Gossamer Bio GOSS

Gossamer Bio Inc is a clinical-stage biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of pulmonary hypertension including pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease. The company is advancing seralutinib as an inhaled small molecule inhibitor targeting platelet-derived growth factor receptor colony-stimulating factor 1 receptor and c-KIT pathways to address pathological vascular remodeling in these diseases. Gossamer Bio aims to improve patient outcomes by developing therapies that target underlying disease mechanisms rather than merely managing symptoms.

Gossamer Bio generates revenue primarily through collaboration agreements and potential future product sales. The company has entered into a collaboration agreement with Chiesi under which Chiesi agreed to pay Gossamer Bio 160.0 million dollars in consideration for development costs and Gossamer Bio is eligible to receive up to 146.0 million dollars in regulatory milestones and 180.0 million dollars in sales milestones. Under this agreement Gossamer Bio leads global development of seralutinib for pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease and will lead potential commercialization for these indications in the United States with Chiesi contributing equally to commercialization efforts in the United States. Chiesi has the exclusive right to commercialize seralutinib outside the United States. The company also holds an option agreement with Respira Therapeutics to advance RT234 an investigational inhaled on-demand dry powder formulation of vardenafil a PDE5 inhibitor for pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease. Revenue generation is currently dependent on milestone payments from collaborations and potential future approval and commercialization of seralutinib or RT234.

The company operates through the following segments: seralutinib development and RT234 development.

• The seralutinib segment focuses on the development and potential commercialization of seralutinib an inhaled kinase inhibitor targeting PDGFRα/β CSF1R and c-KIT for the treatment of pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease. Gossamer Bio is completing analyses of the Phase 3 PROSERA study dataset engaging with the U. S. Food and Drug Administration to obtain feedback on potential regulatory paths forward and advancing NDA-readiness activities. The company has paused enrollment in the SERANATA Phase 3 study in pulmonary hypertension associated with interstitial lung disease to evaluate the PROSERA dataset and support disciplined resource allocation while continuing to believe seralutinib may have meaningful potential in fibrotic lung disease. Gossamer Bio is also advancing RT234 under its option agreement with Respira Therapeutics in a capital-efficient manner to support limited foundational manufacturing and device readiness activities while preserving focus on seralutinib.

• The RT234 segment involves the development of RT234 an investigational inhaled as-needed dry powder formulation of vardenafil a PDE5 inhibitor for pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease. Gossamer Bio entered into an option agreement with Respira Therapeutics in September 2025 to acquire RT234 which has completed open-label Phase 2 clinical trials and is intended to address an unmet need for on-demand symptom management that may complement existing chronic pulmonary hypertension therapies. Current activities by Respira Therapeutics are focused on foundational manufacturing and device readiness and subject to these ongoing activities RT234 could reenter clinical development as early as 2027. Gossamer Bio believes RT234 represents a complementary on-demand therapeutic opportunity in pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease.

Gossamer Bio operates in a highly competitive biopharmaceutical industry focused on pulmonary hypertension therapies. The company faces competition from established and investigational treatments for pulmonary arterial hypertension including prostanoids such as Orenitram Uptravi Tyvaso Yutrepia and Remodulin endothelin receptor antagonists such as Tracleer Letairis and Opsumit phosphodiesterase type 5 inhibitors such as Revatio and Adcirca soluble guanylate cyclase stimulators such as Adempas and activin ligand traps such as Winrevair. For pulmonary hypertension associated with interstitial lung disease Gossamer Bio expects competition from approved therapies such as Tyvaso and Yutrepia in the United States and investigational agents such as L606 sirolimus treprostinil palmitil inhalation powder mosliciguat mirivadelgat APL-9796 and ROC-101. Gossamer Bio’s competitive advantages include seralutinib’s differentiated mechanism of action targeting multiple kinase pathways involved in vascular remodeling its inhaled delivery system designed to reduce systemic exposure compared to prior kinase inhibitors like imatinib and its potential to address both pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease. The company also benefits from orphan drug designation granted by the U. S. Food and Drug Administration the European Commission and the Pharmaceuticals and Medical Devices Agency of Japan for seralutinib in pulmonary arterial hypertension.

Gossamer Bio serves patients with pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease. The company’s therapeutic candidates are intended for use by individuals diagnosed with these rare and progressive diseases who are receiving background pulmonary hypertension therapy. Gossamer Bio does not disclose specific customer names such as hospitals or clinics in the filing but its therapies are designed for use in clinical settings under physician supervision. The patient population includes individuals across functional classes II and III of pulmonary arterial hypertension and those with connective tissue disease-associated pulmonary arterial hypertension a subgroup identified in the PROSERA study.