Regeneron Investors Face September Deadline in Securities Class Action

The lawsuit, Cheatham v. Regeneron Pharmaceuticals, Inc., filed in the Southern District of New York, claims top executives violated the Securities Exchange Act of 1934. The core of the complaint centers on allegations that the company provided false impressions about the reliability and statistical validity of its Phase III Fianlimab-Libtayo study. Plaintiffs argue that Regeneron failed to disclose flawed statistical assumptions and that the treatment arm was not showing meaningful differentiation from standard therapies.

Financial consequences for investors followed two specific disclosures. On April 29, 2026, the company announced an expansion of the study's patient eligibility criteria, triggering a share price decline of more than 6%. Further pressure arrived on May 15, 2026, when Regeneron confirmed the trial failed to reach statistical significance for its primary endpoint of progression-free survival, causing the stock to drop an additional 10%. Investors interested in serving as lead plaintiff must demonstrate a significant financial interest and meet legal standards for adequacy and typicality under the Private Securities Litigation Reform Act of 1995.