Merck (MRK) Stock After Hours: FDA Fast‑Track Vouchers, Keytruda‑Padcev Trial Win, and What to Watch Before the Dec. 18 Market Open
Merck & Co., Inc. (NYSE: MRK) finished regular trading on Wednesday, Dec. 17, 2025 in positive territory, then held near the $99 level in extended hours as investors weighed two major pipeline headlines—one before the opening bell and another after the close—alongside a renewed policy backdrop around U.S. drug pricing. Investing.com+1 Below is what moved MRK today, what the late-breaking after-hours news could mean, and what to keep on your radar before U.S. markets open Thursday, Dec. 18. Merck stock recap: where MRK stands after the bell (Dec. 17) Merck shares closed at $99.18 on Dec. 17, up 0.93% on