Amgen is trading 6.1% down at $410.70 after falling sharply following the September 4, 2026 regular-session close, with no clear catalyst identified.

  • No fresh company-specific announcement, earnings release, regulatory action, or other clear catalyst was identified for September 4.
  • Amgen’s latest major reported development was its August 4 outlook increase and discontinuation of early-stage obesity candidate AMG 513.
  • That development appears stale as an explanation for this after-hours move.