As previously reported, since November 2024, MSD has filed a number of petitions for review with the US Patent Trial and Appeal Board (PTAB) challenging the validity of patents relating to Halozyme’s MDASE™ subcutaneous delivery platform. Halozyme has alleged in US court proceedings that those patents are infringed by MSD’s subcutaneous pembrolizumab (Keytruda Qlex™/ Keytruda SC™).
The following developments have occurred over the last few months in relation to those petitions:
● PTAB instituted inter partes review for three of MSD’s petitions on 9 September 2026: IPR2026-00312 (10,865,400), IPR2026-00313 (11,041,149) and IPR2026-00314 (11,066,656); and
● PTAB issued final written decisions finding all challenged claims of 4 Halozyme patents invalid:
a) US 12,110,520 (PGR2025-00017, decision of 1 September 2026);
b) US 12,123,035 (PGR2025-00009, decision of 24 June 2026);
c) US 12,018,298 (PGR2025-00004, decision of 8 June 2026); and
d) US 12,152,262 (PGR2025-00006, decision of 18 May 2026).
In summary, the Halozyme patents currently the subject of US litigation and PGR or IPR proceedings are as follows:
| US Patent No. | PGR/IPR No. | Status of PGR/IPR | At Issue in US Proceeding? |
| 11,952,600 | PGR2025-00003 | Patent Invalidated, 12 May 2026 | Yes |
| 12,018,298 | PGR2025-00004 | Patent invalidated, 8 June 2026 | Yes |
| 12,152,262 | PGR2025-00006 | Patent invalidated, 18 May 2026 | Yes |
| 12,123,035 | PGR2025-00009 | Patent Invalidated, 24 June 2026 | No |
| 12,110,520 | PGR2025-00017 | Patent Invalidated, 1 Sept 2026 | Yes |
| 12,060,590 | PGR2025-00024 | Instituted 16 Oct 2025 | No |
| 12,054,758 | PGR2025-00030 | Instituted 16 Oct 2025 | Yes |
| 12,049,652 | PGR2025-00033 | Instituted 1 Oct 2025 | Yes |
| 12,104,185 | PGR2025-00039 | Instituted 1 Oct 2025 | Yes |
| 12,037,618 | PGR2025-00042 | Instituted 13 Nov 2025 | Yes |
| 12,091,692 | PGR2025-00046 | Instituted 10 Oct 2025 | Yes |
| 12,077,791 | PGR2025-00050 | Instituted 19 Nov 2025 | Yes |
| 12,264,345 | PGR2025-00052 | Instituted 16 Oct 2025 | Yes |
| 12,195,773 | PGR2025-00053 | Instituted 19 Nov 2025 | Yes |
| 12,371,685 | PGR2025-00087 | Institution Denied 15 May 2026 | Yes |
| 11,066,656 | IPR2026-00314 | Instituted 9 September 2026 | Yes |
| 11,041,149 | IPR2026-00313 | Instituted 9 September 2026 | Yes |
| 10,865,400 | IPR2026-00312 | Instituted 9 September 2026 | Yes |
In December 2025, the Munich Regional Court granted Halozyme’s application for a preliminary injunction preventing MSD from distributing and offering Keytruda SC™ for sale in Germany. 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. MSD has filed invalidation lawsuits in relation to EP 2797622 in four countries: Germany, the United Kingdom, the Netherlands, and France.
In July 2026, The District Court of the Hague dismissed Halozyme’s application for a preliminary injunction to prevent MSD from marketing Keytruda SC™ in Denmark and Sweden pending the outcome of substantive proceedings.
MSD’s subcutaneous formulation of pembrolizumab was approved in the US, as Keytruda Qlex™, in September 2025 across 38 indications.