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Court of Appeal confirms invalidity of patent for EXELON because it was obvious to resolve racemate using standard techn

09/01/2013

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Court of Appeal confirms invalidity of patent for EXELON because it was obvious to resolve racemate using standard techniques

snIPpets – January 2013

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Novartis AG v. Generics (UK) Limited (t/a Mylan) [2012] EWCA Civ 1623

The Court of Appeal has upheld the High Court's ruling that Novartis AG's patent covering a (-)-enantiomer was invalid for obviousness.

Background

The Patent (UK Patent No. 2,203,040 and associated SPC) covered the chemical rivastigmine, which Novartis markets in the UK as Exelon for the treatment of Alzheimer’s disease. Rivastigmine is composed of a (-)-enantiomer(1) and, at the priority date, a racemic compound containing rivastigamine (-) enantionmer had already been disclosed in two prior publications which had identified RA7 as a potential treatment for Alzheimer’s disease but did not suggest the compound should be resolved into its individual enantiomers.

Generics had applied to revoke the Patent. The High Court held that it would have been obvious to a skilled team working in the pharmaceutical industry at the priority date of the Patent (1987) to select RA7 for development, to separate RA7 into its enantiomers and to use the (-)-enantiomer for the treatment of Alzheimer’s disease. The Patent and associated SPC were therefore found to be invalid.

The Law

Section 3 of the Patents Act 1977 states that an invention involves an inventive step "if it is not obvious to a person skilled in the art, having regard to any matter which forms part of the state of the art".

The Courts have recently cautioned against substituting a test such as "is it obvious to try" for the statutory test in section 3.  However, it has also been acknowledged that, in certain circumstances, the "obvious to try" formula can sometimes be useful in determining the obviousness question, particularly if there is a reasonable or fair expectation of success within a reasonable timeframe (eg Kitchin LJ in Medimmune Ltd v Novartis Pharmaceuticals UK Ltd & Ors [2012] EWCA Civ 1234).

The Dispute

Novartis contended that the High Court had incorrectly used the "obvious to try" test and had not considered whether there was a fair expectation of success. At the priority date, it was not obvious: (i) to stop the process of Weinstock's investigations and move a compound into development; (ii) to try the (-)- enantiomer for a particular therapeutic purpose.

The Respondent, however, argued that Novartis was simply inviting the court to reverse the judge's evaluation of the facts.

The Decision

The Court of Appeal held that in deciding whether an invention was obvious to the skilled but unimaginative addressee at the priority date, the Court will have regard to all the circumstances of a case, including where appropriate whether it was obvious to try a particular route with a reasonable or fair expectation of success. This might be the case in the pharmaceutical area where researchers are unsure which of the many avenues they face could be fruitful. However it is not correct that an obviousness attack can only succeed where it is manifest that a test ought to work.

The Court of Appeal confirmed the line of reasoning set out in its recent decision in MedImmune Ltd v Novartis Pharmaceuticals UK Ltd [2012] EWCA Civ 1234. The High Court judge had correctly applied these principles which outlined that whether or not a route has a reasonable or fair prospect of success will depend upon all the circumstances including:

  • an ability rationally to predict a successful outcome;
  • how long the project may take;
  • the extent to which the field is unexplored;
  • the complexity or otherwise of any necessary experiments;
  • whether such experiments can be performed by routine means; and
  • whether the skilled person will have to make a series of correct decisions along the way.

The Court of Appeal upheld the judge's decision that it was obvious to take RA7 into development and it was obvious to attempt to separate its enantiomers. "It required no insight or invention to follow the teaching of Professor Weinstock, to take the compounds she disclosed as having promise…and to investigate whether that promise translated into a useful therapeutic effect". Furthermore, the Court concluded that "the skilled team would consider that resolution of the racemate might bring practical benefits and would see resolution as a routine step".

Key Points

  • This case does not bar future patents of chemical enantiomers in the UK. However, there may be a rebuttable presumption of obviousness against patent applications for single enantiomers of identified racemic compounds unless there is evidence of practical difficulties in isolating the enantiomer from the racemic compound.
  • Evidence in this case indicated that RA7 could be separated into its enantiomers using conventional techniques. This may be contrasted with cases where patents relating to enantiomers were found not obvious because the resolution of the enantiomers was difficult or uncertain (Generics (UK) Limited v. Daiichi Pharmaceutical Co Ltd [2009] EWCA Civ 646) or the skilled person simply didn’t know how to resolve the enantiomers at the priority date (H Lundbeck A/S v. Generics (UK) Limited [2008] EWCA Civ 311).
  • The Courts continue to criticise reliance on the "obvious to try" test. Nonetheless, it appears that in pharmaceutical cases such as this one, the Courts do still have to consider whether the inventive step was obvious to try. However, this needs to be restricted to those circumstances where there is also a reasonable or fair expectation of success within a reasonable timeframe.

Nicola Bex, Trainee Solicitor and Beatriz San Martin, Senior Associate, IP Enforcement and Litigation Group.


(1) Enantiomers are two non-superimposable mirror-image molecules. They can be available as a pure enantiomer or as a mixture of (+) and (-) enantiomers (called a racemic compound).

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