In Canada, claims to methods of medical treatment are considered to fall outside the defi nition of invention according to section 2 of the Patent Act and a decision of the Supreme Court of Canada.1

Claims that provide a practical therapeutic benefi t to a subject, even if the benefi t is not its primary or intended purpose, are considered methods of medical treatment in Canada, and therefore not patentable. Also, methods that include a surgical step on a human or animal body will not be allowed, even if the effect of the surgery is not therapeutic.  

Fortunately, the prohibition against methods of medical treatment does not include methods of diagnosing a disease or a medical condition, whether practised in vivo or in vitro, or methods of treating an animal to derive an economic benefi t. Moreover, methods directed at achieving a cosmetic result or directed to certain natural conditions, such as aging, pregnancy, baldness and wrinkles, may be patentable as such conditions are not considered pathological.2 Where appropriate, terms such as “cosmetic,” “diagnostic” or “non-medical” can be used to render a claim acceptable, provided the claim can reasonably be understood to be directed to a non-medical method that does not produce a practical therapeutic effect.

In addition, methods of medical treatment claims may be converted to “use” or “composition” claims in alternative formats.3,4 Nonetheless, care must be taken in drafting. Use claims that, for example, recite administration of a drug to treat a disease in active terms, such as “administering a drug,” may be equated to a method of medical treatment and therefore considered unpatentable.  

A problem may also arise when use or composition claims for a pharmaceutical specify a dosage regimen, such as dosage ranges (e.g., 50 to 300 units)5 and dosages expressed on a weight basis or plasma concentration in a patient (e.g., 13 to 15 mg/kg/day),6 because such claims may be considered to fall within the purview of a medical professional. The Federal Court recently held that claims directed to an optimal dosage regime (e.g., slow titration of the pharmaceutical) were not patentable.7

However, dosage forms, or pharmaceutical packages or kits that may physically embody a dosage regime or prescribed dosage amount, may be considered patentable subject matter. Accordingly, a claim directed to a fi xed dosage has been deemed allowable (e.g., a claim to a 1.0 mg tablet).9,10

The distinction between dosage claims that are patentable and those that are not, seems to depend on whether the claims are directed at a vendible product having economic value in trade, industry and commerce, based on the rationale that physicians should not be prevented or restricted by patented monopolies from applying their best skill and judgment in treatment decisions. A claim for a vendible product may therefore be patentable as it is distinguishable from the work of a physician, which requires the exercise of specialized skill.11,12 Thus, claims that do not seek to limit the range within which physicians must exercise their professional skill and judgement have been held patentable.13

Therefore, if required, claims may be directed to a unit dosage form. On the other hand, it is advisable to avoid claims directed to dosing schedules and regimes specifying how a pharmaceutical agent should be used.  

In Europe, there is an explicit statutory prohibition excluding methods of medical treatment from being patentable.14 As in Canada, this applies to medical treatment of humans or animals by surgery or therapy. However, contrary to Canadian practice, diagnostic methods are also not patentable in Europe.  

Europe does permit claims to the use of a substance or composition in a method of medical treatment.15 The Enlarged Board of Appeal recently held that the use of a known substance or composition for a subsequent, different method of medical treatment may be patentable in the form of a purpose-limited product claim having the general format: “Substance X for use in treating disease B.”16 In so deciding, the Enlarged Board also held that so-called “Swiss-type” claims (e.g., claims in the format: “Use of compound X in the manufacture of a medicament for the treatment of disease B”) are no longer acceptable.  

The Enlarged Board further held that a specifi c dosage regime (e.g., once per day prior to sleep) for a drug already known to treat a certain disease may be patentable because subsequent medical uses under European law are not restricted to the treatment of a different disease but include “any specifi c use,” which could, for example, be a new and inventive dosage regime of the pharmaceutical.

In contrast to Canada and Europe, methods of medical treatment are not excluded by the U.S. Patent Act, nor have they been expressly excluded by the courts. Rather, a recent decision upheld the patentability of methods of medical treatment claims in the U.S.17 Thus, surgical techniques and methods of diagnosis or treatment are patentable, provided that novelty and inventive step are met.18 An interesting provision of the U.S. Patent Act, however, makes patents for medical treatment unenforceable against doctors or the medical facilities with which they are associated, at least with respect to surgical and medical procedures;19 this effectively provides the same practical result as that in Canada and Europe.  

It is, therefore, prudent to ensure these various constraints are considered when preparing patent applications that include methods of medical treatment so that appropriate protection may be obtained when fi ling in various countries.