This decision from the House of Lords provides a less complicated approach to the assessment of inventive step in the UK and is therefore to be welcomed. When considering this issue it appears that a patent specification should disclose enough information to make the invention plausible rather than having to demonstrate that the invention actually works.

In Conor Medsystems v. Angiotech Pharmaceuticals, both the UK High Court and the Court of Appeal revoked Angiotech’s patent for lack of inventive step relating to stents coated with Taxol. Stents are used following surgery to enlarge narrowed coronary arteries. The stent prevents re-narrowing of the arteries (restenosis). A common problem with stents is that their insertion can lead to the local proliferation of blood vessel cells (angiogenesis) which can actually cause restenosis. The release of Taxol from the stent was found to inhibit restenosis by preventing angiogenesis. The main reason for the finding of obviousness in the High Court and the Court of Appeal was the lack of any experimental evidence provided in the specification that a Taxolcoated stent actually reduces restenosis.

In the House of Lords,4 Lord Hoffman did not follow the approach of the lower courts. He stated that there was no requirement when assessing inventive step to actually prove that the invention worked. Whilst the law does require that the patent teach how to make the invention work, this does not form part of the inventive step requirement. According to Lord Hoffmann, the invention should not be determined by “some vague paraphrase based upon the extent of (the patentee’s) disclosure in the description.”

In deciding what the inventive concept was, Lord Hoffman’s approach was to look at the claim since the purpose of the claim is to define the invention. He concluded that the invention was the use of a taxol-coated stent to prevent restenosis. This was not obvious. All that is required to fulfil the inventive step requirement is that the invention will plausibly work, based on the contents of the patent specification (assuming, of course, that the claimed invention, once considered plausible, is not obvious over the prior art). The Angiotech patent contained data (an angiogenesis-inhibition assay) showing that it was plausible that a Taxol-coated stent would prevent or treat restenosis. Since the prior art did not contain a clear pointer that Taxol could be used in this way, Lord Hoffman concluded that the criterion for inventive step was met.