Halozyme Sues Merck Over Subcutaneous Keytruda Patent Infringement

In a significant development within the pharmaceutical industry, Halozyme Therapeutics has filed a lawsuit against Merck & Co., alleging patent infringement related to a subcutaneous formulation of the blockbuster cancer drug Keytruda. The legal action, filed in a New Jersey federal court, marks a dramatic escalation in the ongoing dispute between the two companies over drug delivery technology.

Patent Dispute Details

Halozyme's lawsuit claims that Merck's proposed subcutaneous (SC) formulation of Keytruda infringes upon 15 of its patents. These patents are part of Halozyme's Mdase family, which covers a broad range of modified human hyaluronidases—proteins that enable under-the-skin administration of drugs typically given intravenously.

The San Diego-based drug delivery specialist is seeking an injunction to prevent Merck from commercializing SC Keytruda, which is currently under FDA review with a decision expected by September 23, 2025. Additionally, Halozyme is pursuing monetary damages, citing willful infringement by Merck.

Background and Failed Negotiations

The lawsuit follows unsuccessful licensing negotiations between Halozyme and Merck. Halozyme had previously reached out to Merck for a potential licensing agreement and publicly warned of potential legal action if an agreement could not be reached. The breakdown in talks has led Halozyme to accuse Merck of planning to launch SC Keytruda while "knowingly infringing" on Halozyme's patents.

Merck, for its part, maintains that the lawsuit is "meritless" and expresses confidence in its legal position. The company is developing SC Keytruda using a hyaluronidase called berahyaluronidase alfa (ATL-B4) from South Korean company Alteogen. Merck argues that ATL-B4 was independently developed and that its sequence is not disclosed in any Halozyme patent.

Implications for the Industry

This legal battle highlights the increasing importance of subcutaneous drug delivery in the pharmaceutical industry. Companies like AstraZeneca and Daiichi Sankyo have also partnered with Alteogen to develop subcutaneous versions of their cancer drugs, indicating a growing trend in this area.

Merck's development of SC Keytruda is part of its strategy to protect its top-selling cancer immunotherapy as the original intravenous formulation approaches patent expiration in 2028. The company aims to convert 30% to 40% of patients to the SC version within the first two years of launch.

As the legal proceedings unfold, the outcome of this case could have far-reaching implications for patent protection and drug delivery technology in the pharmaceutical industry. The dispute underscores the complex interplay between innovation, intellectual property, and market competition in the development of next-generation drug formulations.