Gossamer Bio, Inc. (including(including its subsidiaries, referred to as “we,“we,” “us,” “our,”, or the “Company”) is a clinical-stage biopharmaceutical company focused on discovering, acquiring, developing and commercializing therapeutics in the disease areas of immunology, inflammation and oncology. The Company was incorporated in the state of Delaware on October 25, 2015 (originally as FSG Bio, Inc.) and is based in San Diego, California.

The unaudited condensed consolidated financial statements include the accounts of Gossamer Bio, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions among the consolidated entity have been eliminated in consolidation.

Stock Split

In January 2019, the board of directors of the Company approved a reverse stock split of the Company’s common stock at a ratio of one for every 4.5 shares previously held. The reverse stock split became effective on January 23, 2019. All share and per share data included in these condensed consolidated financial statements reflect the stock split.

Initial Public Offering in February 2019

On February 12, 2019, the Company completed its initial public offering (“IPO”) with the sale of 19,837,500 shares of common stock, including shares of common stock issued upon the exercise in full of the underwriters’ option to purchase additional shares, at a public offering price of $16.00 per share, resulting in net proceeds of $291.3 million, after deducting underwriting discounts, commissions, and offering expenses.

In addition, in connection with the completion of the IPO, all of the Company’s outstanding shares of convertible preferred stock were automatically converted into 30,493,460 shares of common stock.

The Company has incurred significant operating losses since its inception. As of March 31, 2019,2023, the Company had an accumulated deficit of $186.5$1,081.4 million. From the Company’s inception through March 31, 2019,2023, the Company has funded its operations primarily through equity financings, including the Company’s IPO which closed on February 12, 2019.and debt financings. The Company raised $601.3$1,062.1 million from October 2017 through March 201931, 2023 through the sale of Series A and Series B Convertible Preferred Stock, convertible note financings,preferred stock, issuance of convertible notes, its initial public offering ("IPO"), the Credit Facility and 2027 Notes (as defined in Note 5 below), and issuance of common stock in May 2020 and July 2022. See Note 5 for additional information regarding the Credit Facility and the completed IPO, after deducting underwriting discounts, commissions, and offering expenses. In addition, the Company received $12.8 million in cash in connection with the January 2018 acquisition of AA Biopharma Inc. 2027 Notes.

The Company expects to continue to incur significant operating losses for the foreseeable future and may never become profitable. As a result, the Company will need to raise additional capital through equity offerings, debt financings or other capital sources, including potential collaborations, licenses and other similar arrangements. Management believes that it has sufficient working capital on hand to fund operations through at least the next twelve12 months from the date these condensed consolidated financial statements were available to be issued. There can be no assurance that the Company will be successful in acquiring additional funding, that the Company’s projections of its future working capital needs will prove accurate, or that any additional funding would be sufficient to continue operations in future years.

2.

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP)(“GAAP”) for interim financial information and with the instructions of the Securities and Exchange Commission (SEC)(“SEC”) on Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, the condensed consolidated financial statements include all adjustments necessary, which are of a normal and recurring nature, for the fair presentation of the Company’s financial position and of the results of operations and cash flows for the periods presented. These financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 20182022 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 22, 2019.17, 2023. The results of operations for the interim period shown in this report are not necessarily indicative of the results that may be expected for any other interim period or for the full year. The balance sheet at December 31, 2018,2022, has been derived from the audited financial statements at that date.

The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at

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the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting period. The most significant estimates in the Company’s condensed consolidated financial statements relate to accrued research and development expenses, the valuation of preferred and common stock, the valuation of stock options and the valuation allowance of deferred tax assets resulting from net operating losses.expenses. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results could differ from those estimates.

Recently Adopted Accounting Pronouncements

The Company adopted Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) (“ASC 842”), as

Basic net loss per share of common stock is computed by dividing net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. The Company uses the if-converted method for assumed conversion of the 2027 Notes to compute the weighted average shares of common stock outstanding for diluted net loss per share. Diluted net loss per share excludes the potential impact of the Company’s Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, and Series B Convertible Preferred Stock, common stock options and unvested shares of restricted stock and the potential shares issuable upon conversion of the 2027 Notes because their effect would be anti-dilutive due to the Company’s net loss. Since the Company had a net loss in each of the periods presented, basic and diluted net loss per common share are the same.

The table below provides potentially dilutive securities not included in the calculation of the diluted net loss per share because to do so would be anti-dilutive:

The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

Level 1: Observable inputs such as quoted prices in active markets;

The Company classifies its cash equivalents and available-for-sale investments within Level 1 or Level 2. The fair value of ourthe Company’s investment grade corporate debt securities and commercial paper is determined using proprietary valuation models and analytical tools, which utilize market pricing or prices for similar instruments that are both objective and publicly available, such as matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, and offers.

The following table presents the hierarchy for assets measured at fair value on a recurring basis as of March 31, 20192023 and December 31, 20182022 (in thousands):