Patents: obviousness in relation to patent for dosage regime

Summary

The Supreme Court has confirmed that a patent for a dosage regime of a drug used to treat erectile dysfunction (ED) was obvious over the prior art.

Background

A patent is invalid for lack of inventive step if the invention claimed in it was obvious to a person skilled in the art having regard to the state of the art at the priority date (section 3, Patents Act 1977).

In Pozzoli SPA v BDMO SA, the Court of Appeal formulated questions to assess obviousness:

• Identify the person skilled in the art, and then identify the relevant common general knowledge of that person.

• Identify the inventive concept of the claim in question.

• Identify what, if any, differences exist between the matter cited as prior art and the inventive concept of the claim.

• Viewed without any knowledge of the alleged invention as claimed, do those differences constitute steps which would have been obvious to the person skilled in the art or do they require any degree of invention? (the Pozzoli questions) (www.practicallaw.com/6-374-1001).

In Actavis UK Ltd v Merck & Co Inc, the Court of Appeal held that there was no policy reason why a novel non-obvious dosage regime, which was the product of expensive and unpredictable research, should not be rewarded with a patent of a Swiss-form claim (www.practicallaw.com/4-382-2625).

Facts

Tadalafil is a drug, used to treat ED, which followed the blockbuster drug sildenafil (VIAGRA). L was the exclusive licensee of two patents related to the dosage of the drug Tadalafil and its formulation.

The dosage patent claims doses of 1-5 mg of Tadalafil up to a maximum total dose of 5mg per day and discloses that such doses exhibit fewer side effects than sildenafil whilst retaining efficacy.

Tadalafil is marketed for the treatment of ED in unit doses of 10mg and 20mg for on-demand administration and in unit doses of 2.5mg and 5mg for daily administration. Sildenafil is marketed on demand at doses of 25mg, 50mg and 100mg.

Four pharmaceutical companies (together, A) applied to revoke L's patents to clear the way to market Tadalafil. Patent protection for Tadalafil itself had expired. A alleged that the patents were not entitled to the claimed priority and were invalid for lack of novelty and inventive step, as well as for added matter and insufficiency. L counterclaimed for infringement.

The High Court held that some patent claims were not entitled to priority and were invalid as lacking novelty, but that other claims were novel and not obvious over the relevant prior art and were not invalid for added matter (www.practicallaw.com/2-633-7924). A appealed.

The Court of Appeal reversed the High Court decision on obviousness. A appealed.

L argued that the correct question to be asked when assessing obviousness was whether at the priority date, before the skilled team embarked on any testing, it was obvious in the light of the prior art that a 5mg daily dose of Tadalafil would be safe and effective with minimal side effects for sexual dysfunction. That is, was it obvious to try a low dose of 5mg because there was a reasonable expectation of success at the outset, before any testing (the "obvious to try" test). L…