Does Double Patenting Need New Rules?

Patents have been described as a quid pro quo – in return for disclosure of the invention, the inventor gets a time limited exclusive period to practice the invention. There are a number of rules and restrictions that restrict the ability to extend patent rights – i.e. get more than the patent owner bargained for, including ‘double patenting’ but some of the earlier concerns about extending patent protection through double patenting no longer apply under our current Patent Act which requires that patents and any divisional patents expire on the same day.

Double patenting is a restriction on getting multiple patents for the same or similar invention. This has been described by the Supreme Court of Canada in Whirlpool Corp v. Camco Inc., 2000 SCC 67 as follows:

The prohibition against double patenting relates … to the “evergreen” problem … The inventor is only entitled to “a” patent for each invention: Patent Act, s. 36(1). If a subsequent patent issues with identical claims, there is an improper extension of the monopoly.

The Supreme Court has described two types of double patenting: “same invention” and “obviousness”. The first type applies where there are two patents for the same invention. The second, which arises more frequently, applies where a second patent is not ‘patentably distinct’ from the first patent by being obvious or lacking novelty in view of the first patent. This may arise when the second patent is an improvement or refinement of the first patent.

Much of the case law on double patenting arises from ‘Old Act’ patents, patents filed prior to 1989 when the term of protection was 17 years from the date the patent was granted. In contrast, patent applications filed after 1989, known as ‘New Act’ patents, last 20 years from the filing date.

This distinction is important particularly for divisional applications – applications which are filed after an original parent application but are so closely related they claim priority back to a parent application such that the divisional application is deemed to have the same filing date as the original application. The Section 36 of the Patent Act governs divisional applications:

36(4) A divisional application shall be deemed to be a separate and distinct application under this Act, to which its provisions apply as fully as may be, and separate fees shall be paid on the divisional application and it shall have the same filing date as the original application.

Under the ‘Old Act’, divisional applications were often granted much later than the original application, so the divisional patent would still be in force after the original patent had already expired. If the divisional patent was the same, or not ‘patentably distinct’, this could give the patent owner an additional period of exclusivity.

In contrast, under the ‘New Act’, including patent applications filed today, a divisional patent, deemed to have the same filing date as the original, expires on the same day as the original patent, regardless of when it is granted.

The United States also has a concept of double patenting to avoid multiple patents on the same invention. In the United States, where instances of obviousness-type double patenting are found, it is often straight forward to file a ‘terminal disclaimer’ on a later expiring patent, shortening the term of protection to be the same as the earlier patent. A terminal disclaimer in this circumstance also requires that the patents at issue stay commonly owned.

It is common in the United States for continuation or continuation-in-part patent applications to be filed having very similar or even broader claims than the original application.

Canada does not have a similar procedure for addressing concerns over double patenting and particular complications can arise, leading to expensive litigation and potentially, invalid patents.

The Federal Court of Appeal in Bayer Schering Pharma Aktiengesellschaft v. Canada (Attorney General), 2010 FCA 275 held that a rejection of a divisional patent to a compound on the basis of double patenting was proper. The parent patent was directed to a process-dependent claim for a compound. The patents were ‘old Act’ patents and at the time the parent patent granted, the Patent Act did not permit patents for medicinal compounds. The law was changed while the divisional patent was pending and the parent patent had already expired.

The Federal Court considered a dedication to the public in Merck & Co. Inc. v. Canada (Health), 2010 FC 1043 as an attempt to cure an allegation of double patenting. The parent patent included claims to dorzolamide and expired in April 2011. The ‘Old Act’ divisional patent had some claims which overlapped with the parent, including to dorzolamide and expired in May 2011. In 2007, Merck had declared that it no longer intended to assert its rights under the parent patent but the Court held that this dedication did not address the ‘extra’ month of monopoly and found the allegations of double patenting justified. The court also considered a ‘terminal disclaimer’ filed by a patentee in Bayer Inc. v. Canada (Minister of National Health and Welfare), 1998 CanLII 8204, which also did not avoid double patenting.

While these cases relate to ‘Old Act’ patents, double patenting has also arisen for ‘New Act’ patents. In Glaxosmithkline Inc. v. Apotex Inc., 2003 FCT 687, the Court held that a divisional patent that expired on the same day as the parent was invalid for double patenting on the basis that a second patent can cause additional injunctions under the Patented Medicines (Notice of Compliance) Regulations and more generally that “that inventive ingenuity was still needed to support the second patent.”

During prosecution of patent applications, an applicant can try to avoid later issues of double patenting by amending the claims of the divisional application to avoid overlap with the parent application. If the Canadian patent office requires that a divisional application be filed pursuant to Section 36(2.1) of the Patent Act, a court has held that it would “be unfair and inequitable” (see Abbott Laboratories v. Canada (Health), 2009 FC 648 and Consolboard Inc. v. MacMillan Bloedel (Sask.) Ltd., [1981] 1 SCR 504) to invalidate a divisional patent because the applicant had followed the direction from the patent office.

Therefore instead of voluntarily filing a divisional application, including all potential claims, such as those pending in US continuation applications, in a single application and having the patent office require a divisional application is often recommended to reduce the risk of double patenting objections. Other mechanisms such as re-issue (Section 47 of the Patent Act), disclaimer (Section 48) or re-examination (Section 48.1) may also be considered for issued patents, but each raises new issues and may not be available or desirable in a specific circumstance.

Is it time to revisit the law of double patenting for ‘New Act’ patents where both parent and divisional patents expire on the same day and concerns about the “improper extension of the monopoly” no longer exists? Perhaps the unique concerns within the Notice of Compliance regime can be addressed without requiring invalidation of the patent in all instances of ‘double patenting’ and procedures that provide sufficient notice to the public and certainty to patent applicants can reduce the risk and uncertainty in this area of patent law.


  1. For those interested in this topic–a little shameless self-promotion–you might want to look at 22 Intellectual Property Journal 155 (2010). The law has changed surprisingly little since…