A legal expert has been analysing the groundbreaking ruling last month which saw the House of Lords back Angiotech over Conor MedSystems in a patent dispute, a decision that will have major repercussions for the pharmaceutical industry in the UK.

Writing for PharmaTimes, Neil Nachshen, a partner at D Young & Co, notes that the Lords upheld the UK designation of Angiotech’s European patent 706376B relating to the use of a taxol-coated stent for treating or preventing restenosis. In doing so, they have reversed the original judgement of the Patents Court from 2006 and that of the Court of Appeal from early 2007.

The decision is of particular interest to the pharmaceutical industry “as it is believed to lay to rest the concept of ‘obvious to try’ previously used successfully in challenging validity,” Mr Nachshen notes. The ‘prior art’ (ie all information that has been made available to the public in any form that might be relevant to a patent's claims of originality) included many suggestions of drugs that may be suitable for stent-related restenosis including anti-proliferative agents, he adds, but Angiotech was able to rely upon a prior art review article stating that in spite of 15 years of research into the prevention of restenosis, a satisfactory result had not yet been achieved.

The article went on to suggest new approaches but these did not include the use of anti-angiogenic agents, Mr Nachshen writes. The invention was based upon Angiotech’s proposal that anti-angiogenic agents would be suitable and the patent was supported by the observation that taxol, an anti-proliferative agent, possessed anti-angiogenic properties as assessed by the chick chorioallantoic membrane (CAM) assay.

The Lords took a different approach to that taken in the lower courts when it came to obviousness. Whereas the latter were satisfied that the skilled person would have considered taxol a candidate worthy of trying (obvious to try), Lord Hoffman disagreed. He felt that the skilled person required more of an expectation of success in order to render a claim obvious.

Mr Nachshen said this difference in opinion “can be understood to lie in the weight given to the data present in the patent specification in contrast to what was known at the priority date”. According to Lord Hoffmann, as long as the invention had been rendered plausible, this was considered sufficient to support the claim and justify an inventive step by distinguishing it from mere speculation.

Mr Nachshen adds that “in raising the bar for a test of obviousness, many see this as bringing the UK assessment into line with the European Patent Office where to succeed in an obvious attack it is not sufficient to demonstrate a concept may be ‘obvious to try’ but there must be ‘a reasonable expectation of success’."

Nevertherless, each case is still going to be judged on its merits and the state of the art at the priority date, he argues. Within the research community, this decision is likely to be considered as strengthening their position and providing support for early patent filing based on initial proof of concept. “Provided this draws the invention far enough away from the prior art, there will be expectation that an inventive step may be acknowledged”, Mr Nachshen concludes.