Amgen (AMGN) Q4 2025 earnings review
Volume Growth Battles Legacy Erosion
Amgen delivered a mixed Q4 where strong volume growth (+10%) successfully offset significant pricing headwinds (-4%), resulting in 9% revenue growth to $9.9B. However, the 'legacy cliff' is steepening: Enbrel revenue collapsed 48% and Prolia turned negative (-10%) due to biosimilar competition and Medicare redesign. While new growth engines like Repatha (+44%) and TEZSPIRE (+60%) are accelerating, heavy R&D investment into the MariTide obesity program compressed non-GAAP operating margins by 350 basis points. FY26 guidance suggests a significant deceleration in top-line growth to low-single digits.
🐂 Bull Case
The transition to new products is working. Repatha (+44%), TEZSPIRE (+60%), and EVENITY (+39%) are accelerating and now comprise a larger portion of the revenue mix, effectively replacing declining legacy assets.
The company is aggressively funding its obesity candidate, MariTide. Phase 2 data showed robust weight loss and maintenance, and multiple Phase 3 trials are actively enrolling. This represents the largest potential upside lever for the stock.
🐻 Bear Case
The erosion of high-margin legacy assets is accelerating. Enbrel sales nearly halved in Q4 (-48%), and Prolia (-10%) has officially tipped into decline due to biosimilars. This creates a massive hole that requires perfect execution from the pipeline to fill.
A rare public conflict with the FDA has emerged. The agency requested voluntary withdrawal of TAVNEOS (ANCA-associated vasculitis) due to clinical trial adjudication concerns. Amgen refused. This creates significant binary regulatory risk for a growing franchise.
⚖️ Verdict: ⚪
Neutral. Amgen is in a high-stakes transition. The volume growth in newer products is impressive, but the speed of Enbrel's collapse and the TAVNEOS regulatory fight introduce significant volatility. The investment thesis hinges almost entirely on MariTide execution.
Key Themes
Legacy Portfolio Erosion Accelerating
The 'patent cliff' is no longer theoretical. Enbrel sales collapsed 48% YoY in Q4 (vs -30% in Q3), driven by a 35% drop in net selling price due to Medicare Part D redesign and 340B mix. Additionally, Prolia sales fell 10% (reversing from +9% in Q3) as biosimilars officially began eating into market share. These two high-margin franchises are now significant drags on growth.
Cardiovascular & Respiratory Hyper-Growth
Repatha and TEZSPIRE are accelerating. Repatha grew 44% (up from 40% in Q3) driven by 31% volume growth. TEZSPIRE grew 60% (up from 40% in Q3) with 51% volume growth. These assets are proving to be durable blockbusters capable of carrying the topline during the legacy transition.
TAVNEOS FDA Conflict
A major red flag: On Jan 16, 2026, the FDA requested Amgen voluntarily withdraw TAVNEOS (acquired via ChemoCentryx) from the market, citing trial adjudication issues and hepatotoxicity risks. Amgen refused on Jan 28. TAVNEOS grew 88% in Q4 to $152M, but this entire revenue stream is now at extreme regulatory risk.
Margin Compression via R&D
Non-GAAP Operating Margin fell 350 basis points to 42.8%. This was driven by a 26% surge in R&D spending ($2.13B), primarily funding the MariTide late-stage clinical program. While this is strategic investment, it creates near-term earnings drag while revenue growth slows.
Obesity Pipeline (MariTide)
Amgen highlighted progress on MariTide (maridebart cafraglutide). Phase 2 data showed sustained weight loss maintenance for 52 weeks even after dose reduction. Multiple Phase 3 trials (MARITIME series) are enrolling across obesity, diabetes, and cardiovascular outcomes. This remains the company's most critical R&D asset.
Otezla Stagnation
Otezla sales were flat (0% growth) at $625M in Q4. Despite being a major acquired asset, it is failing to contribute to growth, weighed down by Medicare price setting (IRA) which triggered a $1.2B impairment charge earlier in the year.
Other KPIs
Decelerating. Down from $10.4B in FY24 (-22%). Management cites timing of working capital, collections, and higher capital expenditures as drivers for the decline.
Deteriorating. Increased by 1.5 percentage points YoY (from 17.6%). Driven by higher profit share expenses and sales mix changes, partially offset by manufacturing efficiencies.
Accelerating. Excluding the TAVNEOS risk, the segment is performing well. UPLIZNA (+131%) and KRYSTEXXA (+26%) are offsetting weakness in TEPEZZA (-1%) and Ultra-Rare products (-27%).
Guidance
Decelerating. The midpoint ($37.7B) implies roughly 2.6% growth vs FY25's 10% growth. This reflects the intense pressure from Prolia and Enbrel erosion offsetting new product launches.
Stable/Slow Growth. Midpoint ($22.30) implies ~2.1% growth over FY25 ($21.84). This indicates that operating leverage will remain constrained by high R&D investment and lower-margin revenue mix.
Accelerating. Up from $1.9B in FY25. This 36% increase signals massive investment in manufacturing capacity, likely preparing for the potential commercialization of MariTide.
Key Questions
TAVNEOS Contigency
With the FDA formally requesting withdrawal of TAVNEOS, what is the specific legal strategy to keep it on the market, and have you modeled a scenario where this $460M+ revenue stream disappears in 2026?
Enbrel Erosion Floor
Enbrel declined 48% this quarter with a 35% price drop. Is this the new run-rate for erosion, or was Q4 an anomaly due to inventory/contract timing? When does this franchise stabilize?
MariTide Phase 3 Velocity
Given the 36% hike in CapEx and surging R&D, are you accelerating the MariTide timeline? When specifically will we see the first Phase 3 data readout?