Gossamer Bio, Inc.

Previous wording

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, including performance under the Chiesi Collaboration Agreement 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, timing and likelihood of success, plans and objectives of management for future operations, 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.

Current wording

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.

Previous wording

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 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. Subject to the outcomes of interactions with the FDA, the Company expects to submit a New Drug Application to the FDA for seralutinib for the treatment of PAH in September 2026. 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. 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. However, we plan to re-continue PH-ILD development work when feasible based on such resource allocation decisions. 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.

Current wording

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

Previous wording

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 March 31, 2026, we had $99.2 million in cash, cash equivalents and marketable securities.

Current wording

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.

Previous wording

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 March 31, 2026 and 2025, our net loss was $46.7 million and $36.6 million, respectively. As of March 31, 2026, we had an accumulated deficit of $1,485.6 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.

Current wording

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.

Previous wording

Our management’s discussion and analysis of our financial condition and results of operations are based on our condensed consolidated financial statements, which have been prepared in accordance with GAAP. The preparation of these financial statements requires us to make judgments and estimates that affect the reported amounts of assets, liabilities, revenue, expenses and the disclosure of contingent assets and liabilities in our condensed consolidated financial statements. We base our estimates on historical experience, known trends and events, and various other factors that are believed to be reasonable under the circumstances. Actual results may differ from these estimates under different assumptions or conditions. On an ongoing basis, we evaluate our judgments and estimates in light of changes in circumstances, facts and experience. During the three months ended March 31, 2026, there have been no significant changes in our critical accounting policies and estimates as discussed in Item 7, “Management’s Discussion and Analysis of Financial Condition and Results of Operations – Critical Accounting Policies and Estimates” in our Annual Report on Form 10-K filed with the SEC on March 17, 2026.

Current wording

Our management’s discussion and analysis of our financial condition and results of operations are based on our condensed consolidated financial statements, which have been prepared in accordance with GAAP. The preparation of these financial statements requires us to make judgments and estimates that affect the reported amounts of assets, liabilities, revenue, expenses and the disclosure of contingent assets and liabilities in our condensed consolidated financial statements. We base our estimates on historical experience, known trends and events, and various other factors that are believed to be reasonable under the circumstances. Actual results may differ from these estimates under different assumptions or conditions. On an ongoing basis, we evaluate our judgments and estimates in light of changes in circumstances, facts and experience. During the six months ended June 30, 2026, there have been no significant changes in our critical accounting policies and estimates as discussed in Item 7, “Management’s Discussion and Analysis of Financial Condition and Results of Operations – Critical Accounting Policies and Estimates” in our Annual Report on Form 10-K filed with the SEC on March 17, 2026. See Note 2, Summary of Significant Accounting Policies, for information about these critical accounting policies.

Previous wording

Results of Operations – Comparison of the Three Months Ended March 31, 2026 and 2025

Current wording

Results of Operations – Comparison of the Three and Six Months Ended June 30, 2026 and 2025

Previous wording

The following table sets forth our selected statements of operations data for the three months ended March 31, 2026 and 2025:

Current wording

The following table sets forth our selected statements of operations data for the three months ended June 30, 2026 and 2025 (in thousands):

Previous wording

Our revenue is generated from our ongoing collaboration with Chiesi and consists of ongoing research and development service performance and cost-sharing payments for performance of research and development and pre-commercial services. For the three months ended March 31, 2026 and 2025, our revenue was $17.0 million and $9.9 million, respectively, for an increase of $7.1 million, which was attributable to an increase in research and development and pre-commercial services.

Current wording

Our revenue is generated from our ongoing collaboration with Chiesi and consists of ongoing research and development service performance and cost-sharing payments for performance of research and development and pre-commercial services. For the three months ended June 30, 2026 and 2025, our revenue was $9.2 million and $11.5 million, respectively, for a decrease of $2.3 million, which was primarily attributable to the decrease in research and development services and costs subject to reimbursement. For the six months ended June 30, 2026 and 2025, our revenue was $26.2 million and $21.4 million, respectively, for an increase of $4.8 million, which was primarily attributable to an increase in research and development and pre-commercial services.

Previous wording

Research and development expenses were $43.1 million for the three months ended March 31, 2026, compared to $38.0 million for the three months ended March 31, 2025, for an increase of $5.0 million, which was primarily attributable to an increase of $6.1 million of costs associated with clinical trials for seralutinib and an increase of $0.7 million of costs associated with Respira, offset by a decrease of $1.8 million of costs associated with preclinical studies and clinical trials for terminated programs.

Current wording

Research and development expenses were $26.4 million for the three months ended June 30, 2026, compared to $41.6 million for the three months ended June 30, 2025, for a decrease of $15.2 million, which was primarily attributable to a decrease of $15.7 million of costs associated with clinical trials for seralutinib, offset by an increase of $0.5 million of costs associated with Respira.

Previous wording

The following table shows our research and development expenses by program for the three months ended March 31, 2026 and 2025:

Current wording

The following table shows our research and development expenses by program for the three and six months ended June 30, 2026 and 2025:

Previous wording

General and administrative expenses were $18.7 million for the three months ended March 31, 2026, compared to $8.7 million for the three months ended March 31, 2025, for an increase of $10.1 million, which was primarily attributable to a $1.7 million increase in commercial expenses, a $4.6 million increase in personnel expense due to severance, a $2.2 million increase in stock-based compensation expense and a $1.2 million increase in professional services expense.

Current wording

General and administrative expenses were $27.6 million for the six months ended June 30, 2026, compared to $17.3 million for the six months ended June 30, 2025, for an increase of $10.3 million, which was primarily attributable to a $0.7 million increase in commercial expenses, a $4.4 million increase in personnel expense due to severance, a $2.8 million increase in stock-based compensation expense and a $1.1 million increase in professional services expense.

Previous wording

We have incurred substantial operating losses since our inception and expect to continue to incur significant operating losses for the foreseeable future and may never become profitable. As of March 31, 2026, we had an accumulated deficit of $1,485.6 million.

Current wording

We have incurred substantial operating losses since our inception and expect to continue to incur significant operating losses for the foreseeable future and may never become profitable. As of June 30, 2026, we had an accumulated deficit of $1,468.7 million.

Previous wording

Our primary use of cash is to fund operating expenses, which consist primarily of research and development expenditures, and to a lesser extent, general and administrative expenditures, including commercial planning expenditures. Cash used to fund operating expenses is impacted by the timing of when we pay these expenses, as reflected in the change in our outstanding accounts payable and accrued expenses. We may also use cash on hand to repurchase 2027 Notes through open-market transactions, including through a Rule 10b5-1 trading plan to facilitate open-market repurchases, or otherwise, from time to time.

Current wording

Our primary use of cash is to fund operating expenses, which consist primarily of research and development expenditures, and to a lesser extent, general and administrative expenditures, including commercial planning expenditures. Cash used to fund operating expenses is impacted by the timing of when we pay these expenses, as reflected in the change in our outstanding accounts payable and accrued expenses. We may also use cash on hand to repurchase 2027 Notes and 2030 Notes through open-market transactions, including through a Rule 10b5-1 trading plan to facilitate open-market repurchases, or otherwise, from time to time.

Previous wording

Under our license agreement with Pulmokine, we have payment obligations that are contingent upon future events such as our achievement of specified development, regulatory and commercial milestones and are required to make royalty payments in connection with the sale of products developed under the agreement. As of March 31, 2026, we were unable to estimate the timing or likelihood of achieving the milestones or making future product sales. Other contractual obligations include future payments under the 2027 Notes and existing operating leases.

Current wording

Under our license agreement with Pulmokine, we have payment obligations that are contingent upon future events such as our achievement of specified development, regulatory and commercial milestones and are required to make royalty payments in connection with the sale of products developed under the agreement. As of June 30, 2026, we were unable to estimate the timing or likelihood of achieving the milestones or making future product sales. Other contractual obligations include future payments under the 2027 Notes and 2030 Notes and existing operating leases.

Previous wording

From our inception through March 31, 2026, our operations have been financed primarily by proceeds of $1,396.9 million from the sale of Series A and Series B convertible preferred stock, proceeds from our IPO, proceeds from the 2027 Notes, proceeds from issuance of common stock in May 2020 and July 2022, proceeds from issuance of common stock and accompanying warrants in July 2023 and the Chiesi Collaboration Agreement. In addition, we have received $48.6 million as of March 31, 2026 through reimbursement related to the Chiesi Collaboration Agreement. As of March 31, 2026 we had cash, cash equivalents and marketable securities of $99.2 million. Cash in excess of immediate requirements is invested in accordance with our investment policy, primarily with a view to capital preservation and liquidity.

Current wording

From our inception through June 30, 2026, our operations have been financed primarily by proceeds of $1,396.9 million from the sale of Series A and Series B convertible preferred stock, proceeds from our IPO, proceeds from the 2027 Notes and 2030 Notes, proceeds from issuance of common stock in May 2020 and July 2022, proceeds from issuance of common stock and accompanying warrants in July 2023 and the Chiesi Collaboration Agreement. In addition, we have received $57.9 million as of June 30, 2026 through reimbursement related to the Chiesi Collaboration Agreement. As of June 30, 2026 we had cash, cash equivalents and marketable securities of $57.0 million. Cash in excess of immediate requirements is invested in accordance with our investment policy, primarily with a view to capital preservation and liquidity.

Previous wording

On May 3, 2024, we entered into the Chiesi Collaboration Agreement. In consideration and as reimbursement for our development costs, Chiesi paid us an up-front, nonrefundable payment of $160.0 million. In addition, we and Chiesi share equally in the costs of ongoing global seralutinib clinical development, with the exception of the PROSERA Phase 3 study, and the costs of commercialization in the U.S. Territory. For the three months ended March 31, 2026, we received cost-sharing payments from Chiesi in the amount of $12.2 million.

Current wording

On May 3, 2024, we entered into the Chiesi Collaboration Agreement. In consideration and as reimbursement for our development costs, Chiesi paid us an up-front, nonrefundable payment of $160.0 million. In addition, we and Chiesi share equally in the costs of ongoing global seralutinib clinical development, with the exception of the PROSERA Phase 3 study, and the costs of commercialization in the U.S. Territory. For the six months ended June 30, 2026, we received cost-sharing payments from Chiesi in the amount of $21.5 million.

Previous wording

On January 28, 2026, we filed a registration statement on Form S-3 ASR, or the 2026 Shelf Registration Statement, covering the offering from time to time of common stock, preferred stock, debt securities, warrants and units, which registration statement became automatically effective upon filing. On March 17, 2026, we filed Post-Effective Amendment No. 1 and Post-Effective Amendment No. 2 to the 2026 Shelf Registration Statement, which became effective on March 18, 2026, to convert the registration statement to a non-automatic shelf registration statement as we were no longer a “well-known seasoned issuer.”

Current wording

On January 28, 2026, we filed a registration statement on Form S-3 ASR, or the 2026 Shelf Registration Statement, covering the offering from time to time of common stock, preferred stock, debt securities, warrants and units, which registration statement became automatically effective upon filing. On March 17, 2026, we filed Post-Effective Amendment No. 1 and Post-

Previous wording

The opinion of our independent registered public accounting firm on our audited financial statements as of and for the years ended December 31, 2025 contains an explanatory paragraph regarding substantial doubt about our ability to continue as a going concern. Future reports on our financial statements may include an explanatory paragraph with respect to our ability to continue as a going concern. Our consolidated condensed financial statements as of and for the three months ended March 31, 2026 and 2025 included in this Form 10-Q do not include any adjustments relating to the recoverability and classification of recorded asset amounts or amounts of liabilities that might be necessary should we be unable to continue our operations.

Current wording

The opinion of our independent registered public accounting firm on our audited financial statements as of and for the years ended December 31, 2025 contains an explanatory paragraph regarding substantial doubt about our ability to continue as a going concern. Future reports on our financial statements may include an explanatory paragraph with respect to our ability to continue as a going concern. Our consolidated condensed financial statements as of and for the three and six months ended June 30, 2026 and 2025 included in this Form 10-Q do not include any adjustments relating to the recoverability and classification of recorded asset amounts or amounts of liabilities that might be necessary should we be unable to continue our operations.

Previous wording

The following table shows a summary of our cash flows for each of the three months ended March 31, 2026 and 2025, respectively:

Current wording

The following table shows a summary of our cash flows for each of the six months ended June 30, 2026 and 2025, respectively:

Previous wording

During the three months ended March 31, 2025, operating activities used approximately $39.7 million of cash, primarily resulting from the net loss of $36.6 million and changes in accrued compensation and benefits of $5.8 million, reduced by changes in stock-based compensation expense of $2.4 million.

Current wording

During the six months ended June 30, 2026, operating activities used approximately $78.1 million of cash, primarily resulting from a net loss of $29.8 million and changes in contract liabilities of $12.4 million, changes in accrued research and development expenses of $12.0 million and gain on debt extinguishment of $43.8 million, reduced by changes in stock-based compensation expense of $8.8 million and changes in prepaid expenses and other current assets of $8.9 million.

Previous wording

During the three months ended March 31, 2026, operating activities used approximately $38.7 million of cash, primarily resulting from a net loss of $46.7 million and changes in contract liabilities of $9.0 million, reduced by changes in accounts payable of $6.2 million, changes in stock-based compensation expense of $6.3 million, changes in receivable from contracts with collaborators of $3.0 million and changes in prepaid expenses and other current assets of $2.4 million.

Current wording

During the six months ended June 30, 2025, operating activities used approximately $86.8 million of cash, primarily resulting from the net loss of $74.9 million and changes in accounts payable of $6.8 million, changes in prepaid expenses and other current assets of $5.4 million and changes in amortization of premium on investments of $4.6 million, reduced by changes in stock-based compensation expense of $5.0 million.

Previous wording

During the three months ended March 31, 2026, investing activities provided approximately $41.6 million of cash, primarily resulting from the maturities of marketable securities of $66.6 million, offset by the purchases of marketable securities of $25.0 million.

Current wording

During the six months ended June 30, 2026, investing activities provided approximately $84.3 million of cash, primarily resulting from the maturities of marketable securities of $109.3 million, offset by the purchases of marketable securities of $25.0 million.

Previous wording

During the three months ended March 31, 2025, investing activities provided approximately $22.1 million of cash, primarily resulting from the maturities of marketable securities of $123.1 million, offset by the purchases of marketable securities of $101.0 million.

Current wording

During the six months ended June 30, 2025, investing activities provided approximately $66.2 million of cash, primarily resulting from the maturities of marketable securities of $242.8 million, offset by the purchases of marketable securities of $176.5 million.

Previous wording

During the three months ended March 31, 2025, financing activities provided $0.5 million of cash, primarily resulting from the proceeds from issuance of common stock pursuant to the ESPP of $0.4 million and the proceeds from the exercise of stock options of $0.1 million.

Current wording

During the six months ended June 30, 2026, financing activities used approximately $2.6 million of cash, primarily resulting from the payment of debt and equity issuance costs in connection with the exchange of the 2027 Notes of $3.1 million, reduced by the proceeds from issuance of common stock pursuant to the ESPP of $0.3 million and the proceeds from the exercise of stock options of $0.2 million.

Previous wording

During the three months ended March 31, 2026, financing activities provided $0.5 million of cash, primarily resulting from the proceeds from issuance of common stock pursuant to the ESPP of $0.3 million and the proceeds from the exercise of stock options of $0.2 million.

Current wording

During the six months ended June 30, 2025, financing activities provided approximately $0.6 million of cash, primarily resulting from the proceeds from issuance of common stock pursuant to the ESPP of $0.4 million and the proceeds from the exercise of stock options of $0.2 million.

Previous wording

Based on our current operating plan, we believe that our existing cash, cash equivalents and marketable securities, will be sufficient to fund our operations into the first quarter of 2027. However, our forecast of the period of time through which our financial resources will be adequate to support our operations is a forward-looking statement that involves risks and uncertainties, and actual results could vary materially. We have based this estimate on assumptions that may prove to be wrong, and we could use our capital resources sooner than we expect. Additionally, the process of testing seralutinib in clinical trials and seeking regulatory approval is costly, and the timing of progress and expenses in these trials is uncertain. Pending feedback from the FDA on a potential path forward for seralutinib, we also expect that the level of spending for our ongoing and planned commercial planning activities for seralutinib may increase.

Current wording

Based on our current operating plan, we believe that our existing cash, cash equivalents and marketable securities, will be sufficient to fund our operations into the first quarter of 2027. However, our forecast of the period of time through which our financial resources will be adequate to support our operations is a forward-looking statement that involves risks and uncertainties, and actual results could vary materially. We have based this estimate on assumptions that may prove to be wrong, and we could use our capital resources sooner than we expect. Additionally, the process of testing seralutinib in clinical trials and seeking regulatory approval is costly, and the timing of progress and expenses in these trials is uncertain. We also expect that the level of spending for our ongoing and planned commercial planning activities for seralutinib may increase.