UK: Case Note: Synthon BV v SmithKline Beecham plc, House of Lords

Last Updated: 8 November 2005
Article by Sally Field and Robert Fitt


The House of Lords has recently provided guidance on the law of novelty, in particular, what constitutes a disclosure and what is meant by enablement. The case in question was between Synthon BV and SmithKline Beecham plc and the dispute related to who was first to disclose, in a fully enabling fashion, paroxetine methanesulfonate. This is a form of the well-known compound paroxetine used to treat depression and related disorders which had been marketed in the form of its hydrochloride hemihydrate salt under the names Paxil or Seroxat. Paroxetine methanesulfonate has properties which make it more suitable for pharmaceutical use in that it is more stable, less hygroscopic and more soluble and can be prepared in high concentrations.

The facts

On 10 June 1997 Synthon filed a patent application which claimed a broad class of sulfonic acid salts including paroxetine methanesulfonate. Example 1 of the patent described how to make paroxetine methanesulfonate in crystalline form and drew attention to its characteristic absorbance spectrum when subjected to infra-red radiation (IR). On 6 October 1998 SmithKline Beecham filed its own patent application claiming paroxetine methanesulfonate and identified a particular crystalline form by reference to its IR spectrum. The IR peaks disclosed in the Synthon application were, however, different to those in the SmithKline Beecham application. This would lead a person skilled in the art reading both applications to believe that the two disclosures identified different crystalline forms or polymorphs of the same compound.

In March 2001 Synthon began proceedings to have the SmithKline Beecham patent revoked on the ground that the crystalline form described in its claim 1 was not new in the light of Synthon’s own patent application. In order to succeed, Synthon had to satisfy the trial judge that their application disclosed what was claimed in claim 1 of the SmithKline Beecham patent and that an ordinary skilled man would be able to perform a disclosed invention by following the instructions and information in the Synthon application, in the light of his common general knowledge.

The difficulty Synthon faced was that when eminent chemists from the University of Oxford tried to carry out the instructions of Example 1 in the Synthon application, and produce crystals of paroxetine methanesulfonate, they were unable to do so. Eventually, after a good deal of skilled manipulation not described in Synthon’s application, the Oxford chemists produced crystals which turned out not to have the IR spectrum disclosed in Synthon’s application but the spectrum described in SmithKline Beecham’s patent.

Synthon then produced evidence to show that the IR spectrum in their application was the result of a mistaken reading. There was only one form of paroxetine methanesulfonate, whose IR spectrum was as per the information set out in SmithKline Beecham’s patent. Secondly, on enablement, Synthon said that although the method described in their application did not produce seeding crystals, it did not mean that the ordinary skilled man would have difficulty in crystallising paroxetine methanesulfonate. By using a different solvent (as set out in the Synthon application) or by routine trial and error, the skilled man would be able to produce the compound in question. The trial judge agreed with this approach, and held as a matter of fact that a skilled man would be able to produce crystals as described in the SmithKline Beecham patent. This meant that not only did the Synthon application disclose paroxetine methanesulfonate, but also that the making of that product was enabled. Consequently, the Synthon application anticipated the SmithKline Beecham patent, which was therefore invalid for lack of novelty.

However, on appeal to the Court of Appeal, the trial judge’s decision was reversed on the basis that the Synthon application did not disclose the invention of claim of the SmithKline Beecham patent sufficiently clearly to enable the skilled man to produce crystals of paroxetine methanesulfonate. The Court of Appeal found support for this finding on the basis of the difficulty the Oxford chemists retained by Synthon had in attempting to prepare the crystals described in the Synthon application.


In the leading judgment on the further appeal to the House of Lords, Lord Hoffmann sought to separate the concepts of disclosure and enablement. On disclosure he summarised the law as follows: namely, that the matter relied upon as prior art must disclose subject matter which, if performed, would necessarily result in an infringement of the patent. He defined enablement as meaning that the ordinary skilled person would have been able to perform the invention which satisfies the requirement of disclosure. Consequently, when applying this two tier analysis to the facts, Lord Hoffmann stated that on disclosure there was no doubt that the Synthon application disclosed the existence of paroxetine methanesulfonate crystals of 98% purity and claimed they could be made. Their existence and their advantages for pharmaceutical use were clearly disclosed and carrying out the invention would produce crystalline paroxetine methanesulfonate. Even if the skilled person reading the patent did not think he was going to infringe it because of the incorrect IR data, he would inevitably do so. On enablement, Lord Hoffmann referred to the finding by the trial judge that the skilled man would have tried some other form of solvent from the range mentioned in the Synthon application or forming part of his common general knowledge and would have been able to make paroxetine methanesulfonate crystals within a reasonable time. Consequently, Lord Hoffmann overturned the findings of the Court of Appeal.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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