GOSS Investor Alert: Gossamer Bio Securities Fraud Lawsuit - Investors With Losses May Seek to Lead the Class Action After Company Allegedly Overstated Trial Prospects: Levi & Korsinsky

Promise vs. Reality: The Gossamer Bio PROSERA Performance Gap

NEW YORK--(BUSINESS WIRE)--"We firmly believe that we have accomplished this patient selection goal." That was the promise. The reality: a Phase 3 trial that failed its primary endpoint, and shareholders who lost over 80% of their investment in a single trading session.

Levi & Korsinsky, LLP notifies investors in Gossamer Bio, Inc. (NASDAQ: GOSS) that a securities class action has been filed on behalf of purchasers who acquired GOSS stock between June 16, 2025 and February 20, 2026. Find out if you can recover your GOSS investment losses or contact Joseph E. Levi, Esq. at [e-mail] or [phone].

Shares collapsed from $2.13 to $0.42, a loss of $1.71 per share (over 80%), after Gossamer disclosed that its Phase 3 PROSERA study for seralutinib in pulmonary arterial hypertension failed to meet the prespecified statistical threshold.

The Promise

Throughout the Class Period, the company projected confidence that PROSERA was on track. Management told investors the trial had enrolled a patient population "that aligns closely with the study's objectives" and was "more likely to exhibit a clinically significant benefit in 24 weeks," drawing on "insights from the Phase 2 TORREY Study." The company further assured investors it was "executing the PROSERA Study with discipline and operational excellence."

The Reality

On February 23, 2026, Gossamer revealed that the study produced only a +13.3 meter placebo-adjusted improvement in six-minute walk distance with a p-value of 0.0320, failing the prespecified 0.025 alpha threshold. The miss was attributed to an outsized placebo response at Latin American clinical sites, where heavily-treated, lower-risk patients performed unexpectedly well on placebo, including "super responders" with over 100-meter walk improvements on placebo alone.

The Numbers: Promised vs. Actual

• Patient selection: Promised alignment with Phase 2 TORREY insights; actual enrollment at Latin American sites allegedly included a heavily-treated, lower-risk population inconsistent with those goals
• Statistical threshold: Required p-value of 0.025; actual p-value was 0.0320
• Placebo response: Expected placebo performance consistent with typical Phase 3 PAH trials (historically -9m to +11m); actual Latin American placebo response was dramatically elevated, compressing the treatment difference by approximately 8 meters
• North America vs. Latin America: North American sites showed a 25.9-meter placebo-adjusted improvement; Latin American sites showed near-parity between placebo and treatment arms
• Stock price: Class Period trading around $2.13; post-disclosure close of $0.42

What the Lawsuit Alleges About the Gap

The action contends that the gap between these projections and the actual outcome was not the product of unforeseeable trial variability. Rather, the complaint charges that management, as the drug sponsor, had access to enrollment data showing the characteristics of patients at Latin American sites and knew or recklessly disregarded that the inclusion of this heavily-treated, lower-risk population created a high risk of an outsized placebo response that would jeopardize the primary endpoint.

"Companies that make specific promises to investors about future performance have an obligation to disclose known risks to those projections. The contrast between what Gossamer told investors about PROSERA's patient selection and what the enrollment data allegedly showed raises serious questions about the adequacy of the company's disclosures." -- Joseph E. Levi, Esq.

LEAD PLAINTIFF DEADLINE: June 1, 2026

Submit your claim to pursue recovery of GOSS losses or call Joseph E. Levi, Esq. at [phone].

ABOUT LEVI & KORSINSKY, LLP -- Levi & Korsinsky, LLP is a nationally recognized shareholder rights firm. Over the past 20 years, the firm has secured hundreds of millions of dollars for aggrieved shareholders. Ranked in ISS Top 50 for seven consecutive years.

Frequently Asked Questions About the GOSS Lawsuit

Q: What is the GOSS class action lawsuit about? A: A securities class action has been filed against Gossamer Bio, Inc. (NASDAQ: GOSS) alleging materially false and misleading statements between June 16, 2025 and February 20, 2026. Shares fell approximately 80% after the truth was revealed, causing significant losses for shareholders.

Q: Who is eligible to join the GOSS investor lawsuit? A: Investors who purchased GOSS stock or securities between June 16, 2025 and February 20, 2026 and suffered financial losses may be eligible. Eligibility is based on purchase date and documented losses, not on whether you still hold the shares.

Q: What do GOSS investors need to do right now? A: Gather brokerage records including purchase dates, share quantities, and prices paid. Contact Levi & Korsinsky for a free, no-obligation evaluation at [e-mail] or [phone]. No immediate action is required to remain eligible as a class member.

Q: What if I already sold my GOSS shares -- can I still recover losses? A: Yes. Eligibility is based on when you purchased, not whether you still hold them. Investors who bought during the class period and sold at a loss may still participate.

Q: Do I need to go to court or give testimony? A: No. The overwhelming majority of class members never appear in court or give depositions. You submit a claim form to receive your portion of recovery.

Q: What does it cost me to participate? A: Nothing. Securities class actions are handled on a pure contingency basis. No upfront fees, no retainer, no out-of-pocket costs.

Q: What if I missed the lead plaintiff deadline? A: The deadline applies only to investors seeking lead plaintiff appointment. Class members who miss it can still participate in any settlement or recovery.