A second shareholder firm, Robbins LLP, is reminding investors of claims tied to the Phase 3 Fianlimab-Libtayo melanoma trial and a Sept. 14, 2026 lead plaintiff deadline.
Regeneron Pharmaceuticals, Inc. is facing a securities fraud class action alleging the company misled investors about the viability and prospects of its Phase 3 Fianlimab-Libtayo clinical trial for advanced melanoma. The proposed class covers investors who purchased or otherwise acquired Regeneron securities between Aug. 1, 2025 and May 15, 2026, and investors have until Sept. 14, 2026 to seek appointment as lead plaintiff. The complaint alleges Regeneron gave investors positive statements about the study while failing to disclose that its preliminary statistical assumptions were fundamentally flawed, that the Fianlimab-Libtayo treatment arm was not achieving meaningful clinical differentiation from standard therapies, and that the trial was unlikely to achieve statistical significance on its primary endpoint of progression-free survival. Fianlimab is a monoclonal antibody targeting the LAG-3 immune checkpoint receptor on T-cells and was being evaluated with Libtayo as a first-line treatment in advanced melanoma. Two 2026 disclosures anchor the case. On April 29, Regeneron said the Phase 3 study had been modified to expand the number of patients eligible for analysis of progression-free survival, sending the stock down 6.2% from $731.77 to $686.36. After markets closed on May 15, Regeneron said the Phase 3 Fianlimab trial failed to achieve statistical significance for improvement in progression-free survival, and the shares fell 9.8% from $698.25 to $629.68 by May 18. Earlier reporting also said Hagens Berman was investigating the claims, while Robbins LLP has now issued a separate investor notice tied to the same case.