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Dutch ruling on validity of Escitalopram

Recently, the Court of Appeal (Hof) at The Hague ruled on the validity of Lundbeck’s patent on the antidepressant Escitalopram (EP 0 347 666).

The ruling is remarkably different from that in several other countries, particularly in denying the patentability of the product claims.

Technological basis
In order to understand the matter, one should realize that many drug substances exist in two different forms which are called “enantiomers,” generally denoted as “S” and “R” forms. Without special synthesis or separation methods, the drug will be a so-called racemic mixture, consisting of both forms in equal amounts. Escitalopram is based on the S-enantiomer of citalopram, which pre-existed as a racemic mixture. Claimed were S-citalopram per se, and a method of making it via a defined precursor.

Novelty and Inventive Step
The individualized S-enantiomer was found novel in accordance with standard caselaw. As to inventive step, the patentee argued that S-citalopram amounted to an inventive selection from within a large group of antidepressant drugs. The Court, however, considered it had been common practice to study the effects of individual enantiomers in a racemic drug. The relevant starting point for the skilled person would therefore have been racemic citalopram. To then arrive at a selection of the more active of the two enantiomers did not entail an inventive step.

Finding the process claim patentable, the Court acknowledged that in other jurisdictions this had played a role in supporting the patentability of the product claims. Reference was made to decision T 595/90 of the Technical Board of Appeal of the European Patent Office. This decision indicates that a product defined by an obvious characteristic, could still be patentable if no suitable way existed in the art to make the product as defined. However, in the case of a racemic mixture, separation techniques did exist, and thus the present case did not satisfy the patentability requirements of T 595/90.

The Court did not stop at this, but opined on “proportionality,” clearly confirming that in their view a patent monopoly should be commensurate with the technical contribution to the art. The invention being a method to make S-citalopram, the protection is for the method, and for the product direcly obtained therefrom. The patentee’s contribution to the art did not relate to S-citalopram per se.

The Court pointed out that where in other jurisdictions the product claims were held patentable, this was expressly in the absence of any discussion on proportionality. The Court added that proportionality was discussed in the UK, but only vis-à-vis the reproducibility of the invention. The UK Court did not opine on the situation at hand, viz. that of a novel, yet not inventive substance that is produced by a novel and inventive process.

Supplementary Protection Certificate
The Dutch Court also ruled on the Supplementary Protection Certificate (SPC) for Escitalopram. One of the main arguments against the SPC was based on the pre-existing market authorization for citalopram. Since the racemic mixture by definition contained the S-enantiomer, the marketing authorization for Escitalopram would not have been the first one for this product, as is required for obtaining an SPC. Particularly, it had been argued that almost the entire activity of citalopram resided in the S-enantiomer. It was also pointed out that, precisely for this reason, the Dutch Medicines Evaluation Board did not accord to Escitalopram the status of “new active substance”. The Court, however, reasoned that the term “product” in the legislation on SPCs should be read as relating to an active substance in the narrow sense as understood in patent law. Accordingly, since S-citalopram was novel over citalopram, it by definition counted as a different product under SPC-legislation.