{"url_path":"/sec/goss/8-k/2026-05-18/item-8-01","section_key":"item-8-01","section_title":"Item 8.01 Other Events.","topic":"sec","document":{"doc_type":"8-K","doc_date":"2026-05-18","source_url":"https://www.sec.gov/Archives/edgar/data/1728117/0001728117-26-000036-index.html","accession_number":"0001728117-26-000036","cik":"0001728117","ticker":"GOSS","issuer_name":"Gossamer Bio, Inc.","edgar_url":"https://www.sec.gov/Archives/edgar/data/1728117/0001728117-26-000036-index.html","primary_entity_key":"0001728117","primary_entity_name":"Gossamer Bio, Inc."},"word_count":1745,"has_tables":true,"body_markdown":"Item 8.01 Other Events.\n\nOn May 18, 2026, the Company announced that it received confirmation of an in-person Pre-NDA Type B meeting with the U.S. Food and Drug Administration (“FDA”), scheduled for mid-June 2026. Following its continued review of the Phase 3 PROSERA Study in PAH patients, the Company elected to pursue a Type B meeting, rather than the previously anticipated Type C meeting, to enable a more comprehensive discussion of the totality of evidence supporting a potential NDA submission for seralutinib in PAH. The Company is pursuing a New Drug Application (“NDA”) submission on the basis of one adequate and well-controlled clinical investigation plus confirmatory evidence. Subject to the outcomes of the Pre-NDA meeting, the Company expects to submit an NDA for seralutinib for the treatment of PAH in September 2026. If the NDA is accepted for filing, seralutinib could be eligible for FDA approval in the third quarter of 2027 and the Company would expect to begin pre-launch commercial activities in 2027.\n\nIn addition, the Company announced topline results from the PROSERA CT functional respiratory imaging (“FRI”) exploratory substudy (n = 162), which demonstrated multiple statistically significant exploratory treatment effects across arterial, venous, fibrosis related, and vascular complexity parameters, yielding what the Company believes is the broadest multi compartment imaging signal reported to date from a controlled therapeutic trial in pulmonary hypertension. Building on the arterial remodeling signal first identified in earlier studies, PROSERA generated what the Company believes is the most comprehensive CT FRI dataset from a controlled PAH trial, expanding the characterization of seralutinib's biologic activity across the pulmonary vasculature and lung parenchyma. All reported p-values were nominal and unadjusted for multiplicity.\n\nTopline results and key findings include the following:\n\n•In the arterial compartment, seralutinib demonstrated a statistically significant reduction in the proportion of blood volume within larger arterial vessels versus placebo (p = 0.0200), consistent with proximal decompression and arterial remodeling in a larger and more heterogeneous Phase 3 population. PROSERA's analytical scope also extended to include more proximal vessels, broadening the portion of the pulmonary vasculature assessed.\n\n•Beyond the arterial compartment, PROSERA identified statistically significant venous and fibrosis related treatment effects not previously detected in the seralutinib program. Seralutinib increased total venous blood volume (p = 0.0155) and small venous vessel volume (p = 0.0341), reduced absolute and normalized fibrosis-like tissue in the parenchyma (p = 0.0260, p = 0.0250), and increased venous vascular fractal dimension (p = 0.0435), consistent with greater vascular complexity. These multi compartment findings were enabled by the scale and scope of the PROSERA dataset.\n\n•While PAH has historically been characterized as a disease of the pulmonary arteries, pathological and imaging literature increasingly recognize the contributions of impaired microvascular perfusion, venous underfilling, inflammation, and perivascular fibrosis to disease progression. The venous and fibrosis signals in PROSERA may provide structural context for these processes and are aligned with seralutinib's non vasodilatory mechanism targeting inflammatory, proliferative, and fibrotic pathways within the pulmonary vasculature and surrounding parenchyma.\n\n•Imaging changes observed in PROSERA were associated with favorable changes in clinical outcomes, including pulmonary hemodynamics, NT proBNP, 6 minute walk distance, and REVEAL Lite 2 risk score. These correlations reinforce the biological relevance of the CT FRI data.\n\nThe Company believes these exploratory findings, taken together with their consistency with clinical results and seralutinib's mechanism of action, provide meaningful structural support for seralutinib's activity across the pulmonary vasculature.\n\nThe information set forth in the Explanatory Note of this Current Report on Form 8-K is incorporated by reference into this Item 8.01.\n\n*   *   *\n\nImportant Information and Where to Find It\n\nThis Current Report on Form 8-K is being made in respect of certain Stockholder Proposals arising out of the Exchange Offer and the Transaction Support Agreement. The Stockholder Proposals will be submitted to the Company’s stockholders for their consideration and approval at a special meeting of the Company’s stockholders. In connection with the Stockholder Proposals, the Company will file with the SEC a proxy statement on Schedule 14A (the “Proxy Statement”), the definitive version of which (if and when available) will be sent or provided to the Company’s stockholders and will contain important information about the Stockholder Proposals and related matters. The Company may also file other relevant documents with the SEC regarding the Stockholder Proposals. This Current Report on Form 8-K is not a substitute for the Proxy Statement or any other document that the Company may file with the SEC. BEFORE MAKING ANY VOTING DECISION WITH RESPECT TO THE STOCKHOLDER PROPOSALS, INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE PROXY STATEMENT AND ANY OTHER RELEVANT DOCUMENTS THAT ARE FILED OR WILL BE FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THESE DOCUMENTS, CAREFULLY AND IN THEIR ENTIRETY IF AND WHEN THEY BECOME AVAILABLE BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE STOCKHOLDER PROPOSALS, THE RISKS RELATED THERETO AND RELATED MATTERS.\n\nInvestors and security holders may obtain free copies of the Proxy Statement and other documents containing important information about the Company and the Stockholder Proposals that are filed or will be filed with the SEC by the Company when they become available at the SEC’s website at www.sec.gov or at the Company’s website at ir.gossamerbio.com.\n\nParticipants in the Solicitation\n\nThe Company and certain of its directors, executive officers and other members of management and employees may, under the rules of the SEC, be deemed to be participants in the solicitation of proxies from the Company’s stockholders in connection with the Stockholder Proposals. Information regarding the Company’s directors and named executive officers, including a description of their direct or indirect interests, by security holdings or otherwise, is contained in the definitive proxy statement for the 2026 annual meeting of stockholders, which was filed with the SEC on April 24, 2026 (the “2026 Annual Meeting Proxy Statement”). To the extent holdings of the Company’s securities by such directors or executive officers (or the identity of such directors or executive officers) have changed since the information set forth in the 2026 Annual Meeting Proxy Statement, such information has been or will be reflected on the Initial Statements of Beneficial Ownership on Form 3 or Statements of Changes in Beneficial Ownership on Form 4 filed with the SEC. Additional information regarding the interests of the Company’s directors and executive officers in the Stockholder Proposals will be included in the Proxy Statement to be filed with the SEC. You may obtain free copies of these documents using the sources indicated above.\n\nNote Regarding Forward-Looking Statements\n\nThe Company cautions you that statements contained in this report regarding matters that are not historical facts are forward-looking statements. These statements are based on the Company’s current beliefs and expectations. Such forward-looking statements include, but are not limited to, statements regarding: the Company’s proposed Exchange Offer and Consent Solicitation relating to its Existing Convertible Notes, including the anticipated benefits thereof; the timing, occurrence and outcome of the Company’s planned Pre-NDA Type B meeting with the FDA; the timing and potential submission of an NDA for seralutinib in PAH; the potential significance, interpretation and implications of data from the Phase 3 PROSERA study, including the CT FRI substudy; and the development potential and market opportunity of seralutinib in PAH, PH-ILD and other indications. The inclusion of forward-looking statements should not be regarded as a representation by Gossamer that any of its plans will be achieved. Actual results may differ from those set forth in this press release due to the risks and uncertainties inherent in Gossamer’s business, including, without limitation: the Company may not be able to complete the Exchange Offer on the anticipated timeline or at all, and the Company may not realize the anticipated benefits therefrom; the Company may not be able to identify a development path forward for seralutinib or submit an NDA on the timeframe we expect or at all, whether as a result of FDA feedback or otherwise, and any path forward may require additional capital and other resources, which may not be available on reasonable terms, if at all, or may limit the commercial opportunity for seralutinib; topline results the Company reports are based on preliminary analysis of key data, and such data may change following a more comprehensive review of the data related to the clinical trial or substudy and such topline data may not accurately reflect the complete results of a clinical trial or substudy; the Company’s interpretation, significance and regulatory relevance of data from the Phase 3 PROSERA study, including the CT FRI substudy, may be inconsistent with the views of the FDA or others; risks related to the proposed Exchange Offer and Consent Solicitation, including whether the transaction is completed and whether the anticipated benefits are realized; potential delays in the commencement, enrollment and completion of clinical trials; disruption to our operations from unexpected events, including clinical trial delays; the Company’s dependence on third parties in connection with product manufacturing, research and preclinical and clinical testing; the results of preclinical studies and early clinical trials with seralutinib are not necessarily predictive of future results; the success of Gossamer’s clinical trials and preclinical studies for seralutinib; regulatory developments in the United States and foreign countries; unexpected adverse side effects or inadequate efficacy of seralutinib that may limit its development, regulatory approval and/or commercialization, or may result in clinical holds, recalls or product liability claims; Gossamer’s ability to obtain and maintain intellectual property protection for seralutinib; Gossamer’s ability to comply with its obligations in collaboration agreements with third parties or the agreements under which it licenses intellectual property rights from third parties; unstable market and economic conditions and changes in healthcare legislation, tariffs and trade policies may adversely affect the Company’s business and financial condition and the broader economy and biotechnology industry; Gossamer may use its capital resources sooner than it expects; and other risks described in the Company’s prior press releases and the Company’s filings with the Securities and Exchange Commission (SEC), including under the heading “Risk Factors” in the Company’s annual report on Form 10-K and any subsequent filings with the SEC. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and Gossamer undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date hereof. 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."}