Court of Appeal upholds SPC on enantiomer of known racemate

Author: Bratin Roy (McDermott Will & Emery UK LLP)

Citation: Journal of Intellectual Property Law & Practice 2009 4(11):775-776; doi:10.1093/jiplp/jpp150

Generics (UK) Ltd v Daiichi Pharmaceutical Co Ltd & Another [2009] EWCA Civ 646 (2 July 2009), Court of Appeal, England and Wales

The Court of Appeal for England and Wales has upheld a decision of the Patents Court confirming the validity of a patent and accompanying supplementary protection certificate to an enantiomer of a known racemate.

Legal Context

A significant number of pharmaceutical products are derived from what are known as chiral compounds. Chiral molecules can take one of two forms, which are mirror images of each other but are not identical, like a person's left and right hands. Thus, the two forms have the same molecular formula, but differ in geometry, and are known as enantiomers. A racemate is a mixture of equal amounts of two enantiomers of a chiral molecule.

This decision confirms that a patent to a specific enantiomer can be inventive, even if the associated racemate is already known. It also confirms that a supplementary protection certificate (SPC), which effectively extends patent protection for medical products to take account of the long time required to obtain regulatory approval, can be valid even if marketing authorization has already been granted for the racemate.

Facts and analysis

The claimant, a manufacturer of generic medicines, brought a claim seeking a declaration of invalidity of European Patent (UK) 0206082 and of associated SPC GB97/085, owned by the defendant. The patent and SPC were to a chiral antimicrobial compound called levofloxacin, the negative enantiomer of a compound whose racemic form is known as ofloxacin, which was a member of the class of compounds called quinolones. The patent had already expired, but the SPC remained in force.

The claimant's case was based on a number of pieces of prior art, including the defendant's prior patent, common general knowledge, and also on a poster briefly displayed at a conference which explained how enantiomers of flumequine, a similar quinolone to ofloxacin, were made. The claimant argued that the patent was obvious in the light of this disclosure.

It was common ground that the relevant claims of the patent did not extend to ofloxacin, which was acknowledged in the patent to be old, having been disclosed by the defendant in a prior patent. The claimant, however, claimed that the SPC was invalid under Article 15 of European Regulation 1768/92: levofloxacin was not to be regarded as a new active ingredient for the purposes granting an SPC, being an active component of ofloxacin, for which there was already a marketing authorization.

Patents Court decision
Mr Justice Kitchin concluded that the patent was valid over all of the cited prior art, and that the SPC was validly granted. He concluded that the patent was inventive over common general knowledge, as knowledge of racemate did not mean that use of only one of the constituent enantiomers was obvious, particularly where that individual enantiomer showed greater efficacy than the racemate, of which the skilled addressee would not have been aware. Further, while the skilled addressee of the patent, reading the poster, would have considered it worthwhile exploring whether ofloxacin could be resolved into its constituent enantiomers, it would not have been obvious that this would be a fruitful exercise.

On the SPC, he held that a marketing authorization for ofloxacin could not be considered authorization to market levofloxacin. Since it had required invention to produce levofloxacin, and marketing authorization was not granted for levofloxacin until 11 years after the patent had been granted, it was just for the defendant to be granted an SPC in respect of that delay. The claimant appealed.

Court of Appeal decision
The Court of Appeal upheld the Patents Court's decision in full. It held that Kitchin J's reasoning regarding the poster was a perfect example of a judge carrying out the balancing task of forming an overall value judgment, and so could not be faulted. As Jacob LJ, giving the lead judgment put it, ‘Only a curmudgeon would say that there is no invention here.’

The Court of Appeal also agreed with the approach taken by the Patents Court over the SPC. This case was one in which the underlying research had led to what was effectively a new medicine. This was precisely the type of research referred to in recital 2 of Regulation 1768/92. The claimant's argument that ofloxacin should be regarded as no more than levofloxacin with an impurity was also rejected. Neither patent law nor the law controlling the marketing of medicines regarded it as such, and there was no reason why the law on SPCs should be any different. The claimant sought to rely on case law from numerous non-EU jurisdictions in support of this contention, which were rejected as being concerned with different statutory language, views of the facts, and policies.

Practical significance

The use of chiral compounds in pharmaceuticals has been, and continues to be, widespread throughout the pharmaceutical industry. The outcome of this latest challenge to the validity of a patent relating to such compounds confirms the approach taken by the UK courts in previous cases, despite the numerous European and non-EU precedents on which the defendants sought to rely. In cases such as this, in which a single enantiomer is unexpectedly found to be superior to its known racemate, that enantiomer is clearly capable of patent protection. This case also confirms that the extremely valuable additional protection afforded by an SPC is also available for such enantiomers.