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Gossamer sheds 63% even as PAH candidate reaches main goal in Phase 2 trial

Gossamer Bio (NASDAQ:GOSS) dropped ~63% pre-market Tuesday despite the company’s announcement that its candidate for pulmonary arterial hypertension (PAH) seralutinib, reached the primary endpoint with statistical significance in a Phase 2 study called TORREY.

The randomized trial was designed to evaluate the tyrosine kinase inhibitor seralutinib in 86 PAH patients who met a criterion named WHO Functional Class (FC) II or III for the disease.

Forty-two patients belonged to the placebo arm, and 44 were part of the seralutinib arm receiving the treatment via a dry powder inhaler.

The study met the primary endpoint of change in pulmonary vascular resistance (PVR) from baseline to week 24, indicating a mean difference of -96.1 dynes (p = 0.0310) between the placebo and seralutinib arms and implying a placebo-corrected improvement of 14.3%.

According to the secondary endpoint of change in six-minute walk distance (6MWD), there was a mean difference of 6.5 meters from baseline to Week 24, numerically favoring the seralutinib arm.

The incidence of treatment-emergent adverse events (TEAEs), a majority of which were mild to moderate in severity, stood at 36 (86%) and 41 (93%) in the placebo and seralutinib arms, respectively.

Meanwhile, one serious adverse event (SAE) related to the study drug was observed in the seralutinib arm compared to none in the placebo arm.

However, the most frequently observed TEAEs in the IMPRES Phase 3 study for tyrosine kinase inhibitor imatinib in PAH were found to be less frequent in TORREY, Gossamer (GOSS) said, adding that seralutinib was generally well tolerated in the study.

According to Wedbush, seralutinib has potential to claim 42% of the market in the U.S. in 2030.