On 4 December 2025, Halozyme announced that the Munich Regional Court has granted its application for a preliminary injunction to prevent MSD from distributing and offering for sale in Germany its Keytruda SC™ (pembrolizumab and berahyaluronidase alfa-pmph). The decision was based on a finding of the Court that there was imminent infringement of one of Halozyme’s European MDASE™ patents, EP 2797622, in relation to modified PH20 hyaluronidase polypeptides and compositions. It is not known whether MSD intends to appeal the decision.
According to the Wall Street Journal, MSD has issued a statement saying that MSD considers Halozyme’s patent “to be invalid globally and their allegation of infringement to be without merit”. MSD commenced legal proceedings against Halozyme’s ‘622 patent in the German Federal Patent Court in August 2025, alleging that it is invalid. MSD also filed a claim in the UK High Court of Justice in August 2025 seeking revocation of the ‘622 patent.
MSD’s subcutaneous (SC) formulation of Keytruda® was approved in Europe in November 2025, following a positive recommendation from the EMA’s CHMP in September 2025. The preliminary injunction in Germany will disrupt MSD’s launch plans in relation to Keytruda SC™ in that jurisdiction, although the IV presentation of Keytruda® will still be available.
Halozyme has also sued MSD in the US in relation to SC pembrolizumab (marketed as Keytruda Qlex™ in the US). In a complaint filed on 24 April 2025, Halozyme alleged that Keytruda Qlex™ infringes 15 patents owned by Halozyme in relation to the MDASE™ subcutaneous delivery platform. The lawsuit followed reports in March 2025 that Halozyme had offered MSD an opportunity to licence its MDASE patents. At the time, a spokesperson from MSD said the enzyme used in Keytruda Qlex™ was “developed independently” from Halozyme and that MSD “strongly believes” that any Halozyme patents that attempt to cover the enzyme variant are invalid.
MSD has filed petitions for post-grant review with the US Patent Trial and Appeal Board challenging the validity of 15 of Halozyme’s US patents. 14 petitions were filed between November 2024 and June 2025 and all have been instituted. The patents at issue are: US 11952600, US 12018298, US 12152262, US 12123035, US 12110520, US 12054758, US 12060590, US 12049652, US 12104185, US 12037618, US 12091692, US 12077791, US 12195773 and US 12264345. An additional petition was filed on 10 November 2025 in relation to US12371685 and is currently pending.