Merck Wins Fight Over Blockbuster Drug
Merck Wins PTAB Fight Over Blockbuster Drug, Again
Highlights
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PTAB invalidates all challenged claims in key immunotherapy patents
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Victory strengthens Merck’s control over Keytruda’s commercial runway
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Dispute centers on cancer-treatment patents held by Johns Hopkins University
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Remaining PTAB challenge due for decision by November 18, 2025
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Implications for academic IP, biosimilar competition, and life-cycle management
The Core Facts
Merck Sharp & Dohme LLC has scored another major victory in a complex patent dispute over its cancer immunotherapy drug, pembrolizumab (marketed as Keytruda). The U.S. Patent Trial and Appeal Board (PTAB) issued a set of final written decisions in four inter partes review (IPR) proceedings, invalidating all claims of patents held by Johns Hopkins University related to the use of pembrolizumab in treating microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) tumors.
These rulings followed a previous PTAB decision from June 2025, in which all 42 claims in another related patent were also found to be unpatentable. In total, Merck has now successfully challenged eight of nine patents in this family. One final IPR remains pending, with a decision expected by mid-November.
These cases are part of a larger litigation and patent-strategy campaign by Merck to clear obstacles as the company defends its dominance in the lucrative immunotherapy market.
Background on Key Individuals and Institutions
Merck Sharp & Dohme LLC is the pharmaceutical giant behind Keytruda, a PD-1 checkpoint inhibitor used to treat a range of cancers. Keytruda is Merck’s top-selling drug and one of the highest-grossing pharmaceuticals globally, generating billions in annual revenue.
Johns Hopkins University holds multiple patents on biomarker-based methods of identifying patients who benefit from immunotherapies, particularly involving MSI-H and dMMR tumor profiles. These patents stem from early clinical trials and research collaborations between Johns Hopkins scientists and corporate partners.
The PTAB is the U.S. Patent and Trademark Office’s tribunal for hearing post-grant patent challenges. Its decisions can have sweeping impacts on the commercial viability of patented products, particularly in pharma and biotech.
Political and Commercial Context
This dispute unfolds at a critical moment in the pharmaceutical sector. Merck is facing growing scrutiny over its patent practices as it prepares for biosimilar competition and works to extend Keytruda’s market exclusivity through new formulations, including a subcutaneous version.
The PTAB rulings benefit Merck commercially by eliminating competing or overlapping patent claims that could complicate future product launches or licensing strategies. At the same time, the loss of academic patents raises questions about how universities protect and enforce intellectual property arising from basic or translational research.
Politically, the outcome plays into ongoing national debates over patent thickets, drug pricing, and the balance between innovation and competition in the U.S. pharmaceutical industry.
Legal Context and Precedent
At the heart of the IPR proceedings were three core legal grounds:
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Obviousness under 35 U.S.C. §103, where the PTAB found that prior art—including published studies and earlier trials—rendered the patent claims obvious to a person of ordinary skill in the art.
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Lack of written description under 35 U.S.C. §112, in which the board found that certain broad claims were not sufficiently supported by the patent’s specification.
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Lack of enablement, also under §112, which argued that the patents failed to teach others how to use the invention without undue experimentation.
The PTAB’s rulings reflect how rigorously courts now examine functional medical claims, especially those based on biomarkers or patient stratification—a growing area in precision medicine.
This case also demonstrates how aggressively branded pharmaceutical companies are using IPRs, a tool once feared by industry, to proactively shape the IP landscape.
Implications
For Merck:
The PTAB victories clear a major legal obstacle to Merck’s commercialization plans. The decisions provide greater freedom to pursue label expansions, reformulations, and next-generation products without being blocked by third-party patents.
For Johns Hopkins University and Academic IP:
The invalidation of its patents may limit Johns Hopkins’ ability to earn royalties from pembrolizumab or similar treatments. It could also discourage other universities from pursuing broad method-of-treatment claims without robust data.
For Biosimilars and Market Competition:
If other Merck patents are also weakened or invalidated, biosimilar manufacturers may find entry points sooner. On the other hand, Merck’s success here may give it broader room to assert its own remaining IP to fend off competitors.
For Legal and Patent Strategy in Biopharma:
The outcome reinforces the need for companies and institutions to carefully craft and defend patents, particularly those relying on clinical trials or complex biomarkers. It also confirms the PTAB as a central battleground in high-stakes pharmaceutical IP conflicts.
What’s Next
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Pending Decision: The PTAB is expected to issue a ruling on the final IPR by November 18, 2025, which will conclude Merck’s current challenge to the Johns Hopkins patent portfolio.
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Appeals: Johns Hopkins may appeal the PTAB decisions to the U.S. Court of Appeals for the Federal Circuit, which could take 12–18 months to resolve.
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Commercial Moves: Merck is anticipated to continue launching reformulated versions of Keytruda, particularly subcutaneous injections, supported by this legal clarity.
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Policy Ramifications: Legislators and regulators may further examine how IP frameworks intersect with academic innovation and drug affordability.
Conclusion
Merck’s string of PTAB victories marks a pivotal moment in its strategy to safeguard Keytruda’s dominance. By systematically dismantling competing academic patents, Merck has reinforced its legal position in a multibillion-dollar market and highlighted how aggressive IP litigation now defines the boundaries of pharmaceutical innovation.
This case is also a cautionary tale for universities and public research institutions about the challenges of maintaining enforceable patent rights in the face of corporate IPR strategy. With billions at stake and regulatory scrutiny growing, the decisions reverberate far beyond the lab and courtroom.
