The UK Court of Appeal recently issued a decision in Idenix Pharmaceuticals Inc. v Gilead Sciences, Inc & Ors. This case concerned Idenix’s EP(UK) 1,523,489 patent which is directed to a family of nucleoside analogues for treating hepatitis C virus (HCV) infection, and which Idenix considered to be infringed by sales of Gilead’s sofosbuvir drug. At first instance Mr Justice Arnold had revoked the patent for both insufficiency and lack of inventive step because the common general knowledge was not considered to make it plausible that the invention would work across the scope of the claims. The Court of Appeal has now endorsed the first instance decision and confirmed that a patent is considered to be insufficient and to lack inventive step if the technical effect relied upon is not demonstrated across the scope of the claims. In reaching this decision the Court of Appeal has emphasised its reluctance to overturn a first instance finding of insufficiency or lack of inventive step unless an error of principle has occurred.

The present appeal focused around the contents of the common general knowledge at the priority date of the patent, and whether this was considered to support a broad claim scope defined by a Markush formula in the absence of data in the patent relating to a large number of compounds falling within this formula. Specifically the court considered whether it would have been common general knowledge at the priority date that 2’-methyl-up-2’-hydroxy-down nucleoside analogues had the potential to treat HCV infection.

Unusually, in this case the Patentee was arguing from the position that the common general knowledge should be considered to include additional information, since this was required for the claims to be sufficiently disclosed across their scope. In coming to its conclusion that the claims were insufficiently disclosed, the Court of Appeal made a number of comments which may be useful in assessing common general knowledge in the future. Firstly the Court of Appeal confirmed that disclosures made closer to the priority date are less likely to form part of the common general knowledge than disclosures made well in advance of the priority date, and that presentations which are not advertised as a highlight of a conference are less likely to form part of the common general knowledge. However, the number of people attending a conference and the interest of a disclosure to an expert were not considered to be relevant to determination of whether a disclosure forms part of the common general knowledge.

Once the Court of Appeal had determined that the common general knowledge determination at first instance was correct, it followed that the patent was insufficiently disclosed and also lacked an inventive step because the therapeutic effect of the claimed compounds was not considered to extend across the scope of the claims. In coming to this conclusion the Court confirmed that an appellate court will be very cautious in overturning a first instance finding of insufficiency or lack of inventive step unless an error of principle has occurred. This highlights the need for a claimant to ensure that all information regarding insufficiency and inventive step is advanced at first instance.

The European patent which was the subject of these proceedings (EP1,523,489) is currently undergoing an appeal at the EPO following revocation of the patent for insufficiency and it remains to be seen whether the European patent will be reinstated upon appeal.