In a recent judgment, the High Court of England and Wales has provided clarity on the interpretation of numerical ranges in patent claims and the de minimis principle in relation to threatened infringement. The full judgment of Napp Pharmaceutical Holdings v Dr Reddy’s Laboratories & Sandoz  EWHC 1517 (Pat) can be found here.
Since 2005, Napp Pharmaceuticals Ltd has marketed a 7-day buprenorphine transdermal patch under the name BuTrans. BuTrans is a highly successful product, having total annual sales approaching 10 million patches. Sandoz and Dr Reddy’s planned to launch generic 7-day buprenorphine transdermal patches in 2016. In response, Napp began quia timet (because he fears) infringement proceedings in February 2016 against Sandoz and Dr Reddy’s for threatening to infringe its patent (EP 2 305 194).
Claim 1 of this patent is directed to: “A buprenorphine transdermal delivery device comprising…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”. A major point of construction related to the numerical ranges. Napp contended that the numerals in the ranges were expressed to the nearest 5%, e.g. 10 to 15% = 7.5 to <17.5%. In contrast, the Defendants argued that they would be understood to be expressed in terms of whole numbers, e.g. 10 to 15% = 9.5 to <15.5%, and Arnold J agreed. The word “about” was held to mean “a small degree of permitted imprecision over and above that implied by the usual rounding convention”, e.g. “about 10%” cannot extend beyond 9.0 to <11.0%. Napp accepted that, on the above assumptions, the product would not fall within the claim regardless of statistical considerations. However, in the event that his construction of the claims were to be overturned on appeal, Arnold J went on to consider the de minimis principle in relation to patent infringement.
There is a general principle of English law encapsulated by the maxim: de minimis non curat lex (the law does not concern itself with trifling matters). While accepting the force of Lord Phillips’ warning in Sienkiewicz v Greif 2011 UKSC 10 about the dangers of defining a quantitative limit, Arnold J commented that: “the court was forced, as a matter of practical reality, to draw a line somewhere”. But where should this line be drawn?
Arnold J referred to a hypothetical scenario in which only 0.01% of products fell within a claim as “precisely the kind of situation covered by the de minimis principle”. In order to avoid infringement, Dr Reddy’s proposed a testing regime and statistical protocol to determine whether the patches fell within the claim other than to a de minimis extent. Arnold J concluded that 1 in 10,000 represents a threshold for application of the de minimis principle; and the appropriate level of confidence should be 50% for the balance of probabilities standard of proof. It was concluded that Dr Reddy’s testing regime was sufficient to avoid any threat of infringement.
In relation to Sandoz’s patches, even if claim 1 were construed broadly to encompass a levulinic acid level of ≥7.5 to <17.5%, only 1 in 69 million or 1 in 153 million patches would have fallen within its scope (based on a 50% confidence interval, and depending on the calculation method), both of which would be de minimis. Even if a 95% confidence level were to be used, only 1 in 25,600 patches would meet the requirements of claim 1, but this was also considered to be de minimis.
Regarding quia timet actions, the court held that if what the Defendant threatened to do would only involve infringement on a de minimis scale, then that threat “does not justify the commencement of proceedings by the patentee”. Moreover, Arnold J considered that if the Defendant is threatening to do acts which would fall within the claim sufficiently often that they cannot be discounted as de minimis that nevertheless amount to infringement “on a very small scale”, an injunction would be “both disproportionate and a barrier to legitimate trade”. Unfortunately, the meaning of “a very small scale” was not defined by Arnold J.
Since the findings of no threat of infringement were dependent upon the findings on construction, permission to appeal was granted on construction alone. We look forward to the outcome of this appeal.
This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.