The proposed suit covers purchases from Aug. 1, 2025 to May 15, 2026 and alleges investors were misled about statistical risks, protocol changes and the likelihood the Fianlimab-Libtayo study would miss its primary endpoint.
Regeneron Pharmaceuticals is facing a proposed securities class action tied to disclosures about its Phase 3 Fianlimab-Libtayo melanoma study after the trial failed to reach statistical significance on progression-free survival. The case covers investors who purchased securities or common stock between August 1, 2025 and May 15, 2026, with lead plaintiff applications due by September 14, 2026. The complaint alleges Regeneron portrayed slowing event accrual as potentially favorable and continued expressing confidence in the study while not fully disclosing what plaintiffs describe as flawed preliminary statistical assumptions, weak differentiation versus standard therapies, protocol changes linked to slow event rates, and an elevated risk of missing the primary endpoint. One release says the selloff erased about $11 billion in market value, while another says shares fell about 13.95%, or $102.09 per share, from the class-period high through the final disclosure-related decline.