On 24 April 2024, Halozyme Therapeutics announced that it has sued MSD (known as Merck in the US and Canada) for patent infringement in the US District Court for the District of New Jersey. Halozyme is alleging that MSD/Merck’s subcutaneous formulation of Keytruda® (pembrolizumab) infringes 15 patents owned by Halozyme in relation to MDASE subcutaneous delivery technology.
Halozyme’s complaint states that the patents “arise out of Halozyme’s extensive research” regarding “modifications to a human hyaluronidase, known as PH20” which, amongst other things “allows for rapid subcutaneous administration of therapeutic drugs”. Halozyme alleges that MSD’s SC Keytruda® includes berahyaluronidase alfa, a modified PH20 which “includes the amino acid modifications … covered by the asserted patents”.
Halozyme is seeking damages and an injunction preventing the manufacture, sale and import of SC Keytruda® in the US. MSD/Merck is yet to file its defence.
The lawsuit follows reports in March 2025 that Halozyme had offered MSD/Merck an opportunity to licence its MDASE patents. At the time, a spokesperson from MSD/Merck said the enzyme used in SC Keytruda® was “developed independently” from Halozyme and that MSD/Merck “strongly believe” that any Halozyme patents that attempt to cover the enzyme variant are invalid.
MSD/Merck has filed petitions for post-grant review with the US Patent Trial and Appeal Board challenging the validity of ten of Halozyme’s US patents, eight of which are asserted in the litigation. The petitions, which are currently pending, were filed between November 2024 and April 2025 in relation to: US 11952600, US 12018298, US 12152262, US 12123035, US 12110520, US 12054758, US 12060590, US 12049652, US 12104185 and US 12037618.
In November 2024, MSD revealed positive topline results from its Phase 3 trial evaluating SC pembrolizumab (MK-3475A), together with Alteogen’s berahyaluronidase alfa, administered with chemotherapy. The SC pembrolizumab demonstrated noninferior pharmacokinetics compared to intravenous (IV) Keytruda® (pembrolizumab) in combination with chemotherapy, in adults with metastatic non-small cell lung cancer (NSCLC). At the JP Morgan Healthcare Conference in San Francisco on 14 January 2025, Merck/MSD announced an expected 2025 launch for SC Keytruda®.