This piece was first published as an article in AIPLA’s Chemical Patent

Double patenting is prohibited in Canada. The prohibition against double patenting is intended to prevent the issuance of more than one patent to an applicant for the same invention or obvious variations of the same invention.

The leading Canadian authority on double patenting is considered to be Whirlpool Corp. v. Camco Inc., 2000 SCC 67; 9 C.P.R. (4th) 129 [hereafter Whirlpool]. In Whirlpool, the Supreme Court of Canada stated that the inventor is only entitled to “a” patent for each invention. The Court reasoned that a patentee who can “evergreen” a single invention through successive patents to the same invention, by way of obvious or uninventive additions, prolongs its monopoly beyond what the public has agreed to pay. Whirpool provides (at para. 65 ff.) that there are two possible bases for a finding of double patenting, namely:

  1. "Same-invention" double patenting, which applies in situations only where the claims under comparison are considered identical (conterminous), i.e. they define and claim the same invention. 
  2. "Obviousness-type" double patenting, which is a more flexible and less literal test that applies in situations where the claims under comparison are not "patentably distinct". 

While the rationale behind the prohibition on double patenting may be sound, there are some practical problems with the implementation of the "one patent for one invention" principle. 

Notably, unlike the USA, Canada does not have terminal disclaimer to remedy double patenting when it occurs. Thus, a first patent should prevent issuance of a second patent having claims to any subject matter that is not patentably distinct (i.e. novel and non-obvious) over the subject matter claimed in the first patent. 

If a first patent or application was published sufficiently before the application for the second patent, then it will simply serve as a piece of prior art and the second patent may be invalid for lack of novelty or obviousness. It is only when the second patent was applied for at a time when the first patent or application cannot serve as prior art that double patenting becomes an issue. Clearly, double patenting should only be a concern where the applications or patents are owned by the same entity.

The Canadian Patent Office sometimes raises double patenting objections where two related applications with overlapping claims are still pending, in which case amendments may be made such that the overlapping subject matter may be claimed in the earlier application (preferred for the earlier claim date) or the later application (for some special reason, such as the presence of working examples), but not in both.

It may also be possible to overcome a double patenting objection during prosecution by abandonment of one of the two cases in question.

Obviousness-type double patenting has to be approached like any other obviousness objection, i.e. by arguing that one set of claims is not obvious in view of the other set or by amendment of one or both sets of claims.

Sometimes, the subject of the later application may qualify as a selection invention. A selection patent is directed to a compound or sub-class of compound that is patentably distinct from the broader genus patent. A proper selection patent will not be invalid for obviousness-type double patenting (Apotex Incv. Sanofi-Synthelabo Canada Inc. (2008) 69 C.P.R. (4th) 251).

However, if the subject matter of a second application is merely an aspect or embodiment of the same invention as a first patent, then the double patenting rejection is proper even if the subject matter of the second application was not specifically claimed in the first patent. For example, in its 2010 decision in Re BASF AG Patent Application No. 2,425,101 82 C.P.R. (4th) 152 [hereafterBASF], the Canadian Patent Appeal Board refused to grant a divisional application directed to medical uses of a protein TNF-BP, in view of the fact that the parent application had issued with claims to the protein TNF-BP per se and the divisional application was directed to medical uses that were disclosed in the parent. The Patent Appeal Board reasoned that there was no inventive ingenuity residing in the inherent medical uses of a previously-claimed product, and thus the claims of the divisional application cannot be considered patentably distinct from the claims of the parent. It did not matter that the patent term for parent and divisional would expire on the same date.

Similar grounds can be used to attack an issued second patent as being invalid for double patenting. For example, in GlaxoSmithKline Inc. et al. v. Apotex Inc. et al.(2003) 27 C.P.R. (4th) 114 [hereafter GSK], the Trial division of the Federal Court of Canada found a divisional application to be invalid for obviousness-type double patenting over the previously granted parent patent. It was argued that there was no “evergreening” in this case, as the parent and the divisional both expired on the same day. However, the Court rejected this argument on the basis that, prior to expiry, there were still two patents extant (i.e. double patenting) and the existence of additional patents would allow the patentee to bring multiple prohibition proceedings under the Patented Medicine (Notice of Compliance) Regulations, which link the patent regime to regulatory approval, and thereby obtain multiple injuctive periods.

It is important to note that, in the BASF and GSK decisions mentioned above, the divisional applications in suit had been filed on a voluntary basis. If the Patent Office forced the filing of a divisional application, the divisional will enjoy a presumption of validity (Consolboard Inc. v. MacMillan Bloedel (Saskatchewan) Ltd. (1981) 56 C.P.R. (2d) 145 (S.C.C.); see also Abbott Laboratories v. Canada (Minister of Health) (2009) 77 C.P.R. (4th) 201 at para. 193 (F.C.), revd in part 85 C.P.R. (4th) 297 (F.C.A.)).

Given the current state of the law on double patenting, we do not recommend filing divisional applications on a voluntary basis in Canada.

It is preferable practice to try to sort out any double patenting problems during prosecution, so as to avoid the possibility of having issued patents attacked for double patenting in court. In this regard, we would generally recommend pursuing the broadest, most important claims in the earlier-filed application, and pursuing narrower or “follow-on” claims in the later-filed application. We would also recommend that, to the extent possible, all of the claims of interest for a given application should be consolidated and presented in a single application, so that the Examiner will have an opportunity to consider whether the claims have unity of invention, and any divisional applications will be filed only under the direction of the Patent Office.

While these issues may require some tailoring of your patent strategy to suit Canadian practice, it is not all bad news, as it is often possible in Canada for an applicant to consolidate all of the desired claims in a single application even after prosecution has begun, which can produce a very economical result. For example, we often deal with cases where granted claims from several US patents can be combined in a single Canadian application. In this regard, unity of invention practice in Canada is similar to that in Europe and the PCT – that is, the claims are considered to have unity of invention if they are so linked as to form a single general inventive concept (this often manifests as a common inventive technical feature) – and thus, it is possible to include different categories of claims in a single application. Also, there are no government fees in Canada for additional claims or multiple dependencies, so the applicant has considerable latitude for developing an optimal claim set for its Canadian applications.