Merck's Keytruda Launch Halted in Germany After Patent Injunction
Court ruling in favor of Halozyme disrupts rollout of a subcutaneous formulation key to defending the blockbuster cancer drug from biosimilar threats.
Merck’s strategic plan to extend the life of its top-selling cancer drug, Keytruda, hit a significant roadblock Wednesday after a German court ordered the company to halt the launch of a new under-the-skin formulation following a patent dispute with Halozyme Therapeutics.
A Munich regional court granted a preliminary injunction that forces Merck to stop distributing and marketing the subcutaneous version of Keytruda in Germany, a major European market. The ruling upholds a patent infringement claim from Halozyme concerning its drug delivery technology. Shares of Merck (NYSE: MRK) fell just over 1% in afternoon trading to $101.12 following the news.
The decision deals a blow to a product central to Merck’s defense of its oncology franchise. The injectable formulation of Keytruda, which generated over $25 billion in revenue last year, is designed to offer a more convenient alternative to the current intravenous infusion, which can take 30 minutes or more. By converting patients to the new version, which can be administered in under five minutes, Merck aims to protect its market share before the main patent on intravenous Keytruda expires in 2028, opening the door to lower-cost biosimilar competition.
Halozyme alleges that Merck’s product infringes on its European patent for the MDASE™ drug delivery platform, which uses an enzyme to help disperse drugs administered under the skin. "We are pleased with the court's decision, which recognizes the validity and importance of our intellectual property," Halozyme stated in a press release.
Merck has vowed to fight the ruling, stating its intention to appeal. The pharmaceutical giant maintains that its technology was developed independently and does not infringe on Halozyme's patents. "We remain confident in our legal position and the value that subcutaneous Keytruda can bring to patients," a Merck spokesperson said. The company noted that the intravenous version of Keytruda remains available to patients in Germany.
The subcutaneous formulation is a cornerstone of Merck's long-term strategy for its most important product. Analysts project the new version could generate peak annual sales between $5 billion and $6.5 billion, providing a crucial buffer against the anticipated revenue decline once biosimilars enter the market. Merck has previously told investors it expects to convert 30% to 40% of its current Keytruda patients to the new formulation.
The legal battle underscores the high stakes involved in pharmaceutical life-cycle management, where companies often develop new formulations or delivery methods—a strategy sometimes criticized as a "product hop"—to extend the commercial viability of blockbuster drugs. This injunction, while limited to Germany, could create uncertainty for the product's rollout in other key markets if similar legal challenges arise.
Analysts are watching the dispute closely, as the success of subcutaneous Keytruda is seen as vital for softening the impact of the looming patent cliff. According to market intelligence firm Evaluate, total annual sales for the Keytruda franchise are forecast to peak at nearly $32.7 billion in 2026 before biosimilar competition begins to erode revenue. The company’s ability to smoothly transition patients to the new formulation is critical to maintaining its dominance in the immuno-oncology space.
The legal proceedings are not fully resolved. Merck had previously initiated nullity proceedings against Halozyme’s patent, which are still pending before the German Federal Patent Court. The outcome of that separate action could ultimately invalidate the patent Halozyme is asserting, but for now, the injunction stands as a significant commercial and strategic setback.