What is interesting about the Lundbeck cases is that Lundbeck initiated several patent infringement cases in Europe (in the Netherlands, Germany and in the UK) and that each court decided differently on the validity of the Lundbeck patent. This shows that despite the implementation of the European Patent Convention, European national courts still come to different conclusions on the validity of (European) patents.

Lundbeck discovered and patented the SSRI anti-depressant escitalopram. By the priority date (1998) citalopram was in advanced development and its beneficial properties were well known. It was known that citalopram was a racemate – a 50/50 mixture of two enantiomers (a (+) and (-) enantiomer). There was also awareness of potential differences in activity/toxicity of the enantiomers (one could be beneficial whereas the other could be toxic, e.g. the Diethylstilbestrol case). This awareness provided a clear motive for the skilled man to isolate and test the enantiomers. Lundbeck found a way to isolate the (+) enantiomer from the citalopram racemate.

This could be achieved by resolving the diol precursor into its enantiomers followed by stereoselective conversion to the enantiomers of citalopram. Lundbeck discovered that this was the effective enantiomer and applied for patent protection. It claimed the (+) enantiomer itself and a pharmaceutical composition containing it.

In the Netherlands these claims were found to be novel. The known racemic mixture (citalopram) and the known spatial configuration of the (-) enantiomer of citalopram were not novelty destroying in respect of the (+) enantiomer of citalopram, because this very compound was not directly and unambiguously disclosed in the form of a technical teaching. However, the patent was invalidated because of lack of inventive step. Following the problem/ solution approach the court found that the skilled man in possession of the citaloprame racemate, knowing that a racemate could be split and being aware of potential differences in activity/ toxicity of enantiomers, would have split the citalopram racemate.

In the UK the claims were found to be novel, inventive and sufficiently disclosed. Novel, because they were to be interpreted as excluding the prior art of the known racemate. The claims involved an inventive step because it was not obvious to the skilled man that the necessary reaction of the resolved diol intermediate could be performed without loss of stereochemistry. It was, furthermore, not found to be obvious to resolve citalopram by chiral HPLC. On insufficiency, the House of Lords held that if a product is novel and non-obvious, the product itself is the ‘technical contribution’ to the art. The patent was therefore held to be valid.

In Germany the patent was invalidated partly because of lack of novelty (claims 1 to 5) and partly because of lack of inventive step (claim 6).