Attacking Divisional Patents: Is A New Approach Emerging?

• Published date: 11 December 2020
• Subject Matter: Intellectual Property, Patent
• Law Firm: Torys LLP
• Author: Mr Henry Federer, Alexandra Peterson and Andrew Shaughnessy

For companies litigating patents in Canada (and beyond), we are seeing a growing trend of attacks on patents on the basis of double patenting-a second patent for the same or similar invention claimed in an earlier patent.

This trend is becoming more common particularly given the rise of divisional patents (often flowing from continuation-in-part applications in the United States).

Courts have traditionally held that once a divisional patent is issued by the patent office, it is beyond attack, and if an improper divisional application is approved, the ensuing divisional patent cannot be attacked-other than on the ground of double patenting¹. A 2020 Federal Court case, however, suggests that a new approach to attacking divisional patents may be emerging².

What is a divisional patent?

The Patent Act requires that "a patent shall be granted for one invention"³. If a patent application contains more than one invention, the surplus invention(s) can be "divided out" into a divisional application⁴, which can either be done voluntarily by the applicant, or may be required by the examiner⁵. A divisional application is given the same filing date as the original, or "parent" application⁶. A divisional application (which is deemed as its own distinct application) can further be divided into other divisional applications⁷. Because a divisional patent is deemed to have the same filing date as its parent application, it should not include any new subject matter outside of that which is already disclosed in the parent. (Of course, as we posit, if new matter is added, the reliance on the parent's filing date is in jeopardy.)

But what happens where new matter is included in a divisional application, and that application is nevertheless allowed by the patent office?

The traditional approach

Traditional case law suggests that the new matter rule only applies to applications that are within the purview of the patent office-the patent office can object on this basis-but that once the application issues to patent, there is no recourse.

Where new matter has been added, double patenting should still apply, but there must be other avenues of recourse available.

This view was discussed in Merck & Co. Inc. v. Apotex Inc⁸. There, the defendant argued that a divisional patent was improperly granted because there was another application covering the same subject matter pending before the patent office⁹. Because the divisional application was improper, Apotex argued it was invalid, or at...