Idenix Pharmaceutical, Inc v Gilead Sciences, Inc & Ors

A patent claim must be supported by a plausible technical contribution across its scope. Where a claim covers a very broad class of compounds, it is insufficient if the specification and common general knowledge do not make it plausible that the invention works throughout that class. A claim is also invalid for lack of inventive step where it covers compounds which make no technical contribution to the art. Later evidence may support, but cannot independently establish, a technical effect absent from the patent disclosure. A purposive construction of a technical term may include a prodrug form where the specification and technical purpose support that meaning.

Idenix and academic institutions claimed infringement of a patent concerning modified nucleosides for treating Flaviviridae infections. Gilead denied infringement and counterclaimed for revocation, relying on lack of priority, novelty, inventive step, insufficiency and added matter. The central issues included whether Pharmasset Barbados was entitled to priority for the Pharmasset PCT, whether the claims made a plausible technical contribution, whether the claimed compounds could be made without undue burden, whether proposed amendments added matter, and whether sofosbuvir fell within or indirectly infringed the claims.

1. Priority. The R&D Agreement was effective under Georgia law to assign Pharmasset Georgia’s rights in the relevant invention to Pharmasset Barbados. Under the applicable Federal patent law principles, the language that Pharmasset Barbados would “at all times” be the sole owner effected an immediate assignment. Alternatively, an agreement to assign gave Pharmasset Barbados equitable title, which was sufficient to make it a successor in title for the purposes of priority. The Pharmasset PCT was therefore entitled to priority from US 368.
2. Construction and infringement. “Phosphate” was purposively construed to include the masked phosphate group in sofosbuvir. The specification’s discussion of nucleotide prodrugs and the skilled team’s knowledge that nucleoside analogues become triphosphates supported that construction. Sofosbuvir therefore fell within claim 1. Alternatively, supply of sofosbuvir indirectly infringed claim 1 under section 60(2) of the Patents Act 1977, because its metabolism produced a compound within the claim and the statutory requirements were otherwise satisfied.
3. Inventive step. The claims covered extremely large numbers of compounds. The specification did not make it plausible that substantially all the claimed compounds had anti-Flaviviridae activity. The claims therefore covered compounds making no technical contribution to the art and lacked inventive step. The proposed narrowed claim also lacked inventive step because the patent contained no data or rationale making the asserted activity plausible.
4. Insufficiency. The court applied a two-stage inquiry: first, whether the patent read with common general knowledge made it plausible that the invention worked across the claim; and secondly, whether later evidence showed that performance across the scope required undue burden. The patent gave no meaningful assistance in making the claimed tertiary fluorinated compounds. Their synthesis was a substantial research project whose success depended on skill and luck. The claims were also insufficient across their breadth because the patent required the skilled team to select, synthesise and test billions of compounds and claim the successful results.
5. Added matter and orders. Claim 4 contained added matter, although the allegations against claim 1 as granted and claim 5 failed. The proposed amendment was not allowable because it created an undisclosed narrower sub-class. All claims other than claims 20 and 37 lacked novelty over the Pharmasset PCT. The independently valid claims lacked inventive step and were insufficient. The amendment application was refused.