Inevitable result required to demonstrate inherent anticipation
Abbott GMBH & Co. KG v Apotex Pty Ltd (No 2)  FCA 940
The Federal Court has reiterated the requirement that for a prior art teaching to inherently anticipate a claimed invention, the invention claimed must be the inevitable result of following the prior art teaching.
Sibutramine hydrochloride was first described in British Patent No 2098602, however, it was found that the compound was undesirably hygroscopic. The invention described in the patent in suit, AU601167, to Abbott, relates to the monohydrate of that compound, which is not hygroscopic. Sibutramine hydrochloride monohydrate is the active agent in Abbott’s weight loss drug Reductil®. Apotex intended to market its own weight loss drug and Abbott sued for infringement. Apotex cross-claimed for revocation on the grounds that the invention lacked novelty and inventive step, was not for a manner of manufacture and further, that the patent was obtained by false suggestion.
The question of novelty turned on the prior teachings of the British patent, with Apotex alleging that Example 11, which described the preparation of sibutramine hydrochloride, if followed, would lead to the formation of sibutramine hydrochloride monohydrate. Both Abbott and Apotex presented expert evidence in support of their respective positions, with the point of contention being whether the skilled person would read certain steps in Example 11 to be carried out under anhydrous conditions – the presence of water being necessary for the monohydrate to form. Not surprisingly, the experts for each side placed a different interpretation on the teachings of Example 11. Abbott put forward the view that whilst the described procedure did not expressly state as much, the skilled addressee would recognise that anhydrous conditions were required at certain steps. Apotex put forward the proposition that no such limitation was implied. In light of the evidence put forward by both experts, the Court acknowledged that, in the main, the four steps at issue could be read either way, although his Honour did appear to ultimately favour Abbott’s view with regard to one of these steps. Thus, on the issue of construction of Example 11, His Honour stated:
“But the ultimate question is …..whether the document discloses the invention in suit either in terms or by mapping out a path which, if followed, would inevitably lead to the compound the subject of that invention. If the document is reasonably open to two or more interpretations, only one of which would lead to the compound of interest, it will, in my view, be impossible to conclude that following the instruction in the document would inevitably lead to that compound.”
Thus, on the evidence presented, His Honour concluded that the skilled addressee might reasonably have read Example 11 in one of two ways and therefore, the formation of sibutramine hydrochloride monohydrate was not inevitable.
Whilst this was sufficient for the purpose of reaching a conclusion, the Court was also further swayed by work carried out by Apotex in repeating Example 11 of the British patent. While the compound produced in the experiment by Apotex was sibutramine hydrochloride monohydrate, His Honour was of the view that there had been a number of deviations from the path set out by Example 11, and that intermediate materials were obtained which did not appear to be in the form specified in 11. His Honour noted
“If a laboratory preparation is to be held out as proof of the inevitability of a particular result, the process used, and all the indications along the way, should, in my view, correspond, very closely, if not exactly, with every integer of the prior art relied on”.
Apotex also attempted to assert that the invention defined by the claims at issue did not possess an inventive step and presented evidence as to what the skilled person would have done at the priority date when faced with the “hygroscopicity problem”. However, the Court was of the view that the routine steps described were merely “in effect identifying alternatives that would have been worth trying or even obvious to try”, but would not have led the skilled person to follow a path in the expectation that it might well produce the non-hygroscopic compound, and the attack on inventive step therefore failed.
Attempts by Apotex to seek revocation on the basis of lack of manner of manufacture and on the ground that the patent was obtained by false suggestion were also readily dismissed.
Finally, His Honour found Apotex’s defence to infringement “faintly put”. The compound Apotex proposed to make and market was held to be sibutramine hydrochloride monohydrate as claimed, notwithstanding that Abbott’s results from the testing of the samples varied slightly from the theoretical water content.
This decision reiterates the importance of establishing the unequivocal inevitability of the result of a prior art procedure when attempting to assert lack of novelty due to inherent prior teaching. However, whilst Abbott was successful in defending its claims and the Court acknowledged success on the infringement aspect of their case, the victory may ultimately be described as somewhat pyrrhic, as sibutramine hydrochloride monohydrate has subsequently been withdrawn from sale in Australia due to concerns regarding the safety of the drug.