Regeneron Pharmaceuticals Crashes 12% On A Surprise Sanofi-Tied Failure

Regeneron's stock price fell 18% to its lowest point since May 2021 after its Sanofi-partnered COPD treatment, itepekimab, failed to meet endpoints in one of two Phase 3 studies, decreasing the likelihood of FDA approval. While one study showed a 21-27% reduction in exacerbations, the other showed almost no benefit, leading analysts to suggest that another Phase 3 trial will likely be needed, adding years to the development program with uncertain prospects for success.

Analysis

Regeneron Pharmaceuticals (REGN) experienced a significant stock decline, plummeting 18% to $495.77 – its lowest level since May 2021 – following the announcement of a critical setback in its Sanofi (SNY)-partnered Phase 3 program for itepekimab, a treatment candidate for chronic obstructive pulmonary disease (COPD). Sanofi shares also declined by over 5% to $49.45. The negative outcome stemmed from divergent results across two pivotal studies: while one trial demonstrated a 21% to 27% reduction in exacerbations after one year, meeting the 25% threshold for clinical meaningfulness as noted by RBC Capital Markets analyst Brian Abrahams, the second study "showed almost no benefit by week 52." This discrepancy significantly jeopardizes the near-term prospects for regulatory submission, with Abrahams suggesting that Regeneron and Sanofi will likely need to conduct an additional Phase 3 trial to seek Food and Drug Administration approval. Such a trial would introduce substantial delays, potentially years, to the development timeline and carries inherent risks, especially given Abrahams' observation of "hints of waning effects for the drug over time across both studies" and the "inherent challenges surrounding COPD studies, including the disease's severity and heterogeneity." Despite these challenges, Abrahams maintained an outperform rating on Regeneron stock, indicating a complex outlook.

Key Decisions for Investors

• Investors should recognize the substantial setback to itepekimab's approval timeline and its diminished near-term commercial prospects for both Regeneron and Sanofi, directly impacting revenue forecasts for this specific drug candidate.
• It is crucial to monitor company disclosures regarding the root cause of the divergent Phase 3 trial results and their strategic decision on whether to pursue a costly and lengthy third Phase 3 study for itepekimab, as this will dictate the drug's viability.