The Court of Appeal recently handed down a Decision in Napp Pharmaceutical Holdings Limited v Dr Reddy’s Laboratories (UK) Limited and Sandoz Limited (Napp v Dr Reddy). One point of interest in this decision is the interpretation of numerical ranges in the courts of England and Wales.

Napp v Dr Reddy is an Appeal from the decision of Arnold J, dated 2 August 2016, regarding a Patent Infringement action brought against two generic manufacturers seeking to launch buprenorphine pain relief dermal patches. In the first instant decision, Arnold J held that neither defendant’s product infringed the claims of European Patent (UK) No. 2,305,194 and 1,731,152.

Only European Patent (UK) No 2,305,194 was considered in any detail, as it was agreed that the second Patent did not raise any additional infringement issues.

Napp appealed against the first instant decision, arguing that the numerical features in claim 1 of the Patent had not been construed correctly.

Claim 1 of the Patent reads as follows: “A buprenorphine transdermal delivery device comprising a polymer matrix layer containing buprenorphine or a pharmaceutically acceptable salt thereof, for use in treating pain in humans for a dosing interval of at least seven days, wherein the transdermal delivery device comprises 10%-wt buprenorphine base, 10 to 15%-wt levulinic acid, about 10%-wt oleyloleate, 55 to 70%-wt polyacrylate and 0 to 10%-wt polyvinylpyrrolidone”.

Napp contended that Arnold J, should have held that the buprenorphine and levulinic acid ranges were expressed to the nearest 5%-wt. One of their reasons for this was that they stated that the Patent dealt with both components in increments of 5%.

In dismissing Napp’s appeal Floyd LJ stated:

“A patent specification is not intended to be a puzzle game in which the skilled person must come up with his own theory as to what degree of precision was intended by the patentee. If the patentee had wished to claim, for example, 7.5 to 12.5%-wt buprenorphine, he was free to do so by making it express in the claim, or stating in the specification that the figures are expressed to the nearest 5%. He cannot expect the skilled reader to assume that, because he has chosen to write the claim in multiples of 5%, he is not concerned about deviations of as much as 2.5% on either side of that figure. The figures he chose may have been the very outer limits of that of what he considered would work. I therefore entirely agree with the Judge that the figures for buprenorphine and levulinic acid are expressed to the nearest whole number”.

It was upheld, therefore, that the buprenorphine and levulinic acid percentages should be construed by using the conventional nearest whole number rounding approach, so extended from 9.5 to 10.5%-wt for buprenorphine and the levulinic acid range extended from 9.5 to 15.5%-wt. With regard to the interpretation of “about 10%-wt” Floyd LJ concluded that the Patentee was intending to claim a more generous degree of imprecision around the figure of 10% than would be accorded by the normal rounding convention. Although there are obvious difficulties with trying to prescribe precise outer limits to an integer which uses the word “about”, Floyd LJ agreed with the Judges conclusion that the claim should be understood to be referring to a slightly broader range, but that it should extend no further than 9 to 11%-wt.

This judgement provides more clarity on the interpretation of numerical ranges in patent claims in England and Wales.