Convatec Ltd & Anor v Smith & Nephew Healthcare Ltd & Ors

Patent claims are construed purposively in context, but the language chosen remains critical and deliberate limitations must be given effect. A claim requiring a blend of modified cellulose gel-forming fibres with another type of gel-forming fibre is not satisfied by two modified-cellulose populations distinguished only by absorbency or processing. A dependent claim requiring a wound-contacting surface consisting of that blend excludes additional non-gelling cellulose fibres. A dressing containing CES gel-forming fibres and Tencel therefore did not infringe. The alternative finding that a broader construction would render the claims obvious over Bahia was upheld, while claim 3 remained valid over Qin because the alleged step was not shown obvious to the skilled wound-care team.

ConvaTec alleged that Durafiber, a wound dressing containing Tencel fibres and cellulose ethyl sulfonate fibres, infringed claims 1 and 3 of European Patent UK No 0 927 013. The High Court rejected attacks on claim 3’s validity, held that the patent was not infringed, and conditionally held that claim 3 would be invalid over Bahia if infringement were established: [2011] EWHC 2039 (Pat).

ConvaTec appealed on construction, infringement and the conditional Bahia finding. The defendants cross-appealed on the finding that claim 3 was valid over Qin. The central issues were the meaning of the claims, whether Durafiber fell within them, and whether claim 3 was obvious over Qin.

Disposition. The appeal and cross-appeal were dismissed. Lord Justice Kitchin gave the judgment, with Lord Justices Tomlinson and Mummery agreeing.

1. Construction principles. Article 69 of the European Patent Convention requires the claims to be construed in context, using the description and drawings to ascertain purpose. The language chosen remains critical. Purposive construction does not extend the technical matter for which protection is claimed, and deliberate limitations must be given effect. The court applied the approach summarised in Virgin v Premium Aircraft [2009] EWCA Civ 1062 and the guidance in Kirin Amgen Inc v Hoechst Marion Roussel [2004] UKHL 46.
2. Claim 1. The claim required a blend of discrete modified-cellulose gel-forming fibres, such as CMC or CES, with at least one other type of discrete gel-forming fibre based on a different basic chemistry, such as alginate, pectin, chitosan or hyaluronic acid. It did not cover two modified-cellulose fibre populations distinguished only by absorbency, substitution or cross-linking.
3. Claim 3 and infringement. Claim 3 required the wound-contacting surface itself to consist solely of the defined blend. The modified-cellulose fibres were the gel-forming fibres required by claim 1. The presence of Tencel meant that Durafiber did not satisfy the claim 3 requirement, while its sole type of gel-forming fibre, CES, also meant that it did not satisfy claim 1.
4. Bahia. Although unnecessary to the result, the court upheld the conditional finding that, if the claims were broad enough to encompass Durafiber because of unspecified absorbency variation, they would also encompass the CMC dressing made according to Bahia and would be obvious over that disclosure.
5. Qin. The skilled addressee was the relevant wound-care team as a whole, including the cellulose chemist and, where necessary, a wound-care scientist or clinician. The judge was entitled to find that moving Qin’s CMC/alginate felt from the second layer to the wound-contacting layer was not shown to be obvious, given the concern that CMC might interfere with alginate’s haemostatic function. The appellate court found no basis to disturb that assessment.

1. Court of Appeal (Civil Division): The appeal against the finding of non-infringement and the cross-appeal concerning validity over Qin were dismissed. The conditional finding concerning obviousness over Bahia was upheld: [2012] EWCA Civ 520.
2. High Court of Justice, Chancery Division (Patents Court): Claim 3 was held valid over the pleaded prior art but not infringed. The judge further held conditionally that claim 3 would be invalid over Bahia if infringement were established: [2011] EWHC 2039 (Pat).