Australian High Court rule on obviousness: the Rosuvastatin (CRESTOR) decision

Why is the decision important?

The decision highlights that the Courts are still grappling with how to correctly interpret provisions of the inventive step requirement under our Patents Act. However, the decision raises two key points:

• With regard to selecting a single prior art document from all available prior art documents that were available to the person skilled in the art (PSA), an invention will still be found to be obvious in light of a single prior art document irrespective of whether another prior art document suggests an alternative candidate which is also promising
• Information in the body of the specification which does not form part of the common general knowledge (CGK) cannot be used to provide a “starting point” for an assessment of obviousness. This was the reasoning of the Full Federal Court which was left unchanged by the High Court.

The decision is also a rare example of a patent being found invalid for lack of inventive step. The wording of the inventive step provisions under the Australian Patents Act (see below), requiring a prior art document to have been “ascertained, understood and regarded as relevant” coupled with the reliance on expert evidence to establish common general knowledge in the art, has typically made it difficult for a challenger to succeed in invalidating a patent for lack of inventive step whether through the post-acceptance opposition process or through the courts.

Background

The patent at issue concerned AstraZeneca’s Australian Patent No. 200023051 which claims a method of treating high cholesterol by administration of a low dose of 5-10 mg of rosuvastatin (CRESTOR). The invention was said to be an advance over the prior art in so far as the low dose, which was delivered once daily, still provided the required efficacy while reducing the risk of adverse side effects It also avoided the need for titration of doses requiring patient supervision and management as required of other prior art statins.

AstraZeneca claimed that the supply of rosuvastatin by various generic companies was an infringement of the claims of the Australian patent.

Inventive step provision

According to s7(2) the Australian Patents Act, a claimed invention is deemed to involve an inventive step unless it would have been obvious to a person skilled in the art (PSA) in light of the common general knowledge (CGK), whether that knowledge is considered separately or together with a single piece of prior art.

Unlike the provisions for inventive step in other countries which merely necessitate that the invention is considered to involve an inventive step if it is not obvious to the PSA having regard to the prior art, the Australian provision explicitly separates concepts of common general knowledge and prior art information. Moreover, the version of this provision in existence at the time of the hearing also required that the PSA could have been reasonably expected to have ascertained, understood and regarded the prior art information as relevant.

Selection of a single prior art document

AstraZeneca argued that lack of inventive step should not be found under circumstances where there is prior art information suggesting more than one relevant approach for solving the problem addressed by the invention. However, according to the Court the test was clear, where there are multiple pieces of prior art available and capable of being regarded as relevant, each needs to be considered separately.

If the invention is obvious in light of the CGK together with a single piece of prior art then the patent is invalid on the ground of lack of inventive step. It is irrelevant whether other prior art documents might suggest an alternative course which is also considered to be relevant.

Another argument put forward by AstraZeneca was that in the process of ascertaining a single piece of prior art information, s7(2) precludes the use of unrelated documents not forming part of the CGK. In other words, documents that were not considered as forming part of the common general knowledge could not reasonably be expected to be ascertained, understood and regarded as relevant by the PSA. This argument was rejected by the Court.

The Court accepted that the PSA might well be required to sift through many documents (expert testimony indicated as many as 4,500 documents identified in an initial search) in order to find documents considered to be relevant, however nothing in the Act precluded the PSA from using combinations of unrelated documents (whether or not they form part of the CGK) to assess the relevance of a particular prior art document.

The High Court effectively confirmed the Full Federal Court finding that invention claimed in the Australian patent lacked inventive step in light of the CGK considered separately with either of two prior art documents. One was a patent document which described a compound which corresponded to rosuvastatin but did not specifically mention it by name and disclosed a broad dosage range between 0.5 and 200 mg/day, preferably between 0.5 and 50 mg/day. The other document was a journal article describing the potency of a particular compound, designated S-4522 which corresponded to rosuvastatin but again not mentioned by name.

The Court applied the approach to obviousness set out in previous case law and found that the PSA would have been directly led as a matter of course to try rosuvastatin in the expectation that it might well be an efficacious treatment. The claimed dosage range was consistent with the starting dose which would be trialled in a clinical trial setting and thus did not carry any inventive weight.

It should be noted that at the relevant time, s7(2) of the Act precluded combining of information in separate publications for the purpose of assessing obviousness. Amendments introduced into the Act in 2002 amended the provision to allow for prior art documents to be combined provided that the PSA would treat them as a single source of information.

Starting point for obviousness

The Courts finding above meant that it was not necessary to consider the issue of “starting point”. The primary judge at first instance incorrectly held that when assessing obviousness it is necessary to determine the nature of the claimed invention and the inventive step as described in the specification and then assess that inventiveness by reference to the CGK and prior art information. This issue was important because it determined whether rouvastatin itself should be the starting point for an inventive step determination.

The fact that this argument was overturned by the Full Federal Court and left unchanged by the High Court is good news for patent applicants. Information in the body of a patent specification which is not part of the CGK as determined in the present case cannot be used to determine obviousness of the claimed invention.

1. Olin Mathieson Chemical Corporation v Biorex Laboratories Ltd [1970] RPC 157 at 187-188