Last updated: September 28, 2026
Pembrolizumab, marketed by Merck as Keytruda, is the largest oncology biologic by global sales. Revenue increased from $17.2 billion in 2021 to $29.5 billion in 2024, making Keytruda approximately 46% of Merck’s 2024 pharmaceutical sales. The product has a broad FDA label across solid tumors, hematologic malignancies and perioperative treatment, but its commercial outlook is increasingly tied to the U.S. loss-of-exclusivity window beginning in 2028.
Keytruda’s main defenses are its extensive indication set, clinical-data scale, combination regimens, global manufacturing network and follow-on formulations. The principal risks are biosimilar competition after patent expiry, concentration of Merck’s revenue in one product, pricing pressure in ex-U.S. markets and competition from other PD-1 and PD-L1 inhibitors.
What is the financial trajectory of pembrolizumab?
Keytruda revenue has grown at a compound annual growth rate of approximately 20% from 2021 through 2024.
| Fiscal year |
Keytruda revenue |
Annual growth |
Share of Merck pharmaceutical sales |
| 2021 |
$17.19 billion |
19% |
Approximately 34% |
| 2022 |
$21.21 billion |
23% |
Approximately 39% |
| 2023 |
$25.01 billion |
18% |
Approximately 42% |
| 2024 |
$29.48 billion |
18% |
Approximately 46% |
Source: Merck annual reports for fiscal years 2021-2024.
The growth has come from new indications, earlier-line treatment, combination therapy and increased use in perioperative settings. Keytruda has moved beyond metastatic treatment into adjuvant and neoadjuvant use, increasing treatment duration and the number of eligible patients.
The product’s revenue concentration creates a material financial exposure. Merck reported total sales of approximately $64.2 billion in 2024. Keytruda therefore represented nearly half of pharmaceutical revenue and about 46% of total company revenue. Any accelerated erosion after U.S. biosimilar entry would materially affect Merck’s earnings profile.
When does pembrolizumab lose exclusivity?
Pembrolizumab has multiple exclusivity layers rather than one single end date.
| Protection |
Event or estimated end point |
Commercial relevance |
| FDA approval |
September 4, 2014 |
Established Keytruda as the U.S. reference biologic |
| FDA biologic reference-product exclusivity |
September 2026 |
Biosimilar applications can generally proceed after the 12-year period |
| Core U.S. patent protection |
May 2028 |
Principal expected U.S. biosimilar launch barrier |
| Potential pediatric extension |
May-November 2028 range, depending on applicable protection |
May add six months to qualifying patents |
| U.S. commercial exposure |
2028 onward |
Expected beginning of material biosimilar erosion |
| International protection |
Country-specific, generally extending into the late 2020s or early 2030s |
Timing varies by patent family and national law |
The key U.S. patent generally associated with pembrolizumab composition protection is U.S. Patent No. 8,354,509. Public patent databases and company disclosures commonly identify May 2028 as the central U.S. patent-expiration date for Keytruda. Merck has described the principal U.S. loss-of-exclusivity period as occurring in 2028.
The 12-year biologic exclusivity period under the Biologics Price Competition and Innovation Act is separate from patent protection. Its expiration does not itself permit commercial biosimilar launch if valid, enforceable patents remain in force.
What patents protect pembrolizumab?
The patent estate covers the antibody, antibody variants, formulations, dosing approaches, manufacturing processes and selected combinations.
Core composition patents
The foundational patent estate covers antibodies that bind PD-1 and block interaction with PD-L1 and PD-L2. The commercial antibody pembrolizumab is protected through patents directed to the antibody sequence, binding characteristics and related anti-PD-1 molecules.
U.S. Patent No. 8,354,509 is the principal patent associated with Keytruda’s base composition protection. Its reported expiration in May 2028 makes it more commercially important than later patents that may cover narrower subject matter.
Formulation and delivery patents
Merck has pursued additional protection for:
- High-concentration liquid formulations.
- Stabilized antibody formulations.
- Subcutaneous delivery.
- Formulations using recombinant hyaluronidase.
- Dosing schedules and administration methods.
- Manufacturing and purification processes.
These patents may delay or complicate substitution if they cover a commercially important presentation. They are less likely than the core composition patent to block every pembrolizumab biosimilar because a biosimilar manufacturer may design around a formulation claim while supplying an intravenous product.
Merck and Moderna are also developing personalized cancer-vaccine combinations involving pembrolizumab. Those products would not extend Keytruda’s core patent term, but they could preserve demand for pembrolizumab in combination regimens.
What is the FDA regulatory status of Keytruda?
Keytruda is an FDA-approved humanized monoclonal antibody targeting the programmed cell death protein 1, or PD-1, pathway. It is approved for multiple tumor types and treatment settings, including:
- Melanoma.
- Non-small cell lung cancer.
- Head and neck squamous cell carcinoma.
- Renal cell carcinoma.
- Urothelial carcinoma.
- Triple-negative breast cancer.
- Esophageal and gastric cancers.
- Endometrial and cervical cancers.
- Classical Hodgkin lymphoma.
- Colorectal cancer with specified biomarkers.
- Tumors with microsatellite instability-high or mismatch-repair-deficient status.
- Tumor mutational burden-high cancers.
- Perioperative treatment in selected early-stage cancers.
The FDA label contains both monotherapy and combination regimens. Keytruda is often administered every three or six weeks, depending on dose and indication.
Because pembrolizumab is a biologic licensed under the Public Health Service Act, biosimilar competition is governed primarily through the Purple Book and the BPCIA framework. The Orange Book is principally associated with small-molecule drugs approved under the Federal Food, Drug, and Cosmetic Act. Patent and exclusivity analysis for Keytruda therefore requires review of the FDA biologics record, Merck disclosures, the relevant patent families and federal litigation.
How many patents cover Keytruda?
No single public count captures the economically relevant Keytruda estate across all jurisdictions. The number depends on whether the analysis includes issued patents, pending applications, continuations, divisionals, foreign counterparts, formulation claims, method-of-use claims and manufacturing patents.
The estate can be divided into four commercial groups:
| Patent category |
Primary purpose |
Expected competitive impact |
| Antibody composition |
Protects pembrolizumab and related anti-PD-1 antibodies |
Highest impact; central to biosimilar entry |
| Formulation and presentation |
Protects concentration, stability and delivery characteristics |
May narrow substitution options |
| Method of use |
Protects treatment of particular cancers, biomarkers or dosing regimens |
Can affect labeled launches and carve-outs |
| Manufacturing |
Protects cell culture, purification and process conditions |
Raises development and validation costs |
The estate is strongest against an unmodified copy seeking broad substitution before the core composition patent expires. It is less certain against a biosimilar launched after May 2028 with a non-infringing formulation, a limited label or a different manufacturing process.
What biosimilar and Paragraph IV risks exist for pembrolizumab?
The first commercial challenge will likely involve a biosimilar application under the BPCIA rather than a conventional small-molecule Abbreviated New Drug Application. Biosimilar applicants may challenge listed patents through the BPCIA patent-exchange process and through declaratory or infringement litigation.
Potential competitors include large biologics manufacturers and companies with established oncology biosimilar platforms, such as:
- Amgen.
- Sandoz.
- Celltrion.
- Samsung Bioepis.
- Biocon Biologics.
- Fresenius Kabi.
- Pfizer.
- Teva.
- Accord BioPharma.
No company had received FDA approval for a pembrolizumab biosimilar as of the latest publicly available regulatory information through 2024. Public confirmation of a specific applicant’s launch date, litigation position or settlement terms requires a filed application, patent notice or court record.
The most likely sequence is:
- Biosimilar development before core patent expiry.
- BPCIA patent exchanges and patent litigation.
- Potential settlement establishing a delayed launch date.
- At-risk launch or negotiated entry after core patent expiry.
- Rapid price and market-share pressure in high-volume indications.
A biosimilar may not need to copy every Keytruda indication. It can seek approval for a subset of uses and omit indications protected by valid method-of-use patents. This could produce a staged erosion pattern rather than an immediate full-market substitution.
What patent litigation affects pembrolizumab?
Keytruda’s most important litigation risk is expected to arise from future BPCIA disputes over the composition patent, formulation patents, manufacturing claims and method-of-use patents.
The commercial questions in a future case will include:
- Whether the biosimilar infringes U.S. Patent No. 8,354,509.
- Whether any later patent claims are valid and enforceable.
- Whether Merck can obtain an injunction before commercial launch.
- Whether the biosimilar applicant can launch with a restricted label.
- Whether Merck agrees to a negotiated entry date.
- Whether a court permits launch before final resolution of all secondary patents.
A settlement could allow entry before the full secondary patent estate expires while preserving Merck’s core patent claims. Such agreements often create a fixed launch date and may include manufacturing, supply or licensing provisions. No definitive public settlement governing U.S. pembrolizumab biosimilar entry had been established through 2024.
How strong is the pembrolizumab patent estate?
The estate is commercially strong through the core patent term but becomes less durable after 2028.
Strengths
- Broad foundational anti-PD-1 composition protection.
- Large clinical and regulatory record.
- Many approved indications.
- High prescriber familiarity.
- Combination use with chemotherapy, targeted agents and other immunotherapies.
- Significant manufacturing complexity for a high-quality monoclonal antibody.
- Potential formulation and delivery patents.
Weaknesses
- The core U.S. composition patent has a defined 2028 expiration.
- Biologic manufacturing patents rarely prevent all biosimilar competition.
- Method-of-use patents can be avoided through label carve-outs.
- Formulation patents may not block an intravenous biosimilar.
- Large revenue concentration increases the incentive for competitors to enter.
- PD-1 antibodies are established targets with extensive biosimilar development interest.
Merck’s patent estate is therefore strongest as a delay mechanism and negotiation asset. It is less likely to support indefinite market exclusivity after the core composition patent expires.
How does pembrolizumab compare with competing immuno-oncology drugs?
Keytruda competes mainly with other PD-1 and PD-L1 inhibitors.
| Drug |
Company |
Target |
Principal commercial position |
| Keytruda |
Merck |
PD-1 |
Broadest indication and revenue base |
| Opdivo |
Bristol Myers Squibb |
PD-1 |
Major competitor with broad oncology use |
| Tecentriq |
Roche |
PD-L1 |
Strong position in lung, urothelial and other cancers |
| Imfinzi |
AstraZeneca |
PD-L1 |
Strong lung-cancer and biliary-tract presence |
| Libtayo |
Regeneron/Sanofi |
PD-1 |
Position in skin cancer and selected solid tumors |
| Jemperli |
GSK |
PD-1 |
Focused position in endometrial cancer and biomarker-defined disease |
Opdivo is the closest commercial comparator. Bristol Myers Squibb reported Opdivo sales of approximately $10.3 billion in 2024, well below Keytruda’s $29.5 billion. Keytruda’s lead reflects its earlier approval, broader label, strong lung-cancer franchise and extensive use with chemotherapy and targeted agents.
The competitive gap may narrow after 2028 if biosimilar pembrolizumab discounts expand and competing branded agents retain protected indications.
What licensing deals support pembrolizumab revenue?
Keytruda’s commercial value is amplified by combination partnerships.
Merck and AstraZeneca formed a strategic collaboration for clinical development and commercialization of Keytruda with Lynparza, AstraZeneca’s PARP inhibitor. The combination has been studied in multiple tumor types, including renal cell carcinoma and selected gynecologic cancers.
Merck and Moderna expanded their collaboration around an individualized neoantigen therapy combined with pembrolizumab. The regimen is designed to use pembrolizumab as the checkpoint-inhibitor backbone. This model could extend pembrolizumab demand in personalized cancer treatment, although it does not extend the underlying Keytruda patent term.
These arrangements create strategic value through combination revenue, clinical differentiation and treatment-line expansion. They also expose Merck to partner economics and dependence on the success of assets it does not control alone.
What generic launch scenarios exist for pembrolizumab?
Traditional generic substitution is not the relevant post-exclusivity model. The likely threat is biosimilar competition.
| Scenario |
Timing |
Likely effect |
| Delayed biosimilar entry |
2028 or later after settlement |
Gradual erosion, particularly in hospital purchasing |
| Single early entrant |
Around core patent expiry |
Moderate discounting and limited initial share loss |
| Multiple entrants |
2029 onward |
Faster price compression and share migration |
| Interchangeable biosimilar competition |
Timing depends on FDA designation |
Greater pharmacy, payer and health-system substitution |
| Formulation-led defense |
Post-2028 |
Preserves some premium through delivery convenience |
| Combination retention |
2028 onward |
Maintains demand where Keytruda is embedded in complex regimens |
The first erosion will likely occur in price-sensitive institutional channels and large payer contracts. Physician-administered oncology drugs are purchased through hospitals, clinics and specialty distributors, so substitution depends on reimbursement policy, buy-and-bill economics, contracting and physician confidence.
What revenue exposure does Merck face after 2028?
Keytruda creates a concentrated but manageable patent-cliff risk.
A simplified exposure framework is:
| Period |
Revenue position |
Main driver |
| 2024-2027 |
Expansion |
New indications, earlier-line use and combination therapy |
| 2028 |
Transition |
Core U.S. patent expiry and potential biosimilar launch |
| 2029-2031 |
Erosion risk |
Multiple biosimilars, contracting pressure and price discounts |
| 2031 onward |
Portfolio replacement |
New products, combinations and vaccines must offset Keytruda decline |
The magnitude of decline will depend on the number of biosimilars, discount depth, interchangeability, payer policy, international patent dates and the share of sales generated by indications that can be carved out of biosimilar labels.
Merck’s mitigation strategy includes expanding Keytruda into earlier disease, developing subcutaneous delivery, advancing combination products and commercializing newer oncology assets. These measures can preserve volume and improve convenience, but they cannot indefinitely prevent erosion of the intravenous reference product after biosimilar entry.
Key Takeaways
- Keytruda generated $29.5 billion in 2024 sales, approximately 46% of Merck’s pharmaceutical revenue.
- Revenue rose at roughly 20% annually from 2021 through 2024.
- FDA biologic exclusivity ends in September 2026, but the main U.S. patent barrier is expected to remain until May 2028.
- U.S. Patent No. 8,354,509 is the central composition patent associated with pembrolizumab.
- No FDA-approved pembrolizumab biosimilar was publicly identified through 2024.
- The principal post-2028 risk is BPCIA biosimilar competition, not conventional generic substitution.
- Formulation, method-of-use and manufacturing patents may delay or narrow competition but are unlikely to preserve permanent exclusivity.
- Merck’s revenue exposure is unusually high because Keytruda represents nearly half of pharmaceutical sales.
- Opdivo is the closest branded competitor, but Keytruda remains substantially larger by revenue and indication breadth.
- Merck’s combination and delivery strategies can soften the patent cliff but do not eliminate it.
FAQs About Pembrolizumab Patent and Market Risk
Is pembrolizumab a biologic or a small-molecule drug?
Pembrolizumab is a biologic monoclonal antibody. It is marketed as Keytruda and targets PD-1.
Can a pembrolizumab biosimilar be launched before 2028?
FDA approval may be possible after the statutory biologic exclusivity period, but commercial launch can remain blocked by valid patents. The principal U.S. commercial barrier is generally identified as May 2028.
Does Keytruda have an Orange Book patent listing?
Keytruda is a biologic, so the Purple Book and BPCIA framework are more relevant than the traditional Orange Book framework used for small-molecule drugs.
Which drug is the largest competitor to Keytruda?
Opdivo, marketed by Bristol Myers Squibb, is the closest branded competitor. Other competitors include Tecentriq, Imfinzi, Libtayo and Jemperli.
Will Keytruda revenue decline immediately after patent expiry?
Not necessarily. Decline will depend on biosimilar timing, the number of entrants, payer substitution, contracting, indication carve-outs, formulation strategy and Merck’s ability to retain combination and perioperative use.
References
- Merck & Co., Inc. (2022). 2021 annual report.
- Merck & Co., Inc. (2023). 2022 annual report.
- Merck & Co., Inc. (2024). 2023 annual report.
- Merck & Co., Inc. (2025). 2024 annual report.
- U.S. Food and Drug Administration. (2024). Keytruda prescribing information.
- U.S. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products.
- U.S. Patent and Trademark Office. (2013). U.S. Patent No. 8,354,509: Anti-PD-1 antibodies.
- Bristol Myers Squibb. (2025). 2024 annual report.
