Tension Between Purposive and Textual Considerations in Claim Construction

Bayer Inc v Apotex Inc / drospirenone (NOC) 2014 FC 436 Hughes J
            2,382,426 / drospirenone & ethinylestradiol / YAZ

In Apotex / YAZ Hughes J refused to grant an order prohibiting the Minister from issuing an NOC to Apotex for its version of Bayer’s YAZ birth control pill, holding that infringement was not established. That issue turned primarily on the construction of the particular patent. While no new principles of law were at issue, the decision adopted a fairly strict textual approach to construction, and the case illustrates the difficulty facing patentees in drafting claims which capture the full scope of the inventive concept. Hughes J also addressed issues relating to eligibility for listing on the patent register, as well an experimental use exception to anticipation, which have wider implications. This post provides background and deals with the infringement issue. Note that Hughes J had previously dealt with the 426 patent in Cobalt / YAZ 2013 FC 1061, blogged here and here, though the evidence and many of the issues were different.

It was known in the prior art that a combination of drospirenone and ethinylestradiol could be used as an oral contraceptive, but “what was not known is that the dissolution of the drospirenone in the stomach could be enhanced by providing it . . . in a form such as micronized, so that it would dissolve rapidly” [Cobalt 80]. Claim 1 of the patent claimed a pharmaceutical composition comprising “micronized drospirenone” and Claims 30 and 31 claimed a composition comprising “drospirenone particles,” with Claim 31 also specifying particular a dissolution profile [50]. In Apotex’s product, drospirenone was present in a solid solution, or “molecular dispersion” [65]-[66]. The claim construction question was whether either “micronized drospirenone” or “drospirenone particles,” encompassed a molecular dispersion. The molecular dispersion of Apotex’s product results in almost exactly the same dissolution profile as Bayer’s YAZ, and meets the dissolution parameters specied in Claim 31.

In broad terms this raises a familiar problem of interpretation: how do we resolve a tension between a purposive and textual interpretation of a claim (or a statute or other legal document). The SCC has held that “the guiding principle” of purposive construction is that “where the uage of the specification, upon a reasonable view of it, can be so read as to afford the inventor protection for that which he has actually in good faith invented, the court, as a rule, will endeavour to give effect to that construction” 2004 SCC 34 [35], [1934] SCR 570, 574. As Bayer argued [Cobalt 57], this implies that since the technical contribution is the discovery is that a rapid dissolution is advantageous, the claim should be construed to encompass this contribution. On the other hand, the text is also crucial, and if the patentee has introduced an unnecessary limitation, which excludes the true invention, this is a “self-inflicted wound” 2000 SCC 66 [51]. The question is whether “micronized” and “particle” are textual contraints which over-ride a purposive construction. While the point was not specifically addressed, it appears that the patentee would have been entitled to draft a claim encompassing a molecular dispersion – such a claim would not have been overbroad – and the question is whether it did so.

Hughes J held that “micronized” refers to a particular method of producing small particles and so achieving a high dissolution rate, and does not cover other methods of achieving the same result, such as spraying or molecular dispersion [52]. The more difficult question relates to Claim 31 and the word “particles.” In Cobalt / YAZ Huighes J accepted Bayer’s argument, and construed Claim 31 as “not limited to drospirenone in its micronized form, but to any form in which the rapid dissolution rate stipulated by that claim can be achieved.” [Cobalt 59], [50], [53]. That suggests that it should encompass a molecular dispersion which achieves the same rapid dissolution profile. However, Hughes J pointed to the following passage of the patent [57]:

The composition of the invention may be formulated in any manner known in the pharmaceutical art. In particular, as indicated above, the composition may be formulated by a method comprising providing drospirenone and, if desired, ethinylestradiol in micrnoized form in said unit dosage form, or sprayed from a solution onto particles of an inert carrier in admixture with one or more pharmaceutically acceptable excipients that promote dissolution of the drospirenone and ethinylestradiol so as to promote rapid dissolution of drospirenone and preferably ethinylestradiol and oral administration.

He then held:

[58] The patent describes, therefore, drospirenone that is provided in one of two forms, in micronized form, or drospirenone that has been dissolved in a solvent, sprayed in to an inert carrier particles, then dried. Reference is also made to formulation by “any manner known in the pharmaceutical art” The formulation of those particles (micronized or sprayed on) with other excipients can then proceed in any manner known in the pharmaceutical art.

I must say that this strikes me as reading examples from the description into limitations in the claim. I don’t see how “in particular” limits “any manner known in the pharmaceutical art.”

He then concluded that

[59] No mention is made of a process whereby drospirenone is dissolved into a matrix [redacted], then mixed in with the other ingredients. In such a process drospirenone is no longer a “particle” or even sprayed onto a “particle”, it is in solution.

This seems to be a purely textual point that a molecule in a solid solution is not a “particle.” (From the context, “solution” means a solid solution, not a liquid solution.) I am not sure that this textual interpretation of “particle” is so compelling as to override the purposive point that Hughes J found convincing in Cobalt / YAZ, but it strikes me rather as the kind of “meticulous verbal analysis” referred to in Catnic [1982] RPC 183, 244 (HL). In any event, it does illustrate the great difficulty facing patent drafters in trying to draft claims language that encompasses all possible ways of implementing the inventive concept.