Merck (MRK) Slides After the Bell on December 9, 2025: Keytruda Biosimilar Jitters and What to Watch Before the December 10 Open

Note: This article is for informational purposes only and does not constitute investment advice.

Merck stock recap: What happened on December 9, 2025?

Merck & Co., Inc. (NYSE: MRK) closed Tuesday, December 9, 2025 at $96.89, down 2.06% on the day, after trading between an intraday low of $96.06 and a high of $99.85. Volume was elevated at about 15.3 million shares, above recent averages, signaling active institutional and trader participation. ^[1]

In after-hours trading, Merck ticked slightly higher to $96.91 around 7:04 p.m. ET, essentially flat versus the close and suggesting no major new company‑specific headline hit the tape after the bell. ^[2]

Zooming out, a technical analysis update from StockInvest.us notes that MRK has now fallen four sessions in a row, and has declined in seven of the last ten trading days, for a roughly 3.5% pullback over that period. Nevertheless, the stock is still in the middle of a “wide and strong rising trend” in the short term, with the service estimating a potential 23% gain over the next three months, implying a possible range of $111.92–$134.06 if the trend holds. ^[3]

Even after Tuesday’s drop, MRK trades well above its 52‑week low of $73.31 and about 9% below its 52‑week high of $105.84, highlighting how strong the recovery from the spring lows has been. ^[4]

At the index level, it wasn’t just a Merck story. The Dow Jones Industrial Average fell about 0.8% (≈395 points) on December 9, with Merck and JPMorgan Chase among the biggest individual drags on the index, together responsible for a sizeable chunk of the intraday Dow loss. ^[5]

The key December 9 news: Biosimilar pressure vs. pipeline strength

1. Keytruda biosimilar partnership rattles long‑term nerves

The most MRK‑specific headline on December 9 was not from Merck itself, but from future competitors.

Formycon AG and Zydus Lifesciences jointly announced a strategic partnership for FYB206, a planned biosimilar to Merck’s blockbuster cancer drug Keytruda (pembrolizumab), covering exclusive licensing and supply in the U.S. and Canada. ^[6]

Key points from that announcement:

FYB206 is a pembrolizumab biosimilar targeting the U.S. and Canadian markets.
Clinical development is nearing completion, with primary endpoint data expected in Q1 2026, and a Biologics License Application (BLA) to the FDA planned afterward. ^[7]
The economics include mid–teens‑million‑euro upfront and 2025 milestone payments plus additional milestones and a profit‑share structure, underlining the sizable commercial opportunity. ^[8]
The release explicitly highlights that Keytruda generated about $29.5 billion in global sales in 2024, underscoring why biosimilar developers are racing toward Merck’s patent cliff. ^[9]

This matters because Keytruda is Merck’s single most important product:

A Zacks report on December 9 notes that Keytruda accounts for more than 50% of Merck’s pharmaceutical sales, with $23.3 billion in revenue in the first nine months of 2025, up 8% year over year. ^[10]
Keytruda’s main U.S. patent protection begins to expire in 2028, opening the door to biosimilar competition much like FYB206. ^[11]

Investors already know about the 2028 patent cliff, but a concrete, late‑stage biosimilar partnership on U.S. soil is a fresh, visible step toward future competition. That helps explain why Merck underperformed the Dow on the day: the market is repricing how much of that long‑dated risk is already “in the stock.”

2. Animal Health win: Screwworm treatment gets FDA green light

Against that negative long‑term headline, Merck also has good news supporting another pillar of the business: Animal Health.

On December 4, 2025, Merck announced that the FDA conditionally approved EXZOLT™ CATTLE‑CA1, a first‑in‑class antiparasitic for the prevention and treatment of New World screwworm larvae and treatment/control of cattle fever tick in U.S. cattle. ^[12]

The product is notable because:

It addresses devastating infestations that have hit portions of the U.S. cattle herd.
It’s the only product conditionally approved for both screwworm and fever tick, giving Merck an early lead in a specialized but important market. ^[13]

CNBC highlighted this approval on December 9 in a piece about a Merck drug for “decimated U.S. cattle herds,” again drawing attention to the Animal Health segment as a growth contributor. ^[14]

While this isn’t the primary reason MRK fell Tuesday, it reinforces the diversification story: Merck is more than Keytruda, and Animal Health is growing in strategic importance.

3. Earnings and guidance backdrop: Solid quarter, cautious narrative

The December 9 trading session also played out against the backdrop of Merck’s Q3 2025 results, reported in late October:

Q3 2025 EPS: $2.58 vs. $2.36 consensus (a beat of $0.22).
Q3 revenue: $17.28 billion vs. $17.0 billion expected, up 3.7% year over year. ^[15]
Keytruda sales: roughly $8.1 billion in Q3, up 8%, continuing to drive overall growth. ^[16]
Full‑year 2025 guidance: revenue $64.5–$65.0 billion and EPS $8.93–$8.98. ^[17]

Management also emphasized:

A deep late‑stage pipeline with around 80 Phase III trials and 20+ potential launches across oncology, vaccines, infectious diseases and cardiovascular/metabolic indications. ^[18]
The integration of recent deals, including:
- The $10 billion acquisition of Verona (bringing COPD drug Ohtuvayre/Winrevair), which some analysts see as a multibillion‑dollar opportunity. ^[19]
- The planned $9.2 billion acquisition of Cidara Therapeutics, adding late‑stage antiviral CD388 for seasonal influenza prevention. ^[20]

So, fundamentally, Merck is beating estimates and investing heavily to diversify away from Keytruda risk. Tuesday’s selling is less about an earnings miss and more about investors balancing that strong pipeline against an ever‑clearer biosimilar future.

How analysts and models view MRK after Tuesday’s drop

Wall Street price targets: Modest upside, mostly positive skew

Analyst sentiment on MRK remains generally constructive:

Goldman Sachs recently raised its price target from $92 to $120 while maintaining a “Buy” rating, citing improved confidence in Merck’s growth outlook. ^[21]
Wells Fargo upgraded Merck to “Overweight” and boosted its price target from $90 to $125 on November 24. ^[22]
A GuruFocus summary of Street targets shows:
- Average 12‑month target: about $103.51, with a range from $82 to $139, implying low‑single‑digit upside from recent prices.
- Average brokerage recommendation: roughly 2.2 on a 1–5 scale, which corresponds to “Outperform.” ^[23]

Separately, MarketBeat data referenced in institutional‑flow pieces suggests another consensus average target around $107.38, also above Tuesday’s close, alongside a “Hold” consensus rating — a reminder that different aggregators pull from slightly different analyst sets. ^[24]

Net: Wall Street mostly sees moderate upside, with a spectrum from cautious “hold” to aggressive “buy,” but the market is wrestling with how to value the post‑Keytruda era.

Zacks: Above key moving averages, but a “Hold”

A December 9 Zacks analysis (published via Nasdaq) highlights that Merck’s stock has been trading above both its 50‑day and 200‑day simple moving averages since early November, a traditionally bullish technical signal. ^[25]

Fundamental points Zacks emphasizes:

Merck has six+ blockbuster drugs, with Keytruda as the workhorse: more than half of pharma sales, and strong growth in earlier‑stage lung cancer and other indications. ^[26]
The newly approved subcutaneous formulation, Keytruda Qlex, offers faster administration and new patent coverage extending beyond the 2028 IV formulation LOE, potentially softening the patent cliff. ^[27]
New launches like the 21‑valent pneumococcal vaccine Capvaxive, Winrevair for pulmonary arterial hypertension, and the RSV antibody Enflonsia are ramping and could become multi‑billion‑dollar franchises over time. ^[28]

However, Zacks also flags risks:

Gardasil faces headwinds, notably in China.
Increasing competitive and generic pressures in parts of the portfolio.
Uncertainty around how smooth the Keytruda LOE transition will be.

Bottom line, Zacks assigns MRK a Rank #3 (Hold) and suggests a wait‑and‑see stance despite the recent rebound and the relatively attractive valuation. ^[29]

Motley Fool long‑term take: Keytruda dependency vs. pipeline depth

A December 7 Motley Fool piece (carried by Nasdaq) puts Merck’s situation in stark terms:

Merck has over 40 marketed products generating roughly $70 billion in annual revenue, but nearly half of that comes from Keytruda. ^[30]
The article frames Keytruda as a “double‑edged sword”: a hugely successful, multi‑indication immunotherapy whose U.S. patents start to expire in 2028. ^[31]
It highlights Keytruda Qlex and the Winrevair (Ohtuvayre) Phase 3 success as important pieces of Merck’s strategy, noting analyst expectations that Winrevair could reach around $8 billion in annual sales in the coming years. ^[32]
Crucially, Merck believes its pipeline could generate more than $50 billion per year by the mid‑2030s, more than replacing Keytruda’s eventual revenue decline when taken in aggregate. ^[33]

Fool’s conclusion is essentially that the bullish thesis is still “plenty strong” for long‑term holders willing to ride out near‑term volatility around the patent story.

Quant and technical models going into the December 10 open

Several algorithmic and technical platforms updated their short‑term outlooks for MRK after Tuesday’s close:

StockInvest.us (pure technical view)

Notes Merck’s 2.06% drop on December 9 (from $98.93 to $96.89), with a 3.95% intraday swing between low and high, and increased volume on a down day — a minor caution flag. ^[34]
Sees support near $96.43 and resistance around $97.76, based on accumulated volume.
Expects Merck to open around $97.60 on Wednesday, December 10, and to trade in a projected range of $95.53–$98.25, implying an intraday move of about ±2.85% from the close. ^[35]
Over three months, their trend model projects roughly 23% upside, but near‑term indicators (including MACD and a recent pivot‑top sell signal) are cautious. They label MRK a “Hold/Accumulate” — not an outright buy, but a potential candidate to hold while watching for a clearer bottom. ^[36]

CoinCodex (statistical/ML forecast)

CoinCodex’s algorithmic forecast, updated just after midnight on December 10 (UTC), sees: ^[37]

A 2.11% gain to about $98.93 for December 10.
A drift toward roughly $101.65 by December 14, representing about 4.9% upside versus current levels.
A model‑based year‑ahead price around $156.35, implying roughly 58% upside over 12 months if the forecast played out.

At the same time, the site labels current sentiment “bearish”, notes a Fear & Greed Index reading in “Fear” territory, and repeatedly stresses that these are not investment recommendations but technically driven projections. ^[38]

These kinds of models can be interesting for scenario‑testing, but they should never be taken as guarantees — especially around key macro events like a Fed decision.

Institutional flows: Who’s been buying and selling?

Several 13F‑based reports published on December 9 shed light on how large investors have positioned in Merck:

WINTON GROUP Ltd disclosed a new position of 47,854 shares worth about $3.8 million (Q2 data), while other heavyweights such as Norges Bank, Franklin Resources and Arrowstreet Capital also added to Merck earlier this year. ^[39]
Investment Management Corp of Ontario boosted its MRK stake by 79.5% in Q2 to 224,147 shares (~$17.7 million). ^[40]
Daiwa Securities Group increased its holdings by 5.2% to 556,980 shares (~$44 million). ^[41]
State Street Corp, one of Merck’s largest institutional shareholders, trimmed its stake by 1.7% but still owns about 118.5 million shares, or roughly 4.7% of the company. ^[42]

Across these filings, MarketBeat tallies show that about 76% of Merck’s float is held by institutions and hedge funds, pointing to deep institutional sponsorship even as some large holders rebalance at the margins. ^[43]

Key levels and catalysts to watch before the December 10, 2025 open

1. Technical levels

Based on Tuesday’s close and current technical overlays:

Immediate support: ≈ $96.43 (accumulated volume), only about 0.5% below the close. ^[44]
Nearest resistance: ≈ $97.76, then the region around $100–$101, where short‑term moving averages and recent highs cluster. ^[45]
Longer‑term reference points:
- 50‑day SMA near $90–91 and
- 200‑day SMA near $85, both still below the current price, reinforcing the broader uptrend noted by Zacks. ^[46]

A sustained break below the $96 area would suggest a deeper consolidation, potentially targeting the low‑90s; a rebound back above $100 would signal that buyers have quickly absorbed Tuesday’s biosimilar‑driven selling.

2. Dividend and upcoming dates

Merck recently raised its quarterly dividend from $0.81 to $0.85 per share, which annualizes to $3.40 — roughly a 3.3–3.5% yield at prices near $97–$100. ^[47]

Key near‑term dates:

Ex‑dividend date:December 15, 2025, with payment scheduled for January 8, 2026. ^[48]
StockInvest.us notes that MRK typically opens about the dividend amount lower (≈0.9%) on the ex‑date as the share price adjusts. ^[49]
Next earnings event: Merck is expected to report Q4 2025 results on February 3, 2026, based on past scheduling patterns. ^[50]

Dividend investors eyeing MRK ahead of the ex‑date should keep in mind that short‑term price moves often cluster around that event as income‑focused buyers and arbitrage strategies reposition.

3. Macro backdrop: Fed day

From a macro lens, December 10 is pivotal:

The Federal Reserve is widely expected to cut interest rates for a third time this year, with futures and commentators focused on how aggressive the policy path will be into 2026. ^[51]

For Merck, which is often viewed as:

A defensive healthcare name,
A high‑quality dividend payer, and
A low‑beta stock (≈0.29), according to recent valuation summaries, ^[52]

a lower‑rate environment tends to be supportive over time, but day‑of Fed volatility can still push all large‑cap stocks around regardless of fundamentals.

What this all means for MRK traders and long‑term investors

If you’re trading MRK short term

Going into the December 10 open, here’s the practical setup:

Price action: Four‑day losing streak, but within a longer‑term uptrend.
Support/resistance: Watch $96–$97 on the downside and $98–$100+ on the upside for signs of whether Tuesday’s decline was a one‑day shake‑out or the start of a deeper pullback. ^[53]
Volatility: Intraday ranges near 4% and technical models suggesting potential ±2–3% daily swings mean position sizing and risk management are critical. ^[54]
Catalysts today: The Fed decision and press conference are likely to dominate tape action; Merck‑specific news may take a back seat unless there’s a surprise regulatory headline. ^[55]

For active traders, MRK on December 10 looks like a liquid, medium‑volatility Dow component trading near short‑term support with a clear macro catalyst (the Fed) and a fresh company‑specific overhang (the Keytruda biosimilar announcement).

If you’re looking at MRK as a long‑term holding

For investors with a multi‑year horizon, Tuesday’s 2% drop is one more data point in a much bigger story:

Positives:

Strong Q3 execution, with beats on revenue and EPS and reaffirmed guidance. ^[56]
A deep and diversified pipeline (≈80 Phase III trials, 20+ launch opportunities) across oncology, vaccines, respiratory and neurodegeneration (e.g., Alzheimer’s candidates MK‑2214 and MK‑1167, which just earned Fast Track designation and were highlighted at CTAD 2025). ^[57]
Ongoing strategic M&A (Verona, Cidara) to add durable assets like Winrevair and CD388. ^[58]
A solid balance sheet and dividend, with a recent increase to $0.85/quarter. ^[59]

Risks:

Extreme reliance on Keytruda, even as Merck deploys multiple strategies — new formulations, new indications, and pipeline build‑out — to cushion the 2028 patent cliff. ^[60]
Evidence that biosimilar competitors are now very real, not theoretical, as the Formycon/Zydus partnership moves toward FDA filing. ^[61]
Ongoing pressure in other franchises (such as Gardasil in China) and rising R&D and launch spending that could weigh on margins in 2026. ^[62]

Third‑party models like CoinCodex and StockInvest see meaningful upside over the next year or two, but they also explicitly warn that their outputs are probabilistic, technical projections, not guarantees. ^[63]

Ultimately, whether Tuesday’s pullback is a buy‑the‑dip opportunity or a warning to stay cautious depends on your view of:

How effectively Merck can replace Keytruda revenue through pipeline launches and deals.
How you weigh a 3%+ dividend yield and defensive profile against the very real patent and pricing headwinds facing large‑cap pharma over the next decade.