Intervet UK Ltd v Merial R.'s University of Belfast the University of Saskatchewan

A patent claim must be construed according to what the skilled reader would understand its language to mean in the context of the specification. A coined virus classification was construed by reference to the disclosed sequence-homology criteria, rather than uncertain serological or hybridisation concepts. Priority requires the claimed subject matter to be derivable directly and unambiguously from the priority document. An invention is obvious where routine investigative steps were obvious to try, with a reasonable expectation that they would succeed, even though the work involved research and success was not guaranteed. A product claim for an antigen suitable for diagnosis does not extend to a preparation requiring modification before it can be used diagnostically.

The patentees sought to enforce a patent concerning type II porcine circovirus diagnostic reagents. The claimant sought revocation and denied infringement of claim 18 by its Porcilis PCV vaccine.

The principal validity issues were priority, insufficiency and obviousness over the Nayar publication. The court also had to construe “type II porcine circovirus”, “responsible in pigs for PMWS” and the requirement that an antigenic preparation allow diagnosis.

1. Construction. “Type II porcine circovirus” meant a class represented by the deposited strains and characterised by greater than 96% nucleotide homology with the sequenced strains and about 76% homology with PCV from PK/15 cells. The uncertain references to significant serological similarity and hybridisation did not define the claimed class. “Responsible in pigs for PMWS” required no proof of causation beyond association with lesions in PMWS-affected pigs. A type II-specific antibody or antigen had to be demonstrably specific rather than cross-reactive.
2. Claim 18. The claim was a product claim, but its antigen had to be capable of being used for diagnosis without modification. Read with the specification, it concerned diagnostic reagents and did not extend to a subunit vaccine merely because its antigen might be useful diagnostically after modification.
3. Priority and sufficiency. Under Patents Act 1977, s 5(2)(a), the claimed invention had to be directly and unambiguously derivable from the Priority Document. That document disclosed neither the existence nor the defining characteristics of the type II class. The proposed amendments did not cure the defect. The alternative construction advanced by the patentees would also render the claims insufficient because “significant serological relationship” supplied no workable boundary.
4. Obviousness. Applying the structured approach in [2007] EWCA Civ 588, the skilled team would have regarded PCR-based sequencing and virus isolation as obvious approaches after Nayar. Both were routine techniques, each offered a reasonable expectation of success, and the evidence from the other research groups strongly supported the conclusion that success was likely. The claims were therefore obvious over Nayar.
5. Disposition. The patent was invalid and had to be revoked. Porcilis PCV could not be used diagnostically without modification and therefore did not infringe claim 18.