In Conor Medsystems Inc v Angiotech Pharmaceuticals Inc [2008] UKHL 49, the House of Lords has revisited the test of “obvious to try” most often raised in patent validity actions. This decision has far reaching implications, especially across the pharmaceutical sector. Led by Lord Hoffmann, the House reversed decisions of both the High Court and Court of Appeal that Angiotech’s patent for taxol coated stents was invalid for obviousness. According to Lord Hoffmann, both lower Courts had wrongly identified the inventive step of the patent by ignoring the clear wording of the claims in issue and giving too much weight to the description of the invention contained in the specification.


Angiotech Pharmaceutical Inc. was a joint owner of European Patent No. 0706376 (the Patent) claiming, among other things, a stent coated with the drug taxol for “treating or preventing recurrent stenosis”. The stent produced under the Patent has been highly successful in acquiring the largest share in the market related to drug eluting stents. Taxol was already known at the Patent’s priority date as an anti cancer drug, especially for the treatment of various stages of breast cancer, by acting as an inhibitor of cell division with unfortunately, some quite unpleasant side effects.

The U.S. medical device company, Conor Medsystems Inc. applied to revoke Angiotech’s Patent on the grounds of obviousness based on an earlier Angiotech European patent that described a stent coated with a polymer containing taxol. At the time Angiotech filed their priority patent in the United States, it was well known that when a bare metal stent was used to keep a coronary artery open, damage to the inner lining of that artery caused a reaction during the healing process, which could ultimately result in a build-up of tissue around the stent, which in turn could cause angina. This tissue growth is known as restenosis.


The Patent in its original form claimed various uses of compounds such as taxol in the treatment of cancer and in the use of such compounds on stents for the treatment of restenosis. The Patent in this form was opposed at the European Patent Office (EPO). As a result of this EPO opposition, the claims for treating cancer and other diseases were abandoned and the Patent confined to the use of taxol on stents, which resulted in various amendments to the claims. The claim at the centre of the dispute was claim 12 for a stent “for treating or preventing recurrent stenosis”.

Conor then filed for revocation of the Patent in February 2005 in both the United Kingdom and the Netherlands, arguing that Angiotech’s Patent merely asserted that taxol was worth trying, and did not show that it actually worked. The UK High Court accepted Conor’s argument. In the Court of Appeal, Lord Justices Mummery, Tuckey and Jacob found that Angiotech’s claim added nothing to existing knowledge in the subject area of the patent and was therefore obvious. The court in the Netherlands, however, found that it was sufficient for Angiotech to provide in its specification an indication that taxol would work. As a result, Conor’s revocation attempt in the Netherlands failed.

Angiotech appealed to the House of Lords on the basis that the decision of the Dutch court was correct, meaning its Patent was valid and therefore the UK decisions should be overturned. Almost immediately after the Court of Appeal decision, Angiotech and Conor reached a settlement, with Conor bestowing on Angiotech its blessing in pursuing its appeal to the House of Lords. The Comptroller General of Patents therefore “assisted” the House of Lords by presenting arguments against the validity of the Patent.


It came as no surprise to Lord Hoffmann that the Dutch courts could rule in a fashion that was directly opposite to their UK counterparts. A European patent was a bundle of national patents over which the national courts had jurisdiction, so it was inevitable that national courts would occasionally give inconsistent decisions about the same patent. Sometimes this was because the evidence was different or, as was the case regarding the Angiotech Patent, the issue was one of degree over which judges could legitimately differ. Obviousness was often in this latter category and it was desirable where possible for national courts and the EPO to find a uniform interpretation of the European Patent Convention. This was especially true when it came to a fundamental determinant of patentability such as how to identify the concept of “inventive step” under Article 56 EPC and Section 1(1)(b) of the Patents Act 1977. Article 56 provides that an inventive step is involved in an invention “if, having regard to the state of the art, it is not obvious to a person skilled in the art”.


Conor argued throughout the numerous proceedings that the alleged inventive concept provided by Angiotech in the specification of the Patent was merely an idea of coating a stent with taxol to deal with the restenosis problem and that the Patent taught nothing further than taxol “was worth a try”. According to Conor, this “worth a try” teaching added nothing to the existing knowledge in the subject area.

Conor further argued that it was common knowledge to anyone skilled in the art that taxol, like many other drugs and medicaments acting as anti-proliferatives, was worth considering. As a result, this was an obvious and natural development in the art.

Lord Hoffmann held that Conor’s argument was “an illegitimate amalgam of the requirements of inventiveness (Article 56, EPC) and either sufficiency (Article 83, EPC) orsupport (Article 84, EPC) or both”. Lord Hoffmann was adamant that it was the claimed invention that had to involve an inventive step and that an invention was, on the face of it, what was claimed by the patentee and not just what was stated or described in the specification of a patent. In this case the inventiveness lay in Angiotech’s claim that the product would have a particular property or quality, namely to prevent or treat restenosis. Whereas it was true that the specification said very little about the details of how or why taxol would be efficacious in preventing restenosis, Angiotech saw and subsequently claimed in its Patent the solution for restenosis in terms of preventing angiogenesis (by use of taxol). Unfortunately, other than the provision of a series of CAM tests, Angiotech had offered little proof that this claimed solution was in fact correct. As a result, Angiotech was at risk of a finding of insufficiency, but if the invention did work (which, as it turned out, it did with great success) then it would not matter actually why it worked as the reason might have nothing to do with anti angiogenesis. Angiotech’s specification would nevertheless still be sufficient if, for whatever reason, taxol coated stents possessed the claimed property of preventing or treating restenosis.

Lord Hoffmann was in complete agreement with the opinion of the Dutch court. The Dutch court was not addressing itself to whether the taxol worked, or whether the specification proved that it would work, but to whether the specification taught that it should be used and it did so by reference to the disclosure of the success of the taxol in the CAM assay and the specific references to taxol in the claims. Jacob LJ had completely dismissed these points as well as the reasoned opinion by the Dutch court.

Therefore, the appropriate question was whether it was obvious to use a taxol coated stent for the prevention or treatment of restenosis and not whether it was obvious that taxol (among many other products) might have this effect. According to Lord Hoffmann, Angiotech was entitled to have “the question of obviousness determined by reference to the claim and not to some vague paraphrase based upon the extent of the disclosure in the description”. There was no requirement in the European Patent Convention or the 1977 Act that the specification had to demonstrate by experiment that the invention would actually work or explain why it would. It was sufficient if, for whatever reason, taxol coated stents possessed the claimed property of preventing or treating restenosis.


According to Lord Hoffmann it was hard to see how the concept that something was worth a try, or might have some effect, could be described as an invention such that a patent should be awarded. Lord Hoffmann therefore had some sympathy for Pumfrey J who issued the first decision in this chain of cases. Nonetheless, the test for obviousness that Pumfrey J devised for such an “invention” was whether it was obvious to try it without any expectation of success. This was an “oxymoronic concept” and had no precedent in the law of patents.

Lord Hoffmann agreed that a patent cannot be granted for an idea that was mere speculation, unsupported by anything disclosed in the specification. Article 84 EPC and Section 14(5)(c) of the 1977 Act state clearly that the claims must be “supported by the description”, but lack of support under these provisions is not a ground on which a patent can be revoked under Section 72(1) of the Act. In Angiotech’s case, since the Patent already had been granted by the EPO, Article 84 was no longer an issue that could be raised.

In the Court of Appeal, Jacob LJ upheld Pumfrey J’s judgment on the ground that the Patent contained no proof that taxol was especially suitable for the prevention of restenosis. Lord Hoffmann agreed that the Patent’s description did not offer any direct evidence or proof regarding taxol’s suitability for the prevention of restenosis, although Angiotech had provided in the Patent a theory regarding taxol’s anti-angiogenic properties and its resulting prevention of restenosis. If Angiotech’s theory had in fact turned out to be false, the Patent would have been insufficient, but according to Hoffmann J “there was no reason as a matter of principle why, if a specification passed the threshold test of disclosing enough to make the invention plausible, the question of obviousness should be subject to a different test according to the amount of evidence which the patentee presented to justify a conclusion that his patent would work”.

The central issue before the Court of Appeal was essentially whether the teaching of the Patent was that “a taxol-coated stent would prevent or treat restenosis”. Jacob LJ wholeheartedly disagreed with the Dutch court which had held that this was precisely what Angiotech’s Patent taught the skilled artisan. According to Jacob LJ, the Dutch court had formed its view “with the hindsight knowledge that taxol stents work”. However, according to Lord Hoffmann this was not a fair criticism. The Dutch court had not been addressing itself to whether taxol worked, or whether the description in the Patent in fact proved that it would work, but to whether the specification taught that it should be used. In reaching his decision, Jacob LJ considered that there was nothing in the Patent specification that indicated taxol was particularly suitable as an anti-angiogenic for a stent. Jacob LJ would have been correct if he had meant there was no proof in the specification that taxol would work. If, however, Jacob LJ meant that the specification did not claim that taxol would work, then Lord Hoffmann considered this “a very narrow approach to the meaning of the Patent, more suitable to old fashioned statutory construction than to what the skilled practitioner in cardio-vascular intervention would have understood”. The evidence was that the teaching of the Patent was to use an anti-angiogenic factor on a stent to prevent or treat restenosis, and that taxol was the best anti-angiogenicknown. Lord Hoffmann, however, simply could “not understand what more the patentee could have said”.

In the Court of Appeal, Jacob LJ had dealt comprehensively with the question of when an invention could be considered obvious on the ground that it was “obvious to try”. According to Lord Hoffmann, he had correctly summarised the authorities, starting with Diplock LJ’s judgment in Johns-Manville Corporation’s Patent [1967] RPC 479, by saying that the notion of something being obvious to try was useful only in a case in which there was a fair expectation of success. How much of an expectation would be needed depended upon the particular facts of the case. Unfortunately, Jacob LJ rejected this approach on the grounds that Angiotech’s Patent “was not an obvious to try case of the Johns-Manville type” because the Patent had not in any way demonstrated that taxol actually worked to prevent restenosis.

Lord Hoffmann commented:

“[N]either the judge nor the Court of Appeal answered what I consider to have been the correct question, namely, whether it was obvious to use a taxol-coated stent to prevent restenosis… I agree with the Dutch court that patent law does not require a demonstration [by Angiotech that taxol actually works to prevent restenosis]. It was not a sufficient reason for not applying ordinary principles of obviousness to the claimed invention.”


Lord Hoffman indicated that the obvious to try approach “was useful only in a case in which there was a fair expectation of success. How much of an expectation would be needed depended upon the particular facts of the case”. Citing with approval the first instance judgment of Kitchin J in Generics v Lundbeck , Lord Hoffman said that this issue should take account of all the relevant circumstances, including the problem the patent addresses, the number and extent of the possible avenues of research and the effort involved in pursuing them.

Lord Walker added some further observations on the “obvious to try” test. The origin of the test had been the Johns-Manville judgment issued by Diplock LJ over 40 years ago in a case about a method for production of asbestos cement, which was a fairly low tech process. According to Lord Walker, during the last 40 years the volume of high tech research had increased enormously, especially in the fields of pharmaceuticals and biotechnology. The resources committed to research were enormous, because the potential rewards in worldwide markets were so great. Competition was fierce. In this climate “obvious to try” had tended to take on a life of its own as an important weapon in the armoury of those challenging the validity of a patent.

In his book Intellectual Property in the New Millennium Sir Hugh Laddie had described this as being “an unworkable or irrational test”, because if the reward for finding a solution to a problem and securing a monopoly for that solution was very high, large companies could judge it worthwhile to try all potential solutions. This had the irrational result that the more valuable the solution and the greater the need for it, the harder it would be to avoid an obviousness attack. This was a similar analysis to that provided by Lord Justice Jacob regarding the present Patent, in particular whether there was nevertheless a requirement to satisfy the inventive step requirement to test a product “without any expectation of success” (which Lord Hoffmann referred to as an “oxymoronic concept” when put forward by Pumfrey J).

Lord Walker was of the firm opinion that the inventors and those who drafted the specification have “brought the tribulations of this litigation on themselves” as the Patent understandably tried to cover and protect as much ground as possible but in doing so “they risked making it so unfocused as to end up with nothing capable of resisting a challenge to its validity”.


As Lord Neuberger stated in his concurrence with Lord Hoffmann’s opinion, “this decision represents a significant development in United Kingdom patent law”. This decision will have particular impact in the pharmaceutical and biotechnology industry where costs of research and the rewards on offer are high. In such areas there are often many groups working toward a common goal and/or addressing the same problems in different ways, which has led to the prevalence of the “obvious to try” approach of attacking validity.

Despite Lord Walker’s discouraging comments on the “obvious to try” approach, Lord Hoffman approved its application in the right type of case. It is therefore likely that such attacks will continue, albeit with greater emphasis on the wider circumstances and whether there was a “fair expectation” of success. What is clear is that those wider circumstances do not include the extent of disclosure of the patent.

This decision sits neatly alongside the recent Court of Appeal decision (in which Lord Hoffman also gave the leading judgment) of Generics v Lundbeck . These decisions emphasise that the invention is defined exclusively by the claims and that it is wrong to paraphrase the specification to identify what has previously been referred to as the “technical contribution” of the Patent for either obviousness or insufficiency purposes.

Provided the patent provides “enough to make the invention plausible” there is no need to provide substantial teaching in the specification as to how or why the invention works, provided that it does indeed work (even by a different mechanism from that set out in the patent). This might be seen as encouraging speculative patent applications before the full extent of research has been carried out, particularly in fast moving industries. However, the judgment did not go so far asto indicate that a “plausible” invention would necessarily be sufficiently described or supported by the specification.

The decision will be welcomed by many patent proprietors as it will be perceived as bringing the English courts more into line with the continental European approach. It will also go some way to alleviate the widely held view that the English courts are significantly more likely to invalidate patents.