In several recent decisions of the Federal Court of Canada, the requirements for what constitutes sufficient disclosure of the invention claimed in a Canadian patent appear to have been expanding, particularly in relation to selection patents. How­­­ever, the Federal Court of Appeal decision delivered on March 20, 2008 in the case of Pfizer v. Ranbaxy [2008 FCA 108] clarifies for Canadian patentees and practitioners the proper scope and extent of the disclosure requirement pursuant to subsection 27(3) of the Patent Act.

In this case, Pfizer sought an Order prohibiting the issuance of a Notice of Compliance to Ranbaxy with respect to atorvastatin calcium (LIPITOR®) until after the expiration of Canadian patent no. 2,021,546. The '546 patent claims a selection of the large class of cholesterol-lowering compounds that is described and claimed in earlier Canadian patent no. 1,268,768.

The Federal Court had dismissed Pfizer's application [2007 FC 91], and held the '546 patent to be invalid on the basis that it promised a tenfold increase in the activity of atorvastatin calcium vis-à-vis a racemic mixture of atorvastatin and its enantiomer, but that the data (both data referred to in the patent and other available data) did not substantiate this promise. The Applications Judge thus concluded that the disclosure of the '546 patent did not accurately describe the advantages of the claimed selection.

The Court of Appeal reversed the decision, holding that the Appli­cations Judge had erred both in: (1) construing the patent as promising a ten-fold increase in clinical acti­vity; and (2) focusing his subsection 27(3) analysis on whether the data substantiates the promise made by the patent. The Court found that the section 27(3) analysis is properly "concerned with the sufficiency of the disclosure, not the sufficiency of the data underlying the invention" and that, by interpreting the disclosure requirement of subsection 27(3) as requiring that a patentee "back up his invention by data," the Applications Judge had confused the disclosure requirements of subsection 27(3) with the utility, novelty, non-obviousness (and truthfulness) requirements provided for elsewhere in the Patent Act.

In relation to construction of the patent, the Court found that the data referred to in the '546 patent was merely illustrative of the in vitro activity of the claimed selection, and that one of ordinary skill in the art would not read the patent as promising a ten-fold increase in activity in vivo. In relation to the disclosure requirement, the Court held as follows:

Only two questions are relevant for the purpose of subsection 27(3) of the Act. What is the invention? How does it work?: see Consolboard v. MacMillan Bloedel, [1981] 1 S.C.R. 504 at 520. In the case of selection patents, answering the question "What is the invention?" involves disclosing the advantages conferred by the selection. If the patent specification (disclosure and claims) answers these questions, the inventor has held his part of the bargain. In the case at bar, the 546 patent answers each of these questions.

What is the invention? The invention consists of having identified an enantiomer, and in particular the calcium salt of that enantiomer, that is better at inhibiting the biosynthesis of cholesterol than would be expected, given the common knowledge and prior art at the time of application for the patent.

How does it work? The 546 patent sets out the methods for producing the compounds covered by the patent.

Accordingly, the Court of Appeal has in this decision confirmed that, while subsection 27(3) of the Patent Act does require the patentee to "correctly and fully" describe his invention, the provision "is concerned with ensuring that the patentee provide the information needed by the person skilled in the art to use the invention as successfully as the patentee." So long as the person skilled in the art understands the answer to the two questions "What is the invention?" and "How does it work?," the disclosure in the patent is sufficient, independent of the data contained therein.