Gossamer Bio (NASDAQ:GOSS) said it is moving ahead with plans to seek U.S. approval for seralutinib in pulmonary arterial hypertension, outlining a September 2026 target for a New Drug Application submission while also detailing new imaging data and steps to address its balance sheet during its first-quarter 2026 earnings call.
The company’s executives said the regulatory strategy is based on the totality of evidence from the Phase 3 PROSERA study and the Phase 2 TORREY study. Chief Executive Officer Faheem Hasnain said Gossamer’s “conviction in seralutinib has increased since the top-line readout, not decreased,” citing PROSERA, TORREY, new CT imaging results and ongoing engagement with the Food and Drug Administration.
FDA meeting set for June ahead of planned NDA filing
Caryn Peterson said Gossamer is pursuing an NDA under a framework of “one adequate and well-controlled clinical investigation plus confirmatory evidence.” She said the company believes PROSERA can serve as the adequate and well-controlled study, while TORREY provides confirmatory evidence.
Peterson said Gossamer had initially considered a Type C meeting with the FDA but is now moving forward with a Type B pre-NDA meeting, which she described as a formal pre-submission interaction. The company submitted the meeting request in April 2026, and the FDA has granted an in-person meeting in mid-June.
“Based on that timing, our NDA submission target remains in September this year, subject to the outcome of the pre-NDA meeting,” Peterson said. If the process proceeds as expected, she said a potential approval could follow in the third quarter of 2027.
Hasnain summarized the PROSERA results by noting that seralutinib produced a placebo-adjusted improvement of 13.3 meters in six-minute walk distance at week 24. Patients receiving seralutinib improved 28.2 meters from baseline, compared with 13.5 meters for placebo. The result had a P value of 0.032, which met the traditional 0.05 threshold for statistical significance but did not meet the study’s pre-specified 0.025 alpha threshold. Hasnain said all four key secondary endpoints favored seralutinib, with a stronger effect in a pre-specified risk-enriched subgroup.
CT-FRI sub-study shows multi-compartment imaging signals
Dr. Rob Roscigno reviewed findings from the PROSERA CT-FRI sub-study, which used Fluidda’s functional respiratory imaging platform to evaluate anatomical changes in the pulmonary vasculature and lung parenchyma. He said 162 patients enrolled in the sub-study, with 125 patients having paired baseline and week 24 CT scans available for analysis.
Roscigno said the imaging data showed statistically significant treatment effects across arterial, venous and fibrosis-like parenchymal parameters. He said the findings extended the arterial reverse remodeling signal first observed in TORREY and suggested effects beyond a single vascular compartment.
According to Roscigno, seralutinib significantly reduced BV10A percentage, a measure of large arterial blood volume as a proportion of total blood volume, which he said was consistent with proximal arterial decompression and redistribution toward smaller peripheral arteries. He also said the company observed statistically significant reductions in fibrosis-like parenchymal volume and normalized fibrosis-like parenchymal volume, while placebo progressed.
In the venous compartment, Roscigno said seralutinib significantly increased total venous blood volume while placebo decreased. He said increases were also seen across venous vessel sizes and vascular branching, including fractal dimension. The company characterized the venous findings as a potential integrated readout of improved upstream arterial, parenchymal and capillary bed biology.
Roscigno said changes in imaging parameters correlated with clinical endpoints, including six-minute walk distance, NT-proBNP and REVEAL Lite 2. However, he emphasized that the CT-FRI work was a pre-specified exploratory sub-study, and that the P values were nominal and unadjusted for multiplicity.
During the question-and-answer session, Dr. Jean-Marie Bruey said FRI is not a surrogate endpoint but provides “mechanistic insight” by separately quantifying arterial, venous, fibrosis-like and vascular complexity changes. Hasnain added that the technology is not standard in routine PAH clinical practice.
Company discusses label and commercial positioning
In response to an analyst question, Peterson said the CT-FRI data were not included in the pre-NDA briefing package because they were not ready in time, though the company plans to highlight them at the June meeting. She said the full dataset is expected to be part of the NDA and could be discussed for inclusion in the pharmacodynamic section of the label.
Chief Commercial Officer Bob Smith said the company believes seralutinib could have a differentiated profile in the PAH market, pointing to the imaging data and prior Phase 1 and Phase 2 results. He said the company expects the label to be “highly differentiated” if the data are included.
Asked about potential commercial use, Hasnain said the treatment effect was “very pronounced” in the intermediate- to high-risk subgroup, but he also suggested clinicians may be interested in using seralutinib across the PAH patient spectrum, including earlier in the disease course, given the company’s view of the drug’s safety profile and mechanism.
Cash runway extends into early 2027; debt exchange announced
Chief Operating Officer and Chief Financial Officer Bryan Giraudo said Gossamer ended the first quarter with $99 million in cash, cash equivalents and marketable securities. Based on current plans, the company expects its cash runway to extend into the first quarter of 2027.
Giraudo said operating expenses are expected to decline now that the PROSERA study has wound down. He also cited a previously implemented reduction in force affecting approximately half the company, broader cost containment measures and a pause in other development activities. He said the first quarter included one-time charges, and the company’s go-forward quarterly cash burn should be lower.
Gossamer also announced a convertible note exchange aimed at addressing $200 million in aggregate principal amount of convertible senior notes maturing in 2027. Under the exchange, holders tendering existing notes will receive a mix of equity consideration, new secured convertible notes and, for early tenders, warrants.
Giraudo said that on a fully subscribed basis, the transaction would reduce outstanding convertible debt from $200 million to $72 million and extend the debt maturity from 2027 to 2030. The new notes will be secured by a first-priority lien on substantially all company assets and bear 7.5% cash interest paid semiannually. The exchange requires minimum participation of 98%, which may be waived.
Hasnain closed the call by saying the company is focused on advancing seralutinib toward approval and thanked patients, advocacy groups, investigators and the clinical community for their involvement in the PROSERA study and broader development program.
About Gossamer Bio (NASDAQ:GOSS)
Gossamer Bio, Inc is a clinical-stage biopharmaceutical company headquartered in San Diego, California. Founded in 2012, the company is focused on discovering and developing oral, once-daily therapies for immune-mediated and inflammatory diseases, as well as oncology indications. Gossamer Bio leverages a deep pipeline of small-molecule candidates aimed at improving patient outcomes in areas of high unmet need.
The company's lead programs include GB004, an S1P1 receptor modulator in late-stage development for ulcerative colitis, and GB1275, a CD11b modulator being investigated in solid tumors and hematologic malignancies.
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