UK Patents Court Rejects MSD's Bid for Wider Disclosure in Halozyme Hyaluronidase Patent Dispute Over Keytruda Subcutaneous Formulation
核心洞察
The UK Patents Court dismissed MSD's application seeking further experimental disclosure from Halozyme in a patent infringement case concerning modified human PH20 hyaluronidase (搜索) enzymes, in a judgment handed down on 20 July 2026.
The dispute centers on whether MSD's subcutaneous Keytruda formulation, containing berahyaluronidase alfa (搜索), infringes Halozyme's European Patent EP(UK) 3 130 347.
Mr Justice Mellor applied a restrictive approach to the waiver of privilege, ruling that the scope must be assessed by reference to the specific experiment relied upon rather than the broader pleaded case.
The UK Patents Court has dismissed an application by Merck Sharp & Dohme (UK) Limited seeking further disclosure of experimental material from Halozyme, Inc, in a significant ruling that reaffirms a restrictive approach to the consequential waiver of privilege in patent litigation. The judgment, handed down by Mr Justice Mellor on 20 July 2026, carries implications for how pharmaceutical companies manage experimental evidence in disputes over biologic drug delivery technologies.
The case, Merck Sharp & Dohme (UK) Limited v Halozyme, Inc [2026] EWHC 1838 (Pat), arose from a dispute over Halozyme's European Patent EP(UK) 3 130 347, which covers modified human PH20 hyaluronidase (搜索) enzymes designed to enable subcutaneous delivery of drugs in larger volumes. Halozyme alleged that MSD's subcutaneous formulation of its blockbuster cancer immunotherapy Keytruda, which contains a recombinant enzyme known as berahyaluronidase alfa (搜索), infringed the patent.
The Underlying Technology and Dispute
The patent at issue relates to engineered hyaluronidase enzymes that temporarily degrade hyaluronan in the subcutaneous space, facilitating the administration of larger-volume injectable biologics that would otherwise require intravenous infusion. A related patent, EP 622, had been submitted for revocation shortly before the hearing, narrowing the action to EP 347 alone.
Following an earlier case management conference, Halozyme served a Notice of Experiments directed to whether MSD's berahyaluronidase alfa (搜索) exhibited the increased hyaluronidase activity required by the patent's claims. The experimental design compared MSD's enzyme against a reference enzyme sourced from Creative Biomart. Alongside the notice, Halozyme provided what is known as Mayne Pharma disclosure — the body of work-up material that a party relying on experiments in patent proceedings must typically disclose as a consequence of waiving privilege — together with a statement identifying categories of material it maintained remained privileged.
MSD's Arguments for Wider Disclosure
MSD contended that Halozyme's disclosure was manifestly deficient, seeking production of material relating to any attempts by Halozyme to produce or test alternative comparator polypeptides. This included one identified by the sequence reference SEQ ID NO: 35, which had featured in an earlier, since-abandoned version of Halozyme's pleaded case.
MSD pointed to correspondence in which Halozyme had sought successive extensions of time to serve its Notice of Experiments, citing difficulties producing comparator polypeptides and, later, an unexplained technical issue with a laboratory reagent. Based on this correspondence, MSD invited the court to infer that Halozyme had attempted and failed to use other comparators before settling on the Creative Biomart product.
The Court's Reasoning
Mr Justice Mellor held that the scope of any consequential waiver of privilege had to be assessed by reference to the specific experiment relied upon in the Notice of Experiments, rather than the pleaded case on infringement or validity more broadly. Applying the principles set out in Magnesium Elektron v Neo Chemicals and the earlier authority of Mayne Pharma Pty Ltd v Debiopharm SA, he determined that a cautious and restrictive approach to waiver was appropriate outside the established categories of "inevitable result" and "completeness of data" cases.
Crucially, Halozyme's evidence confirmed that no experiments had in fact been conducted comparing MSD's enzyme against any comparator other than the Creative Biomart product, and that no comparison had been made between different candidate comparators to determine a preference. The judge therefore concluded that MSD's invited inferences were unsupported and that the disclosure already provided represented the whole of the material properly relevant to the experiment relied upon.
The fact that difficulties in producing comparator polypeptides also underpinned a separate insufficiency plea did not, the judge held, extend the scope of the waiver.
Redactions Dispute Also Rejected
A related dispute over redactions to work-up documents for two earlier experiments was also rejected. The judge accepted Halozyme's unchallenged evidence that the redacted material fell outside the protocols actually used in the notified experiment. MSD had suggested that the redactions were connected to a separate costs appeal concerning the revoked EP 622, but the judge found no basis for that inference once the grounds of that appeal were examined.
MSD's application was dismissed in full, with the remaining procedural matters agreed between the parties. The ruling underscores the English courts' disciplined approach to privilege waiver in patent proceedings, limiting disclosure obligations to material directly connected to the experiments a party elects to rely upon at trial.