May 27 2010
In the U.S., section 2173.05(g) of MPEP defines a functional limitation as an attempt to define something by what it does, rather than by what it is. MPEP dictates that a functional limitation is to be evaluated and considered, just like any other limitation of the claim, for what it fairly conveys to a person of ordinary skill in the pertinent art in the context in which it is used.
Similarly, in Canada, functional limitations are permissible so long as the means by which to achieve the defined function is common general knowledge of the person skilled in the art. Moreover, since the functional language can widen the breadth of the claim, whether the description provides proper support for such claims is an important consideration.
What happens when a functional limitation becomes the crux of the claim? In a recent decision of the Federal Court of Canada, Sanofi-Aventis Canada Inc. v. Ratiopharm Inc. 2010 FC 230, >Justice Michael Phelan held that where a patent contains the promise of a desired result, failure to fulfill that promise is grounds for invalidity.
Canadian Patent No. 2,177,772 (the “‘772 Patent”) teaches pharmaceutical compositions containing Irbesartan as the active ingredient. Irbesartan belongs to a family of drugs known as angiotensin II receptor blockers, used in the treatment of various cardiovascular ailments. The ‘772 Patent was held to be invalid because of its breadth and its unproven utility.
One of the claims at issue claims:
- A pharmaceutical composition comprising, based on weight: (a) from about 20 to about 70% irbesartan or a pharmaceutically acceptable salt thereof, (b) from about 1 to about 70% diluent, (c) from about 2 to about 20% binder; (d) from about 1 to about 10% disintegrant, (e) from about 0.1 to about 5% antiadherent, and (f) from about 0.2 to about 5% lubricant, and, optionally (g) from about 0.2 to about 6% surfactant, and/or (h) up to about 2% coloring agent, wherein a tablet formed from said composition has a dissolution performance such that about 80% or greater of the irbesartan or salt thereof contained in said tablet dissolves within 30 minutes.
A central question in the case was whether the dissolution performance of 80% or greater in 30 minutes is a promise of performance or is a limitation on the formulation, i.e. that only once the formulation reaches the dissolution performance does it fall within the claim.
Justice Phelan interpreted the broad claim of the ‘772 Patent as a promise that the tablet formed from the composition of ingredients will have the stated dissolution performance. Therefore, the dissolution performance is at the crux of what is being claimed.
Justice Phelan also noted because the claims were construed so that the dissolution rate was a limitation, the claim was invalid due to the breadth of what was claimed. Infringement would result “if someone were fortunate enough somehow to find, from the broad ranges claimed, the precise composition that gives the desired dissolution rate” since the claim is to the result, not the process. “The claims cannot be stretched to allow the patentee to monopolize anything that achieves the desired result.” (Free World Trust v. Électro Santé Inc., 2000 SCC 66,  2 S.C.R. 1024).
Obviousness was also a “significant problem” for the functional claim. The court held that, as the “patentably distinct” advantage was the capacity to manufacture tablets with a preferred dissolution rate, that advantage was “obvious to try”.
The decision is consonant with long-standing Canadian jurisprudence that allows for functional claim language only to the extent that the full scope of the invention may be practiced without undue burden or the need to exercise inventive ingenuity. The skilled person should not be required to do experimental work in order to discover how the invention may be made operative. “The patentee is not to tell a man to make an experiment but to tell him how to do the thing.” (Rice v. Christiani & Nielsen  Ex.C.R. 111 at p. 9; rev’d on other grounds). On the Court’s construction of the claims, the ‘772 patent promised a formulation with a preferred dissolution but did not give a factual basis or sound line of reasoning to a skilled person in terms of which element and in which proportions. Expert evidence proffered on behalf of both parties suggested that testing and experimentation would be necessary in order to come to the promised result.
As such, the ‘772 Patent was invalidated on the basis of inutility, overly broad claims, lack of sound prediction, failure to provide sufficient disclosure to achieve its promise, as well as for being “obvious to try”.
This case is instructive for those involved in prosecuting or opinionating on chemical/pharma patents in Canada. Many Canadian patents and applications express the invention in functional terms. These should be scrutinized carefully to make sure that the functional terms are enabled by the disclosure, and are not merely “obvious to try”.
This article is for information purposes only and does not constitute legal or professional advice.
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Tags: David J. Heller