Since the Supreme Court of Canada decision in Whirlpool Corp. v. Camco Inc., 2000 SCC 67, double-patenting has become a common challenge to patent validity in Canada. The Canadian double-patenting doctrine is similar to the U.S. double-patenting doctrine, but subtle differences between the two can potentially lead to a fatal double-patenting issue for a Canadian patent that would otherwise be easily resolved for its U.S. counterpart under U.S. practice. Similarities and differences between the Canadian and U.S. double-patenting doctrines are discussed in this article and some strategies are identified for potentially mitigating double-patenting risks in Canada.
Contrast between Canadian and U.S. double-patenting laws. The Supreme Court of Canada held in Whirlpool (supra 157-159) that the prohibition against double-patenting has two separate "branches": (1) the "same invention" branch, also known as the "coterminousness" branch; and (2) the "obviousness" branch. The "same invention" branch will invalidate any claim of a pending application or issued patent that is identical in scope to a claim of an earlier-issued patent. This branch is similar to "statutory" or "same invention" double-patenting in the U.S. The "obviousness" branch will invalidate any claim of a pending application or issued patent that is not patentably distinct (novel and non-obvious) from any claim of an earlier issued patent. This branch is similar to the judicially created doctrine of obviousness-type double-patenting in the U.S.
In the U.S., "statutory" ("same invention") double-patenting is fatal, whereas obviousness-type double-patenting can be obviated with a terminal disclaimer. A terminal disclaimer disclaims the non-overlapping term of the later-issued patent and also provides that the later-issued patent will cease to be enforceable if it does not remain commonly owned with the earlier-issued patent. In contrast, Canadian patent law does not provide any equivalent to a U.S. terminal disclaimer. Both "branches" of double-patenting are equally fatal in Canada and no direct procedural remedy exists to cure either branch. Due to this difference, greater care must be taken to avoid "obviousness" double-patenting situations in Canada that may have been dealt with by way of a terminal disclaimer in the U.S. counterpart.
Like the U.S., if a Canadian examiner effectively forces the filing of a divisional application by raising a lack of unity of invention objection (equivalent to U.S. restriction/election requirement), then the claims retained in the parent and the claims divided out are immune from double-patenting attacks based on one another. However, Canadian practice differs from U.S. practice on this point in that the limited immunity provided under Canadian practice is purely based on Canadian case-law (Consolboard Inc. v. Macmillan Bloedel Ltd.,  1 SCR 504), whereas the similar immunity provided under U.S. practice is conferred directly from statute by 35 U.S.C. §121.
Typical double-patenting problems. In general, potential double-patenting risks may arise in any situation where the claims of one application arguably fail to recite any further non-obvious element or limitation in comparison to the claims of another co-pending application or issued patent.
One common scenario in which obviousness-type double patenting can arise relates to selection patents. For example, an initial patent application may be filed with claims to a broad class or genus of compounds. Subsequent work may identify a specific compound or species within the genus that has some advantage over other compounds within the genus, and a selection patent application may be filed with claims for the narrower species. The Supreme Court of Canada ruling in Sanofi-Synthelabo Canada Inc. v. Apotex Inc., 2008 SCC 61, has confirmed that selection patents are not, per se invalid for lack of novelty, obviousness or double-patenting. In this decision, the Court found that there was no double patenting in a later issuing selection patent claiming clopidogrel and its hydrogen sulfate salt over an earlier issued patent of the same applicant that claimed the genus encompassing clopidogrel and its salts. However, it is not uncommon for a narrower species application to proceed through examination to issuance more quickly than the earlier filed genus application. In the U.S., if the later-filed species application were to issue first, the still-pending genus application may receive an obviousness-type double-patenting rejection which, as noted earlier, could be overcome by filing a terminal disclaimer. In contrast, no procedural equivalent to a terminal disclaimer exists in Canada.
A further example stems from the fact that Canadian law does not include any direct equivalent of U.S. continuation practice. While Canadian practice does permit the filing of voluntary divisional applications (Canadian Patent Act, Subsection 36(2)), care must be taken to ensure that the claims that issue for a voluntary divisional application are patentably distinct (novel and non-obvious) from the claims of the parent. This can be particularly problematic if a voluntary divisional is filed to pursue the claims of a corresponding U.S. continuation that includes claims that are broader than those of the parent. Due to the absence of any terminal disclaimer or equivalent remedy in Canada, the issuance of the narrower parent claims while the broader divisional claims are still pending could prove fatal to those broader divisional claims.
Another common scenario arises when multiple applications with substantially identical disclosures but different claim sets are filed on the same day. Even if the independent claims of each application are directed to a different inventive concept than the independent claims of the other applications, the dependent claims often combine the various inventive concepts together, leading to double-patenting problems when one of the applications issues.
Strategies for avoiding double patenting problems. From a foreign practitioner's standpoint, a proactive measure to avoid double-patenting problems in Canada is to consolidate all related applications for the same applicant or assignee with a single Canadian patent agent and to inform the Canadian patent agent of the relationship. Even the most diligent Canadian practitioner will be unable to proactively avoid double-patenting problems if he or she is unaware that a related application is being prosecuted by another firm.
Developments in the prosecution of U.S. and other foreign counterpart and related applications may also serve as alarm bells to indicate that a review of related Canadian applications would be beneficial. In particular, whenever a terminal disclaimer is filed in the U.S., informing the Canadian agent and instructing him or her to conduct an immediate comparison of the two corresponding Canadian applications may be beneficial, to assess whether the absence of any equivalent terminal disclaimer procedure in Canada may pose obviousness-type double-patenting risks.
Claim consolidation is a valuable strategy for avoiding double-patenting problems in situations where multiple claim sets are supported by the specification of a single application. This may include situations involving a parent application and its pending or proposed divisional application, or situations involving multiple applications with substantially identical disclosures filed on the same day. Combining two desired claim sets into a single application will result in the examiner either allowing both claim sets to co-exist in the same application, or issuing a unity objection. The unity objection would then permit a divisional application to be filed, and the divisional and its parent would then enjoy a judicial immunity against double-patenting attack which they would not have enjoyed if the divisional had been voluntarily filed without any such objection. In either case, double-patenting risks are avoided.
For other situations, there are procedural mechanisms available under Canadian practice to control the relative timing of the applications. This control can be used to cause a broader "genus" application to issue before a narrower "species" application, thereby ensuring that the later-issued claims are inventive over the earlier-issued claims. The control of the timing of applications can also be used to keep a parent patent application pending as long as possible, until the applicant has determined all of the claims the applicant ultimately wants to pursue. The claims can then be consolidated into the parent application as discussed above, rather than filing a voluntary divisional application.
To control the relative timing of applications, a number of techniques are available to accelerate or decelerate the examination of an application. For example, one technique for decelerating examination is to defer the request for examination. Examination in Canada does not have to be requested until five years after the filing date.
Delaying the examination of an application may, however, be detrimental in the rare, though possible, situation where double patenting arises with a third party application or patent.
Conversely, techniques for accelerating examination are discussed in the concurrently published article titled, "Amendments to Canadian Patent Rules and Office practice bring opportunities for expedited patent examination", by Daphne C. Lainson.
Conclusions. Unwary applicants may face risks associated with one or more of the unique aspects of Canadian double-patenting laws. Fortunately, procedural mechanisms, such as those discussed above, are available to mitigate these risks.
The preceding is intended as a timely update on Canadian intellectual property and technology law. The content is informational only and does not constitute legal or professional advice. To obtain such advice, please communicate with our offices directly.