Sigma Pharmaceuticals (Australia) Pty Ltd v Wyeth [2010] FCA 1211

In a decision currently under appeal, the Federal Court has once again highlighted the importance of identifying “the invention” when determining fair basis and inventive step and the limitations of the “problem-solution” approach. The decision also demonstrates the pitfalls of obtaining expert evidence in circumstances where recognition of the problem may form part of the inventive step.

Facts of the case

Australian Patent No. 2003259586 (“the patent”) is the grandchild divisional of Australian Patent Application AU16400/97 (“the grandparent”), which claims priority from US 60/14006 filed on 25 March 1996. Before the priority date, venlafaxine hydrochloride (VH) was a known antidepressant, tablets of which dissolved rapidly after administration leading to a rapid increase in blood plasma levels followed by a decrease in plasma levels over a period of hours until sub-therapeutic plasma levels were obtained after about twelve hours. Plural daily dosing and rapid dissolution of VH were also believed to cause significant nausea and vomiting amongst patients.

Both the grandparent and the patent describe an approach to addressing these side effects which, broadly-speaking, involves extending the duration of release of VH from a medicament so as to provide a single daily dosing form.

The grandparent claimed an encapsulated, extended release formulation containing film-coated spheroids of VH in a cellulose ether matrix. The features of the claimed formulations largely corresponded to the formulations specifically exemplified in the patent that provided a desirable release rate.

On the other hand, the patent claimed a number of methods of medical treatment, not limited to the use of the spheroid technology, but rather defined with reference to the desired outcome ie achieving therapeutic blood plasma level of venlafaxine over a 24 hour period.

Sigma Pharmaceuticals, Alphapharm and Generic Health (the applicants) each threatened to infringe a number of claims of the patent by selling their own TGA approved extended release VH formulations, and sought revocation of the patent on a number of grounds.

The decision

Fair Basis

The applicants asserted that the method claims, defined without reference to the spheroid formulation, were not fairly based on the description of the invention. Wyeth’s evidence, on the other hand, supported the assertion that the spheroid formulation was not an essential feature of the invention but rather just one way of obtaining the desired (and claimed) therapeutic profile and argued for the application of the principle restated in Lockwood1:

When a combination claim states an invention which gives an old result by a new means, the monopoly is limited, at any rate prima facie, to the new means. But when by a new application of principle the inventor has obtained a new result or thing, even when it be done by a combination, he may claim all the alternative means by which the thing or result may be achieved.

Against the “narrow” test for internal fair basis approved in Lockwood1, Jagot J held that the method claims did not “travel beyond” the invention described in the specification - the “embodiments and examples do not confine the method disclosed” - and accordingly a claim to all ways of achieving the desired (and defined) therapeutic profile was held to be fairly based on the description of the invention.

Inventive Step

At [262] Jagot J characterised the applicants’ case as not in perceiving “the true nature of the problem” but rather having focussed narrowly on the problem of finding an extended release, single daily dosing form of venlafaxine hydrochloride.

Unfortunately for the applicants, the expert evidence provided in support of their argument was coloured by knowledge not possessed by the skilled person before the priority date. For example, Dr Marshall’s (expert called by Alphapharm) approach to formulating VH initially involved gathering information from specific texts that were not published until after the priority date. Furthermore, it was established that Dr Marshall was aware from the time of engagement by Alphapharm’s solicitors that the matter related to a Wyeth patent and had assumed that Alphapharm was “seeking to market a similar product”. As stated by Jagot J, Dr Marshall “believe[d] he could successfully produce a once-aday formulation” of VH. This sentiment emerged from the evidence of both Drs rowe (expert called by Sigma) and reece (expert called by Alphapharm). Whilst not nullifying, Jagot J stated that evidence based on knowledge that the invention could be achieved and the use of information not available at the relevant date approached “mere speculation”.

On the other hand, Professor Charman’s evidence in support of Wyeth’s position indicated that the invention resides in “the unexpected finding… that the described plasma profile is efficacious and unexpectedly reduces the level of nausea and incidence of vomiting while surprisingly maintaining efficacy” rather than the specific formulation on which the applicants based their evidence.

In considering the relevant question under section 7(2) of the Patents Act 1990, Jagot J held that the problem-solution approach was not sufficient, of itself, to answer the question of whether the claimed invention was obvious. The evidence in respect of the broader approach to the question suggested that the therapeutic profile (absorption, metabolism, etc) of an extended release formulation of VH could not have been predicted from a knowledge of existing VH immediate release formulations. In fact, even the applicants’ experts acknowledged that the steps taken to arrive at the invention would not have been a matter of routine, and so the claims were held to possess an inventive step.

Other Grounds and Infringement

The applicants also sought revocation on a suite of other grounds that were systematically overcome, leading to the finding that the claims were valid and would be infringed. The Court restrained the activities of the applicants.

Commentary

This decision highlights the importance of correctly identifying the nature of the invention, gathering expert evidence with an appreciation of what the claimed invention is and that the recognition of the problem may form part of the invention. hindsight knowledge that a particular problem had been overcome at the priority date may also adversely undermine the relevance of the evidence.