With the patent court siding with Halozyme, Merck faces restrictions on a product that won approval in Europe last year.
A Dutch court has blocked Merck from manufacturing and selling a subcutaneous Keytruda formulation in multiple European markets.
The court found Merck’s drug, which European authorities approved in November, infringes a Halozyme Therapeutics patent. Having reached that conclusion, the patent court ordered Merck not to produce or sell the subcutaneous product in Belgium, Denmark, France, Ireland, Italy, Sweden, Switzerland or the Netherlands.
Merck argued that Halozyme’s patent, which covers the drug delivery specialist’s modified hyaluronidase (MDASE) technology, is invalid. However, the court rejected the argument and found that subcutaneous Keytruda infringed the patent, triggering the order to stop producing, importing, stocking or selling the product in certain European markets. The subcutaneous formulation is branded Keytruda SC in Europe.
The court case is part of a global dispute between Halozyme and Merck. Halozyme provides its Enhanze subcutaneous delivery technology to multiple drugmakers, facilitating under-the-skin delivery of drugs including Johnson & Johnson’s Darzalex and Roche’s Ocrevus.
Merck partnered with South Korea’s Alteogen on technology for delivering Keytruda subcutaneously. Halozyme alleged that certain patents in its MDASE portfolio cover an ingredient in the subcutaneous formulation. Over the past two years, Halozyme and Merck have argued before the Patent Trial and Appeal Board and a district court in the U.S., as well as in European courts.
Decisions are pending in the U.S., but cases have progressed in Europe. In December, a German court hit Merck with a preliminary injunction, prohibiting sales of Keytruda SC in the country. Merck appealed the German ruling, with a hearing expected next month.
The Dutch and German rulings block Merck from three of the four largest markets in Europe. Germany is the largest pharmaceutical market in the region, followed by France, the U.K. and Italy. In May 2026, Halozyme consented to revocation of the disputed patent in the U.K.
Merck’s intravenous Keytruda product is unaffected by the rulings. The intravenous product continues to dominate, accounting for $7.9 billion of the $8.4 billion generated across the Keytruda franchise in the second quarter.
While subcutaneous Keytruda sales are relatively small, totaling $463 million in the second quarter, the formulation is important to the franchise’s mid- to long-term prospects. A key Keytruda patent is set to expire in 2028. Merck could delay the launch of biosimilar rivals until the 2030s, but at some point its intravenous product will face off-patent challengers.
Converting customers to the subcutaneous formulation, which is covered by other patents, could soften the impact of biosimilar copies of intravenous Keytruda. The legal setbacks delay Merck’s work to switch key European markets to Keytruda SC.
