In a closely-watched patent decision, the High Court has unanimously dismissed AstraZeneca's appeal concerning its low-dose patent for the cholesterol-lowering drug rosuvastatin (AstraZeneca AB v Apotex Pty Ltd [2015] HCA 30).

In doing so, the High Court has adopted a common sense approach to the way in which prior art publications can be used to attack a patent based on lack of inventive step. It held that the invention claimed in AstraZeneca's "low dose patent" was obvious when considered in the light of the common general knowledge, taken together with either of two prior art publications.

The origins of the dispute

The patent in suit (the "low dose patent") related to the single, once-daily oral administration of 5mg to 10mg of rosuvastatin, a drug used in the treatment of high cholesterol (or hypercholesterolemia). Rosuvastatin is marketed by AstraZeneca under the brand name "Crestor".

Both the trial judge, and a special five member bench of the Full Federal Court on appeal, had found that the low dose patent was invalid as it did not involve an inventive step. AstraZeneca was granted special leave to appeal to the High Court.

Question of obviousness

The basis upon which inventive step is assessed is governed by sections 7(2) and 7(3) of the Patents Act 1990. The interpretation and operation of these two provisions was the central issue addressed by the High Court in its judgment.

In essence, section 7(2) provides that an invention involves an inventive step when compared with the prior art base, unless the invention would have been obvious to a relevantly skilled person in light of the common general knowledge at the priority date of the patent. Section 7(3) permits certain documents to be combined with the common general knowledge in limited circumstances.

Does section 7(3) require that each document be considered separately to determine relevance?

AstraZeneca argued that, in determining whether prior art information was relevant for the purposes of section 7(3), each document must be considered separately. It contended that it was impermissible for the person skilled in the art to compare multiple documents that they had ascertained and to select from these the relevant document or documents to be used for answering the question of obviousness under section 7(2).

The High Court emphatically rejected this approach, holding that there is nothing impermissible in such an exercise of selection. Justices Gageler and Keane noted that "[n]othing in s7(3) suggests that the notional skilled addressee may not trawl through multiple documents, discarding the irrelevant and retaining the useful, as part of the ascertainment of relevant information".

It noted that section 7(3) is directed towards the identification of prior art that can be used for the purposes of section 7(2). Section 7(2) is directed to how that information is used. What section 7(2) requires is that, where multiple pieces of prior art are available and capable of being regarded as relevant, each must be considered separately, together with the common general knowledge, to answer the statutory question as to whether the invention is obvious.

The purpose of the requirement in section 7(2) that documents be considered separately is directed at preventing what is called "mosaicing". Mosaicing occurs where select pieces of information from a number of prior publications are assembled such that the mosaic of information reveals what is claimed in the patent. Such an approach is impermissible in relation to patents filed before April 2002 (as the low-dose patent was). However, in the present case, the document under consideration by the High Court was a single document. AstraZeneca had sought to rely on the requirement that documents be considered separately to impugn a single piece of prior art selected from multiple documents on the basis of relevance. AstraZeneca's position on this point was rejected by all five justices of the High Court.

Must each document qualifying as relevant be considered separately under section 7(2)?

In addition, AstraZeneca submitted that not only must each document qualifying as relevant be considered separately, but that each must be considered under section 7(2). None may be discarded. In these circumstances, a person skilled in the art would have had more than one candidate drug to choose from as the prior art documents identified by the expert witnesses as relevant did not relate solely to rosuvastatin. On this basis, AstraZeneca submitted that the claim of obviousness must fail because the expert witnesses did not discuss what they would do in such a situation.

This submission was rejected by the Court based on the expert evidence ‒ the hypothetical question did not arise, as the respondents' experts selected rosuvastatin as the candidate they would proceed with.

The High Court finds the claimed invention was obvious 

The Court accepted that the prior art relied upon by the respondent generic companies would have been regarded as relevant by the hypothetical person skilled in the art based on the expert evidence before the Court. The Court then considered the operation of section 7(2) and whether the invention was obvious to a person skilled in the art armed with the common general knowledge and the relevant prior art. The High Court upheld the decisions of the trial judge and the Full Court that the invention claimed in the patent was obvious, based on the expert evidence that it had before it.

Issues the Court did not address

Having found that the invention claimed in the low dose patent was obvious, the High Court did not consider the other issues agitated.

One of the most interesting of those issues related to the appropriate "starting point" for assessing whether a claimed invention involves an inventive step. The approach to this issue can be a significant determinant of the outcome of an inventive step fight. Using the present case as an example, does one ask:

  • whether it is possible to invent a new method of treating high cholesterol; or, alternatively
  • whether it is possible to invent a new method of treating high cholesterol using rosuvastatin?

In other words, is the use of rosuvastatin a "given"?

As the High Court declined to express any opinion on this issue, the law concerning the appropriate "starting point" when assessing inventive step under the Patents Act 1990 remains as stated by the Full Federal Court in this case (AstraZeneca AB v Apotex Pty Ltd [2014] FCAFC 99): the inventive step must be assessed by reference to the common general knowledge of the person skilled in the art, whether alone or taken together with the relevant prior art information permitted to be considered under section 7(3).

The description of the invention in the patent specification, including any problem that the invention is explicitly or implicitly directed at solving, is not to be considered unless:

  • this formed part of the common general knowledge of the person skilled in the art; or
  • it is information of a kind permitted to be taken into account together with common general knowledge pursuant to section 7(3).

In other words, as Justice Jessup put it in the Full Federal Court in this case, in circumstances where it was held that rosuvastatin did not form part of the common general knowledge and the selection of rosuvastatin was an integer of the invention claimed, the question for determining whether the invention was obvious is: "given a patient suffering from hypercholesterolemia, would the treatment of him or her with rosuvastatin in the claimed doses be obvious?", rather than "given rosuvastatin, would the administration of it at the claimed doses be obvious?".

Under the Patents Act 1952the Full Court's reasoning in Apotex Pty Ltd v Sanofi-Aventis(2009) 82 IPR 416 regarding "starting point" remains the law as it was not formally overruled by the expanded bench of the Full Court in this case (and was not addressed at all by the High Court).

Implications of the High Court's decision

The High Court has adopted a sensible interpretation of the operation of sections 7(2) and 7(3) of the Patents Act 1990 that provides certainty for innovators and generic companies.

The judgment means that AstraZeneca's defence of Crestor has ended in defeat.

There was an interlocutory injunction in place until the final decision at first instance dissolved the injunction. In exchange for the injunction, AstraZeneca gave the usual undertaking as to damages to the generic parties. The generic parties may now make a claim on the undertaking for losses they suffered by reason of their generic products having been kept off the market due to the interlocutory injunction, while the litigation took its course.

The Commonwealth may also seek to make a claim on the undertaking as to damages for the costs it incurred during this period when the generics were prevented from obtaining listing on the Schedule of Pharmaceutical Benefits, as it has done in at least two proceedings currently on foot in the Federal Court (Alphapharm v Wyeth and Apotex Pty Ltd v Sanofi-Aventis).