In a revocation action brought by Conor, Angitech’s patent for taxol coated stents was found invalid for being obvious. The case is Conor Medsystems Inc. v Angiotech Pharmaceuticals Inc. and another and was decided by the Court of Appeal this month, upholding the decision of the High Court. The main judgment is that of Lord Justice Jacob, with which the other members of the court agreed.


The technology in this case was not the simplest. Angioplasty was a well-known alternative to vascular by-pass surgery. Angioplasty basically involves manoeuvring a small balloon to the problematic site in the blood vessel and then inflating it there to open up what would otherwise be a blockage (or a stenosis). However when the balloon is taken out, restenosis often occurs. Stents are essentially tubes of wire-like structure which are expandable. It was known that they could be used in conjunction with these balloons. The inflation of the balloon expands the stents, which would then hold the lumen open like scaffolding. Even with stents, restenosis still occurred for various reasons, including that the body would react to the foreign object by growing tissue over and through it. It was known to coat stents with drugs applied locally at the site of the stent to try to prevent restenosis.

The description in the patent and the claims as originally filed were not limited to taxol coated stents or to stents used in coronary angioplasty. Other applications described in the patent were to treating blockages in other body passageways, for example, caused by tumours. However, the angioplasty application was important because of Conor’s commercial activities in that area.

A range of anti-proliferative drugs (drugs which prevent vascular growth), including taxol, were described in the patent. In the High Court amendment of the patent had been allowed to avoid prior art so that the main claim in dispute was specifically to taxol in a drug-coated stent.

The question was whether it was obvious to use taxol in a drug-coated stent.


In upholding the decision of the High Court, the Court of Appeal reiterated that findings of obviousness should only be overturned where the appeal court thinks that the first instance court has made an error in principle. It decided that no such error had been made.

The main item of prior art was a prior specification of Wolff. It disclosed the use of drug coated stents and it disclosed the use of anti-proliferative drugs, as a class, but not taxol specifically. Some specific drugs disclosed by Wolff were also in the list of possible anti-proliferative drugs disclosed (and originally claimed) in the Angiotech patent.

The essence of the Court of Appeal finding of obviousness in the light of Wolff is found in a passage that reads:

“….. all the patentee has done different from Wolff is to name taxol as a suitable drug along with many others. The fact that now, by amendment, he has reduced his claimed monopoly to just using taxol is irrelevant here. A skilled reader is invited by Wolff to consider "other" anti-replicate drugs. Just to name one "other" anti-replicate which, on the information given in the patent, is no more and no less likely to be found to work in practice is not to make an invention.

Things would be different, of course, if the patentee had disclosed that in some way "taxol" was different, or better, or one of only a few anti-proliferatives that would work. His contribution to human knowledge would then be of value ……”

The Court of Appeal also upheld the finding of the judge at first instance that taxol was “obvious to try”. Despite indications from witnesses who were actually trying to solve the problem the subject of the claimed invention at the relevant time, and although there were toxicity concerns with taxol, there did not need to be an expectation of success in trying to use it with stents; it was enough that it was an avenue that might work and would not be rejected out of hand from being tried out.

The patentees argued that the alleged inventive step was supported by commercial success. Again this was rejected by the Court of Appeal, which considered that the patentee had not shown the success had resulted from the alleged invention, but rather had been based on extraneous factors. This reinforces the view that commercial success as a rebuttal to arguments of obviousness is very difficult to prove.


Generally, the decision confirms the view that the level of inventive step required by the English Courts is relatively high. This is emphasised by the fact that the Court of Appeal had the opportunity to see a decision of the Dutch court in the Hague on the equivalent patent (but involving slightly different parties) before making its decision. The court in the Hague found the patent valid, but the Court of Appeal disagreed with it.

The Dutch court’s decision was based on the view that the selection of taxol was of itself inventive. It said “….the selection of taxol from this large group (of anti-proliferative drugs disclosed by Wolff) did not produce an expectable optimal effect but rather a precisely surprising effect ….”.

One has some sympathy with the point made by Jacob LJ that this was not found in the patent as originally filed. If the patent could really be construed as a selection patent, which seems to be what the Dutch court was saying, maybe the real objection was that matter had been added.

The patent is also being litigated in the USA. The tendency for the courts there is to take more account of secondary evidence of non-obviousness. It will be interesting to see how the case is decided there.