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May 18, 2026 8:01 AM

Why Is Regeneron Stock Sinking Monday?

On Friday, Regeneron Pharmaceuticals, Inc. (NASDAQ:REGN) reviewed results from the Phase 3 trial evaluating two dose levels of fianlimab (LAG-3 inhibitor) in combination with Libtayo (cemiplimab) for unresectable locally advanced or metastatic melanoma.

Phase 3 Melanoma Trial Misses Primary Endpoint

The trial did not reach statistical significance for the primary endpoint of improvement in progression-free survival (PFS) compared to Merck & Co. Inc. (NYSE:MRK) Keytruda (pembrolizumab) monotherapy.

High-dose fianlimab combination showed a numerically higher median progression-free survival of 11.5 months compared to 6.4 months on Keytruda, but failed statistically with a p-value of 0.0627.

Low-dose combination showed a progression-free survival of 9.6 months, with a p-value of 0.4661.

No new safety ...