The Exact Science of Patent Claims

Originally published March 2004

Patentees cannot use the claims of their patents against alleged infringers as merely guidelines in order to gain wider protection of their invention. This recent decision brings more certainty for third parties, at a cost to patentees.

Merck & Co, the claimant, owns a patent for the process for making alendronate, a pharmaceutical used for the treatment of osteoporosis. The trial judge ruled that the patent was valid, but not infringed as the defendant’s (Generics (UK) Ltd) process did not fall within claim 1 of the patent.

The claimant applied for leave to appeal against the trial judgment. The only issue was the construction of claim 1. The claim stated, amongst other things, that the process comprises use of methane sulphonic acid within a specific temperature range (20-25^oC). The defendant’s process used a different type of sulphonic acid within a different temperature range.

The claimant argued that the defendant’s process varied from claim 1 only in a manner which was obvious to any reader of the specification and therefore, despite such variations, the defendant infringed the patent.

Article 69 of the European Patent Convention outlines the extent of protection of a European patent. The integers of the claims are fundamental to the scope of a patent, with the description and drawings as helpful tools in interpreting the claims.

The Protocol, which gives guidance on the interpretation of Article 69, states that patent claims are "…to be interpreted as defining…a fair protection for the patentee with a reasonable degree of certainty for third parties."

In refusing permission to appeal, Lord Justice Jacob indicated that in a precise act such as chemistry, there is less latitude for interpretation. Further, he was of the view in the present case that the defendant’s variants to the process would not "in any way be described as something within the language of the claim as properly interpreted." Jacob LJ emphasised that the claims of a patent cannot be used as a guide only, even if the variant is obvious.

Patent owners should take care not to try to widen the scope of their patents by using the claims as guides only, especially where the claims use precise scientific terms.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.