Gossamer Bio reacquires worldwide seralutinib rights from Chiesi, targets September NDA

Gossamer Bio announced on July 27, 2026 a set of regulatory and corporate updates tied to seralutinib, its inhaled PDGFR, CSF1R and c-KIT inhibitor for pulmonary arterial hypertension (PAH). After a Pre-NDA Type B meeting with the FDA and receipt of the official meeting minutes, the company said it is moving toward a new drug application submission for seralutinib in PAH in September 2026.¹ The company said the FDA's minutes characterized the statistical significance and treatment effect seen in the Phase 3 PROSERA trial as review issues rather than filing issues, and that it plans to submit the NDA based on PROSERA as the single adequate and well-controlled study, supported by Phase 2 TORREY data and additional analyses.¹ If the FDA accepts the filing, Gossamer said seralutinib could be eligible for an approval decision in the third quarter of 2027.¹ The company noted that FDA's final view on approvability will depend on its review of the full NDA package.

On the corporate side, Gossamer and Chiesi Farmaceutici S.p.A. and Chiesi USA, Inc. entered a Rights Reacquisition Agreement dated July 23, 2026, under which the parties agreed to terminate their May 2024 Collaboration and License Agreement and to have Gossamer reacquire seralutinib assets and worldwide development and commercial rights, including for PAH, PH-ILD, and potential future indications.¹ Under the new agreement, Chiesi will pay Gossamer $5 million within 10 days as reimbursement for outstanding development costs, while Gossamer has agreed to make success-based milestone payments and pay royalties on net sales up to a capped amount, after which no further payments would be owed.¹

Separately, at a special meeting held July 14, 2026, stockholders approved proposals tied to Gossamer's prior exchange of about $181.1 million, or 90.5%, of its $200.0 million in 5.00% Convertible Senior Notes due 2027 for about $65.2 million of new 7.50% Convertible Senior Secured First Lien Notes due 2030, along with related equity and warrants, and authorized a reverse stock split.¹ Gossamer estimated cash, cash equivalents and marketable securities of approximately $57.0 million as of June 30, 2026, on a preliminary, unaudited basis.¹