Merck 2024: how Keytruda became the world's best-selling drug at $25 billion annually and how Merck is preparing for the patent cliff that arrives in 2028
Merck's Keytruda (pembrolizumab) generated approximately $25 billion in 2023 revenue and is on trajectory toward $30 billion+ annually before US patent expiration in 2028. The PD-1 inhibitor immunotherapy treats over 30 different cancer indications and is the world's best-selling drug by annual revenue. Keytruda represents approximately 40% of Merck total revenue, creating both a category-leading position and a substantial patent-cliff exposure. CEO Robert Davis (since July 2021) has executed multi-year preparation for the patent cliff: subcutaneous Keytruda formulation development (could extend patent life by years), acquisition strategy (Prometheus $10.8B 2023, Daiichi Sankyo ADC partnership), pipeline diversification, and biosimilar-defense legal strategy. Merck's structural challenge is that even with successful diversification, replacing $25B+ in Keytruda revenue is operationally difficult.
- Story: Merck's Keytruda (pembrolizumab, FDA-approved September 2014) generated ~$25B in 2023 revenue and is on trajectory toward $28-30B in 2024 — the world's best-selling drug by annual revenue. Treats 30+ cancer indications. Represents ~40% of Merck total revenue, creating substantial 2028 US patent-cliff exposure. CEO Robert Davis (since July 2021) executes multi-year cliff preparation: Acceleron $11.5B 2021, Prometheus $10.8B 2023, Daiichi Sankyo ADC up to $22B 2023, subcutaneous Keytruda formulation, pipeline diversification. Q3 2024 Keytruda revenue $7.4B (+17% YoY). Structural challenge: replacing $25B+ annual revenue post-cliff requires both successful pipeline and effective biosimilar-defense.
- Why it matters: Merck Keytruda concentration is the worked example of single-asset dependency in pharma: dominant current revenue + inevitable cliff exposure. Best-case patent-cliff management requires preparation 5-10 years before cliff.
- Takeaway: Single-asset concentration produces enormous current revenue but inevitable structural challenge at patent cliff.
- Takeaway: Patent-cliff preparation must begin 5-10 years before; M&A + pipeline diversification + formulation extensions + biosimilar-defense all required.
- Takeaway: Even best-case patent-cliff navigation typically produces 30-50% revenue decline in 4-5 years post-cliff.
Merck Keytruda + 2028 cliff — the four-step story
Merck Keytruda + 2028 cliff at a glance
Quick facts
The Keytruda development and the immunotherapy revolution
Keytruda (pembrolizumab) was developed by Schering-Plough (subsequently acquired by Merck in 2009). Initial FDA approval came September 4, 2014 for advanced melanoma. The immunotherapy mechanism — blocking the PD-1 checkpoint protein that some cancer cells use to evade immune attack — was novel at the time:
- 2014 melanoma approval: initial Keytruda label. Limited initial commercial scale.
- Label expansion 2015-2024: Keytruda received FDA approval for over 30 cancer indications including non-small cell lung cancer, head and neck cancer, classical Hodgkin lymphoma, urothelial carcinoma, microsatellite instability-high cancers (any tumor type), gastric cancer, cervical cancer, hepatocellular carcinoma, renal cell carcinoma, endometrial carcinoma, triple-negative breast cancer, esophageal cancer, biliary tract cancer, and many others.
- Revenue growth trajectory: 2015 revenue ~$0.6B; 2018 ~$7B; 2021 ~$17B; 2023 ~$25B; 2024 trajectory $28-30B.
- Largest oncology franchise globally: Keytruda has been the foundation of modern immunotherapy and is the world's best-selling drug by annual revenue.
- Combination-therapy expansion: Keytruda used in combination with chemotherapy, targeted therapies, and other immunotherapies extending therapeutic utility.
- Real-world evidence: Keytruda extended overall survival in multiple cancer types, fundamentally changing oncology treatment standards.
- Competitive context: Bristol-Myers Squibb's Opdivo (nivolumab) is the other major PD-1 inhibitor. Roche's Tecentriq, AstraZeneca's Imfinzi compete in selected indications. Keytruda has maintained ~50%+ of PD-1 inhibitor market share.
The Robert Davis CEO tenure and the patent-cliff preparation
Robert Davis became Merck CEO on July 1, 2021, succeeding Kenneth Frazier. Davis had been Merck CFO 2014-2021. His tenure has focused substantially on patent-cliff preparation:
- Acquisition strategy for pipeline diversification: Acceleron Pharma $11.5B (closed November 2021) added Reblozyl for blood disorders. Prometheus Biosciences $10.8B (closed June 2023) added MK-7240 for ulcerative colitis (formerly PRA023).
- Daiichi Sankyo antibody-drug-conjugate (ADC) partnership October 2023: up to $22B commitment for three ADC drugs (HER3-DXd, MK-6070 / DS-7300, MK-3475 ifinatamab deruxtecan). The deal substantially boosted Merck's ADC pipeline alongside Keytruda combinations.
- Internal pipeline acceleration: vaccine candidates (V940 individualized neoantigen mRNA, with Moderna), HIV treatments, oncology beyond Keytruda.
- Subcutaneous Keytruda formulation: subcutaneous version of pembrolizumab being developed. If approved (expected 2025+), could extend Keytruda patent life by years through formulation-based patent protection.
- Combinations with new agents: ongoing Keytruda combination trials with own pipeline drugs and partnered drugs (Lynparza with AstraZeneca, etc.).
- Biosimilar-defense legal strategy: Merck has filed numerous patent applications and infringement cases related to Keytruda. The strategy targets biosimilar entry delay but won't prevent eventual 2028 generic competition.
- Operating-margin discipline: maintained while funding pipeline investment.
The 2028 patent cliff and the structural revenue concern
Keytruda's US patent expiration in 2028 creates structural revenue concern:
- Biosimilar entry expected 2028: multiple biosimilar manufacturers (Amgen, Celltrion, Samsung Bioepis, others) have biosimilar Keytruda in development.
- Typical biosimilar economic impact: in oncology specifically, biosimilars produce 30-70% price erosion within 2-3 years of launch (Avastin biosimilar, Herceptin biosimilar, Rituxan biosimilar all showed this pattern).
- Subcutaneous formulation potential extension: if subcutaneous Keytruda is approved and meaningfully different from IV biosimilars, could extend patent-protected period for that formulation by years. Specific extension timeline depends on regulatory and legal outcomes.
- Revenue replacement requirement: even with subcutaneous extension and pipeline diversification, replacing $25B+ in annual revenue is operationally difficult. Most pharma patent cliffs produce 50-70% peak-revenue decline within 5 years.
- Pipeline diversification timing: replacement drugs from Prometheus, Acceleron, and Daiichi Sankyo partnerships should generate revenue contribution 2026-2032 timeframe, partially offsetting Keytruda decline.
- Strategic positioning for post-2028: Merck likely to be smaller and lower-margin in 2030 than 2024, even with successful diversification execution. Stock-market implications depend on biosimilar timing and pipeline success.
The 2024 financial performance and the strategic continuation
Through 2024 Merck has continued strong financial execution while preparing for cliff:
- Q3 2024 revenue $16.7B (+4% YoY excluding LAGEVRIO): solid growth though LAGEVRIO COVID antiviral revenue declined sharply.
- Keytruda Q3 2024 revenue $7.4B (+17% YoY): continued strong growth.
- Animal Health and Vaccines segments contributing: Merck's diversified portfolio includes substantial Animal Health (Bayer Animal Health acquired 2017 plus organic growth) and Vaccines businesses.
- Stock performance through 2024: relatively stable; investors appear to be discounting 2028 cliff already.
- Capital-allocation discipline: substantial dividend ($3.20+ annualized), continued buybacks, M&A investment.
- Acquisition appetite continuing: Merck has signaled continued willingness to pursue $5-15B acquisitions for pipeline-building.
- Robert Davis continued tenure: Davis's strategic-direction focus on patent-cliff preparation continues.
How RGM thinks about single-asset concentration and patent-cliff preparation
Merck's Keytruda 2014-2024 chapter and 2028 patent-cliff preparation is the worked example of single-asset concentration management in pharma. The structural challenge: dominant single drug produces enormous current revenue but creates inevitable cliff exposure. Best-case patent-cliff management requires beginning preparation 5-10 years before cliff with substantial pipeline investment, strategic acquisitions, formulation-based patent extensions, and operational discipline through transition.
Our framework for clients with similar single-asset concentration situations: the AbbVie Humira-to-Skyrizi/Rinvoq transition is the best-case worked example of patent-cliff navigation; Pfizer's post-COVID decline shows what happens when single-asset windfall isn't sustainably replaced. Merck's Keytruda situation is between these — better-positioned than Pfizer's COVID concentration because Keytruda's underlying utility persists post-cliff (biosimilars will replace branded Keytruda, but immunotherapy demand continues) but less successful than AbbVie's because no single replacement franchise on Skyrizi/Rinvoq scale has emerged. Merck likely faces 30-50% revenue decline 2028-2032 even with successful diversification execution. The case is a sobering example of how dominant single-asset success creates inevitable structural challenge.
Frequently asked questions
Is Keytruda really the best-selling drug in the world?
Yes, by annual revenue. 2023 revenue ~$25B was the largest single-drug annual revenue in pharma history; 2024 trajectory toward $28-30B continues that record. Previous Humira peak was ~$21B. Keytruda's leadership reflects both immunotherapy mechanism utility and Merck's commercial execution across 30+ cancer indications.
Will subcutaneous Keytruda actually extend the patent cliff?
Partial extension likely but limited. If subcutaneous formulation is approved and clinically meaningful (vs IV biosimilars), it could capture 30-50% of post-2028 Keytruda volume at preserved pricing for several additional years. But biosimilar IV pembrolizumab will still capture significant volume; total Keytruda franchise revenue will substantially decline 2028-2032. Subcutaneous extension is meaningful but not patent-cliff-elimination.
Is Merck's M&A strategy working?
Mixed early results. Prometheus's MK-7240 has shown early ulcerative colitis efficacy but full Phase 3 results pending. Acceleron's Reblozyl is contributing revenue. Daiichi Sankyo ADC partnership has Phase 3 trials reading out 2025-2027. Specific commercial outcomes will be visible 2026-2030. The M&A strategy is appropriate scale; whether it produces sufficient replacement revenue is the open question.
How will Merck stock perform through the cliff?
Genuinely uncertain. Pharma analyst models typically discount near-term Keytruda cliff already; current stock price reflects expected revenue decline. Whether pipeline replacement exceeds analyst expectations or falls short will determine stock trajectory. Best-case scenario: replacement franchises develop on schedule and stock holds; worst-case: replacement franchises disappoint and stock declines significantly. The structural answer depends on factors largely outside Merck's current control.
What about Bristol-Myers Squibb's Opdivo cliff?
Similar situation. Opdivo also faces patent cliff (2028-2029 timeframe). Bristol-Myers Squibb has been pursuing similar pipeline-diversification strategies (Celgene acquisition 2019, MyoKardia, RayzeBio, others). The PD-1 inhibitor category broadly faces concurrent biosimilar pressure 2028-2030. Multiple major pharma companies will be navigating cliffs simultaneously.
Sources & references
- Merck Q3 2024 earnings — Merck SEC filings and quarterly earnings.
- Daiichi Sankyo ADC partnership announcement — Merck October 19 2023 announcement.
- Prometheus acquisition close — Merck June 16 2023 close announcement.
- Keytruda patent-cliff analyst coverage — Bloomberg coverage of patent-cliff strategy.
- Robert Davis succession — Merck Robert Davis CEO appointment.