The Canadian Intellectual Property Office (CIPO) has, in the past, objected to some forms of therapeutic "use" claims on the grounds that the claims are, in effect, claims to methods of treatment, and as such, ineligible subject matter. In two recent decisions, the Patent Appeal Board (PAB) found in favour of the applicants, thereby expanding the ambit of "use" claims available in Canada reciting dosage regimens.
In Commissioner's Decision #1555, the PAB concluded that the recital of the use of a dosage regimen that involves dosing based on a patient's body surface area does not amount to a claim to a method of treatment.
In Commissioner's Decision #1561, the PAB determined that claiming the use of a dosage regimen where the dose is recited in units per patient weight does not thereby recast the subject matter of the claim as a method of medical treatment. The PAB similarly concluded that the recital of an indeterminate duration of treatment did not thereby convert the "use" claim to a method of treatment claim.
As recently as 2016, CIPO frequently granted medical "use" claims reciting various forms of dosage regimen. One example is Canadian Patent No. 2,443,555, issued July 19, 2016, in which claim 1 is as follows:
1. Use of a recombinant N-acetylgalactosamine-4-sulfatase to prepare a medicament in a parenteral-infusion administrable form, at a dose of at least 1 mg/kg up to 2 mg/kg or at least 50 units/kg up to 100 units/kg weekly to a human subject with a disease caused all or in part by a deficiency in N-acetylgalactosamine-4-sulfatase activity, wherein the medicament is for use over a period of between about 2 to 4 hours.
However, in the face of challenging jurisprudence on the issue, CIPO changed course and adopted a practice of objecting to "use" claims that recited virtually any degree of variability in a dosage regimen, on the basis that the adoption of a particular dosage regimen from within the claimed range of possibilities required the exercise of professional skill by a medical professional - and therefore encompassed patent ineligible methods of treatment. This approach was reflected in a Patent Notice published by CIPO in 2015.
In 2020, in response to jurisprudence that took issue with the approach CIPO had been taking to subject matter eligibility, CIPO issued an updated Practice Notice that acknowledged that a dosage range or regimen does not necessarily require the professional skill of a medical practitioner:
"It is noted that in cases where at least one of the essential elements of the actual invention limits the claimed use to a dosage, a range of potential dosages that a patient may receive, and/or a dosage regimen, regardless of whether these are fixed and/or cover a range, this fact alone is not determinative of whether the claim is patentable subject-matter. It is also necessary to consider whether the exercise of professional skill and judgment of a medical professional is part of the actual invention. For example, professional skill and judgment may be involved if a medical professional is expected to monitor or make adjustments to the treatment, or make a selection of a dosage from a claimed range (i.e., in cases where not all dosages in the range will work for all subjects within the treatment group). In such cases, the subject-matter defined by the claim would encompass a method of medical treatment and would not be patentable subject-matter."
The 2020 Practice Notice therefore admitted the prospect of claiming dosage regimens that recite a dosage range, in some circumstances. The 2020 Practice Notice did not comment on dosing regimens that specify the dose in units that depend on a characteristic of the patient.
Recent PAB decisions
In CD #1561, dated March 17, 2021, the patent application under consideration by the PAB included claims directed to the use of an antibody that involved a specific pattern of dosing, recited in Claim 1 as: "use in dosage forms comprising an initial dose of 8mg/kg; and a plurality of subsequent doses in an amount that is 6mg/kg, wherein the doses are separated in time from each other by three weeks."
In a Final Action, as summarized in the PAB decision, the application was rejected on the basis that the recited dosage regimen would require the exercise of a physician's skill and judgement for a number of reasons:
"First, the description indicates that determining the appropriate dose is at the discretion of the physician and depends on patient-specific factors such as the severity and course of the disease and the patient's clinical and treatment history. Second, a physician would need to exercise their skill and judgment in order to determine how many subsequent doses should be used. Third, the dosage is not fixed because it is based on the weight of the patient, which is variable, and would need to be calculated to practice the claimed invention."
The PAB evaluated each of these three reasons, and concluded that none could be sustained. With respect to the first reason, the PAB agreed that it would be inappropriate to evaluate the "use" claims under review by considering and applying statements from the description that pertained to a different invention (i.e. the description of a method of treatment). With respect to the second reason, the PAB indicated that the decision to stop treatment was outside the scope of the claims, so that the claims did not require the exercise of skill and judgment in order to determine how many subsequent doses should be used. Finally, with respect to the third reason, the PAB agreed that weighing a patient does not invoke a requirement for professional expertise, and the expression of a dose in mg/kg is not, on its own, determinative that skill and judgment is required merely because, in practice, the dose would have to be calculated for a patient based on their weight.
The PAB expressed the rationale for its decision as follows:
"There is no evidence contradicting that the doses in these claims are fixed at 8mg/kg and 6mg/kg, or that the physician would need to make adjustments or select a different dose. Likewise, there is no indication on the record that changes in the patient's weight would be expected or that monitoring of any kind, including the monitoring of a patient's weight, would be required. Based on the record as it stands, our view is that the doses are fixed and the calculation to convert each dose from mg/kg to a specific dose based on a patient's weight would not require the skill and judgment of a medical professional."
CD #1561 is consistent with earlier CD #1555, dated January 1, 2021. CD #1555 considered claims that recited a therapeutic use in which an antibody was to be administered "for at least 1 week in a daily dose of 10μg to 80μg per square meter patient body surface area and wherein the daily dose is for administration over at least 6h." In recognizing the eligibility of the claimed subject matter, the PAB concluded that:
"The evidence in this case indicates that any dosage falling within the claimed range would be appropriate for all those to whom it is administered and merely converting to a specific dose based on a patient's body surface area does not require skill and judgment...[and] there is no evidence that a physician requires any skill and judgment to determine a patient's body surface area …[and therefore] the skilled person would consider that no skill and judgment is associated with calculating the daily dose to administer based on the dosage and the patient's body surface area".
Commissioner's Decisions #1555 and #1561 are promising developments, as they indicate a return to the availability of at least some "use" claims that recite patient-specific dosage regimens.
 Amgen Research (Munich) GmbH (Re), 2021 CACP 2 ("CD #1555"). The successful Applicant was represented by Gowling WLG.
 Genentech, Inc. (Re), 2021 CACP 8 ("CD #1561"). The successful Applicant was represented by Gowling WLG.
 Revised Examination Practice Respecting Medical Uses – PN 2015-01.
 Yves Choueifaty v Attorney General of Canada, 2020 FC 837.
 "Patentable Subject-Matter under the Patent Act".
 CD #1561, supra, at para. 27.
 CD #1561, supra, at para. 37.
 CD #1555, supra, at para. 29.