In Gilead Sciences v. Natco Pharma (Fed. Cir. 2014), the United States Court of Appeals for the Federal Circuit held that in certain circumstances, a patent that issues after but expires before another patent may qualify as an obviousness-type double patenting reference for that other patent.
The two patents at issue named the same inventors, were commonly owned by Gilead, and had similar written descriptions. But they were not part of the same family of patents, and were not examined by the same patent examiner.
The decision includes a helpful diagram of the relevant dates:
For the purpose of the appeal, the majority assumed that the later-expiring patent claims obvious variants of the invention claimed in the earlier-expiring patent. With this assumption in mind, the majority reasoned that to best serve the purpose of the doctrine of double patenting the inquiry should not look not to the filing or issue dates, but rather "to the earliest expiration date of all patents an inventor has on his invention and its obvious variants".
Notably, the majority indicated that a terminal disclaimer can be used to preserve the validity of the later-expiring patent by aligning its expiration date with that of the earlier-expiring patent. (Gilead had filed a terminal disclaimer for the '375 patent, disclaiming any term that extended beyond the '483 patent, but no terminal disclaimer was filed for the '483 patent.)
In dissent, Chief Judge Rader argued that the majority's new rule that the expiration dates of the patents govern the inquiry – irrespective of filing or issue dates – was an unwarranted expansion of the doctrine of obviousness-type double patenting. In doing so, he noted, inter alia: i) there was no subsequent extension of patent term, as the later-issued patent expired first; ii) had the second patent not issued, there would be no apparent grounds to reduce the term of the earlier-issued patent; iii) there is no potential for harassment by multiple assignees asserting essentially the same patented invention (due to the terminal disclaimer filed on the '375 patent, the '375 patent is only enforceable so long as it and the '483 patent are commonly owned); and iv) by not claiming priority as far back as the earlier-expiring patent, the later-expiring patent is subject to about 10 months of intervening prior art.
Canada has a similar non-statutory prohibition against obviousness-type double patenting "that prohibits the issuance of a second patent with claims that are not "patentably distinct" from those of the earlier patent".1
One justification for this prohibition is to prevent a patentee from obtaining an improper extension of their monopoly (i.e. patent term) "through successive patents by the expedient of obvious or uninventive additions".2 But even where extension of the monopoly is not possible (e.g. where two patents will expire on the same day, as is typically the case for divisional applications and their parents), Canadian courts have invalidated later-issued patents to prevent a patentee from obtaining additional patents for the same invention.3 Also, the Canadian Patent Office has rejected applications from issuing to patent on the basis of obviousness-type double patenting based on earlier-issued patents that would nonetheless expire later than a patent granted from the pending application.4
However, a 2013 decision of the Federal Court of Canada appeared to focus exclusively on the potential extension of patent term when considering obviousness-type double patenting: "Given the expiry date of each of the '426 patent (August 31, 2020) and the '728 patent (December 22, 2019), it is obvious that the '426 patent may be challenged for Double Patenting in light of the '728 patent, but not the other way around".5 Unfortunately, Justice Hughes' decision did not specifically address the fact that the '426 patent, while filed later, was issued first (February 27, 2006) – well before the '728 patent issued (September 1, 2009) – making the '728 patent the apparent 'second patent' whose issuance could be challenged.
This recent uncertainty in Canadian law places holders of two or more patents claiming similar subject matter at a greater risk of validity challenges based on obviousness-type double patenting. Also, unlike the U.S., Canada does not have an effective terminal disclaimer practice for addressing potential double-patenting issues that may arise during prosecution or after issuance.
Canadian patent applicants should turn their mind to potential obviousness-type double patenting issues when forming their initial Canadian filing strategy, and keep these issues in mind throughout prosecution.
1 Whirlpool Corp. v. Camco Inc.,  2 S.C.R. 1067 at para. 66.
2 Ibid. at para. 37.
3 See e.g. GlaxoSmithKline v. Apotex (2003), 27 C.P.R. (4th) 114.
4 See e.g. Re Orasure Technologies Inc. Patent Application No. 2,023,636 (2009), 79 C.P.R. (4th) 205 (P.A.B., Commr.).
5 Bayer Inc. v. Cobalt Pharmaceuticals Company, 2013 FC 1061 at para. 144.
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