The Hague dismisses Halozyme’s PI bid against MSD over Keytruda

The dispute centres on Halozyme’s European patent EP 2 797 622, entitled ‘Polypeptide variants, formulations and uses thereof’. The patent, which expires in December 2032, is in force in numerous European countries, including the Netherlands, Denmark, and Sweden. It protects a new variant of Keytruda. The cancer drug is one of the world’s best-selling medicines, generating sales of approximately €25.8 billion for MSD in 2024.

Currently, doctors administer the cancer drug by infusion. However, the new variant, Keytruda SC, is injected subcutaneously under the skin, which would make administration easier, particularly for older and less mobile patients. Halozyme licenses the underlying Enhanze and MDASE technologies, which enable the subcutaneous administration of drugs.

Merck Sharp & Dohme (MSD) received a central EU marketing authorisation for Keytruda SC, a subcutaneous formulation of pembrolizumab containing the enzyme berahyaluronidase alfa (ALT-B4). Halozyme believes that this infringes its EP 622. Accelerated main proceedings between the parties are pending before the District Court The Hague, with an oral hearing scheduled for 31 July 2026. In those proceedings, MSD is seeking a declaration of non-infringement and revocation of the Dutch part of EP 622, whilst Halozyme has filed cross-border infringement counterclaims covering all countries where the patent is in force, except Germany.

Statement in written pleadings

However, MSD’s product has been listed in the Danish and Swedish price lists. Through the preliminary injunction proceedings in The Hague, Halozyme aims to have Keytruda SC removed from these lists, and to ensure it remains removed for the duration of the first-instance accelerated main proceedings (VRO proceedings).

The preliminary injunction proceedings centred on a statement MSD made in its reply to the counterclaim filed in April 2026. In response to Halozyme’s allegation of an imminent Europe-wide launch, MSD stated that the suggestion that the group intended to bring Keytruda SC to market “as quickly as possible in the other countries of the European Union where EP622 is in force” was “unfounded and incorrect”. MSD further stated that it explicitly denied operating outside the Netherlands and that there was no threat of infringement.

Shortly afterwards, MSD’s Swedish and Danish sister companies had Keytruda SC listed in the national pricing databases, with the Swedish listing showing the product as “available for sale” as of 11 May 2026. MSD rejected Halozyme’s cease-and-desist letter of 15 May 2026.

Binding untertaking

Halozyme argued before the Dutch court that MSD had either given a binding undertaking or, at the very least, created a legitimate expectation that neither MSD nor any other entity within the MSD group would launch Keytruda SC in the relevant countries before the conclusion of the main proceedings.

Judge H.F.R. van Heemstra dismissed the application (case ID: C/09/706206 / KG ZA 26-576). The court held that even if MSD’s statement in the written pleading were incorrect, it constituted a procedural position taken to counter an argument by Halozyme and could not be qualified as an undertaking enforceable under Article 3:296 of the Dutch Civil Code.

According to the court, Halozyme had less far-reaching options available to address the alleged threat of infringement, such as seeking a preliminary injunction on the merits of the patent. The company could also have verified with MSD whether an undertaking was intended and requested a formal cease-and-desist declaration. Given the far-reaching consequences of an undertaking of this nature, the court held that Halozyme could not reasonably have interpreted the statement without further verification as a declaration of intent giving rise to legal effects within the meaning of Article 3:33 of the Dutch Civil Code.

Parallel European proceedings

The Dutch ruling forms part of a wider European dispute over Keytruda SC in countries including the Netherlands, UK, France, Switzerland, Sweden, Denmark, and Germany. In 2025, Munich Regional Court granted Halozyme a preliminary injunction prohibiting MSD from launching Keytruda SC in Germany. MSD has filed nullity actions against EP 622 in Germany, the Netherlands, France, and the UK, with Halozyme filing a counterclaim for infringement in the UK.

Earlier this week, the UK High Court dismissed an application by MSD for expanded disclosure of experimental documents from Halozyme in the dispute over the subcutaneous version of Keytruda. Judge James Mellor found that Halozyme had adequately fulfilled its disclosure obligations regarding the experiments relied upon in the proceedings (case ID: HP-2025-000041).

Halozyme is also pursuing MSD in the US federal district court in New Jersey, alleging that the subcutaneous formulation of Keytruda, marketed in the US as Qlex, infringes 15 patents relating to Halozyme’s MDAS technology.

Hogan Lovells represents MSD across Europe

A team from Brinkhof respresented Halozyme. Partner Mark van Gardingen led the team and is also leading the Dutch proceedings on the merits. He worked with partner Rien Broekstra and associates Barbara Mooij, Charlotte Tiems, and Eveline Lots. Patent attorney Atze van Stralen supported the team in technical matters.

In Germany, the US, and the UK, the biotech company relies on Quinn Emanuel Urquhart & Sullivan, with Marcus Grosch leading the German team, David Lancaster advising the client in the UK, and David Nelson and Zach Summers handling the US cases. In the UK proceedings, a team from Osborne Clark is acting for Halozyme.

MSD instructed its long-standing patent counsel, Hogan Lovells. Amsterdam-based partners Gertjan Kuipers and Dirk-Jan Ridderinkhof led the Dutch proceedings. Counsel Rik Zagers and associates Bram Jaarsma, Floris Patijn, and Anne Schreibers provided support.

In parallel proceedings, Hogan Lovells partners Miriam Gundt and Andreas von Falck are leading the German case, working with patent attorney Felipe Zilly. Stanislas Roux-Vaillard and Iris Accary are acting in the French proceedings, while Stephen Bennett, Helen Poulson, and Katie Barton lead the UK case. In the US, Jeff Kushan of Sidley Austin represents MSD.