Written by Corinne Day on 11 February 2009« Return to Reading Room
An invention, to be patentable, must be novel and involve an inventive step. However, selection patents appear to have developed as an exception to this rule.
The case of IG Farbenindustrie sets out a three-step test for a selection patent to be valid:
- The patent had to be based on a substantial advantage secured (or disadvantage avoided) by the selction;
- all the selected members had to possess the advantage; and
- the advantage of the selection had essentially to be peculiar to the selected group.
However, selection patents are prone to a finding that they are anticipated or being rendered obvious by the prior disclosure of the class of compounds from which the selection is made. The recent High Court decision of Dr Reddy's Laboratories v Eli Lilly clarifies the test for novelty and inventive step of a patent for a pharmaceutical compound and also provides, obiter, an opinion on the current status of the selection patent test in English law.
In the Dr Reddy's Laboratories v Eli Lilly case, the patent claimed olanzapine, a treatment for schizophrenia. However, a prior patent application had disclosed a class of compounds (amongst which olanzapine was one of the compounds) described in the form of a 'Markush' formula. In his decision, the judge held that the prior patent application did not anticipate the olanzapine patent. However, he did not do so on the basis of the patent in dispute being a 'selection' patent. Instead, he referred to the leading case on anticipation of Synthon v SmithKline Beecham, where it was stated that anticipation requires that the prior art disclose subject-matter which, if performed, would necessarily result in an infringement of the patent in suit. He concluded from this general principle that a generic disclosure will not normally take away the novelty of a subsequent claim to a member of a class. A Markush formula would not normally anticipate a claim to an individual compound unless that compound was disclosed in 'individualised' form, e.g. by disclosure as a specific example of the Markush formula. The judge went on to hold that the patent was inventive.
Therefore, it can be seen from this case that the courts are likely to rely on orthodox patent principles for holding a patent valid, rather than on the three-step test above which applies to selection patents. This means that the three-step will not save a selection patent where the selected compound is anticipated by a prior disclosure of that individual compound.
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