Amgen Stock After Hours (AMGN) on Dec. 22, 2025: FDA Clears New Prolia/Xgeva Biosimilars, Fitch Upgrades Credit — What to Know Before the Dec. 23 Open
The FDA approved new denosumab biosimilars referencing Amgen’s Prolia and XGEVA after markets closed Monday. Amgen shares ended the day up 1.2% at $331.39. Fitch upgraded Amgen’s credit rating to BBB+ with a stable outlook. Post-market trading showed little immediate reaction.