Merck (MRK) Stock After Hours Today (Dec. 22, 2025): Why Shares Jumped and What to Watch Before Tuesday’s Open

Merck & Co. (NYSE: MRK) is ending Monday’s session with fresh momentum—and investors heading into Tuesday’s open (Dec. 23, 2025) have a lot to digest.

After a strong regular-session rally, Merck stock closed at $104.72, up $3.63 (+3.59%), and traded slightly lower in after-hours at about $104.69 as of early evening. The day’s range ran from $100.40 to $104.95, putting MRK within roughly 1% of its 52-week high ($105.84)—a level traders will be watching closely into the holiday-shortened week. ^[1]

Merck stock price recap: the key numbers after the bell

Here are the most important MRK data points investors are checking tonight:

Close (Dec. 22): $104.72 (+3.59%) ^[2]
After-hours: ~$104.69 (-0.03%) ^[3]
Day’s range: $100.40 to $104.95 ^[4]
52-week range: $73.31 to $105.84 ^[5]
Volume: ~17.1M shares (notably active versus typical days) ^[6]

Merck’s strength also showed up at the index level: market coverage during the session flagged Merck as one of the notable contributors to the Dow’s advance on Monday. ^[7]

Why Merck stock surged Monday: “pricing and tariff uncertainty” is the story

While Merck did not post a brand-new late-day earnings update or blockbuster FDA decision on Dec. 22, the dominant narrative driving pharma sentiment—and showing up in MRK’s tape—has been Washington policy clarity.

1) MFN drug-pricing agreements back in focus, with analysts framing it as a 2026 “relief valve”

A major BioSpace policy roundup published today said the White House struck Most Favored Nation (MFN) drug-pricing agreements with nine additional large biopharma companies, explicitly naming Merck among the firms covered. More importantly for traders, the piece highlighted how Wall Street firms are interpreting the development:

Truist analysts described the agreements as stabilizing pricing and tariff uncertainty, supporting potential positive sector momentum into the new year.
Leerink Partners analysts argued the deals signal President Trump is unlikely to attack the industry in 2026 (their view, as quoted in the report). ^[8]

That “uncertainty reduction” angle matters for Merck because MRK has spent much of the past year trading not just on pipeline headlines, but also on policy risk (pricing pressure, tariffs, and reimbursement dynamics). When investors believe the downside policy tails are shrinking—at least temporarily—large-cap pharma often catches a bid.

2) Merck’s own MFN-linked program details: deeper discounts and direct-to-patient access

A Business Wire release republished today (via BioSpace) lays out Merck-specific elements of the agreement, including:

A plan to offer JANUVIA, JANUMET, and JANUMET XR to eligible U.S. patients at a cash price ~70% below current list price through a direct-to-patient program.
An intention to expand that direct-to-patient approach in the future to include enlicitide decanoate following FDA approval.
An understanding with the U.S. Department of Commerce to delay Section 232 tariffs for three years, tied to U.S. investment and reshoring commitments.
Merck’s stated commitment of more than $70 billion in U.S. investments (capex and R&D) over the coming years. ^[9]

For investors, this package cuts two ways: near-term revenue/margin questions around discounted legacy products, but also a potentially more favorable risk backdrop on tariffs and broader policy conflict—especially if markets interpret MFN as “the deal instead of the fight.”

3) Enlicitide is becoming a policy + pipeline crossover catalyst

The same BioSpace policy report notes that Merck agreed to make its oral PCSK9 inhibitor enlicitide broadly available as an affordable option after approval—an approach analysts described as aligned with Merck’s strategy to drive revenue through broad access. ^[10]

And last week, Reuters reported that the U.S. FDA had moved to accelerate review pathways for two experimental Merck drugs—including enlicitide—under the Commissioner’s National Priority Voucher program, which is designed to shorten review timelines dramatically versus standard processes. ^[11]

That matters tonight because it helps explain why Merck can rally even on a day without a classic “new Phase 3 win” headline: MRK investors are trading a stack of catalysts (policy framework + pipeline acceleration + access strategy) rather than a single datapoint.

Today’s broader market backdrop helped, too

Monday’s gains weren’t just a Merck story. U.S. stocks rose to start the holiday-shortened week, with major indexes closing higher and risk appetite supported by a mix of sector leadership and macro positioning. ^[12]

Reuters’ market coverage also emphasized that investors are heading into a holiday-shortened schedule and watching upcoming U.S. economic data releases closely. ^[13]

That context is important for MRK specifically: when liquidity thins around holidays, large-cap defensives like Merck can see sharper, cleaner moves—especially if the sector is being repriced around policy headlines.

Forecasts and analyst sentiment: what the “street view” looks like tonight

Forecasts vary by provider, but several widely followed consensus snapshots point to a generally constructive view:

Investing.com’s aggregated analyst summary lists an average 12-month price target around $110.04, with a high estimate of $139 and low estimate of $83, and notes 17 analysts recommending “buy” (with none shown as “sell” in that snapshot). ^[14]
Finviz’s compiled analyst-action feed shows BMO upgrading Merck to Outperform on Dec. 18 with a $130 target, along with other recent rating changes from major banks over the past few months. ^[15]

Separately, a fundamentals-style analysis published today argues Merck’s narrative hinges on whether newer products and pipeline depth can offset eventual Keytruda exclusivity pressure, while also highlighting the recent U.S. pricing move and oncology progress as key pillars investors are debating. (This is third-party commentary, not company guidance.) ^[16]

Technical setup: strong trend, but “overbought” flashes are rising

Technically, MRK is ending the day with strong upside momentum—but also with indicators suggesting the stock may be stretched in the very short term.

Investing.com’s technical dashboard (timestamped the evening of Dec. 22) shows:

Overall “Strong Buy” signals across daily/weekly/monthly views
RSI(14) ~76.6, flagged as overbought
Multiple moving averages (5/10/20/50/100/200-day) listed as buy signals ^[17]

For traders, that combination often translates into a simple question for Tuesday: does MRK consolidate near $105 and build support, or does profit-taking show up quickly in thin holiday liquidity?

Options and volatility: what the derivatives market implies

Options activity can provide a “temperature check” on expected movement. An MRK options overview today showed implied volatility in the low-to-mid 20% range and detailed contract-level activity and volume for the day. ^[18]

That’s not a directional call by itself—but it supports the idea that markets are pricing MRK as a large-cap mover right now, not a sleepy defensive.

What to know before the stock market opens Tuesday (Dec. 23, 2025)

Here’s a practical checklist for what MRK investors typically watch between tonight’s close and Tuesday’s opening bell:

1) After-hours is calm—so premarket headlines may decide direction

MRK is only marginally lower after hours (around $104.69), suggesting no obvious shock headline hit the tape immediately after the close. ^[19]
That puts extra weight on Tuesday morning headlines—especially anything incremental on MFN deal implementation, tariff details, or follow-on commentary from policymakers and industry groups.

2) Watch for additional pharma-policy ripple effects

BioSpace reported Trump suggested Johnson & Johnson could announce its agreement next week and that more large companies may be coming into the MFN framework. If investors interpret the next steps as broadening clarity (or broadening constraints), the whole pharma group could move together, pulling MRK with it. ^[20]

3) Macro calendar + holiday trading conditions can move defensives unexpectedly

Markets are in a holiday-shortened week, with widely reported schedule changes (including an early close midweek and a full closure on Christmas Day). Reuters also flagged investor attention on upcoming economic data releases. ^[21]
In practice, that means lower liquidity and potentially bigger-than-usual price swings on relatively modest news.

4) Keep an eye on the oncology competitive landscape

Even when there’s no Merck-specific clinical readout on a given day, oncology headlines can shift sentiment around Merck’s core franchise positioning. For example, Reuters reported today that AstraZeneca said a late-stage Imfinzi combination trial missed an overall survival endpoint in advanced lung cancer—another reminder of how competitive and data-driven the immunotherapy landscape remains. ^[22]

5) Key levels to watch: $105.84 and the “gap” question

With MRK closing near $104.72 and the 52-week high at $105.84, traders will be watching whether the stock:

Breaks cleanly above that prior high (a technical “blue sky” move), or
Fails near resistance and pulls back toward short-term support levels (often around recent moving averages). ^[23]

Bottom line for MRK tonight

Merck stock is heading into Tuesday’s session with a powerful tailwind: policy clarity optimism, renewed attention on direct-to-patient pricing mechanics, and a pipeline narrative that increasingly ties into potential accelerated FDA review pathways. ^[24]

But with overbought technical signals showing up and a holiday-shortened trading week underway, the near-term setup may be less about long-term fundamentals and more about whether fresh headlines (or simply thin liquidity) amplify volatility into the open. ^[25]

This article is for informational purposes only and does not constitute investment advice or a recommendation to buy or sell any security.

References

Rigetti Computing (RGTI) Stock After Hours (Dec. 22, 2025): What Investors Should Know Before the Market Opens Tuesday

Procter & Gamble (PG) Stock After Hours: Shares Close at $142.69 on Dec. 22, 2025—What to Know Before Tuesday’s Open