GOSS: CT FRI Substudy Provides More Support for Seralutinib's Potential Treatment Effect, But Regulatory, Commercial and Financial Questions Remain; 1Q 2026 Earnings Recap

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GOSS: CT FRI Substudy Provides More Support for Seralutinib's Potential Treatment Effect, But Regulatory, Commercial and Financial Questions Remain; 1Q 2026 Earnings Recap

May 18, 2026

Vamil Divan, M.D. vamil.divan@guggenheimpartners.com GOSS: CT FRI Substudy Provides More Support

212 823 6543 for Seralutinib's Potential Treatment Effect, But

Daniel Krizay, Ph.D.

daniel.krizay@guggenheimpartners.com Regulatory, Commercial and Financial Questions

212 823 6561 Remain; 1Q 2026 Earnings Recap Arseniy Shabashvili

arseniy.shabashvili@guggenheimpartners.com

212 699 1971 Key Message: Gossamer reported 1Q 2026 earnings and provided a corporate update

Edouard Mullarky, Ph.D. this morning. In this update, the company released topline data from their PROSERA

edouard.mullarky@guggenheimpartners.com CT functional respiratory imaging (FRI) substudy, announced their convertible notes

212 518 9579 exchange offer, and communicated their updated regulatory plans for seralutinib in

PAH. We believe the data from the CT FRI substudy supports our view that seralutinib

does have a moderate treatment effect in this patient population, with positive structural

changes observed in the pulmonary arteries, veins, and parenchyma. However, we still

question if this supportive data will be compelling enough to move the needle fromGOSS NEUTRAL a regulatory perspective, given the lack of a statistically significant improvement in Gossamer Bio, Inc. important clinical endpoints like six-minute walk distance (6MWD) and time to clinical Sector: Biotechnology

worsening. A Type B pre-NDA meeting has been scheduled with the FDA for mid-June,

Earnings Release with the company anticipating sharing FDA feedback from this meeting with the Street