TLDR
- Regeneron dips 3% despite FDA win for Libtayo in high-risk skin cancer cases.
- Libtayo gets FDA approval, but REGN stock retreats after midday weakness.
- REGN falls after Libtayo’s CSCC approval, despite strong Phase 3 data.
- FDA backs Libtayo for CSCC, but Regeneron stock finishes sharply lower.
- Breakthrough approval for Libtayo can’t stop REGN’s mid-session selloff.
REGN closed lower on Tuesday despite securing a major regulatory win for its immunotherapy Libtayo. The stock fell 3.32% to $563.86, with only a mild rebound to $566.00 in after-hours trading. The sharp intraday decline suggested a strong reaction to market sentiment rather than the approval itself.
Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN)
The U.S. Food and Drug Administration approved Libtayo as an adjuvant treatment for adult patients with cutaneous squamous cell carcinoma (CSCC) at high risk of recurrence. This approval marks a significant milestone for Regeneron, strengthening its oncology portfolio. The market’s muted response indicated limited short-term momentum following the announcement.
Analysts noted that the decline may reflect profit-taking or broader market softness in biotech stocks. Regeneron’s long-term prospects remain supported by expanding indications for Libtayo. The company’s continued leadership in immuno-oncology reinforces its strategic position within the competitive PD-1 inhibitor landscape.
FDA Approval Expands Libtayo’s Clinical Reach
The FDA based its approval on data from the pivotal Phase 3 C-POST trial. This study evaluated adjuvant Libtayo versus placebo in patients with CSCC at high risk of recurrence after surgery and radiation. The trial showed that Libtayo reduced the risk of disease recurrence or death by 68%, demonstrating strong efficacy.
The results, published in the New England Journal of Medicine and presented at the 2025 ASCO Annual Meeting, highlighted Libtayo’s clinical benefit. The safety profile remained consistent with prior Libtayo indications, reinforcing confidence in its therapeutic use. Common side effects included rash, pruritus, and hypothyroidism, aligning with known immune-related reactions.
Regeneron emphasized that Libtayo is now the first and only immunotherapy approved for this adjuvant CSCC setting. The decision followed the FDA’s Priority Review process, reflecting the treatment’s significant potential to improve patient outcomes. An additional regulatory review remains under consideration in the European Union, with a decision expected by mid-2026.
Regeneron Strengthens Oncology Portfolio Amid Market Reaction
Libtayo now holds five FDA-approved indications, cementing its place as a key growth driver for Regeneron Pharmaceuticals. The company continues to expand its oncology research efforts, advancing next-generation immunotherapies and antibody-based treatments. Regeneron launched Libtayo Surround™, a support program offering financial and educational resources for eligible patients.
CSCC represents one of the most common skin cancers, affecting millions globally. Many patients remain at risk of recurrence despite surgery and radiation, underscoring the need for effective adjuvant therapies. With this approval, Regeneron reinforces its leadership in non-melanoma skin cancer research and clinical innovation.
Regeneron’s share price reaction reflected market caution rather than fundamental weakness. The stock’s decline followed a sharp midday selloff, although the modest after-hours rebound suggested stabilizing sentiment. As Regeneron Pharmaceuticals advances Libtayo’s market rollout, attention will turn to commercial performance and long-term growth across global oncology markets.
