Generics (UK) Ltd & Ors v H Lundbeck A/S

A product claim for an enantiomer must be construed in the context of the specification. A claim directed to the isolated enantiomer does not extend to that enantiomer as part of a disclosed racemate.

For sufficiency, the breadth of the monopoly must correspond to the technical contribution. Where isolating and testing an enantiomer is an obvious goal, but the inventive contribution is a particular method of achieving it, a claim to the enantiomer however made is excessively broad. A claim to the non-obvious method may nevertheless be valid.

Three generic pharmaceutical companies sought revocation of Lundbeck’s European patent for escitalopram, the (+) enantiomer of the known racemic antidepressant citalopram.

Claims 1 and 3 covered the enantiomer and a pharmaceutical composition containing it. Claim 6 covered a method of preparing it by resolving a diol intermediate and converting it stereoselectively. The claimants alleged lack of novelty, obviousness and insufficiency.

The central issues were whether the product claims encompassed the enantiomer within the racemate, whether the claimed route or preparative chiral HPLC was obvious, and whether product claims extending to all methods of obtaining escitalopram exceeded the patent’s technical contribution.

1. Claims 1 and 3 were invalid for insufficiency; claim 6 was valid. The revocation claims therefore succeeded only to that extent.
2. On their proper construction, claims 1 and 3 were confined to the isolated (+) enantiomer and compositions containing it. Read with the specification, they did not cover the (+) enantiomer while present in the known citalopram racemate. The novelty attacks based on the earlier patents accordingly failed. This applied the contextual approach in Kirin-Amgen Inc v Hoechst Marion Roussel [2005] UKHL 59.
3. The claimed stereoselective conversion of the resolved diol was not obvious. Although the skilled team had a motive to investigate the enantiomers of citalopram, it would not have expected the required ring closure to proceed by the stereospecific S_N2 route. Preparative chiral HPLC was also an immature and uncertain research technique, rather than a routine route to the quantities required for testing and formulation. The court applied the structured inquiry in Windsurfing International Inc v Tabur Marine (Great Britain) Ltd [1985] RPC 59 without hindsight.
4. Unexpected clinical advantages discovered after the priority date could not support inventive step. They were neither described nor foreshadowed in the specification. Commercial success attributable to those later discoveries could not assist either.
5. Applying Biogen v Medeva [1977] RPC 1, the technical contribution was the discovery of a non-obvious way to resolve the diol and retain stereochemistry during conversion. Separating and testing citalopram’s enantiomers was an obvious objective. Claims 1 and 3 monopolised all ways of achieving that objective, including routes owing nothing to the patent’s teaching, and were therefore too broad.

not stated in the judgment.