Teva Pharmaceutical Industries Ltd & Anor v Merrell Pharmaceuticals Inc & Anor

For novelty, an earlier document anticipates a claim where it clearly discloses the claimed invention and enables the skilled person to perform it. A document is construed at its publication date, using the common general knowledge then available.

For obviousness, the court asks whether the claimed differences from the state of the art required invention. A proposed test or research step may be obvious where it was worth trying and had a good prospect of success, but “obvious to try” is not a standalone test.

A Swiss-form claim cannot obtain novelty from merely discovering that an established therapeutic use avoids a side effect. Applying the binding approach to second medical use claims, treatment of allergic rhinitis or urticaria by an antihistamine was not a new therapeutic application.

Teva sought revocation of patents concerning the use of terfenadine carboxylate, the acid metabolite of terfenadine, as an antihistamine and in treating allergic conditions while avoiding terfenadine’s cardiac side effects.

The defendants relied on patents covering use in hepatically impaired and unimpaired patients, including Swiss-form claims and a claim to a 60 mg composition. Teva alleged lack of novelty and inventive step, relying principally on Carr, common general knowledge, Chen, and publications concerning terfenadine-associated QT prolongation and torsades de pointes.

The central issues were whether Carr disclosed the acid metabolite’s antihistaminic use, whether the claims embodied a new therapeutic application, and whether it would have been obvious to test and develop the metabolite.

1. Novelty. A prior-art document must disclose the invention and enable the skilled reader to perform it. The document is construed as at its publication date, in the light of the common general knowledge then available. The acid metabolite was expressly included in Carr’s disclosure of compounds useful as antihistamines, capable of administration in pharmaceutical forms, and supported by the guinea-pig ileum assay.
2. Carr therefore disclosed the use of the acid metabolite as an antihistamine and the manufacture of medicaments. It did not expressly disclose use for allergic rhinitis or urticaria as a separate indication. However, applying the binding approach in Bristol-Myers Squibb v Baker Norton [2001] RPC 1, those conditions did not constitute a new therapeutic application distinct from antihistamine treatment. Avoidance of terfenadine’s cardiac side effects was a discovery about the known use, not a novel therapy.
3. Obviousness. The skilled pharmaceutical team would have known that the acid metabolite supplied most, if not all, of terfenadine’s antihistaminic effect. The available evidence, particularly Monahan and Mathews, pointed towards parent terfenadine, rather than the metabolite, as the cause of QT prolongation and torsades de pointes. Although uncertainty remained, it would have been obvious to test the metabolite and terfenadine for potassium-channel blocking and QT effects using recognised techniques, including the test described in Chen.
4. The satisfactory result of that testing would have made development of the acid metabolite as an antihistaminic medicament, including for allergic rhinitis and urticaria, obvious. The defendants’ alternative research strategy did not prevent that course from being obvious. The 60 mg dosage in claim 12 of 443 was also obvious in light of the known dosage and pharmacological information.
5. Claims 1, 5 and 12 of 976, claim 1 of 443, and claims 1 and 3 of 860 were invalid for lack of novelty. Those claims, together with claim 12 of 443, were invalid for lack of inventive step. Teva was entitled to declarations accordingly.

First-instance decision. No prior appellate decision is stated in the judgment.