Gossamer Bio, Inc. (GOSS)

ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion and analysis and the unaudited interim condensed consolidated financial statements included in this quarterly report on Form 10-Q should be read in conjunction with the consolidated financial statements and notes thereto for the year ended December 31, 2025 and the related Management’s Discussion and Analysis of Financial Condition and Results of Operations, both of which are contained in our Annual Report on Form 10-K filed with the Securities and Exchange Commission, or SEC, on March 17, 2026.

Forward-Looking Statements

This quarterly report on Form 10-Q contains forward-looking statements within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act, and Section 27A of the Securities Act of 1933, as amended, or the Securities Act. All statements other than statements of historical facts contained in this quarterly report, including statements regarding our future results of operations and financial position, business strategies and plans, research and development plans, the anticipated timing, costs, design and conduct of our ongoing and planned preclinical studies and planned clinical trials for seralutinib, the timing and likelihood of regulatory filings and approvals for seralutinib, including the timing and potential submission, and potential acceptance for filing and approval, of an NDA for seralutinib in PAH, timing and likelihood of success, plans and objectives of management for future operations, the anticipated benefits of the termination of the Company’s Collaboration and License Agreement with Chiesi, the anticipated benefits of any reverse stock split, and the timing of the completion of any such reverse stock split, the potential impact of U.S. trade policy, including tariffs, and future results of seralutinib, are forward-looking statements. These statements involve known and unknown risks, uncertainties and other important 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 the forward-looking statements.

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of these terms or other similar expressions. The forward-looking statements in this quarterly report are only predictions. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition and results of operations. These forward-looking statements speak only as of the date of this quarterly report and are subject to a number of risks, uncertainties and assumptions, including those described in Part II, Item 1A, “Risk Factors” of this report, Part I, Item 1A, “Risk Factors” in our most recent Annual Report on Form 10-K filed with the SEC on March 17, 2026, and Part II, Item 1A, “Risk Factors” of our subsequently filed quarterly reports. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise. All forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

Overview

We are a clinical-stage biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of PH, including PAH and PH-ILD. Our goal is to be an industry leader in, and to enhance the lives of patients living with PH. In July 2026, we entered into the Rights Reacquisition Agreement with Chiesi, pursuant to which we reacquired worldwide development and commercial rights to seralutinib. In December 2022, we announced positive topline results from the Phase 2 TORREY Study in PAH patients. In February 2026, we announced topline results from the Phase 3 PROSERA Study in PAH patients. Seralutinib demonstrated a placebo-adjusted improvement in the primary endpoint, 6MWD at Week 24, of 13.3 meters (p = 0.0320), missing the prespecified alpha threshold of 0.025. Following a Pre-NDA Type B meeting with the FDA held in mid-June 2026 and receipt of the official meeting minutes, we plan to proceed with an NDA submission for seralutinib for the treatment of PAH in September 2026. The Company intends to submit an NDA supported by one adequate and well-controlled study (Phase 3 PROSERA) plus confirmatory evidence (Phase 2 TORREY and supportive analyses).  If the NDA is accepted for filing, seralutinib could be eligible for an FDA approval decision in the third quarter of 2027. In addition to PAH, we believe that seralutinib holds potential as a therapeutic for the treatment of PH-ILD, and this indication remains an area of focus for us. We have assembled a deeply experienced and highly skilled group of industry veterans, scientists, clinicians and key opinion leaders from leading biotechnology and pharmaceutical companies, as well as leading academic centers from around the world. Our employees are a team of highly dedicated, passionate individuals who pride themselves on a

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culture of respect, humility, transparency, inclusion, dedication, collaboration and fun. Our ultimate goal is to enhance and extend the lives of patients.

We were incorporated in October 2015 and commenced operations in 2017. To date, we have focused primarily on organizing and staffing our company, business planning, raising capital, identifying, acquiring and in-licensing our product candidates and conducting preclinical studies and clinical trials. We have funded our operations primarily through equity and debt financings and the Chiesi Collaboration Agreement. As of June 30, 2026, we had $57.0 million in cash, cash equivalents and marketable securities.

We have incurred significant operating losses since our inception and expect to continue to incur significant operating losses for the foreseeable future. For the three months ended June 30, 2026 and 2025, our net gain was $16.9 million and net loss of $38.3 million, respectively. For the six months ended June 30, 2026 and 2025, our net loss was $29.8 million and $74.9 million, respectively. As of June 30, 2026, we had an accumulated deficit of $1,468.7 million. We expect to incur expenses and operating losses for the foreseeable future as we continue our development of and seek regulatory approvals for seralutinib, including the conduct of ongoing and planned clinical trials and other research and development activities; and as we hire additional personnel, protect our intellectual property and incur costs associated with being a public company. In addition, as seralutinib progresses through development and toward commercialization, we will need to make milestone payments to Pulmokine from whom we have in-licensed seralutinib. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending in particular on the timing of our clinical trials and preclinical studies and our expenditures on other research and development activities.

On May 3, 2024, we announced a strategic global partnership with Chiesi. Under the terms of the Chiesi Collaboration Agreement, we granted Chiesi exclusive licenses for the worldwide development, manufacture and commercialization of seralutinib and licensed products and an Equity Option to purchase our common stock, which expired in November 2025. On July 23, 2026, we entered into the Rights Reacquisition Agreement, under which we and Chiesi have agreed (a) to terminate the Chiesi Collaboration Agreement, subject to survival of certain provisions, and provide for assistance and cooperation in connection with certain wind-down activities conducted by or on behalf of Chiesi; (b) to provide for the reacquisition by us of seralutinib assets (including by termination of licenses granted under the Chiesi Collaboration Agreement by us to Chiesi and assignment or transfer or license of related assets, including regulatory filings and certain intellectual property rights related to seralutinib, by Chiesi to us) and worldwide development and commercial rights to seralutinib, including control of PAH, PH-ILD and potential future indications, and (c) to provide for certain post-termination payments and related obligations in consideration of the rights granted under the Rights Reacquisition Agreement.

We do not expect to generate any revenue from product sales unless and until we successfully complete development and obtain regulatory approval for seralutinib, which we expect will take a number of years, if at all. If we obtain regulatory approval for seralutinib, we expect to incur significant commercialization expenses related to product sales, marketing, manufacturing and distribution. Accordingly, until such time as we can generate substantial product revenues to support our cost structure, if ever, we expect to finance our cash needs through equity offerings, debt financings or other capital sources, including potentially collaborations, licenses and other similar arrangements. However, we may be unable to raise additional funds or enter into such other arrangements when needed on favorable terms or at all. Our failure to raise capital or enter into such other arrangements when needed could have a negative impact on our financial condition and on our ability to pursue our business plans and strategies. If we are unable to raise additional capital when needed, we could be forced to delay, limit, reduce or terminate seralutinib development or future commercialization efforts or grant additional rights to develop and market seralutinib even if we would otherwise prefer to retain such right.

Components of Results of Operations

Revenue

To date, we have generated all of our revenue from the Chiesi Collaboration Agreement. Our revenue consists of a one-time development cost reimbursement payment for licenses and ongoing cost-sharing payments for performance of research and development services classified as revenue from contracts with collaborators.

In the future, we may generate revenue from a combination of license fees and other upfront payments, other funded research and development agreements, milestone payments, product sales, other third-party funding, U.S. profit/loss share and royalties in connection with strategic alliances. We expect that any revenue we generate will fluctuate from quarter-to-quarter as a result of the timing of performance of research and development services, the timing of our achievement of regulatory and commercialization milestones, the timing and amount of payments relating to such milestones and the extent to which any of our products are approved and successfully commercialized. If we are unable to fund our development costs or we are unable to

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develop product candidates in a timely manner or obtain regulatory approval for them, our ability to generate future revenues and our results of operations and financial position would be adversely affected.

Operating expenses

Research and development

Research and development expenses relate prima

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Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations.

You should read the following discussion and analysis of our financial condition and results of operations together with our consolidated financial statements and related notes included elsewhere in this annual report. This discussion and analysis contains forward-looking statements based upon our current beliefs, plans and expectations that involve risks, uncertainties and assumptions. Our actual results may differ materially from those anticipated in these forward-looking statements as a result of various factors, including those set forth under “Risk Factors” or in other parts of this annual report.

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Overview

We are a clinical-stage, clinical biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of PH, including PAH and PH-ILD. Our goal is to be an industry leader in, and to enhance the lives of patients living with PH. In May 2024, we entered into the Chiesi Collaboration Agreement focused on the development and commercialization of seralutinib. In December 2022, we announced positive topline results from the Phase 2 TORREY Study in PAH patients. In February 2026, we announced topline results from the Phase 3 PROSERA Study in PAH patients. Seralutinib demonstrated a placebo-adjusted improvement in the primary endpoint, 6MWD at Week 24, of 13.3 meters (p = 0.0320), missing the prespecified alpha threshold of 0.025. We believe seralutinib demonstrates a risk benefit profile that supports continued regulatory dialogue, and we plan to engage with the FDA, including through requesting a Type C meeting, to understand their perspective on the totality of the PROSERA and TORREY datasets and potential regulatory paths forward. In addition to PAH, we believe that seralutinib holds potential as a therapeutic for the treatment of PH-ILD. In October 2025, we activated the first clinical site for the global registrational Phase 3 SERANATA Study for the treatment of PH-ILD. Enrollment in the SERANATA Study was paused in February 2026 to support disciplined resource allocation and to evaluate the implications of PROSERA as we engage with regulators. We have assembled a deeply experienced and highly skilled group of industry veterans, scientists, clinicians and key opinion leaders from leading biotechnology and pharmaceutical companies, as well as leading academic centers from around the world. Our employees are a team of highly dedicated, passionate individuals who pride themselves on a culture of respect, humility, transparency, inclusion, dedication, collaboration and fun. Our ultimate goal is to enhance and extend the lives of patients.

We were incorporated in October 2015 and commenced operations in 2017. To date, we have focused primarily on organizing and staffing our company, business planning, raising capital, identifying, acquiring and in-licensing our product candidates and conducting preclinical studies and clinical trials. We have funded our operations primarily through equity financings and the Chiesi Collaboration Agreement. We raised $1,396.9 million from October 2017 through December 31, 2025 through the sale of Series A and Series B convertible preferred stock, issuance of convertible notes, proceeds from our IPO completed in February 2019, proceeds from the 2027 Notes (as defined below), issuances of common stock in May 2020 and July 2022, issuance of common stock and accompanying warrants in July 2023 and entry into the Chiesi Collaboration Agreement in May 2024. As of December 31, 2025, we had $136.9 million in cash, cash equivalents and marketable securities.

We have incurred significant operating losses since our inception and expect to continue to incur significant operating losses for the foreseeable future. For the years ended December 31, 2025 and 2024, our net loss was $170.4 million and $56.5 million, respectively. As of December 31, 2025, we had an accumulated deficit of $1,438.9 million. We expect to incur expenses and operating losses for the foreseeable future as we continue our development of and seek regulatory approvals for seralutinib, including the conduct of ongoing and future clinical trials and other research and development activities; and as we hire additional personnel, protect our intellectual property and incur additional costs associated with being a public company. In addition, as seralutinib progresses through development and toward commercialization, we will need to make milestone payments to Pulmokine from whom we have in-licensed seralutinib. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending in particular on the timing of our clinical trials and preclinical studies and our expenditures on other research and development activities.

On May 3, 2024, we announced a strategic global partnership with Chiesi. Under the terms of the Chiesi Collaboration Agreement, we granted Chiesi exclusive licenses for the worldwide development, manufacture and commercialization of seralutinib and licensed products and an Equity Option to purchase our common stock, which expired in November 2025 and is no longer exercisable. The total potential transaction value includes the one-time $160.0 million development cost reimbursement payment for licenses, research and development funding, and certain regulatory and commercial milestones. We and Chiesi share equally in the costs of ongoing global seralutinib clinical development and the costs of commercialization in the U.S. Territory, with the exception of the PROSERA Phase 3 study, for which we bear all costs. We are also eligible for double-digit royalties in the mid-to-high teens percentage on tiers of annual net sales outside of the U.S. Territory and to an equal share of profits and losses from the commercialization of seralutinib and licensed products in the U.S. For additional information regarding the collaboration agreement, as well as our license agreement with Pulmokine, see the section titled “Business—License and Collaboration Agreements” in this annual report.

We do not expect to generate any revenue from product sales unless and until we successfully complete development and obtain regulatory approval for seralutinib, which we expect will take a number of years, if at all. If we obtain regulatory approval for seralutinib, we expect to incur significant commercialization expenses related to product sales, marketing, manufacturing and distribution. Accordingly, until such time as we can generate substantial product revenues to support our cost structure, if ever, we expect to finance our cash needs through equity offerings, debt financings or other capital sources, including potentially collaborations, licenses and other similar arrangements. However, we may be unable to raise additional funds or enter into such other arrangements when needed on favorable terms or at all. Our failure to raise capital or enter into

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such other arrangements when needed could have a negative impact on our financial condition and on our ability to pursue our business plans and strategies. If we are unable to raise additional capital when needed, we could be forced to delay, limit, reduce or terminate seralutinib development or future commercialization efforts or grant additional rights to develop and market seralutinib even if we would otherwise prefer to retain such right.

Components of Results of Operations

Revenue

To date, we have generated all of our revenue from the Chiesi Collaboration Agreement. Our revenue consists of a one-time development cost reimbursement payment for licenses and ongoing cost-sharing payments for performance of research and development services classified as revenue from contracts with collaborators.

In the future, we may generate revenue from a combination of license fees and other upfront payments, other funded research and development agreements, milestone payments, product sales, other third-party funding, U.S. profit/loss share and royalties in connection with strategic alliances. We expect that any revenue we generate will fluctuate from quarter-to-quarter as a result of the timing of performance of research and development services, the timing of our achievement of regulatory and commercialization milestones, the timing and amount of payments relating to such milestones and the extent to which any of our products are approved and successfully commercialized. If we are unable to fund our development costs or we are unable to develop product candidates in a timely manner or obtain regulatory approval for them, our ability to generate future revenues and our results of operations and financial position would be adversely affected.

Operating expenses

Research and development

Research and development expenses relate primarily to preclinical and clinical development of seralutinib, as well as our discontinued clinical product candidates. Research and development expenses are recognized as incurred and payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received.

Research and development expenses include or could include:

•salaries, payroll taxes, employee benefits, and stock-based compensation charges for those individuals involved in research and development efforts;

•external research and development expenses incurred under agreements with contract research organizations, or CROs, investigative sites and consultants to conduct our clinical trials and preclinical and non-clinical studies;

•laboratory supplies;

•costs related to manufacturing our product candidates for clinical trials and preclinical studies, including fees paid to third-party manufacturers;

•costs related to compliance with regulatory requirements; and

•facilities, depreciation and other allocated expenses, which include direct and allocated expenses for rent, maintenance of facilities, insurance, equipment and other supplies.

Our direct research and development expenses consist principally of external costs, such as fees paid to CROs, investigative sites and consultants in connection with our clinical trials, preclinical and non-clinical studies, and costs related to manufacturing clinical trial materials. We deploy our personnel and facility related resources across all of our research and development activities. We track external costs and personnel expense on a program-by-program basis and allocate common expenses, such as facility related resources, to each program based on the personnel resources allocated to such program. Stock-based compensation and personnel and common expenses not attributable to a specific program are considered unallocated research and development expenses. We categorize Terminated Programs as any research and development expenses attributable to our clinical stage product candidates that were terminated prior to December 31, 2023 or any research and development expenses that are not directly allocated to seralutinib.

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We expect to incur research and development expenses for the foreseeable future as we continue the development of seralutinib. We cannot determine with certainty the timing of initiation, the duration or the completion costs of current or future preclinical studies and clinical trials of seralutinib due to the inherently unpredictable nature of preclinical and clinical development. Clinical and preclinical development timelines, the probability of success and development costs can differ materially from expectations. We anticipate that we will make determinations as to how much funding to direct to seralutinib on an ongoing basis in response to the results of ongoing and future preclinical studies and clinical trials, regulatory developments and our ongoing assessments as to seralutinib's commercial potential

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