Amgen Inc. (NASDAQ: AMGN) ended Monday, December 22, 2025, modestly higher, but the more important story for Tuesday’s open is what hit after the closing bell: fresh FDA approvals for new denosumab biosimilars that reference Amgen’s blockbuster bone-drug franchises Prolia and XGEVA—plus a credit-rating upgrade from Fitch that underscores improving balance-sheet flexibility.
Below is a complete, investor-focused rundown of what moved (and what could move) Amgen stock before the U.S. market opens Tuesday, December 23, 2025.
AMGN stock recap: where Amgen closed and what after-hours traders saw
Amgen shares finished the regular session at $331.39, up about 1.2% on the day, with trading contained roughly between the mid-$320s and low-$330s. MarketWatch
In post-market trading shortly after the close, the price action appeared muted—but that calm may not last into Tuesday’s premarket because the most material headline for Amgen arrived right after the bell (more on that below).
After the bell headline #1: FDA approves new denosumab biosimilars referencing Prolia and XGEVA
Late Monday, Amneal Pharmaceuticals and mAbxience announced that the U.S. Food and Drug Administration approved their biologics license applications for:
- Boncresa (denosumab-mobz) — a biosimilar referencing Prolia
- Oziltus (denosumab-mobz) — a biosimilar referencing XGEVA
The companies said mAbxience will handle development/manufacturing, while Amneal holds exclusive U.S. commercialization rights. GlobeNewswire
Why this matters for Amgen investors
For Amgen, the Prolia/XGEVA complex is a core cash generator—exactly the kind of franchise the market watches closely when biosimilar pressure rises. The new approvals are not happening in a vacuum: 2025 has been a heavy year for denosumab biosimilar momentum, with multiple approvals and launches documented across the market. Managed Healthcare Executive
What investors should focus on before Tuesday’s open:
- Launch timing and market impact: FDA approval is a big step, but real revenue pressure depends on when products launch and how aggressively payers push switching.
- Pricing dynamics: Denosumab competition tends to accelerate rebate pressure and net-price compression across the class.
- Street narrative shift: Even if the direct financial hit is gradual, biosimilar headlines can quickly shift the short-term “multiple” debate—especially for large-cap biopharma names.
MarketWatch and other outlets quickly framed the approvals as meaningful for Amneal—one clue for Tuesday is whether that “win” narrative spills into a sympathetic negative read-through for Amgen at the open. MarketWatch
After the bell headline #2: Fitch upgrades Amgen’s credit rating to BBB+ (Stable)
Also Monday, Fitch upgraded Amgen’s Long-Term Issuer Default Rating to BBB+ from BBB, with a Stable outlook (and similarly lifted senior unsecured ratings). Fitchratings
Why a credit upgrade matters for the stock (even if it’s not always a “day-trader” catalyst)
Equity investors don’t always react instantly to credit moves, but Fitch’s rationale is equity-relevant:
- The upgrade highlights deleveraging progress after the Horizon acquisition, including more than $10 billion of debt repayment per the summary of Fitch’s action. Investing.com Canada
- Fitch expects leverage metrics to remain in a range consistent with the new rating and projects a multi-year financial profile that is stable enough to support investment-grade strength. Investing.com Canada
- Fitch’s published projections (as reported) include expectations for revenue growth through 2028 and high EBITDA margins, which reinforces the “Amgen as a cash-compounder” bull case. Investing
Bottom line: The upgrade is a positive counterweight to biosimilar worries because it supports the idea that Amgen can fund R&D, dividends, and strategic flexibility while absorbing competitive headwinds.
The policy overhang still in focus: Trump drug-pricing deals and Medicare pricing pilots
While not brand-new after-hours on Monday, investors are still digesting fast-moving U.S. drug-pricing developments that directly touch large pharma.
1) Drug price deals (Amgen included)
On December 19, 2025, Reuters reported that the Trump administration and nine major drugmakers—including Amgen—finalized agreements aimed at reducing prices for certain drugs (with elements tied to “most-favored-nation” pricing). Reuters’ report specifically noted Amgen’s pricing actions on migraine and arthritis medicines. Reuters
Amgen itself has also described expanding its direct-to-patient discount program (AmgenNow) to include Aimovig and Amjevita at $299 per month, while highlighting prior pricing on Repatha via the same channel. Amgen
Why it matters into Tuesday: Policy headlines can swing sentiment quickly across pharma—sometimes more than single-product updates—because they impact how investors model long-term U.S. pricing power.
2) Medicare pilot programs using international benchmarks
Reuters and others have also covered new/updated government efforts that would align certain Medicare payments with international pricing benchmarks. Reuters
What to watch: Any sign that these programs broaden, accelerate, or shift the “rulebook” can move the whole group—and AMGN tends to trade with sector sentiment on policy days.
Today’s market/flow signal: Reuters flags hedge funds turning more cautious on healthcare
One more “today” datapoint worth noting: Reuters reported on December 22 that hedge funds have been reducing exposure in parts of healthcare amid policy uncertainty, with positioning skewing more defensive in places and more skeptical in others. Reuters
This matters for Amgen specifically because:
- AMGN is large enough to be part of sector baskets and factor trades.
- In holiday weeks with lighter liquidity, sector-level flow can amplify single-stock headlines (like biosimilar approvals).
Wall Street forecasts and positioning: what analysts are broadly implying for AMGN
Analyst views on Amgen remain mixed-to-positive, but not uniform—important context when the tape is reacting to biosimilar headlines.
- MarketWatch’s analyst snapshot shows an average price target around the low-$330s with an “overweight”-leaning consensus. MarketWatch
- Barchart’s roll-up of analyst ratings characterizes the consensus as roughly “Moderate Buy,” but with a meaningful number of Holds in the mix—typical of mega-cap pharma where upside debates hinge on pricing and pipeline execution. Barchart
How to interpret this going into Tuesday:
- When consensus targets sit close to the current price, the market often needs a clear catalyst to break out (up or down).
- Biosimilar news tends to pressure the “multiple,” while credit upgrades and cash-flow durability support the floor—setting up a potential tug-of-war at the open.
The “know before the open” checklist for Tuesday, Dec. 23, 2025
Here’s what matters most in the hours leading into Tuesday’s opening bell:
1) Premarket reaction to the denosumab biosimilar approvals
The key question: does the market treat the FDA approvals as a meaningful incremental threat to Amgen’s Prolia/XGEVA economics, or as “already expected” within the broader 2025 biosimilar wave? U.S. Food and Drug Administration
2) Whether Fitch’s upgrade changes the tone
Credit upgrades don’t always move stock prices sharply in a single session, but they can influence institutional narratives—especially for dividend-focused holders. Fitchratings
3) Macro events that can override single-stock stories
Several high-profile U.S. releases are scheduled for Tuesday, December 23, including items like GDP and durable goods in the morning window (ET), plus additional high-impact data later in the day depending on the calendar source. MarketWatch
If rates move sharply on the data, large-cap defensives like Amgen can trade more on macro factor exposure than company-specific news.
4) Holiday-week liquidity and trading hours
The week of Christmas often brings thinner volume, and markets are approaching shortened hours:
- Early close on Wednesday, Dec. 24, 2025 (1:00 p.m. ET listed by major exchange calendars)
- Closed on Thursday, Dec. 25, 2025 NYSE
Thin liquidity can make premarket price moves look larger than they are—and can increase the odds of gap opens.
5) Calendar awareness: next earnings window
Nasdaq’s earnings page lists an estimated upcoming earnings date around early February 2026 (algorithm-derived until confirmed). Nasdaq
This matters because if investors don’t expect “official” Amgen updates soon, the stock may be more reactive to external headlines (FDA approvals for competitors, policy moves, rating actions).
Bottom line for AMGN heading into the Dec. 23 open
Amgen closed higher on Dec. 22, but the real setup for Tuesday is shaped by two after-hours forces pulling in opposite directions:
- Negative read-through risk: FDA approval of new denosumab biosimilars referencing Prolia and XGEVA adds to competitive pressure on a marquee Amgen franchise. GlobeNewswire
- Positive durability signal: Fitch’s BBB+ upgrade reinforces improving financial structure and supports the “cash-flow resilience” narrative. Fitchratings
Layer on top the still-active U.S. drug-pricing policy cycle and a packed Dec. 23 macro calendar, and AMGN is set up for a session where sentiment could shift quickly—especially in a holiday-shortened trading week. Reuters
