UK and EPO Obviousness Contrasted

Ranbaxy UK Ltd v. Warner-Lambert Co [2006] F.S.R. 14

Pfizer’s cholesterol pill Lipitor® is the best-selling drug in the world for the fifth year in a row. Its annual sales last year were $12.9 billion, more than twice as much as its closest competitors. The drug was invented by Warner-Lambert, which was acquired by Pfizer in 2000. Ranbaxy, headquartered in Haryana, India, is challenging the Lipitor patent in many countries around the world. Lipitor goes by the generic name “atorvastatin”.

Warner-Lambert filed a patent application in May 1986 describing how to make atorvastatin by a procedure that results in a racemate mixture. Their patent gave one example describing the free acid form of the compound, and another describing the sodium salt. The description also listed seven possible metal ions that might form pharmaceutically acceptable salts. In July 1989, after publication of these examples, they filed another patent application directed to the calcium salt of one of the two enantiomers of the racemate mixture. European patents were granted, and in the UK they were extended beyond their 20-year term by grant of a Supplementary Protection Certificate (see our review article later in this issue) lasting until 2011. Ranbaxy and Arrow, their co-claimants, filed in the UK for revocation of the later patent and Ranbaxy requested a declaration of non-infringement of the earlier patent.

On a problem-solution approach, the EPO Board of Appeal found the selection of the calcium salt and the particular enantiomer to be inventive. The UK Patents Court found otherwise, expressing preference for the historical English approach in Windsurfing v. Tabur Marine [1985] RPC 59 (CA)) (the Windsurfer analysis) over the EPO’s problem-solution approach. The judgement is of interest in comparing and contrasting the working of the two rival tests for obviousness, at a time when the UK test for obviousness is under review.

An EPO Board of Appeal in this case had been persuaded, during prosecution, to reverse an obviousness rejection on the basis that the selection of calcium from among previously described pharmaceutical metal salts (potassium, sodium, calcium, iron, aluminium, magnesium and zinc), together with selection of one of the two enantiomers from the racemic mixture, formed an inventive selection because this combination was said to improve the handling properties of the solid salt (particularly its hygroscopicity and solubility). But it seems that the patentee had pulled the wool over the eyes of the Board.

First, according to Mr Justice Pumfrey, the senior English Patents Court judge, there was no inventiveness in resolving the racemate into its enantiomers and selecting a particular enantiomer. This was common general knowledge and a preferred procedure in the industry generally (see below). On the evidence, there was no particular difficulty in performing resolution in this particular case.

Second, there was no inventiveness in selecting a particular salt, and least of all the calcium salt, from among the seven possibilities already disclosed. Once a pharmaceutically active component is isolated, conducting a salt screen is a standard procedure to identify the best salt for administration. Potassium, sodium and calcium salts are the most commonly used. In the judge’s criticism of the Board of Appeal he said. “We find ourselves in the strange position that if the sodium salt had been satisfactory, there would have been no invention in going for the calcium instead, but since it was not, there is an invention.”

So why did the EPO Board of Appeal go so far wrong? One fundamental reason pointed out by the judge is that, in this appeal during prosecution, the EPO heard only the patentee’s argument, which is inherently risky. A second source of error is that the EPO possibly chose the wrong example from the earlier patent document as the closest prior art. The EPO began its analysis from the example of the sodium salt, rather than the free acid along with the description of possible metal ions.

Thirdly, in a finding that strikes at the normal basis of EPO inventive step assessment, the judge found there to be no technical problem to be solved. The sodium salt tended to form a gel, but this was not an objective problem with the prior art, because the tendency was discovered at the same time as the calcium salt was being tested. The judge was critical of permitting the patentee to reformulate the problem on the basis of an advantage discovered after the priority date, or one known before the priority date to the patentee, but not disclosed by him in the patent application. “How can one solve an objective problem that one did not know existed?” It was, indeed, already the case in the UK and at the EPO that after-discovered advantages are unlikely to support a finding of inventiveness (Richardson-Vick’s Inc’s Patent [1995] RPC 568 and T 867/95 RICHARDSON-VICK’S/Cough/cold mixtures).

Pfizer has declared the decision a victory, as the other part of the judgement (not discussed here) held that although the formula claimed by Warner-Lambert in the earlier patent was a formula that denotes the racemate, the claim was not so limited, but extends also to the individual enantiomers, one of which Ranbaxy intended to offer for sale. Thus, the judge held that Ranbaxy’s proposed sale of the enantiomer fell within Warner-Lambert’s claim.

Pfizer is still fighting elsewhere. It is currently fighting a rear-guard action over the enantiomer patent for atorvastatin calcium in Austria, appealing a decision by the Austrian Patent Office in March 2005 to invalidate the patent. Why will the enantiomer patent remain of value after the racemate becomes generic? It is said that the pure atorvastatin enantiomer shows a 10-fold increase in activity over the racemic mixture, without any increased toxicity. This alleged fact did not feature in the UK Patents Court judgement, but is mentioned in relation to ongoing proceedings between the parties over the US patents for the racemate and the enantiomer before the Federal Court of the District of Delaware.

 

Comment

Mr. Justice Pumfrey expresses concern over the methodology used by the EPO Board of Appeal in analysing obviousness, but in the end he concludes that he cannot discern in this case or in others any differences in principle. Any differences that emerge are mere differences in appreciation, and the same result is often reached.

He also compared UK and EPO law on novelty of selection and identified a possible difference. Under English law, unless the later patent states the advantage possessed by the selected class, it is merely an arbitrary selection among things already disclosed and will lack novelty (Hallen v. Brabantia [1991] RPC 195). On the other hand, before the EPO, a newly discovered effect can never add novelty to a narrower class if the narrower class is otherwise old (T 198/84 HOECHST)