Prior Patent Valid In Spite of Error in Decribing the Invention

The House of Lords has ruled that a patent application which was effectively anticipated by a prior invention cannot be valid. The case involved a method of crystallising paroxetine methanesulfonate, which was the subject of an international patent application under the Patent Cooperation Treaty by Dutch pharmaceutical company Synthon BV. In its application, the company incorrectly described a method for synthesising the chemical, which is an active ingredient in an antidepressant drug. A similar application was filed shortly afterwards in the UK by drugs giant SmithKline Beecham plc (SKB). At the time the SKB application was made, the Synthon patent had not yet been published, but SKB was granted a UK patent in 2000, at which point Synthon commenced proceedings.

Synthon was able to persuade the Lords that an ordinary skilled person examining its application would be able both to understand the application and to produce paroxetine methanesulfonate, despite the fact that there was an error in the disclosure. Synthon’s application described a process which used an unsuitable solvent for the crystallisation reaction and which would prevent the formation of crystals. The company argued, successfully, that an ordinary person would try a different solvent if the first one failed and as such their process was one which met the test of ‘enablement’, in that an ordinary person would find the right answer using it. The Lords accordingly declared the patent granted to SKB in 2000 to be invalid.

Conclusion

This case clarifies the law relating to the way in which ‘prior art’ is considered when determining the validity of patents and is notable for the fact that the Lords agreed that Synthon’s application should succeed despite the error in the description. Whilst it is better to get applications right in the first place, a small error may well not invalidate the application. What is essential is to keep intellectual property private and well protected.