On 7 October 2026, Halozyme Therapeutics announced that it has won an injunction from the specialised Dutch patent court of The Hague, preventing MSD from manufacturing, selling, importing and stockpiling Keytruda SC™ (pembrolizumab and berahyaluronidase alfa-pmph) in Belgium, Denmark, France, Ireland, Italy, Sweden, Switzerland and the Netherlands.
The Court ordered the injunction based on its finding that Halozyme’s patent, EP 297 622 (EP 622) is valid and infringed by MSD. EP 622 relates to modified PH20 hyaluronidase polypeptides and compositions, which Halozyme claims allow for rapid subcutaneous administration of therapeutic drugs.
MSD’s subcutaneous pembrolizumab formulation uses Alteogen’s ALT-B4 technology, a recombinant human hyaluronidase enzyme platform (berahyaluronidase alfa) designed to convert intravenous (IV) drugs into subcutaneous formulations. Under licensing terms with MSD, Alteogen obtains milestone payments and ongoing commercial royalties linked to Keytruda SC™ sales. However, according to Korea Economic Daily, Alteogen expects little financial impact from the Dutch court ruling, with the outcome estimated to affect only 3% of Keytruda SC™’s global market.
The final injunction granted by the Dutch Court follows a ruling of the District Court of The Hague in July 2026 dismissing Halozyme’s application for a preliminary injunction to prevent MSD from marketing Keytruda SC™ in Denmark and Sweden pending the outcome of the substantive proceedings.
MSD and Halozyme are also in dispute elsewhere over patents to Halozyme’s MDASE™ subcutaneous delivery technology. In December 2025, the Munich Regional Court granted a preliminary injunction, preventing MSD from distributing and offering for sale in Germany Keytruda SC™, based on a finding of the Court that there was imminent infringement of EP 622.
In April 2024, Halozyme sued MSD in the US, alleging that MSD’s subcutaneous pembrolizumab (Keytruda Qlex®) infringes 15 patents. As of 7 October 2026, MSD had successfully invalidated claims of 9 of Halozyme’s US patents before the Patent Trial and Appeal Board (PTAB) and had a further 8 petitions pending before PTAB.
MSD’s subcutaneous pembrolizumab was approved in Europe in November 2025. It has also been approved in the US as Keytruda Qlex™ (September 2025); in Canada (February 2026), Korea (May 2026, launched September 2026) and Australia (July 2026), as Keytruda SC™; and in Japan as Keyject™ (September 2026).
While there are no reports of biosimilar subcutaneous pembrolizumab development to date, there are multiple pembrolizumab (IV) biosimilars approved or in development. For example, Samsung Bioepis and Celltrion each applied for Korean approval of their pembrolizumab biosimilars in August 2026 (SB27 and CT-P51, respectively). In June 2026, Samsung Bioepis claimed to be the first developer of a pembrolizumab biosimilar to announce global phase 3 trial results. Amgen also confirmed on 15 September 2026 that its Keytruda® biosimilar has successfully completed clinical trials with an FDA submission likely later this year. Formycon announced successful Phase 1 results in February 2026, with its US commercialisation partner, Zydus, expressing optimism that it is well-placed to file the first BLA in the US for biosimilar pembrolizumab.