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Federal Court Finds a Salt Patent to be an Inventive Selection

Justice Furlanetto, in an action under the NOC Regulations, has held that Canadian Patent No. 2,529,400 (the “400 Patent”) which claimed the dihydrogen phosphate (“DHP”) salt of sitagliptin in crystalline monohydrate form was not obvious. Justice Furlanetto categorized the 400 Patent as a selection patent, which selected a particular salt and crystalline form of sitagliptin, with stated advantages over the sitagliptin free base and hydrochloride salt disclosed in the prior art WO 03/004498 (“WO498”).

The Court accepted that salt and polymorph screening methods were well known, but nonetheless held that it was not self-evident that applying them to sitagliptin would lead to a crystalline monohydrate usable as an active pharmaceutical ingredient. As WO498 did not differentiate between, or disclose problems with, any of its listed compounds, there was no motivation to take further steps with sitagliptin. Though the inventors’ path to the DHP salt was in fact straightforward, arriving at the crystalline monohydrate required significant work without predictable results. As a secondary factor, Justice Furlanetto acknowledged that JANUVIA, which uses the claimed solid form of sitagliptin, was the first DPP-4 inhibitor to come to market.

A copy of the decision is available here.