A securities class action has been filed against Gossamer Bio, Inc. (GOSS) on behalf of all investors who purchased or otherwise acquired Gossamer securities between June 16, 2025 through February 20, 2026. This case has been filed in the USDC – SDCA.
Seralutinib was Gossamer Bio’s lead pipeline candidate and the PROSERA study was the Company’s pivotal Phase 3 trial evaluating the drug in pulmonary arterial hypertension. The Company had publicly characterized the PROSERA patient population as well-suited to demonstrate a treatment effect.
During the Q1 2025 earnings call on May 15, 2025, CEO Faheem Hasnain stated that baseline characteristics were “precisely what we have targeted” and that the Company was “more optimistic than ever about the likelihood of achieving positive results.” Management also claimed “over 90% power given the sample size.” The trial reached its planned enrollment target but the primary efficacy endpoint did not achieve the prespecified level of statistical significance.
The complaint alleges that defendants acted with scienter in that they knew or otherwise were deliberately reckless in not knowing that the public statements disseminated on behalf of Gossamer were materially false and misleading at the time they were made. Defendants had actual knowledge of, or access to, non-public information concerning the trial design and clinical test site selection as the drug sponsor, thereby knowing or recklessly disregarding the protocol design issues that ultimately caused the Phase 3 PROSERA study to fail to meet its primary endpoint of improved six-minute walk distance at week 24. In fact, Defendants knew or deliberately disregarded that patients at the Latin American clinical testing sites were largely heavily-treated as well as lower risk and, therefore, performed particularly well on the placebo. Defendants knew or deliberately disregarded these issues that gave rise to the acute risks that ultimately.
Gossamer’s stock price fell in response to the corrective event on February 23, 2026, as alleged supra. On February 23, 2026, Defendants disclosed information that was directly related to their prior misrepresentations and material omissions concerning the Phase 3 PROSERA trial’s defects in Latin America.