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
Amgen Inc. (NASDAQ: AMGN) ended Monday, December 22, 2025, modestly higher, but the more important story for Tuesday’s open is what hit after the closing bell: fresh FDA approvals for new denosumab biosimilars that reference Amgen’s blockbuster bone-drug franchises Prolia and XGEVA—plus a credit-rating upgrade from Fitch that underscores improving balance-sheet flexibility. Below is a complete, investor-focused rundown of what moved (and what could move) Amgen stock before the U.S. market opens Tuesday, December 23, 2025. AMGN stock recap: where Amgen closed and what after-hours traders saw Amgen shares finished the regular session at $331.39, up about 1.2% on the