $ 7,214 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trade Discounts, ​ ​ ​ ​ ​ ​ ​ ​ Allowances and ​ ​ ​ ​ Rebates and ​ ​ Chargebacks (1) Product Returns (2) Incentives (3) Balance as of December 31, 2019 ​ $ 1,783 ​ $ 180 ​ $ 10,044 Provision related to current period sales ​ ​ 725 ​ ​ — ​ ​ 4,576 Changes in estimate related to prior period sales ​ ​ 2 ​ ​ (66) ​ ​ 93 Credit/payments made ​ ​ (1,114) ​ ​ — ​ ​ (8,090) Balance as of March 31, 2020 ​ $ 1,396 ​ $ 114 ​ $ 6,623 (1) Trade discounts, allowances and chargebacks include fees for distribution service fees, prompt pay and other discounts, and chargebacks. Estimated trade discounts, allowances and chargebacks are deducted from gross revenue at the time revenues are recognized and are recorded as a reduction to accounts receivable on the Company’s condensed consolidated balance sheets. (2) Estimated provisions for product returns are deducted from gross revenues at the time revenues are recognized and are included in accrued expenses and other current liabilities on the Company’s condensed consolidated balance sheets. (3) Rebates and incentives include managed care rebates, government rebates, co-pay program incentives, and sales incentives and allowances. Estimated provisions for rebates and discounts are deducted from gross revenues at the time revenues are recognized and are included in accrued expenses and other current liabilities on the Company’s condensed consolidated balance sheets.

INVENTORY (Tables)

INVENTORY (Tables)3 Months Ended
Mar. 31, 2021
INVENTORY
Schedule of InventoryInventory consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Raw materials ​ $ 995 ​ $ 801 Work in progress ​ ​ 9,303 ​ ​ 6,437 Finished goods ​ ​ 4,143 ​ ​ 4,210 Total inventory ​ $ 14,441 ​ $ 11,448

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)3 Months Ended
Mar. 31, 2021
ACCRUED EXPENSES
Schedule of accrued expenses​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Compensation and benefits ​ $ 5,550 ​ $ 9,676 Accrued revenue reserves (1) ​ ​ 6,345 ​ ​ 5,224 Commercial costs ​ ​ 949 ​ ​ 2,103 Professional services ​ ​ 750 ​ ​ 926 Contract manufacturing ​ ​ 826 ​ ​ 336 Development costs ​ ​ 206 ​ ​ 154 Other ​ ​ 523 ​ ​ 552 Accrued expenses ​ $ 15,149 ​ $ 18,971 (1) There were additional revenue reserves included in accounts payable of $1,325 and $280, as of March 31, 2021 and December 31, 2020, respectively.

LEASES (Tables)

LEASES (Tables)3 Months Ended
Mar. 31, 2021
LEASES
Schedule of lease costThe components of lease expense and related cash flows were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ 2021 2020 Lease cost ​ ​ Operating lease cost ​ $ 1,216 ​ $ 1,185 Variable lease cost ​ ​ 509 ​ ​ 410 Total lease cost ​ $ 1,725 ​ $ 1,595 ​ ​ ​ ​ ​ ​ ​ Operating cash outflows from operating leases ​ $ 1,584 ​ $ 1,444
Schedule of weighted average remaining lease term and weighted average discount rate of operating leasesThe weighted average remaining lease term and weighted average discount rate of operating leases are as follows: ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Weighted average remaining lease term 10.1 years ​ 10.3 years Weighted average discount rate 9.6% ​ 9.8%

DEBT (Tables)

DEBT (Tables)3 Months Ended
Mar. 31, 2021
DEBT
Schedule of carrying value of debtThe components of the carrying value of the debt as of March 31, 2021 and December 31, 2020 are detailed below: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Principal loan balance ​ $ 75,000 ​ $ 75,000 Unamortized debt discount and issuance cost ​ ​ (2,848) ​ ​ (3,088) Cumulative accretion of exit fee ​ ​ 369 ​ ​ 331 Long-term debt, net ​ $ 72,521 ​ $ 72,243
Schedule of maturities of long-term debtThe annual principal payments due under the Athyrium Credit Facility as of March 31, 2021 were as follows: ​ ​ ​ ​ Years Ending December 31, ​ ​ 2021 (remaining nine months) ​ $ — 2022 ​ ​ 16,665 2023 ​ ​ 33,330 2024 ​ ​ 25,005 Total ​ $ 75,000

WARRANTS (Tables)

WARRANTS (Tables)3 Months Ended
Mar. 31, 2021
WARRANTS
Schedule of outstanding warrantsThe following table summarizes the common stock warrants outstanding as of March 31, 2021 and December 31, 2020, each exercisable into the number of shares of common stock set forth below as of the specified dates: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shares Exercisable at ​ ​ Exercise Expiration Exercisable March 31, December 31, Issued Price ​ Date ​ From ​ 2021 ​ 2020 2013 ​ $ 7.50 ​ April 2021 ​ July 2017 ​ 33,333 ​ 33,333 2014 ​ $ 7.50 November 2024 July 2017 ​ 16,000 ​ 16,000 2016 ​ $ 8.27 October 2026 September 2017 ​ 14,512 ​ 14,512 2018 ​ $ 12.18 ​ October 2025 ​ October 2018 ​ 184,660 ​ 184,660 ​ ​ ​ ​ ​ ​ ​ ​ ​ 248,505 ​ 248,505

STOCKBASED COMPENSATION (Tables

STOCKBASED COMPENSATION (Tables)3 Months Ended
Mar. 31, 2021
STOCKBASED COMPENSATION
Schedule of assumptions used in determining fair value of the stock options granted​ ​ ​ ​ ​ ​ Three Months Ended March 31, 2021 Expected volatility 73.0% – 73.7% Risk-free interest rate 0.50% – 1.07% Expected dividend yield ​ 0% ​ Expected term (in years) 6.03 – 6.08
Schedule of stock based compensation expense​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ 2021 2020 Cost of product revenues ​ $ 34 ​ $ 20 Research and development ​ ​ 966 ​ ​ 723 Selling, general and administrative ​ ​ 3,702 ​ ​ 1,754 Total ​ $ 4,702 ​ $ 2,497

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)3 Months Ended
Mar. 31, 2021
COMMITMENTS AND CONTINGENCIES.
Schedule of minimum purchase obligations​ ​ ​ ​ ​ Years Ending December 31, ​ ​ 2021 (remaining nine months) ​ $ 2,295 2022 ​ ​ 5,390 2023 ​ ​ 6,285 2024 ​ ​ 7,875 2025 ​ ​ 8,199 Thereafter ​ ​ 17,925 Total minimum purchase commitments ​ $ 47,969

NATURE OF BUSINESS AND BASIS _2

NATURE OF BUSINESS AND BASIS OF PRESENTATION (Details) - USD ($) $ in Thousands3 Months Ended
Mar. 31, 2021Mar. 31, 2020Dec. 31, 2020
Stock-based compensation
Accumulated deficit $ (430,195) $ (399,783)
Options
Stock-based compensation
Outstanding securities excluded from the computation of diluted weighted average shares outstanding (in shares)10,120,453 8,817,943
RSU and PSU
Stock-based compensation
Outstanding securities excluded from the computation of diluted weighted average shares outstanding (in shares)1,365,592
Warrants
Stock-based compensation
Outstanding securities excluded from the computation of diluted weighted average shares outstanding (in shares)248,505 297,988

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring and Nonrecurring Fair value Measurements Within Hierarchy (Details) - Recurring - USD ($) $ in ThousandsMar. 31, 2021Dec. 31, 2020
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Financial assets by level within fair value hierarchy $ 140,086 $ 140,087
Level 1 | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Financial assets by level within fair value hierarchy112,071 63,811
Level 1 | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Financial assets by level within fair value hierarchy28,015 76,276
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Financial assets by level within fair value hierarchy140,086 140,087
Fair Value | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Financial assets by level within fair value hierarchy112,071 63,811
Fair Value | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Financial assets by level within fair value hierarchy $ 28,015 $ 76,276

FAIR VALUE OF FINANCIAL INSTR_4

FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair value measurement levels (Details) - USD ($) $ in Thousands3 Months Ended12 Months Ended
Mar. 31, 2021Dec. 31, 2020
FAIR VALUE OF FINANCIAL INSTRUMENTS
Transfer from level 1 to level 2, Assets $ 0 $ 0
Transfer from level 2 to level 1, Assets0 0
Transfer from level 1 to level 2, Liabilities0 0
Transfer from level 2 to level 1, Liabilities0 0
Transfer into level 3, Assets0 0
Transfer out of level 3, Assets0 0
Transfer into level 3, Liability0 0
Transfer out of level 3, Liability $ 0 $ 0

INVESTMENTS (Details)

INVESTMENTS (Details) - USD ($) $ in ThousandsMar. 31, 2021Dec. 31, 2020
Investments by security type
Amortized Cost $ 28,012 $ 76,272
Gross Unrealized Gains3 4
Fair Value28,015 76,276
U.S. treasury securities
Investments by security type
Amortized Cost9,700 26,744
Gross Unrealized Gains1 2
Fair Value9,701 26,746
U.S. government agencies securities
Investments by security type
Amortized Cost18,312 49,528
Gross Unrealized Gains2 2
Fair Value $ 18,314 $ 49,530

REVENUE & ACCOUNTS RECEIVABLE_3

REVENUE & ACCOUNTS RECEIVABLE, NET - Co-pay Assistance Program (Details)-Q - USD ($) $ in Thousands3 Months Ended
Mar. 31, 2021Mar. 31, 2020
Trade Discounts, Allowances and Chargebacks
Beginning balance $ 1,157 $ 1,783
Provision related to current period sales2,201 725
Changes in estimate related to prior period sales3 2
Credit/payments made(1,823)(1,114)
Ending balance1,538 1,396
Product Returns
Beginning balance600 180
Provision related to current period sales245
Changes in estimate related to prior period sales30 (66)
Credit/payments made(419)
Ending balance456 114
Rebates and Incentives
Beginning balance4,904 10,044
Provision related to current period sales10,216 4,576
Changes in estimate related to prior period sales(26)93
Credit/payments made(7,880)(8,090)
Ending balance $ 7,214 $ 6,623

REVENUE & ACCOUNTS RECEIVABLE_4

REVENUE & ACCOUNTS RECEIVABLE, NET - Accounts Receivable, net (Details) - USD ($) $ in ThousandsMar. 31, 2021Mar. 31, 2020
Allowance for doubtful accounts $ 0 $ 0
Sales discounts and contractual fee for service arrangements
Allowance for doubtful accounts $ 1,538 $ 1,396

INVENTORY (Details)

INVENTORY (Details) - USD ($) $ in ThousandsMar. 31, 2021Dec. 31, 2020
INVENTORY
Raw Materials $ 995 $ 801
Work in Progress9,303 6,437
Finished Goods4,143 4,210
Total inventory14,441 11,448
Inventory8,241 5,229
Long-term inventory $ 6,200 $ 6,219

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in ThousandsMar. 31, 2021Dec. 31, 2020
Compensation and benefits $ 5,550 $ 9,676
Accrued revenue reserves6,345 5,224
Commercial costs949 2,103
Professional services750 926
Contract manufacturing826 336
Development costs206 154
Other523 552
Accrued expenses15,149 18,971
Accounts payable
Accrued revenue reserves $ 1,325 $ 280

LEASES (Details)

LEASES (Details) $ in Thousands3 Months Ended12 Months Ended
Mar. 31, 2021USD ($)itemMar. 31, 2020USD ($)Dec. 31, 2019USD ($)itemDec. 31, 2020USD ($)
Leases
Restricted cash $ 12,492 $ 12,584
Variable lease cost $ 509 410
Number of vehicles leased under a master fleet lease agreement | item65
Number of additional vehicles leased | item54
Term of vehicle lease3 years3 years
Amount borrowed $ 450
Lease cost
Operating lease cost $ 1,216 1,185
Variable Lease, Cost509 410
Total lease cost1,725 1,595
Operating cash outflows from operating leases $ 1,584 1,444
Remaining lease term10 years 1 month 6 days10 years 3 months 18 days
Weighted average discount rate9.60%9.80%
Operating Lease, Right-of-Use Asset $ 28,542 $ 27,853
Watertown Lease
Leases
Restricted cash2,042
Variable lease cost $ 363 348
Remaining lease term10 years 7 months 6 days
Lease cost
Variable Lease, Cost $ 363 $ 348

DEBT - Athyrium Credit Facility

DEBT - Athyrium Credit Facility (Details) $ / shares in Units, $ in ThousandsOct. 01, 2018USD ($)$ / sharessharesMar. 31, 2021USD ($)item$ / sharessharesMar. 31, 2020USD ($)Dec. 31, 2020USD ($)shares
Debt instruments
Warrant exercisable | shares248,505 248,505
Interest expense $ 2,141 $ 2,128
Warrants 2018
Debt instruments
Exercise Price | $ / shares $ 12.18
Warrant exercisable | shares184,660 184,660
Athyrium Credit Facility
Debt instruments
Aggregate principal amount $ 75,000 $ 75,000
Cumulative accretion of exit fee369 331
Debt issuance costs2,848 3,088
Interest expense2,092 2,089
Amortization of debt discount241 217
Contractual coupon interest $ 1,851 $ 1,872
Athyrium | Athyrium Credit Facility
Debt instruments
Aggregate principal amount $ 110,000
Debt term (in years)6 years
Present value of prepayments if prepayment occurs prior to the second anniversary (as a percent)105.00%
Prepayments if prepayment occurs on or after the second anniversary of the applicable date of issuance but prior to the third anniversary (as a percent)3.00%
Prepayments if prepayment occurs on or after the third anniversary (as a percent)2.00%
Prepayments if prepayment occurs after the fourth anniversary (as a percent)0.00%
Additional interest rate upon an event of default accrued (as a percent)3.00%
Total interest rate (as a percent)12.875%
Number of features of embedded derivative | item2
Number of derivatives | item1
Financial covenant amount $ 10,000
Restricted Cash and Cash Equivalents $ 10,000 $ 10,000
Effective interest rate11.63%11.63%
Athyrium | Athyrium Credit Facility | Warrants 2018
Debt instruments
Warrant to purchase shares of common stock | shares270,835
Exercise Price | $ / shares $ 12.18456
Warrant exercisable | shares184,660
Remaining warrant exercisable upon condition | shares86,175
Initial fair value of the Warrant $ 1,900
Unamortized discount1,980
Athyrium | Tranche A term loan
Debt instruments
Aggregate principal amount $ 75,000
Interest rate (as a percent)9.875%
Exit fee of the total principal payments (as a percent)1.00%
Cumulative accretion of exit fee $ 750
Athyrium | Contingent tranche B term loan
Debt instruments
Aggregate principal amount $ 35,000

DEBT - Carrying Value (Details)

DEBT - Carrying Value (Details) - USD ($) $ in ThousandsMar. 31, 2021Dec. 31, 2020
Debt instruments
Long-term debt, net $ 72,521 $ 72,243
Athyrium Credit Facility
Debt instruments
Principal Loan Balance75,000 75,000
Unamortized debt discount and issuance cost(2,848)(3,088)
Cumulative accretion of exit fee369 331
Long-term debt, net $ 72,521 $ 72,243

DEBT - Future annual principal

DEBT - Future annual principal payments (Details) - Athyrium Credit Facility $ in ThousandsMar. 31, 2021USD ($)
Maturities of long-term debt
2022 $ 16,665
202333,330
202425,005
Total $ 75,000

WARRANTS (Details)

WARRANTS (Details) - $ / shares3 Months Ended12 Months Ended
Mar. 31, 2021Dec. 31, 2020
Preferred stock warrants
Shares Exercisable248,505 248,505
Warrants 2013
Preferred stock warrants
Exercise Price $ 7.50
Shares Exercisable33,333 33,333
Warrants 2014
Preferred stock warrants
Exercise Price $ 7.50
Shares Exercisable16,000 16,000
Warrants 2016
Preferred stock warrants
Exercise Price $ 8.27
Shares Exercisable14,512 14,512
Warrants 2018
Preferred stock warrants
Exercise Price $ 12.18
Shares Exercisable184,660 184,660

EQUITY FINANCINGS (Details)

EQUITY FINANCINGS (Details) - USD ($) $ / shares in Units, $ in ThousandsApr. 01, 2021May 07, 2020Apr. 03, 2020Mar. 11, 2020Oct. 05, 2018Aug. 27, 2018Mar. 31, 2021Dec. 31, 2020Mar. 31, 2020
Equity Offerings
Common stock offering, net of offering costs $ 118,207
Net proceeds $ 34,709 130,754
Offering costs $ 8,011
Underwriter's option
Equity Offerings
Common stock offering, net of offering costs (in shares)979,371 2,400,000
Net proceeds $ 7,216
Period granted30 days
Price per share $ 7.89
Shelf Registration
Equity Offerings
Additional authorized value of securities $ 275,000
Common stock offering, net of offering costs (in shares)30,549,976
Common stock offering, net of offering costs $ 231,666
Share authorized value (shelf)18,334
Registration period3 years3 years
Sales agreement $ 50,000
Shelf Registration | Maximum
Equity Offerings
Additional authorized value of securities $ 350,000 $ 250,000
2020 Offering
Equity Offerings
Common stock offering, net of offering costs (in shares)16,979,371 16,000,000
Price per share $ 7.89
Net proceeds $ 125,423 $ 118,207
ATM
Equity Offerings
Additional authorized value of securities $ 18,051
Common stock offering, net of offering costs (in shares)837,257 4,746,072 2,821,059 4,945,605
Common stock offering, net of offering costs $ 6,022 $ 34,709 $ 20,612
Net proceeds $ 25,605
ATM | Maximum
Equity Offerings
Additional authorized value of securities $ 75,000

STOCKBASED COMPENSATION - Induc

STOCKBASED COMPENSATION - Inducement Stock Option Awards (Details) - $ / shares1 Months Ended3 Months Ended
Jan. 31, 2021Mar. 31, 2021
Stock-based compensation
Granted (in shares)1,512,964
Weighted average grant date fair value of options granted $ 4.42
ESPP
Stock-based compensation
Issuance under employee stock purchase plan (in shares)74,847
Non-statutory Stock Options
Stock-based compensation
Granted (in shares)56,700
RSU
Stock-based compensation
Granted (in shares)431,333

STOCKBASED COMPENSATION - Fair

STOCKBASED COMPENSATION - Fair Value Assumptions (Details)3 Months Ended
Mar. 31, 2021
Assumptions used in determining fair value of the stock options granted
Expected volatility (minimum)73.00%
Expected volatility (maximum)73.70%
Risk-free interest rate (minimum)0.50%
Risk-free interest rate (maximum)1.07%
Expected dividend yield0.00%
Minimum
Assumptions used in determining fair value of the stock options granted
Expected term (in years)6 years 10 days
Maximum
Assumptions used in determining fair value of the stock options granted
Expected term (in years)6 years 29 days

STOCKBASED COMPENSATION - RSU a

STOCKBASED COMPENSATION - RSU and PSU (Details) - shares1 Months Ended
Jun. 30, 2020Mar. 31, 2021
Stock-based compensation
Non-vested and outstanding balance at end of period (in shares)1,365,592
Executive Officer | PSU | First anniversary
Stock-based compensation
Granted (in shares)693,537
Vesting percentage50.00%
Executive Officer | PSU | Second anniversary
Stock-based compensation
Vesting percentage50.00%

STOCKBASED COMPENSATION - Stock

STOCKBASED COMPENSATION - Stock-based compensation expense (Details) - USD ($) $ in Thousands3 Months Ended
Mar. 31, 2021Mar. 31, 2020
Stock-based compensation
Stock based compensation expense $ 4,702 $ 2,497
Cost of product revenues
Stock-based compensation
Stock based compensation expense34 20
Research and development
Stock-based compensation
Stock based compensation expense966 723
Selling, general and administrative
Stock-based compensation
Stock based compensation expense $ 3,702 $ 1,754

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($)3 Months Ended
Mar. 31, 2021Mar. 31, 2020
INCOME TAXES
Uncertain tax positions $ 0 $ 0
Interest or penalties recorded $ 0 $ 0

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - License Agreement (Details) - USD ($) $ in Thousands3 Months Ended
Mar. 31, 2021Mar. 31, 2020
Contingencies
Research and development expenses $ 3,126 $ 5,434
The Johns Hopkins University ("JHU")
Contingencies
Minimum annual payment38
License fee, if the company achieves the first commercial sale113
First commercial sale milestone22 12
Research and development expenses51 $ 46
Milestone payment $ 150

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Future minimum obligations (Details) $ in ThousandsMar. 31, 2021USD ($)
Minimum obligations due under its license agreements
2021 (remaining nine months) $ 2,295
20225,390
20236,285
20247,875
20258,199
Thereafter17,925
Total minimum license payments $ 47,969

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ in ThousandsMay 04, 2021Mar. 31, 2021Dec. 31, 2020
Athyrium Credit Facility
Subsequent Events
Aggregate principal amount $ 75,000 $ 75,000
Subsequent Event | Athyrium Credit Facility
Subsequent Events
Exit fees paid $ 750
Prepayment premium2,250
Subsequent Event | Loan and Security Agreement with Oxford Finance LLC
Subsequent Events
Aggregate principal amount $ 125,000
Floating interest rate (as a percent)0.11%
Exit fees paid $ 400
Percentage of final payment fees7.00%
Subsequent Event | Loan and Security Agreement with Oxford Finance LLC | Neither the tranche B term loan nor the tranche C term loan is made
Subsequent Events
Duration of periodic monthly payment installments under a scenario18 months
Subsequent Event | Loan and Security Agreement with Oxford Finance LLC | Either tranche B term loan nor tranche C term loan is made
Subsequent Events
Duration of periodic monthly payment installments under a scenario12 months
Subsequent Event | Loan and Security Agreement with Oxford Finance LLC | Advance is prepaid during the first 12 months following the applicable advance date
Subsequent Events
Percentage of pre-payment fees3.00%
Subsequent Event | Loan and Security Agreement with Oxford Finance LLC | Advance is prepaid after 12 months but prior to 24 months following the applicable advance date
Subsequent Events
Percentage of pre-payment fees2.00%
Subsequent Event | Loan and Security Agreement with Oxford Finance LLC | Advance is prepaid any time after 24 months following the applicable advance date but prior to the Maturity Date
Subsequent Events
Percentage of pre-payment fees1.00%
Subsequent Event | Loan and Security Agreement with Oxford Finance LLC | 30-day LIBOR
Subsequent Events
Spread on variable rate7.89%
Subsequent Event | Tranche A term loan
Subsequent Events
Aggregate principal amount $ 80,000
Subsequent Event | Contingent tranche B term loan
Subsequent Events
Aggregate principal amount $ 20,000
Revenue achievement trailing period6 months
Minimum target revenue $ 75,000
Exit fees paid100
Subsequent Event | Contingent tranche C term loan
Subsequent Events
Aggregate principal amount $ 25,000
Revenue achievement trailing period6 months
Minimum target revenue $ 100,000
Exit fees paid $ 125