LOS ANGELES, April 15, 2026 (GLOBE NEWSWIRE) -- The Portnoy Law Firm advises Gossamer Bio, Inc., (“Gossamer” or the "Company") (NASDAQ: GOSS) investors of a class action on behalf of investors that bought securities between June 216, 2025 and February 20, 2026, inclusive (the “Class Period”). Gossamer investors have until June 1, 2026 to file a lead plaintiff motion.
Investors are encouraged to contact attorney Lesley F. Portnoy, by phone 310-692-8883 or email: lesley@portnoylaw.com, to discuss their legal rights, or join the case via https://portnoylaw.com/gossamer-bio-inc. The Portnoy Law Firm can provide a complimentary case evaluation and discuss investors’ options for pursuing claims to recover their losses.
According to the complaint, during the class period, defendants provided investors with material information concerning Gossamer’s Phase 3 PROSERA study evaluating seralutinib for the treatment of pulmonary arterial hypertension (PAH). Defendants’ statements included, among other things, confidence in PROSERA’s trial design. Defendants provided these overwhelmingly positive statements to investors while, at the same time, disseminating false and misleading statements and/or concealing material adverse facts concerning the study design for the Company’s Phase 3 PROSERA study, particularly, controlling for the placebo response at the Latin American testing sites. This caused Plaintiff and other shareholders to purchase Gossamer’s securities at artificially inflated prices.
Plaintiff alleges that the truth emerged on February 23, 2026 when Gossamer published a press release and hosted a Special Call announcing topline results for its Phase 3 PROSERA study, which failed to meet the primary endpoint of improved six-minute walk distance (6MWD) at Week 24, with a +13.3 meter placebo-adjusted gain (p-0.0320) failing to meet the required 0.025 alpha threshold. Gossamer attributed this miss to patients at Latin American sites performing particularly well on placebo due to enrollment of a heavily-treated lower-risk population. On this news, the price of Gossamer’s common stock declined from a closing market price of $2.13 per share on February 20, 2026 to $0.42 per share on February 23, 2025, a decline of over 80% in the span of just a single day.
The Portnoy Law Firm represents investors in pursuing claims caused by corporate wrongdoing. The Firm’s founding partner has recovered over $5.5 billion for aggrieved investors. Attorney advertising. Prior results do not guarantee similar outcomes.
Lesley F. Portnoy, Esq.
Admitted CA, NY and TX Bar
lesley@portnoylaw.com
310-692-8883
www.portnoylaw.com
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