Regeneron Pharmaceuticals is trading 7.22% up in after-hours trading at $841.51, after closing at $784.85 on September 18, 2026; no verified company-specific catalyst was found.
- Investor relations lists no new September 18 press release; the latest listed release is dated August 19.
- Broader equities were mixed, with the Nasdaq Composite up 0.80%, which does not clearly explain the unusually large move.