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Smith & Nephew PLC v Convatec Technologies Inc., High Court of Justice, Patents Court, London, UK, 12 December 2013, [2013] EWHC 3955 (Pat)

The High Court has found that Smith & Nephew’s process for preparing silverised wound dressings did not infringe Convatec’s patent.  Earlier development work which did infringe the patent and which was used to obtain regulatory (CE) approval for Smith & Nephew’s product did not justify the granting of a springboard injunction.

Background This case is the most recent in a series of disputes between Smith & Nephew and Convatec related to wound dressings.  Convatec owns European Patent (UK) no. 1343510, entitled “Light Stabilized Antimicrobial Materials” (the “Patent”), and markets the wound dressing Aquacel Ag, which uses silver as the antimicrobial agent.  Smith & Nephew developed a competing product, Durafibre Ag and planned a launch in the UK.  In earlier proceedings (here), the Patent had been found to be valid in amended form, a decision which was upheld by the Court of Appeal (here).


In these proceedings, Smith & Nephew sought a declaration of non-infringement and Convatec counterclaimed alleging infringement by the commercial process for making Durafiber Ag.  In addition Convatec alleged that Smith & Nephew’s development work infringed the Patent, and was subsequently used to obtain regulatory approval, and so sought a springboard injunction on that basis.

The claim in issue described a process for silverising the fibres contained used in wound dressings.  The claim described the addition of an agent which facilitates the binding of silver to the fibres “in a concentration of between 1% and 25% of the total volume of treatment”.  Smith & Nephew sought to declare that its commercial process, which used sodium chloride as the relevant agent in a concentration of 0.77%, did not infringe this claim.

Infringement rested on the construction of this part of the claim.  Convatec argued that 1% included the range 0.5% to <1.5% whereas Smith & Nephew argued that 1% meant exactly that and no less, with a fall-back position of “significant figures” resulting in a range of 0.95% to <1.5%.

Birss J was referred to a number of previous English and EPO authorities on rounding, the majority of which took the “one significant figure” approach.  The judge emphasised that the true construction of numerical ranges depended on the construction of the patent specification in its own context, which included the common general knowledge, and the approach of the skilled reader in rounding numbers. 

Convatec’s lower limit of 0.5% was rejected – the judge did not believe that the skilled reader would: (i) round 0.5 to 1, given the other ranges used in the Patent; or (ii) consider the ends of the range as unimportant (and thus broadly defined), given the breadth of the range. 

Smith & Nephew’s starting position of 1% was also rejected: the common general knowledge did not support such a construction, and expressed as one significant figure, 1% had to capture lower values (e.g. 0.96%).  1% could not be considered an “exact number” (compared to for example, π), and the precision of exactly 1% would not give fair protection to the patentee.

The judge concluded that the “one significant figure” approach should be followed, being the “natural approach of the skilled person” to interpreting the value 1.  The asymmetrical nature of the rounding which results was discussed (0.95% to <1.5%) and contrasted with the usual symmetrical method of expressing error (e.g. ±5%).  The asymmetry was however, determined to be insignificant in construing this claim.  Smith & Nephew’s Durafibre Ag did not infringe the Patent.

The second issue to be determined was whether the developmental (non-commercial) process deployed by Smith & Nephew to generate data to support the regulatory (CE) application infringed the same claim. 

Smith & Nephew’s Process Description indicated that the concentrations of sodium chloride used were between 1.01% and 10.2%, which prima facie infringed the Patent.  Smith & Nephew argued that a certain amount of liquid was retained by the fibres during the silverisation process, which resulted in a reduced concentration, and advanced formulae and methods for calculating the total volume of treatment and the resulting concentrations.  The judge was not convinced that the evidence submitted by Smith & Nephew could lead to a reliable conclusion of non-infringement, given the above construction.  The developmental work was therefore found to infringe the Patent.

Given the finding of infringement, as Smith & Nephew had obtained their regulatory (CE) approval based on the development work which infringed the Patent, Convatec sought to keep Smith & Nephew off the market by obtaining a springboard injunction, in order to prevent Smith & Nephew from benefiting from its infringement. 

Birss J reviewed the law generally on springboard relief, and in particular its use in patent cases.  He considered the following points relevant when deciding whether springboard relief is appropriate in patent cases (paragraph 133):

(i) “Caution is required before a final injunction is granted restraining an otherwise lawful activity.  Nevertheless in a proper case it will be.

(ii) The nature of any unwarranted advantage relied on should be identified.  The precise relationship between the unlawful activity in the past and the later acts which are said to exploit that unwarranted advantage needs to be considered. 

(iii) If an injunction is to be granted it must be in an appropriate form and for a duration which is commensurate with the unwarranted advantage relied on.

(iv) The court must be particularly careful not to put the claimant in a better position than it would be if there had been no infringement at all, especially if otherwise lawful competitive activity will be restrained.

(v) In considering what relief to grant, the availability of other remedies apart from an injunction needs to be taken into account, not only damages but, as in Vestergaard, the availability of an account of profits should be considered too.”.

The judge considered the CE approval process generally, how it played out in this particular case, and the impact of a further hypothetical CE application based on data generated from the non-infringing process. He concluded that by waiting until the conclusion of this trial before launching in any event, Smith & Nephew would have been able to secure CE approval by other (non-infringing) means by this time.  Accordingly, Birss J considered it unnecessary to grant a springboard injunction.

Read the decision (in English) here.

Head note: Scott Parker and Adrian Dykes