Gossamer Bio faces securities class action; lead plaintiff named, amended complaint due Aug. 10

Gossamer Bio, Inc. (Nasdaq: GOSS) disclosed in its 10-Q filed August 13, 2026 that a securities class action over statements about its business is in its early stage in federal court in California. Daniel Kinnamon filed Kinnamon v. Gossamer Bio, Inc., et al., Case No. 3:26-cv-2016-CAB-AHG, on March 31, 2026 in the U.S. District Court for the Southern District of California. The suit names the company and "certain of its executive officers and directors".

The 10-Q does not name the individuals. Gossamer's 10-K filed March 17, 2026, two weeks before the suit, was signed by Faheem Hasnain as president, chief executive officer and chairman of the board, and by Bryan Giraudo as chief operating officer and chief financial officer. Six other directors signed it: Russell Cox, Thomas Daniel, Sky Drynan, Sandra Milligan, Steven Nathan and John Quisel. No filing reviewed says which of them are defendants.

The case

Kinnamon sued for himself and for everyone who purchased or otherwise acquired Gossamer securities between June 16, 2025 and February 20, 2026. The complaint alleges that the company and certain officers and directors made false or misleading statements and failed to disclose material adverse facts about the company's business, operations and prospects. It claims violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5.

The plaintiff seeks damages, interest, costs, attorneys' fees and other unspecified equitable relief. The 10-Q does not say which statements the complaint challenges. Gossamer's risk factors say that in February 2026 it announced topline results from the Phase 3 PROSERA trial of seralutinib in pulmonary arterial hypertension, and that the study did not meet its primary endpoint. The 10-Q does not link that announcement to the suit.

Defendants

The defendants are Gossamer Bio, Inc. and unnamed executive officers and directors. The 10-K signature page, dated two weeks before the suit, shows a board of Hasnain, Cox, Daniel, Drynan, Milligan, Nathan and Quisel, with Giraudo as chief financial officer. The filings do not say which of them, if any, are defendants.

Where it stands

On May 4, 2026, the court entered an order staying any answer or response to the complaint until a lead plaintiff and lead counsel were appointed. On July 7, 2026, it appointed Martin Meienhofer as lead plaintiff and his counsel as lead counsel. On July 20, 2026, the court ordered the lead plaintiff to file an amended complaint by August 10, 2026.

The 10-Q does not say whether the amended complaint was filed, and no later filing reviewed reports on the case. Gossamer says it intends to defend the matter vigorously.

Why it matters to shareholders

Gossamer says that given the uncertainty of litigation, the preliminary stage and the legal standards for class certification and success on the merits, it cannot estimate the reasonably possible loss or range of loss. The filings reviewed give no accrual and say nothing about insurance coverage or indemnification of the individuals.

Related matters

Gossamer's 10-K says that on April 3, 2020 the company, certain executive officers and directors, and the underwriters of its initial public offering were named in an earlier purported securities class action. A court entered a judgment on September 30, 2022 approving a settlement in which Gossamer agreed to pay approximately $2.4 million.

The 10-K adds that such suits may be expensive and time consuming and may divert management's attention.

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