Overview

A judgment of the Court of Appeal has stressed the importance of conducting experiments carefully when seeking to attack the validity of a patent on the ground of anticipation.

In this case, Leo Pharma A/s & another v Sandoz, the issue for the Court of Appeal to consider was the validity of Leo's patent for a single chemical entity, calcipotriol monohydrate, a crystalline substance. Sandoz sought to attack the validity on two grounds; anticipation and obviousness. It was Sandoz's case that carrying out a prior art process would lead to the substance claimed as new in the patent, and undertook an experiment to show this.

Lord Justice Jacob, who gave the leading judgment, criticised the methodology for the experiment relied on by Sandoz to attack the patent on the ground of anticipation. In this case, he said that the experiment departed from the prior art by failing to ensure a seed-free environment and not following the recipe of the claimed prior art.

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