Gossamer Bio (GOSS) investor relations material

Regulatory and clinical progress

• Completed a Type B pre-NDA meeting with the FDA in June, with positive and collaborative feedback, and plan to file the NDA within weeks, expecting acceptance by late November.

• Addressed upcoming debt and refinanced, improving cash position; regained worldwide rights to seralutinib from Chiesi, now only owing low single-digit royalties.

• Phase III top-line results showed a p-value of 0.032, clearing the traditional 0.05 threshold, though not the EMA's stricter 0.025; FDA's updated guidance now supports 0.05 for rare diseases.

• FDA focused on the totality of data, clinical meaningfulness, and risk-benefit, especially regarding liver safety; subgroup analyses requested and provided.

• NDA will include comprehensive data: phase II and III results, imaging, echo, preclinical, and CMC studies.

Clinical data and market positioning

• Imaging data from PROSERA (125 patients) and TORREY (19 patients) show promising effects on pulmonary vasculature, with unprecedented results in phase III.

• Subgroup analyses reveal strong efficacy in CTD-associated PAH (37-meter improvement), less sick patients, and those diagnosed over five years, covering about 90% of the target population.

• Geographic discrepancies noted: strong results in the US and Western Europe, neutral in Latin America, attributed to different patient phenotypes and treatment paradigms.

• Expectation for a broad label, as subgroup populations align with the majority of US PH patients.

• Clinical community highly supportive, especially due to tolerability and efficacy in difficult-to-treat populations.

Commercial and strategic outlook

• Seralutinib expected to be used after dual upfront therapy, with potential for rapid uptake due to unmet need and tolerability advantages over prostacyclins and other therapies.

• CTD-associated PAH represents about 30% of the US market, with seralutinib showing superior results and safety in this group.

• Company is prepared for self-launch, citing a focused commercial team and sufficient resources.

• PH-ILD remains a priority, with plans to restart and streamline trials, aiming for aggressive development post-PAH approval and anticipated cash flow positivity.

• Open to an AdCom, confident in support from clinicians and patient advocates.