Small Error Will not Invalidate Patent

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 chemical synthesis for an antidepressant drug, which was the subject of an international patent application by Dutch pharmaceutical company Synthon BV. In its application, the company incorrectly described the method for synthesising the chemical, describing a process which used an unsuitable solvent for the crystallisation reaction. 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. When SKB was granted a UK patent in 2000, 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 the chemical, despite the fact that there was an error in the procedure described in the patent application. They argued that an ordinary person would try a different solvent if the first one failed and using a different solvent would lead to the reaction being successful. 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.

This case clarifies the law relating to the way in which ‘prior art’ is considered when determining the validity of patents. Minor errors that do will not prevent a reader of the patent application from correctly following the described process will not invalidate the patent.