Smith & Nephew v ConvaTec No 2: a well rounded performance


On 12 December 2013, the Patents Court handed down its judgment in Smith & Nephew v ConvaTec No.2. The court granted Smith & Nephew a declaration of non-infringement on a commercial process for the manufacture of silverised wound dressings, holding that the claim, which is limited to a process utilising “between 1 and 25%” salt, has a lower limit of 0.95% (rejecting 0.5% and 1% as alternative constructions). The court also held that 4 work-up experiments infringed ConvaTec’s patent, but refused to grant a springboard injunction to prevent reliance on regulatory approval obtained on the basis of those infringing experiments.
In defining the scope of the numerical range in the claim, the court noted that it is not always the case that the question of whether a value should be held to fall within a numerical limit should be decided by rounding that value to the same number of significant figures as the range is expressed in the claim. It was, however, the construction adopted in this case: 1% is expressed to one significant figure, therefore anything greater than or equal to 0.95 would round to 1% when expressed to one significant figure. This would be the natural approach of the skilled person and there was nothing to dissuade Birss J. from applying it: the patent did not consistently apply an alternate rounding convention; nor was it relevant that the significant figures approach proved asymmetric in relation to the patented values. This approach also ensures that the relative error margins at the lower and upper limits of the claim are comparable.
The result of this construction was that Smith & Nephew’s commercial process, which utilizes a concentration of 0.77% agent, does not infringe. However, it was held that four of the many work-up experiments which led to it being granted its regulatory approval for the product did. As such, the court was also required to consider whether ConvaTec should be granted a springboard injunction to prevent Smith & Nephew from exploiting its non-infringing 0.77% process prior to patent expiry on the basis of infringing work-up experiments that assisted in obtaining its regulatory approval. In this instance, the Court refused to grant an injunction. However, in doing so, Birss J. discussed the relevant factors to consider in deciding whether to grant a springboard injunction, noting that caution must be exercised.
This case adds to the body of law suggesting that the rounding of values to the number of significant figures expressed in the claim is generally accepted scientific convention, and an approach likely to be adopted in the absence of evidence or a patent specification suggesting the contrary. It also provides further details on how the court may exercise its discretion in deciding whether to grant springboard relief in circumstances where a party has worked around a patent that is still in force.
In a hearing on 17 January Birss J granted both parties permission to appeal on the issues of construction and springboard.

Robert Bond