Canada: Pharma In Brief - Canada: Federal Court Dismisses Prohibition Application For Drospirenone [YASMIN®] Due To Non-Infringing Process

Case: Bayer Inc. v. Cobalt Pharmaceuticals Company
Drug: Drospirenone (YASMIN®)
Nature of case: Prohibition application pursuant to PM(NOC) Regulations
Successful party: Cobalt Pharmaceuticals Company and Cobalt Pharmaceuticals Inc.
Date of decision: May 29, 2013


Bayer Inc. and Bayer Pharma Aktiengesellschaft ("Bayer") brought an application pursuant to section 6 of the Patented Medicines (Notice of Compliance) Regulations for an order prohibiting the Minister of Health from issuing a Notice of Compliance to Cobalt Pharmaceuticals Company and Cobalt Pharmaceuticals Inc. ("Cobalt") in respect of tablets containing drospirenone (sold under the brand name YASMIN®) until the expiry of Canadian Patent No. 2,261,137 (the "'137 Patent").  YASMIN® is an oral contraceptive.

The court was satisfied that Cobalt's non-infringement allegation was justified and dismissed Bayer's prohibition application. The only claim at issue was claim 13, which the court construed as claiming a drospirenone product made by the three-step process set out in the patent, an essential element of which is oxidation in the presence of a ruthenium salt.  The court found that as this essential element would not be used in Cobalt's process for making its generic version of drospirenone, Cobalt's allegation of non-infringement was justified. The court found it unnecessary to consider Cobalt's allegation of invalidity for obviousness.

The '137 Patent

The '137 Patent is entitled "Process for Producing Drospirenone" and relates to a new process for making drospirenone, which is said to be more selective, ecological and simpler to execute than the prior art. The patent sets out a process consisting of three steps: (1) hydrogenation; (2) oxidation through the use of ruthenium salts; and (3) dehydration.

Claims construction

Claim 13 was the only claim in issue.  It claims a product "prepared according to the process of claim 12, wherein the product comprises drospirenone and less than 0.2%" of the two contaminants identified in claim 12. The process of claim 12 includes the three-step process set out in the '137 Patent: (1) hydrogenation; (2) oxidation; and (3) dehydration.  The second step, oxidation, is described in the '137 Patent as being a "key reaction."

Bayer submitted that claim 13 is a pure product claim and should be construed without a reference to the words "prepared according to the process of Claim 12."  Bayer made two arguments in support of its construction: (1) the Supreme Court's decision in Hoffman-LaRoche & Co. v. Commissioner of Patents, [1955] S.C.R. 414 [Hoffman-LaRoche] stands for the proposition that product-by-process claims should be read as hypothetical claims for the product alone; and (2) the interpretation proposed by Bayer conforms with how a person skilled in the art would construe claim 13.  The court rejected both of these submissions.

The court held that Hoffman-LaRoche does not establish a rule requiring that all product-by-process claims be read as if there was no reference to the process within the claims. Rather, it tells us that a new patent cannot be obtained for a known compound, even if a new process has been discovered for making it. Therefore, the court held that in considering whether Bayer would be entitled to a patent for the drospirenone product made by its new process, it would have to consider whether the product (regardless of how it was made) was new. This was an issue of invalidity, not claims construction. In the court's view, product-by-process claims should not always be read without reference to the specified process.

The court also held that a person skilled in the art would not interpret claim 13 to be a pure product claim. Bayer argued that a skilled person would read claim 13 as a claim for the purer form of drospirenone, regardless of how it was made. The court rejected this argument, noting that while claim 13 does make reference to certain impurities, nothing in the disclosure of the '137 Patent suggested that this purity profile was an object of the invention, nor was there any evidence that the previously known drospirenone product was impure. Most importantly, the court held that claim 13 "clearly and expressly" incorporates the process described in claim 12.

Bayer argued in the alternative that if claim 13 was construed as containing the process of claim 12, then the process of claim 12 should not be read as requiring oxidation in the presence of a ruthenium salt as an essential element.  Rather, any metal salt – not necessarily ruthenium – would be included. The court rejected this argument. The court held that the only salts mentioned in the '137 Patent (both in the specification and the claims) as being possible in the oxidation step of the process were ruthenium salts. Based on a reading of the '137 Patent as a whole, the court found that the presence of a ruthenium salt at the oxidation stage was an essential element of the invention.


Cobalt's Notice of Allegation stated that its product would not infringe for three reasons:  (1) it would not yield two intermediate compounds described in the '137 Patent; (2) it would not use the three-step process provided in the '137 Patent; and (3) it would not employ a ruthenium salt as an oxidizing agent. The court held that in light of its conclusion that claim 13 incorporates the process for making drospirenone set out in the '137 Patent, which includes the key oxidation reaction using a ruthenium salt, Bayer failed to show that Cobalt's allegation of non-infringement was not justified.  As such, the court dismissed Bayer's prohibition application.

Link to decision

Bayer Inc. v. Cobalt Pharmaceuticals Company, 2013 FC 573.

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