Hospira UK Limited v. Cubist Pharmaceuticals LLC, Patents Court, Henry Carr J, 10 June 2015

The English Patents Court gave judgment in an action for revocation of three patents concerning the known antibiotic daptomycin.  There were many issues in the case, much of which were factual, but a point of general interest arose on entitlement to priority in the light of the “same invention” requirement  of Article 87 EPC.

One of the patents, EP (UK) 1,115,417 had a main claim in the Swiss form, directed to a dosage regime for daptomycin, which is a potent antibiotic effective against a range of pathogens including MRSA. It was however known to cause muscular dysfunction.  Studies showed that muscle toxicity was dose-related, both in terms of quantity and frequency of administration.

The dosage regime in the claim of the granted patent was 3-10 mg/kg of daptomycin every 24 hours.  The patent claimed priority from two documents.  The precise values in the claim were not in the first priority document; it disclosed daptomycin at a dose of 2-10 mg/kg at intervals of between 12 and 24 hours.   The evidence accepted by the court was that differences in the dosing interval were significant to toxicity.

Given that there had been no actual disclosure of the combination of 3-10 mg/kg once-daily, the court then had to address the question as to whether there was enough in the first priority document to give the skilled person essentially the same information as forms the subject of the claim, and enable that person to work the invention in accordance with the claim.  In doing so, the court had to decide whether the claim was to the “same invention” as that disclosed in the priority document, following the guidance on Article 87 contained in the Enlarged Board’s decision in G2/98.
The claim is, in effect, to a selected sub-range within the wider range disclosed in the first priority document.  The sub-range itself had not been disclosed.  The court held that to say that it was nonetheless entitled to priority would be contrary to the strict, narrow interpretation of “same invention” required by the Enlarged Board decision.  The skilled person can use common general knowledge in weighing the disclosure of the priority document, but the subject-matter of the claim must be derivable directly and unambiguously from it.

The patentee sought to moderate the “same invention” requirement by saying that it meant “the same crux of the invention” or the “key concept”, but this was rejected.  Likewise, a submission that the claimed range was not a novel selection over the disclosed range was rejected.

The patentee fared better with the second priority document.  This was more detailed than the first, and drew the conclusion from studies that the dosing interval had a greater effect on muscle toxicity then the dosing quantity.   The document disclosed 2-10 mg/kg or 3-9 mg/kg every 24 hours.  Even though these did not exactly correspond to the claim’s 3-10 mg/kg, it was enough to confer priority.  The document had disclosed that once-daily dosing can minimise muscle toxicity while optimising antimicrobial efficacy.  That general teaching, coupled with ranges given, was sufficient to disclose the “same invention” to the skilled person.

The judge noted that the “same invention” question is not a formulaic one.  One must look at the prior document as a whole in order to assess its disclosure.

As a footnote, gaining the priority of the second document did not save the patent.  Dosage regimens falling within the main claim had been disclosed in a press release by the patentee some 3 weeks before the second priority date.   Having lost the first priority date, the claims of the patent were then held by the court on the evidence to lack inventive step over the content of the press release.

A copy of the case can be found here.

Head note: Gregor Grant, Marks & Clerk Solicitors