GOSS Investor Alert: Gossamer Bio Securities Fraud Lawsuit - Investors With Losses May Seek to Lead the Class Action After Allegedly Concealing Clinical Execution Failures: Levi & Korsinsky

Alert: Claims Focus on Alleged Misrepresentations About PROSERA Trial

NEW YORK, May 20, 2026 /PRNewswire/ -- Levi & Korsinsky, LLP reminds purchasers of Gossamer Bio, Inc. (NASDAQ: GOSS) securities of a pending securities class action.

THE CASE: A class action seeks to recover damages for investors who purchased Gossamer securities between June 16, 2025 and February 20, 2026.

YOUR OPTIONS: You may be entitled to compensation without payment of any out-of-pocket fees. See if you can recover losses or contact Joseph E. Levi, Esq. at [email protected] or (212) 363-7500.

Gossamer shares collapsed from $2.13 to $0.42 on February 23, 2026, destroying over 80% of shareholder value in a single trading session, after topline Phase 3 PROSERA results revealed the study failed to meet its primary endpoint. Investors have until June 1, 2026 to seek lead plaintiff status.

How a Clinical-Stage Biopharma Company Monitors Trial Execution

A clinical-stage biopharmaceutical company sponsoring a global Phase 3 trial bears responsibility for monitoring enrollment characteristics and site-level performance throughout the study. The drug sponsor selects the clinical research organization, approves site locations, reviews enrollment demographics, and tracks interim data. When a company tells investors it is executing a pivotal study "with discipline and operational excellence," the market reasonably expects that the sponsor is actively managing geographic and demographic variables that could affect the primary endpoint.

The lawsuit contends that Gossamer failed to disclose that its Latin American clinical sites enrolled a heavily-treated, lower-risk patient population whose baseline characteristics diverged from what the Company publicly described as its patient selection goals.

Alleged PROSERA Trial Execution Breakdown by the Numbers

• The filing states that the operational failures at Latin American sites materially compressed the treatment effect:
• 55% of PROSERA patients were on triple or quadruple background PAH therapy, indicating a heavily-treated population
• 61% were on background prostacyclin therapy at baseline
• North American placebo arm showed a 25.9-meter improvement, consistent with historical PAH trials
• The placebo response reduced the overall treatment effect by approximately 8 meters, as set forth in the complaint
• The primary endpoint result of p=0.0320 narrowly missed the pre-specified 0.025 alpha threshold

Clinical Site Selection and the Latin American Anomaly

As detailed in the action, Gossamer's COO and CFO acknowledged during the February 23, 2026 Special Call that the company had made "a significant investment in Latin America" based on prior PAH trial geography data. Yet the complaint alleges Gossamer did not disclose to investors during the Class Period that the actual enrollment profile at those sites was inconsistent with the patient selection criteria the Company publicly touted. Key opinion leaders who reviewed the data characterized the Latin American irregularity as a "trial execution issue, not a drug effect issue," with one analyst report pointing to potential "human measurement error during 6MWD lap counting."

Calculate your potential recovery or call (212) 363-7500.

"The complaint raises serious questions about whether investors received accurate information regarding the operational integrity of this pivotal clinical trial." -- Joseph E. Levi, Esq.

Find out if you qualify to recover your investment or contact Joseph E. Levi, Esq. at (212) 363-7500.

ABOUT LEVI & KORSINSKY, LLP -- Over the past 20 years, Levi & Korsinsky has secured hundreds of millions of dollars for aggrieved shareholders. The firm has extensive expertise in complex securities litigation and a team of over 70 employees. For seven consecutive years, Levi & Korsinsky has ranked in ISS Securities Class Action Services' Top 50 Report.

Frequently Asked Questions About the GOSS Lawsuit

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: How much did GOSS stock drop? A: Shares fell approximately 80%, a decline of $1.71 per share, after the company disclosed topline Phase 3 PROSERA results that failed to meet the primary endpoint. Investors who purchased shares during the class period at artificially inflated prices may be entitled to compensation.

Q: What specific misstatements does the GOSS lawsuit allege? A: The complaint alleges Gossamer made materially false or misleading statements regarding the trial design and execution of its Phase 3 PROSERA clinical trial. When the true state was revealed, the stock price declined sharply.

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 [email protected] or (212) 363-7500. 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.

CONTACT:
Levi & Korsinsky, LLP
Joseph E. Levi, Esq.
Ed Korsinsky, Esq.
33 Whitehall Street, 27th Floor
New York, NY 10004
[email protected]
Tel: (212) 363-7500
Fax: (212) 363-7171

SOURCE Levi & Korsinsky, LLP