UK House of Lords discusses obviousness law in Conor Medsystems v Angiotech decision

The House of Lords has unanimously allowed Angiotech Pharmaceutical's appeal against the revocation of their patent for a stent coated with the anti-angiogenic factor paclitaxel. In a decision dated 9 July 2008, the law lords rejected the reasoning of Jacob LJ in the Court of Appeal and affirmed that the question of obviousness is to be determined by reference to the claimed invention, which is independent of the extent of disclosure in the description. This decision brings the UK Courts in line with the Dutch Courts who previously found the patent partially valid in parallel proceedings, and provides confirmation of the delineation between obviousness and insufficiency. It also includes a warning against drafting overly broad patent specifications.

Background
Angiotech Pharmaceuticals Inc. and the University of British Columbia are joint proprietors of European patent 0706376. The patent, entitled "anti-angiogenic compositions and methods of use" was a lengthy document containing no less than 37 pages of description and 34 pages of figures, originally disclosing such diverse applications as the treatment of cancer, stenting and a medicament for treating arthritis. The patent was amended extensively in Opposition proceedings before the European Patent Office, with the claims eventually being confined to the use of paclixatel (commonly known as "taxol") on stents. The granted patent was exclusively licensed to Boston Scientific, who subsequently marketed the invention in a commercially successful product called Taxus. Conor Medsystems Inc., an American competitor, filed for revocation of the patent in the UK and the Netherlands on the ground that the claimed invention was obvious. In the UK, the revocation action succeeded before the Patents Court (Pumfrey J) and the Court of Appeal (Mummery, Tuckey and Jacob LJ) whereas in the Netherlands, the patent was found partially valid, allowing the proprietor to take a successful infringement action against Sahajanand Medical Technologies PVT Ltd and Conor Medsystems Inc.

Patents Court and Court of Appeal
The claims at issue in these proceeding were directed to a stent coated with a polymer which was loaded with the anti-proliferative drug taxol. A stent is a tube used as a mechanical scaffold in vascular intervention to keep open a body conduit. Stents are most commonly used to maintain coronary arteries which have been widened during a technique called angioplasty, in which a catheter carrying a tightly folded balloon is inserted percutaneously through the coronary arteries to the constricted area, at which point the balloon is inflated to mechanically widen the artery. The stent is then used to prop open the widened artery and prevent further narrowing. However, a problem associated with this technique is the occurrence of restenosis, or reconstriction of the artery by proliferation of smooth muscle cells through interstices of the stent. It is this problem which the patent in question sought to address, by providing a stent coated with the anti-angiogenic agent taxol to inhibit proliferation of smooth muscle cells.

At first instance, the facts of the case seemed relatively straightforward. The claims had been attacked for non-obviousness in light of three prior art documents, here designated as Wolff, Kopia and Katsuda. The Wolff document was a PCT patent publication which proposed using drug elution from an intravascular stent as a method of limiting restenosis. While this document listed several suitable anti-proliferative drugs for this purpose, paclixatel was not specifically mentioned. Kopia was a second PCT patent publication which proposed a method of administering a drug directly to the site of post-angioplastic restenosis by chemically modifying the drug molecule. The document specifically cited paclixatel among a list of various anti-proliferative drugs it deemed suitable for this purpose. Finally, the Katsuda document was an abstract of a paper on atherosclerosis which described in vitro studies on the effect of paclixatel in the inhibition of proliferation of smooth muscle cells in the intima of an artery. The Claimant (Conor Medsystems) contended that the patent in question lacked validity for obviousness over these documents, whereas the patentee submitted that taxol was not an obvious agent to use in light of previous concerns about its toxicity following systemic delivery.

At first instance, and confirmed on appeal, it was found that the patent was invalid for obviousness in light of these citations and revocation of the patent was ordered. This decision has now been overturned by the House of Lords with the test for obviousness used by Justice Pumfrey in his reasoning before the Patents Court, attracting criticism from Lord Hoffmann in the main House of Lords judgement.

Expectation of Success
In their submissions before the Patents Court, Conor Medsystems sought to draw an association between the disclosure of the invention and the inventive concept thereby defined in the patent. Specifically, it was submitted that the inventive concept of the patent resided in the idea of seeking to treat or prevent restenosis by coating a stent with a paclixatel/polymer composition. Conor Medsystems argued that the specification merely disclosed the idea and did not show that the concept worked or that any particular polymer or amount of paclixatel was suitable, thus leaving it to the addressee to determine whether the composition was in fact effective to prevent restenosis. On this basis Conor Medsystems contended that it was sufficient to invalidate the claims of the patent that paclixatel was worth experimentation and would not be dismissed a priori by a skilled person seeking to prevent restenosis.

On the other hand, the patentees argued that the patent would be vulnerable for non-obviousness only if the skilled person had an expectation of success "sufficient to induce him to incorporate paclixatel in a drug eluting stent to be used in human beings to treat or prevent restenosis". Justice Pumfrey, at paragraph 61 of the decision, summarised this point of contention thus "is the patent vulnerable only if it can be shown that the skilled person would have had an expectation of success sufficient to induce him to incorporate taxol in a drug-eluting stent, or is it sufficient that without any expectation of success he would test or screen taxol?". He directed that the question was to be answered by assessing the contribution to the art made by the specification.

Describing the specification as "speculative", Justice Pumfrey observed that the disclosure in the application in respect of taxol-eluting stents was slight, and that the specification did not show that the concept worked at all, or to any particular extent. Accordingly, he dictated that success in preventing restenosis was not to be a relevant consideration when assessing the obviousness of the stent. Rather, he concluded that "a sufficient motive is the testing of such a stent to see if it has potential in the treatment of restenosis".

Thus, under this much maligned decision, the extent of the specification was used to set the threshold against which obviousness was to be determined, in this case setting the bar for inventive step at a low level in response to what the justice saw as deficiencies in the specification itself. The ramifications of this decision were potentially far-reaching, in that it would have required large amounts of experimental data to be provided in the specification, in effect to "prove" that the subject-matter of the claims worked effectively, and thus allow obviousness to be adjudged at the higher level.

House of Lords Decision
Lord Hoffmann, giving the main judgement before the House of Lords, criticised this approach and confirmed that "the invention is the product specified in a claim and a patentee is entitled to have the question of obviousness determined by reference to his claim and not to some vague paraphrase based upon the extent of his disclosure in the description". At paragraph 27 of his decision, Lord Hoffmann opined that it was absolutely clear that the teaching of the specification was that a taxol-coated stent would prevent or treat restenosis. Agreeing with the reasoning of the Dutch courts, he stated that "the Dutch court was not addressing itself to whether taxol worked, or whether the specification proved it would work, but to whether the specification taught it should be used". On this basis, he allowed the appeal, confirming that the lack of technical disclosure was relevant only to an attack on the grounds of insufficiency, not obviousness. The patent now stands, the earlier revocation having been reversed.

The notion that the inventive concept of the patent is to be assessed with reference to the extent of the disclosure has thus been firmly rejected. This judgement affirms that the inventive concept embodied in a patent is to be determined solely with reference to the claims, and not to the extent of the disclosure. This judgement will come as a relief to patent proprietors, who can be assured that the threshold for inventive step is to be adjudged independently of the technical disclosures of the specification. As a word of warning to those filing overly broad specifications, however, Lord Walker of Gestingthorpe, in concurring with Lord Hoffmann's reasoning on inventive step, pointed out that the inventors and those who drafted the specification had in some way contributed to the tribulations of the litigation by drafting a patent so broadly that "they risked making it so unfocused as to end up with nothing capable of resisting a challenge to its validity".

Eimear Ward 31 Aug 2008

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