Regeneron Pharmaceuticals Inc. stuck with the tradition of releasing bad news on Friday afternoon and good news on Monday morning with a pair of announcements bracketing the weekend. On May 15, 2026, the Tarrytown, N.Y.-based company announced disappointing data for its LAG-3 inhibitor fianlimab. And then on May 18, 2026, Regeneron announced better news in the form of a deal with Parabilis Medicines Inc.