Robbins LLP Encourages GOSS Stockholders to Join Class Action Against Gossamer Bio

Law firm seeks lead plaintiff for lawsuit alleging Gossamer Bio misled investors about its PROSERA drug trial.

Apr. 16, 2026 at 1:12am

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A minimalist studio still life photograph featuring a stack of legal documents, a pen, and a calculator on a clean, monochromatic background, conceptually representing the abstract themes of corporate strategy, finance, and legal proceedings.A legal case against a pharmaceutical company highlights the need for transparency and accurate disclosures in the biotech industry.San Diego Today

Robbins LLP, a law firm specializing in shareholder rights litigation, is encouraging investors who purchased Gossamer Bio, Inc. (NASDAQ: GOSS) stock between June 16, 2025 and February 20, 2026 to contact the firm about potentially serving as the lead plaintiff in a class action lawsuit. The lawsuit alleges that Gossamer Bio misled investors about the viability of its PROSERA study, which evaluated the company's drug seralutinib for the treatment of pulmonary arterial hypertension (PAH).

Why it matters

This lawsuit represents an opportunity for Gossamer Bio shareholders who lost money on their investments to potentially recoup those losses. The case also highlights the importance of transparency and accurate disclosures from publicly traded companies, as investors rely on this information to make informed decisions.

The details

According to the complaint, Gossamer Bio provided investors with overly positive information about the PROSERA study's trial design and the drug's prospects, while concealing material issues with the study, particularly related to the placebo response at Latin American testing sites. This allegedly caused the company's stock price to be artificially inflated. The truth emerged on February 23, 2026, when Gossamer announced that the PROSERA study had failed to meet its primary endpoint, causing the stock price to plummet by over 80% in a single day.

  • The class period is from June 16, 2025 to February 20, 2026.
  • Shareholders have until June 1, 2026 to submit papers to the court to potentially serve as the lead plaintiff in the class action lawsuit.

The players

Robbins LLP

A law firm specializing in shareholder rights litigation that is investigating the allegations against Gossamer Bio and encouraging affected investors to join the class action lawsuit.

Gossamer Bio, Inc.

A clinical-stage biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of pulmonary hypertension associated with interstitial lung disease.

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What’s next

Shareholders who wish to serve as the lead plaintiff for the class must submit their papers to the court by June 1, 2026. The lead plaintiff is a representative party who acts on behalf of other class members in directing the litigation.

The takeaway

This lawsuit highlights the importance of transparency and accurate disclosures from publicly traded companies, as investors rely on this information to make informed decisions. The outcome of this case could have significant implications for Gossamer Bio shareholders who lost money on their investments.