Regeneron Pharmaceuticals faces securities fraud lawsuit over Fianlimab-Libtayo Study allegations
News provided byRegeneron Pharmaceuticals, Inc · 1 min read
SAN DIEGO, Sept. 3, 2026 /CourierPR/ -- Regeneron Pharmaceuticals, Inc. investors who purchased the company's stock between August 1, 2025, and May 15, 2026, have until September 14, 2026, to seek appointment as lead plaintiff in a class action lawsuit alleging securities fraud. The lawsuit, captioned Cheatham v. Regeneron Pharmaceuticals, Inc., No. 26-cv-06026 (S.D.N.Y.), names Regeneron and certain top executives as defendants.
The complaint alleges that during the class period, the company and its executives made false or misleading statements and failed to disclose critical information. Specifically, it claims that Regeneron created a false impression that its Phase III Fianlimab-Libtayo Study was well-positioned for success, while downplaying the study’s risks and its overall statistical validity. The lawsuit also contends that the company’s preliminary statistical assumptions were flawed, the active treatment arm failed to show meaningful clinical differentiation over standard therapies, and the trial was unlikely to reach statistical significance on its primary endpoint.
On April 29, 2026, during Regeneron’s first quarter earnings call, the company disclosed that the Phase III Fianlimab-Libtayo Study had been altered, expanding the analysis of progression-free survival. This news led to a significant decline in the company’s stock price, with a more than 6% drop reported. The following day, on May 15, 2026, Regeneron issued a press release stating that the Phase 3 Trial of Fianlimab did not reach statistical significance for the primary endpoint of improvement in progression-free survival. This announcement triggered an additional 10% drop in the stock price.
Robbins Geller Rudman & Dowd LLP, a leading law firm in securities fraud litigation, is handling the case. The firm has a history of significant recoveries, having ranked #1 on the most recent ISS Securities Class Action Services Top 50 Report, recovering more than $916 million for investors in 2025. This marks the firm's fourth #1 ranking in the past five years, and it has recovered a total of $8.4 billion for investors in that period, more than any other law firm.