This article was written by David Nickless (Managing Associate).

This article was updated on 30 July 2015.



This Appeal derives from a judgment of Mr Justice Birss which we covered in detail in an earlier edition of Life Sciences & Healthcare Update.

Briefly, ConvaTec owns European Patent (UK) No 1 343 510 (the Patent) which is concerned with a process for the silverisation of gel-forming fibres used in wound dressings. A part of the patented method required a binding agent “being present in a concentration between 1% and 25% of the total volume of treatment". Following a failed attempt to have the Patent revoked, Smith & Nephew developed its own range of wound dressings in accordance with the method described in the Patent, except that it used a concentration of binding agent of no more than 0.77%. It sought a declaration that its product (‘Durafiber Ag’) did not infringe the Patent. ConvaTec counter-claimed for infringement of the Patent.

Before Birss J, ConvaTec contended that the expression "between 1% and 25%" did not define precise values but would be seen in terms of whole numbers. Accordingly, applying the basic rounding convention, the claim encompassed all concentrations greater than or equal to 0.5% and less than 25.5%. By contrast, Smith & Nephew's primary contention was that the expression meant what it said and that it defined a range of concentrations, with a lower limit of precisely 1% and an upper limit of precisely 25%. But Smith & Nephew also had a fall-back position, namely that the 1% and 25% limits would be read in terms of significant figures, and that 0.95% and above would be understood to round up to 1%, and that 25.49% and below would be understood to round down to 25%, and so the claim encompassed all concentrations greater than or equal to 0.95% and less than 25.5%.

The judge rejected ConvaTec's contention that the lower limit of the claim was 0.5%, but he also rejected Smith & Nephew's primary contention that its lower limit was precisely 1%. He concluded that the skilled person would look at the limits in terms of significant figures and that the claim therefore included concentrations greater than or equal to 0.95% and less than 25.5%. This conclusion meant that Smith & Nephew's product did not infringe (since the concentration of binding agent was never more than 0.77%). However, importantly, in support of its application for marketing approval, Smith & Nephew had relied on data generated using an earlier process in which the concentration of binding agent used ranged from 0.93% to 0.97%. Therefore, those experiments had infringed the Patent, but Birss J denied ConvaTec’s application for an injunction. Both parties appealed the findings.

The Appeal Decision

On appeal the parties maintained their favoured constructions for “between 1% and 25%”. Kitchin LJ, giving the Court’s judgment, conducted a thorough review of authorities in which numerical range claims had been considered, noting that the construction of such claims was no different in principle to any other claims, but highlighted principles which had been established by the various authorities. Of particular relevance to this case was his observation that, in light of the common general knowledge and the teaching of the specification, the skilled person may understand that the patentee has chosen to express the numerals in the claim to a particular, but limited, degree of precision. Accordingly, they would understand the patentee as having intended the claim to include all values which fall within the claimed range when stated with the same degree of precision. Whether that was so or not would depend upon all the circumstances including the number of decimal places or significant figures to which the numerals in the claim appear to have been expressed.

With those principles in mind the Court addressed the two questions on appeal:

First, whether the skilled person would believe the patentee intended the values of 1% and 25% to be taken as exact values, or whether the skilled person would understand that the patentee has used a standard number convention to express the limits of the claim to a lesser degree of accuracy, and so intended to include within the scope of the claim concentrations falling within the range when expressed with the same degree of precision. In relation to this question, the Court of Appeal, like Birss J, quickly concluded that the Patent specification made clear to the skilled person that the patentee had not intended to restrict the claimed range only to whole numbers.

Second, whether the skilled person would understand the numbers to be expressed in terms of whole numbers (zero decimal places) or in terms of significant figures. On this issue, the Court of Appeal overruled Birss J (who had favoured the significant figures approach) finding that there was "no logical basis” for preferring that approach over the whole number (or zero decimal places) approach. The Court therefore dismissed Smith & Nephew's appeal and upheld ConvaTec's appeal, concluding that the patentee intended the claim to embrace all concentrations of binding agent ≥ 0.5% and < 25.5%. As a result, the Smith & Nephew product now falls within the claim as construed and infringes.

Comment

Patent cases considering the construction of claims containing numerical ranges are heavily fact dependent (what is being measured, how and by whom, and to what levels of accuracy are figures in the specification quoted?). However, this case represents a comprehensive summary of key authorities and principles concerning the construction of such claims.

Although claim construction is a matter of law for the Court, it is somewhat surprising that the Court of Appeal considered there was sufficiently clear evidence to find that Birss J made an error of law, particularly given that he had had the benefit of seeing the parties’ respective experts give their evidence and be cross-examined. Furthermore, as noted by Clarke LJ, it may seem a surprising result that a claim to a concentration “between 1% and 25%” could be infringed by a product with a 0.5% concentration, a level which literally does not fall within the claimed range. While this surprising result is explicable given the conventions the relevant skilled addressee would be familiar with, it does raise a question of the interpretation of Article 69 EPC, which is intended to provide a balance between fair protection for the patent proprietor with a reasonable degree of legal certainty for third parties.

In this case, one could make a compelling argument that the Patents Court's construction provided a better balance once Article 69 is considered. This is because, under the Patents Court’s construction, the claimed range of "between 1% and 25%" already benefited from a measuring error of 0.05% (i.e. this was an additional range of protection for the patentee beyond that literally defined in the claim) and third parties were given a greater degree of legal certainty (since the range was closer to the literal range). The broader range favoured by the Court of Appeal gives the patentee a considerably broader range of protection beyond the literal range claimed in the Patent. As Smith & Nephew's predicament evidences, third parties attempting to design around the Patent are now faced with a claim construction further removed from its literal reading, which tips the balance in favour of protection for the patentee over legal certainty for third parties.

Update

On 30 July, the Court of Appeal refused Smith & Nephew permission to appeal to the Supreme Court (on the grounds that its appeal did not raise a significant point of general legal importance), and so it will now need to apply to the Supreme Court for that permission.



However, the Court did grant Smith & Nephew’s request for a suspension of the injunction against it (and the order for delivery up/destruction) until the Supreme Court has decided whether to grant it permission. It also decided that it would be proportionate to grant a similar suspension until the decision of the Technical Board of Appeal at the EPO (which, the Court anticipated, should be delivered no more than a few months after the Supreme Court has decided whether to grant permission).



