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UK Court of Appeal upholds Arnold J’s judgment on Idenix v Gilead

The UK Court of Appeal has upheld Arnold J’s first-instance decision that Idenix’s EP(UK) 1,523,489 patent for a family of nucleoside analogues for the treatment of hepatitis C and other Flaviviridae viruses was invalid for lack of novelty and inventive step and for insufficiency. Invalidity for both lack of inventive step and insufficiency was found on substantially the same ground: that it was not plausible that substantially all of the claimed compounds would be effective against Flaviviridae viruses. The patent was also found to be insufficient on two independent grounds: (i) it did not enable synthesis of the 2’-methyl-up-2’-fluoro-down nucleoside analogues claimed without undue burden; and (ii) even if it had been plausible that the claimed nucleoside analogues had activity against Flaviviridae viruses, the patent did not enable across its breadth (as the skilled team would have faced a research project in screening the billions of analogues covered by the claims to discover which would work in fact). On this second ground of insufficiency, the Court of Appeal felt it unnecessary to express a final conclusion, but indicated that Arnold J was entitled to come to his conclusion. Had Idenix’s patent been valid, Kitchen LJ also confirmed Arnold J’s finding that it would have been infringed by Gilead’s hepatitis C drug sofosbuvir (marketed as Sovaldi®).

The judgment provides useful guidance on how to assess the scope of the common general knowledge. That a publication is interesting to an expert witness does not mean that its contents would have been “generally known and accepted without question by the bulk of those … engaged in the particular art” – even if published in an eminent journal and particularly if the article did not attract much comment. Whether a presentation given at a conference is CGK will depend on the number of relevant attendees, with likelihood diminishing if the presentation was “not identified as a highlight” and if the date of the presentation was close to the patent’s priority date.

With regards to lack of plausibility, the Court of Appeal stated that the same approach should be adopted in considering lack of inventive step and insufficiency on this ground: “There must be a real reason for supposing that the claimed invention will indeed have the promised technical effect.”

Furthermore, the Court reiterated that in respect of insufficiency, as with obviousness, “absent an error of principle, an appellate court will be very cautious” in challenging first-instance evaluations which have involved “an assessment and the weighing of a number of factors”. Reinforcing the high threshold for interference with first-instance decisions of this type appears to be a developing trend for the Court of Appeal.

Also of interest was Kitchen LJ’s obiter commentary that possessing equitable title to an invention is sufficient to make the possessor a “successor in title” within the meaning of Article 4A of the Paris Convention. As a result, Gilead’s International Patent Application was held to be entitled to its priority date (despite lack of evidence that an agreement to assign the right, title, and interest in the US priority application had ever actually been signed), thereby anticipating Idenix’s invention. However, “a final view” on whether the transfer of title should depend on substantive rights rather than compliance with legal formalities was “better left to be decided in another case”. In any event, it behoves patentees to ensure that their formalities procedures are up-to-scratch.