REGN SHAREHOLDER INVESTIGATION: SueWallSt Investigates Regeneron Pharmaceuticals for Possible Securities Law Violations

Regeneron executives pointed to optimistic outcomes for a study that was revealed to have failed to achieve its primary endpoint only two months later; shares dropped sharply when the results came in. NEW YORK, May 19, 2026 /PRNewswire/ -- Regeneron Pharmaceuticals (NASDAQ: REGN) shareholders saw the stock decline more than 10% when the market opened on May 18, 2026 after investors digested the weekend news that Regeneron's Phase 3 melanoma trial of Fianlimab + Libtayo failed to meet its primary endpoint versus Merck's Keytruda (pembrolizumab).