Chiesi just paid Gossamer $5 million to walk away from a deal it signed more than two years ago for $160 million upfront.
In May 2024, Chiesi handed Gossamer $160 million as a development reimbursement for seralutinib, an inhaled tyrosine kinase inhibitor for pulmonary arterial hypertension, plus rights to up to $146 million in regulatory milestones and $180 million in sales milestones tied to the original collaboration. Chiesi got exclusive ex-US commercialization rights and a 50/50 US profit split. That’s gone.
Under the termination agreement Gossamer disclosed Monday, Chiesi pays a one-time $5 million fee, keeps only a capped worldwide royalty and milestone payments, and hands back every commercial right. Gossamer pays nothing to get it back.
The trigger: seralutinib’s Phase 3 PROSERA trial missed its prespecified 0.025 significance threshold in February, printing a p-value of 0.0320 on a 13.3-meter six-minute-walk benefit. FDA’s June pre-NDA minutes called the numbers a “review issue,” not a filing issue, clearing Gossamer to file in September for a decision by August 2027.
Chiesi isn’t leaving PAH for nothing better to do. Three months ago it paid $1.9 billion, or $27 a share, for KalVista and its hereditary angioedema drug Ekterly, a 36% premium and a much cleaner rare-disease bet. Seralutinib’s borderline stats don’t fit that portfolio anymore.
Gossamer now owns 100% of a drug it can’t fully fund. Cash was $57 million as of June 30, and a reverse split is coming to avoid delisting. Full economics on a maybe-drug beats a split stake in a dead one.
— Diana Kowalski