Merck & Co., Inc. (NYSE: MRK) ended Thursday, December 18, 2025, on a strong note—and then barely budged after the closing bell—after a day that mixed a bullish analyst upgrade with a fresh round of healthcare-policy headlines and pipeline developments that investors are still digesting.
MRK closed up 1.52% at $100.69 and was fractionally higher in after-hours trading at last check. [1]
Below is a complete, investor-focused rundown of what happened after the bell, what drove today’s coverage, and what matters most before Friday’s U.S. market open (Dec. 19, 2025).
MRK after-hours check: where Merck stock stands tonight
Merck stock finished the regular session at $100.69 (+1.52%), logging a second straight day of gains. Trading volume was 14.2 million shares, above its 50-day average cited in end-of-day coverage—often a sign that institutions were active. [2]
After the bell, MRK was little changed to slightly higher—around $100.73 at one widely cited after-hours update—suggesting the market did not see a single “new shock” headline late in the day that would force immediate repricing. [3]
A few context points from today’s tape:
- MRK remains below its 52-week high of $105.84 (hit Nov. 25), which is one technical level many traders will keep on the radar into year-end positioning. [4]
- Merck outperformed some large pharma peers on the day in end-of-day comparisons (with Johnson & Johnson down and Pfizer flat in the same recap). [5]
The Merck news cycle today: everything investors were reading on Dec. 18
1) BMO turns bullish on Merck, lifts target to $130 as “Keytruda cliff” debate shifts
The biggest clearly stock-specific catalyst in today’s analyst/news flow was BMO Capital Markets upgrading Merck to Outperform and raising its price target to $130. [6]
Why it mattered today:
- The upgrade directly addresses the market’s central Merck question: how Merck replaces growth as Keytruda approaches loss of exclusivity later this decade. BMO argued Merck is assembling a portfolio that can sustain growth beyond that period and said it believes Merck can replace a large portion of Keytruda peak sales over time. [7]
- BMO also pointed to catalysts in 2026 (including clinical updates and commercialization of newer products) and said sentiment has started improving after a long stretch of investor concern around Gardasil, particularly in China, where expectations have been repeatedly reset. [8]
What to watch Friday: upgrades can influence positioning for more than a single session. If MRK holds green in premarket and early trade, it often signals that institutional buyers are leaning into the “post-Keytruda plan is credible” narrative rather than fading it.
2) Oncology momentum stays in focus: Keytruda + Padcev read-through spreads into Thursday coverage
Even though Merck’s own topline announcement hit the tape Dec. 17, it continued to drive coverage and commentary today, including in medical and pharmacy trade reporting.
Merck said the Phase 3 KEYNOTE‑B15 (EV‑304) trial in cisplatin-eligible muscle-invasive bladder cancer (MIBC) met key endpoints, with Keytruda (pembrolizumab) + Padcev (enfortumab vedotin) showing a statistically significant and clinically meaningful improvement in event-free survival (EFS), overall survival (OS), and pathologic complete response (pCR) versus neoadjuvant chemotherapy and surgery. [9]
A Dec. 18 clinical summary highlighted the same theme: that EV‑304 adds to evidence supporting a potentially platinum-free perioperative option in earlier bladder cancer settings, building on earlier-stage data and approvals. [10]
Why this still matters for MRK stock into Friday:
- “Earlier-stage” oncology opportunities are a key lever for extending franchise value—especially when investors are constantly modeling durability and breadth of Keytruda-based regimens.
- Anything that reinforces Keytruda’s clinical relevance, particularly in combinations and earlier lines of therapy, can be supportive for sentiment even as the patent timeline remains the long-term overhang.
3) A real risk headline: partial clinical hold in a Daiichi–Merck ADC program after reported fatal lung events
On the other side of the ledger, a safety-driven pipeline headline also surfaced today—and it’s the type of story that can weigh on biotech-pharma sentiment quickly if investors fear broader read-through.
Fierce Biotech reported that the FDA placed a partial clinical hold on the global Phase 3 IDeate‑Lung02 study tied to Daiichi Sankyo and Merck’s investigational ADC ifinatamab deruxtecan (I‑DXd) after a “higher than anticipated” incidence of grade 5 interstitial lung disease (ILD) events (fatal ILD). [11]
Key details from that report that matter for investors:
- The companies initiated a voluntary pause in recruitment/enrollment, and then the FDA placed the trial on partial hold. [12]
- Patients already enrolled can continue treatment, but no new participants will be recruited during the hold. [13]
- The partners said the hold does not impact other studies in the I‑DXd development program, and they are working with the FDA and monitoring committees to evaluate safety data. [14]
Why this matters heading into Friday’s open:
- ADCs have been one of the most watched growth vectors across big pharma, and ILD risk has been a recurring focal point in some deruxtecan-based programs.
- Even if the headline is “contained,” the market sometimes reacts first and clarifies later—especially if sell-side notes start debating probability-of-success or timing.
4) Medicare and drug-pricing headlines: possible pressure points and sentiment cross-currents
Healthcare stocks rarely trade on only one variable. Today also brought policy-related headlines that investors will keep in mind as they price U.S. pharma in 2026 and beyond.
Medicare out-of-pocket costs: Reuters reported that, beginning in 2026, Medicare enrollees are expected to pay roughly 50% less out of pocket for certain drugs in a multi-state analysis, including Merck’s diabetes drug Januvia. The report also referenced a $2,100 annual out-of-pocket cap taking effect in 2026. [15]
MFN pricing deal watch into Friday: A separate Reuters report late Wednesday said additional pharma companies may announce agreements with the Trump administration related to lowering certain drug prices and meeting other demands, and it explicitly listed Merck (MRK.N) among companies that received letters earlier in the year but had not yet agreed at the time of that report. [16]
Adding to the “pricing deal” drumbeat on Thursday, Reuters also covered statements from Novartis and Roche supporting U.S. efforts to lower drug prices amid talk of a potential agreement—another signal that pricing headlines could stay active into the end of the week. [17]
How to think about this before Friday’s open:
- Lower out-of-pocket costs can be politically popular and may improve access, but investors typically focus on net price and margin implications, which aren’t always obvious from consumer-facing savings headlines.
- The MFN-style deal process is headline-driven and can create overnight risk (and opportunity) if a company is named—or conspicuously not named—in announcements.
5) A bullish regulatory “accelerator” headline remains fresh: FDA national priority vouchers for two Merck pipeline assets
While not dated “today,” this item is recent enough that it can still affect tomorrow’s positioning—especially when paired with an upgrade.
Reuters reported that the FDA is accelerating review paths for two experimental Merck drugs—enlicitide decanoate (a cholesterol-lowering pill) and sacituzumab tirumotecan (sac‑TMT) (an oncology therapy)—under the Commissioner’s National Priority Voucher program, with Reuters citing internal documents and projected blockbuster potential. [18]
Why it matters:
- The market cares about credible “next wave” assets that can help bridge the post‑Keytruda era.
- Faster review mechanisms can compress timelines—though they don’t remove clinical, manufacturing, or competitive risks.
What to watch before the U.S. market opens Friday, Dec. 19, 2025
Here’s the practical, pre-open checklist for MRK shareholders and anyone trading Merck stock tomorrow:
Watch 1: Whether the BMO upgrade continues to pull in buyers
Upgrades don’t always fade in a single day—especially when they introduce a high target price ($130) and a clear narrative shift around the Keytruda patent cliff. [19]
Pre-market tell: if MRK trades firmer than the broader healthcare group early, it suggests the market is rewarding the “portfolio beyond Keytruda” thesis.
Watch 2: Any overnight follow-up on the ADC clinical hold story
Because the Fierce report said the hold had not been broadly announced by the companies at the time, traders will be alert to:
- additional medical-news pickups,
- any statement/clarification from the partners,
- and analyst notes that frame whether this is “program-specific” or a broader ADC safety read-through. [20]
Watch 3: Washington policy headlines that could name Merck
Reuters’ reporting suggests Friday announcements are possible in the drug-pricing deal context, and Merck is among the companies investors will watch for explicit mention. [21]
Watch 4: Key levels and positioning
From today’s close:
- MRK is back above the psychologically important $100 area.
- The $105–$106 zone is the neighborhood of the recent 52-week high referenced in end-of-day coverage. [22]
Watch 5: The next items on Merck’s calendar
For longer-horizon investors, the next major scheduled company catalyst on the calendar is Merck’s Q4 2025 earnings call on Feb. 3, 2026 (9:00 a.m. ET). [23]
On shareholder returns, Merck previously announced a $0.85 quarterly dividend scheduled to be paid Jan. 8, 2026 to shareholders of record as of Dec. 15, 2025 (the record date has already passed). [24]
Bottom line for MRK heading into Friday
Merck stock’s steady after-hours trade suggests the market is treating Thursday as a “net positive” session: the bullish BMO upgrade and continued digestion of oncology upside helped, while policy and ADC safety headlines remain live wires that could move sentiment quickly if they intensify overnight. [25]
Going into Friday, Dec. 19, 2025, MRK investors should be prepared for a headline-driven open—especially around U.S. drug pricing policy—and should also watch whether analyst-upgrade momentum keeps supporting the stock above $100.
References
1. www.marketwatch.com, 2. www.marketwatch.com, 3. sg.finance.yahoo.com, 4. www.marketwatch.com, 5. www.marketwatch.com, 6. www.investing.com, 7. www.investing.com, 8. www.investing.com, 9. www.merck.com, 10. www.pharmacytimes.com, 11. www.fiercebiotech.com, 12. www.fiercebiotech.com, 13. www.fiercebiotech.com, 14. www.fiercebiotech.com, 15. www.reuters.com, 16. www.reuters.com, 17. www.reuters.com, 18. www.reuters.com, 19. www.investing.com, 20. www.fiercebiotech.com, 21. www.reuters.com, 22. www.marketwatch.com, 23. www.merck.com, 24. www.merck.com, 25. www.investing.com
