Canada: Ethinylestradiol/Drospirenone Formulation Patent Valid And Infringed

Last Updated: October 21 2016
Article by Scott Beeser

On September 7, 2016, Justice Fothergill released his public Reasons and Judgement in consolidated patent infringement/impeachment actions brought by Bayer against Apotex and Cobalt in relation to their various drospirenone/ethinylestradiol products.The patent at issue, Canadian Patent No. 2,382,426, relates to an oral formulation comprising ethinylestradiol and drospirenone particles having a specific dissolution profile. The only asserted independent claim reads:

31. A pharmaceutical composition comprising:

from about 2 mg to about 4 mg of drospirenone particles, wherein the drospirenone is in a form, which when provided in a tablet containing 3 mg of drospirenone, has a dissolution such that at least 70% of said drospirenone is dissolved in 900 ml of water at 37° C. (±0.5° C) within 30 minutes, as determined by USP XXIII Paddle Method using a USP dissolution test apparatus 2 at a stirring rate of 50 rpm, including 6 covered glass vessels and 6 paddles;

about 0.01 mg to about 0.05 mg of 17α-ethinylestradiol; and one or more pharmaceutically acceptable carriers; the composition being in an oral dose form, and the composition being effective for oral contraception in a human female.

Previous proceedings

This is not the first time that the Court has considered the 426 Patent. In a previous prohibition application involving Cobalt under the PM(NOC) Regulations, Justice Hughes rejected Cobalt's allegation that the relevant claim was limited to micronized drospirenone particles. Justice Hughes also rejected all of Cobalt's allegations of invalidity and accordingly granted Bayer's prohibition application in respect of the 426 Patent. Cobalt's appeal of Justice Hughes Judgment in respect of the 426 Patent was subsequently dismissed by the Court of Appeal, which held that the claim covered all drospirenone particles, micronized or not, that met the claimed dissolution criteria.

In a separate prohibition application under the PM(NOC) Regulations against Apotex, Justice Hughes concluded that while Apotex' allegations of invalidity were not justified, based on his construction that drospirenone praticles do not include Bayer had failed to demonstrate that Apotex's allegation of non-infringement was not justified.Justice Hughes accordingly dismissed Bayer's prohibition application in respect against Apotex.

Stare Decisis

In affirming Justice Hughes in the Cobalt PM(NOC) proceedings, the Court of Appeal concluded that Justice Hughes had not erred in his construction of the relevant claim. Before Justice Fothergill the parties raised the issue of whether this construction was binding given that the construction, while a question of law, is heavily dependent on expert evidence. Justice Fothergill held that he was bound to follow the Court of Appeal's construction, inventive concept, and promise of the patent, unless a party provides a good reason not to:

[53] To the extent that this Court may have discretion to follow or depart from the  previous construction adopted in the NOC proceedings, I consider the Federal Court of Appeal's prior construction to be prima facie binding, but acknowledge that it may be revisited if warranted by the evidence. In other words, I will adhere to the construction given to the '426 patent by Justice Hughes and by the Federal Court of Appeal unless a party provides good reason not to. The same holds true when defining the "inventive concept" of the patent and determining the "promise" of the patent, both of which are aspects of claim construction and are therefore questions of law (Sanofi-Synthelabo Canada Inc v Apotex Inc, 2008 SCC 61 at para 67 [Sanofi-Synthelabo]; Weatherford Canada Ltd v Corlac Inc, 2011 FCA 228 at para 24, leave to appeal to SCC refused [Weatherford]; Astrazeneca Canada Inc v Mylan Pharmaceuticals ULC, 2011 FC 1023 at para 87, aff'd on other grounds 2012 FCA 109 [Astrazeneca Canada]).

In application, Justice Fothergill held that was there were no good reasons to depart from the Court of Appeal's previous construction or determination of the inventive concept or promise of the relevant claims. With respect to anticipation, Justice Fothergill held that several phase III clinical trial conducted prior to claim date wherein study subjects had not signed a non-disclosure agreement, was not enabling disclosure. While it was possible that one or more tablets may have found their way in to the hands of the public, this would not enable the skilled person to discover and reverse-engineer the invention without inventive insight. Alternatively, if the distribution of tablets to patients in the phase III trials was enabling, this disclosure fell within the common law experimental use exception.

Justice Fothergill also rejected the other grounds of invalidity:

[188] Based on the preceding analysis, I find claims 31, 48 and 49 of the '426 patent are not invalid based on the asserted grounds of: (i) obviousness; (ii) anticipation; (iii) overbreadth; (iv) insufficiency or ambiguity of the specification; or (v) inutility

Apotex non-infringement – "particles"

Apotex asserted non-infringement on the basis that its tablets did not contain drospirenone particles, but instead contained a "molecular dispersion" that is not in the form of particles. On the basis of substantial competing analytical testing adduced by the parties, Justice Fothergill concluded that at least 90% of the drospirenone in Apotex' tablets is present in the form of particles, such that Bayer had discharged its burden of demonstrating infringement.

Cobalt non-infringement  – admission in pleadings

Cobalt's Statement of Defence and Counterclaim stated:

The Cobalt Product is made by dissolving drospirenone into solution and then spraying this solution onto inert carrier particles. The drospirenone particles that crystallize out once the solution is sprayed on in the Cobalt Product may or may not be in the micron range as per the standard sieve measurement ...

Prior to the hearing, Cobalt unsuccessfully tried to amend its pleading to remove the above passage and brought a second motion to amend supported by additional evidence. Since Cobalt later abandoned both its appeal and its second motion to amend, Justice Fothergill concluded that Cobalt's admission that its product contains some drospirenone particles must be taken as final. Although Cobalt was precluded by its admission from arguing that its product does not contain any drospirenone particles, it was allowed to argue that its tablets did not contain at least 2 mg of drospirenone particles as required by the asserted claims. However, based on the extensive analytical testing adduced by both parties, Justice Fothergill held that Bayer had discharged its burden of showing that Cobalt's tablets infringe each of the asserted claims.

A copy of Justice Fothergill's Judgment may be found here.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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