Regeneron Pharmaceuticals faces a securities class action lawsuit regarding its Phase 3 melanoma trial for Fianlimab and Libtayo. The lawsuit alleges the company made false statements about the trial's preliminary statistical assumptions. Plaintiffs claim the treatment failed to show significant differentiation from the current standard of care.
Regeneron announced on May 15, 2026, that the trial missed its primary endpoint. The announcement triggered an estimated $11 billion loss in market capitalization.
Shareholder rights firms publicized the legal action on July 23, 2026. Investors have until September 14, 2026, to seek the role of lead plaintiff.