What is a Method of Medical Treatment?

David Park is a 3L J.D. Candidate at Osgoode Hall Law School, enrolled in Professor David Vaver’s 2021-2022 Intellectual Property Law & Technology Intensive Program. As part of the course requirements, students were asked to write a blog on a topic of their choice.

In Canada, methods of medical treatment are unpatentable subject matter. This prohibition originated from an old provision of the Patent Act (Section 41) interpreted by the Supreme Court of Canada in Tennessee Eastman. The statutory provision has since been repealed but the subject matter prohibition survives as a common law doctrine. The justification for the prohibition is agreeable: fear of patent infringement should not deter medical practitioners from applying their exercise of skill and judgment (see Janssen v Mylan at para 53). However, the scope of the prohibition is less agreeable. To this day, the definition of a “method of medical treatment” remains unclear, especially in the context of pharmaceutical use patents. Phelan J. in Hospira Healthcare v Kennedy Trust admitted that the jurisprudence on this matter “is not entirely consistent” (also see Manson J’s comment at para 195 of Hoffman La Roche).

For example, consider the following two types of claims:

  • “the use of compound X to treat disease Y in a dosage range of A to B mg”
  • “the use of compound X to treat disease Y, at a dosage of A mg”

The first claim is invalid because the dosage range encompasses a choice to be made by a medical practitioner prescribing compound X. The second claim specifies a fixed dosage rather than a range and is therefore patentable. The Federal Court made this distinction in Bayer v Cobalt. There are many problems with this rule. One problem is that this distinction does not serve the primary goal of unimpeded medical practice, even if a claim for a fixed dose can theoretically be infringed by a physician and therefore interfere with physicians’ exercise of skill and judgment. Furthermore, an interesting criticism by Norman Siebrasse is that the distinction is purely formal, as a patentee could simply split a claim with a dosage range into multiple claims with fixed doses. While I agree that courts have fixated too much on form over substance, I am curious about whether a court would treat multiple claims with different doses the same as one claim with a dosage range. Another interesting criticism from Siebrasse is that invalidating a claim for encompassing a physician’s exercise of skill and judgment is difficult to reconcile with the Supreme Court’s decision in Apotex v Wellcome Foundation where a claim for the use of a compound at an “effective amount” was held patentable. Surely, a physician deciding an “effective amount” exercises the same (if not more) skill and judgment required to choose a dosage within a dosage range.  

In a case from this year, Hoffman-La Roche v Sandoz, the common law doctrine became even more convoluted. The Federal Court held that a fixed dose claim, similar to the example above, was unpatentable because the specified dose was “not appropriate for all patients” (partly due to potential adverse effects) and a prescribing physician would need to exercise skill and judgment in deciding whether to prescribe at the claimed dose amount (Manson J at para 204). This illustrates another problem with the earlier distinction, that a claim with a fixed dose would still encompass a choice to be made by a medical practitioner – the choice to prescribe at the fixed dose or at a different one (or not at all).

So, what is the solution to this confused area of law? Could not courts create a common law defence for medical practitioners against patent infringement claims? Obviously, some caveats would be needed. One should be that courts must assess whether an infringement action could deter medical practitioners from their duty of care to patients. But a common law solution may be preferable to waiting indefinitely for legislative change. Currently, patents do not pose a serious threat to medical practice because medical practitioners are not targeted by pharmaceutical patentees which prefer going after the generic companies which directly compete with them.

Courts have already virtually created a common law defence, but a needlessly complex and roundabout one that depends on seemingly arbitrary claim-by-claim rulings on patentability. If the jurisprudence remains as it is or continues to develop along these lines, the public could be deprived of some valuable potentially life-saving inventions.

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