Canada: Methods Of Medical Treatment – A New Twist On An Old Prohibition

Last Updated: November 28 2006

Article by Santosh Chari, © 2006, Blake, Cassels & Graydon LLP

Originally published in Blakes Bulletin on Intellectual Property, November 2006

It has long been established in Canada that claims to methods of medical treatment are not patentable. However, many such claims can often be re-written as "use" or "composition" claims, which have generally been found acceptable. In Axcan Pharma Inc. v. Pharmascience Inc. (Axcan), the Federal Court has cast doubt on the viability of this approach.

Introduction

In Canada, the marketing of a drug requires regulatory approval in the form of a Notice of Compliance (NOC). If someone, such as a generic manufacturer, seeks a further NOC for a patented drug, but is not the patentee or someone authorized under the patentee, the issuance of the NOC will depend upon showing that the manufacture of the drug will not infringe any patents listed on the Patent Register associated with the first NOC. In such cases, the person seeking the NOC may argue non-infringement of the listed patent or patents by showing: (1) that the relevant patents (as listed on the Patent Register) are expired; (2) that its manufacture of the drug will not infringe any listed patents; or (3) that the listed patents are invalid. Such allegations are rebuttable by the patentee by an application to the Federal Court. For further discussion on the Patented Medicines (Notice of Compliance) Regulations and the Canadian government’s recent amendments see Canada Amends Regulations Governing Drug Approval Process in this issue of Blakes Bulletin on Intellectual Property.

Background

The "linkage" of marketing approval for a medicine to the status of its patent protection has resulted in a considerable amount of litigation in Canada. These cases have also provided a fair amount of jurisprudence on issues of the infringement and validity of patents. Axcan is an example of one such case.

Axcan obtained Canadian patent number 1,318,590 (the ’590 patent) on June 1, 1993 based on a patent application filed on November 18, 1987. The ’590 patent is directed to ursodeoxycholic acid, or Ursodiol, which is used in the treatment of primary biliary cirrhosis. The patent is listed on the Patent Register associated with the NOC for the subject drug.

The ’590 patent includes the following single claim directed to a composition containing Ursodiol:

"Pharmaceutical composition for the treatment of primary biliary cirrhosis, characterized in that it includes ursodeoxycholic acid as well as a vehicle and if necessary pharmaceutical excipients, the said composition being processed in a form allowing for the said treatment of primary biliary cirrhosis based on a dose of 13 to 15 mg/kg/day."

Pharmascience, a generic manufacturer, applied for an NOC for its version of Ursodiol alleging non-infringement of the ’590 patent on the basis that the sole claim of the patent was invalid. In particular, Pharmascience alleged that the claim lacked novelty in view of a prior publication and that the claim was invalid for being directed to non-patentable subject matter. On the latter point, Pharmascience alleged that the claim, although reciting a composition, was directed to a method of medical treatment. Axcan applied to the Federal Court for an order prohibiting the issuance of an NOC to Pharmascience and argued against the allegations.

The Axcan Decision

In forming its decision, the Court first construed the claim of the ’590 patent and found that the dosage of 13 to 15 mg/kg/ day was an essential element of the invention. The Court reasoned that the recitation in the claim of a specific dosage range, and the lack of any other claims in the patent supported such conclusion. The Court then addressed the prior art, which included prior knowledge of Ursodiol (which was known as a liver medication since 1957) and the prior publication of a dosage of 10 mg/kg/day of the drug for treating chronic liver diseases. Notwithstanding this, the Court found the claim to be novel for reciting a dosage range outside the teachings of the prior art. The Court also commented that, were it not for the dosage constituting an essential element of the claim, it would have failed for lack of novelty.

The Court then turned to Pharmascience’s allegation that the claim was directed to a method of medical treatment. Citing prior Supreme Court of Canada decisions, the Court first reiterated the prohibition in Canada against patenting methods of medical treatment. The Court pointed out that prior decisions also held that a new use for a known compound, pharmaceutical or otherwise, may comprise patentable subject matter. However, the Court went on to find that the "composition" claim of the ’590 patent comprised a "method of medical treatment" and, therefore, held the claim to be invalid.

In its reasoning, the Court stated that the essential element of a specific dosage regime (i.e., mg/kg/day) recited in the claim requires the intervention of a medical practitioner to prescribe Ursodiol at amounts that vary from one patient to another. As stated by the Court:

"It is up to the physician based on his or her knowledge of the patient’s rate of metabolism and other factors to determine the appropriate daily dosage … There is a distinction between the dosage in a capsule and a dosage range based on the patient’s weight. As I read the claim, the emphasis is on the dosage range, and a dosage range is not a vendable (sic) product."

On finding the sole claim of the ’590 patent to be invalid for claiming non-patentable subject matter, the Court found no reason to prohibit the issuance of an NOC to Pharmascience.

Conclusion

It is common in Canada to claim a new use of a drug or a new composition containing the drug instead of claiming a method of treatment. Quite often, such use or composition claims also recite a dosage of the drug based on the weight of the patient being treated as opposed to pre-set dosage formulations. In light of the comments made by the Court in Axcan, the viability of enforcing such claims may now be questionable.

It should be noted that the issue addressed by the Court was restricted to whether Pharmascience should be prohibited from obtaining an NOC for Ursodiol. The Court’s decision does not have any direct effect on the validity of the ’590 patent. However, the direction taken by the Court in its interpretation of the ’590 claim may have future ramifications.

In view of the Axcan decision, care should be taken when drafting claims to drug compositions or uses to avoid incorporating elements that may be construed as a treatment step.

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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