Canada: Federal Court of Appeal Clarifies Test For Double-Patenting

Last Updated: May 13 2016
Article by Kevin Siu

On April 20, 2016, the Federal Court of Appeal issued its decision in Mylan Pharmaceuticals ULC v Eli Lilly Canada Inc, 2016 FCA 119, a case relating to tadalafil (Eli Lilly's CIALIS). The Court dismissed the appeal, thereby upholding the Federal Court's Order of prohibition regarding Canadian Patent No. 2,226,784 ("784 patent").

In its reasons, the Court of Appeal clarified the test for obviousness-type double-patenting and addressed the relevant date for the double-patenting analysis. The Court also made some important remarks on use of prior art, and on the distinction between prior art and common general knowledge.

Background and decision under appeal

The 784 patent claimed the use of tadalafil and 3-methyl tadalafil for the treatment of erectile dysfunction (ED). In a proceeding commenced by Eli Lilly under the Patented Medicines (Notice of Compliance) Regulations (PMNOC Regulations), Mylan alleged that the relevant claims in the patent were invalid because of double-patenting and inutility on the basis of lack of sound prediction.

Eli Lilly also had an earlier patent, Canadian Patent No. 2,181,377 ("377 patent"), which claimed tadalafil as a novel compound, as well as use of tadalafil for treatment of certain disorders, but not ED. The specification of the 377 patent described tadalafil as a PDE V inhibitor, although this was not claimed.

Between the priority date of the 377 patent and the priority date of the 784 patent, Pfizer's PCT patent application (WO 1994/028902, "902 application") for sildenafil (Pfizer's VIAGRA) was published. The 902 application taught, inter alia, that PDE inhibitors could treat ED.

At first instance (2015 FC 17) the applications judge, de Montigny J, allowed Eli Lilly's application, holding that Mylan's allegations of invalidity on both double-patenting and inutility were not justified. Mylan appealed.

Federal Court of Appeal decision

Rennie J.A., writing for the Federal Court of Appeal, dismissed Mylan's appeal. Although the Court found that the applications judge erred in some aspects of the legal framework on both issues, the Court ultimately held that Eli Lilly's 784 patent was neither invalid for double-patenting nor lacking utility. In its analysis, the Court clarified and re-stated some important points of patent law.

Difference between prior art and common general knowledge

The Court in its preliminary remarks summarized the jurisprudence distinguishing between prior art and common general knowledge.  The Court held that prior art is the collection of learning in the field which "comprises any publically available teaching, however obscure or not generally accepted." Prior art has specific purposes, such as to found an allegation of anticipation or obviousness.

In contrast, the common general knowledge is "knowledge generally known by persons skilled in the relevant art ... at the relevant time", and unlike prior art, "a piece of information only migrates into the common general knowledge if a skilled person would become aware of it and accept it as 'a good basis for further action'" (citing General Tire & Rubber Co v Firestone Tyre & Rubber Co, [1971] FSR 417 (CA). Further, the Court noted that "[a]ny inquiry in patent law that is performed from the perspective of a skilled person will import the common general knowledge."

Difference between obviousness-type double-patenting and obviousness

The Court also made some important distinctions between obviousness-type double-patenting and "classical" obviousness:

Invalidity on the basis of obviousness-type double-patenting is not the same as invalidity on the basis of obviousness. Obviousness is directed at the question of whether an "invention" (in the legal sense) exists at all. Obviousness-type double-patenting has a different policy justification; the prevention of evergreening an existing patent through what would otherwise be a valid patent but is, in effect, an extension of the patent that has already been granted [...].

Based on those considerations, the Court noted two important differences between the two tests:

  1. For obviousness, any piece of prior art, including a collection of works, can be cited. For obviousness-type double-patenting, only the earlier patent can be cited, and any other prior art is only relevant insofar as it contributes to the common general knowledge.
  2. In the obviousness analysis, s. 28.3(a) of the Patent Act prevents any disclosures made by the patentee within one year of the filing date to be cited against it. However, it does not apply to double-patenting, such that an earlier patent published within the one year grace period may be cited against the later patent for these purposes.

Legal framework for obviousness-type double-patenting

Following those preliminary observations, the Court set out the correct legal test for obviousness-type double-patenting. Mylan argued that the test for obviousness should apply, with the earlier patent taking the place of the prior art. Conversely, Eli Lilly argued that the inquiry should be whether the second invention constitutes an "improper extension" of the original patent, in other words whether what was claimed in the second patent could or should have been claimed in the first patent.

The Court resolved these arguments by holding that there was "no substantive distinction between the two approaches", as they are "reformulations of the same inquiry". In both cases, the question is "whether there is an inventive step from the first patent to the second".

Nonetheless, there are some important considerations specific to the double-patenting analysis. The Court, relying on Merck v Pharmascience, 2010 FC 510, emphasized that in the obviousness analysis for double-patenting, the claims of the first patent and the second patent are to be compared, to determine whether the claims of the second patent exhibit inventiveness over the first patent. 

As ordinary rules of claim construction apply in the comparison, if the claims of the first patent are unambiguous, it is improper to refer to the specification to vary the scope of the claims. Further, the Court distinguished between construing the inventive concept from claims construction. Whereas recourse to the specification is acceptable in the former, it is not in the latter where the claims are unambiguous.

Applying the legal framework, the Court found that the applications judge erred by referring to the specification of the earlier 377 patent to read PDE V inhibition into the claims. However, the Court held that the error did not affect the conclusion.

Relevant date for obviousness-type double-patenting

The Court also considered the relevant date for obviousness-type double-patenting. Despite commenting that this was an "unsettled" point of law, the Court declined to definitively decide the issue.

Of the three possible dates – priority date of the first patent; priority date of the second patent; and publication date of the second patent – the Court held only that the last was not appropriate. This is because using any date after the claim date of the second patent would circumvent s. 28.3(a) of the Patent Act and allow a challenger to raise prior art after the claim date for the purposes of double-patenting but not for the purposes of obviousness.

As to the other two dates, the Court found that it was not necessary to decide the issue, because both dates result in a finding that there was no double-patenting in this case. In particular, the Court relied on the factual finding that although Pfizer's 902 patent application was published between the two dates, its teachings about the use of PDE V inhibitors to treat ED were "counterintuitive" and did not form part of the common general knowledge. Thus the second claims were inventive over the first claims on either date.

Utility and sound prediction

On the issue of utility, the Court reiterated that utility need not be demonstrated and can instead be soundly predicted as of the filing date. The Court found that the application judge erred by his failure to consider the utility of 3-methyl tadalafil in claim 18 based on his interpretation that only one compound in a Markush group required utility. Instead, all compounds in a claimed class must have utility. Nonetheless, the Court found that there was a factual basis and sound line of reasoning to support a sound prediction.

Conclusion and future developments

The Federal Court of Appeal decision clarifies the state of the law on obviousness-type double-patenting. In particular, the well-known Sanofi obviousness test applies in this context, with the important caveat that the "prior art" to be considered for double-patenting is limited to the claims of the earlier patent, and that the earlier patent may be cited for double-patenting even if it was published within one year before the filing date of the second patent.

However, the relevant date for obviousness-type double-patenting remains unsettled. The Federal Court of Appeal has a second chance to decide the issue. In Eli Lilly Canada Inc v Apotex Inc, 2015 FC 875, Gleason J. of the Federal Court granted Eli Lilly's prohibition order against Apotex in respect of the same drug (tadalafil) and patent (784 patent). In the Apotex case, Gleason J. discussed the relevant date at length, including suggesting that the appropriate date may depend on the way in which a patent is alleged to be void for obviousness-type double-patenting. The appeal of the Apotex case was heard on May 5, 2016 (Court File No. A-330-15) and the decision is under reserve.

Mylan can only appeal this decision if leave is sought and granted by the Supreme Court of Canada.

For more information, please contact a member of our firm's Patents group.

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.

To print this article, all you need is to be registered on

Click to Login as an existing user or Register so you can print this article.

Kevin Siu
In association with
Related Video
Up-coming Events Search
Font Size:
Mondaq on Twitter
Register for Access and our Free Biweekly Alert for
This service is completely free. Access 250,000 archived articles from 100+ countries and get a personalised email twice a week covering developments (and yes, our lawyers like to think you’ve read our Disclaimer).
Email Address
Company Name
Confirm Password
Mondaq Topics -- Select your Interests
 Law Performance
 Law Practice
 Media & IT
 Real Estate
 Wealth Mgt
Asia Pacific
European Union
Latin America
Middle East
United States
Worldwide Updates
Mondaq Ltd requires you to register and provide information that personally identifies you, including what sort of information you are interested in, for three primary purposes:
  • To allow you to personalize the Mondaq websites you are visiting.
  • To enable features such as password reminder, newsletter alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
  • To produce demographic feedback for our information providers who provide information free for your use.
  • Mondaq (and its affiliate sites) do not sell or provide your details to third parties other than information providers. The reason we provide our information providers with this information is so that they can measure the response their articles are receiving and provide you with information about their products and services.
    If you do not want us to provide your name and email address you may opt out by clicking here
    If you do not wish to receive any future announcements of products and services offered by Mondaq you may opt out by clicking here

    Terms & Conditions and Privacy Statement (the Website) is owned and managed by Mondaq Ltd and as a user you are granted a non-exclusive, revocable license to access the Website under its terms and conditions of use. Your use of the Website constitutes your agreement to the following terms and conditions of use. Mondaq Ltd may terminate your use of the Website if you are in breach of these terms and conditions or if Mondaq Ltd decides to terminate your license of use for whatever reason.

    Use of

    You may use the Website but are required to register as a user if you wish to read the full text of the content and articles available (the Content). You may not modify, publish, transmit, transfer or sell, reproduce, create derivative works from, distribute, perform, link, display, or in any way exploit any of the Content, in whole or in part, except as expressly permitted in these terms & conditions or with the prior written consent of Mondaq Ltd. You may not use electronic or other means to extract details or information about’s content, users or contributors in order to offer them any services or products which compete directly or indirectly with Mondaq Ltd’s services and products.


    Mondaq Ltd and/or its respective suppliers make no representations about the suitability of the information contained in the documents and related graphics published on this server for any purpose. All such documents and related graphics are provided "as is" without warranty of any kind. Mondaq Ltd and/or its respective suppliers hereby disclaim all warranties and conditions with regard to this information, including all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement. In no event shall Mondaq Ltd and/or its respective suppliers be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of information available from this server.

    The documents and related graphics published on this server could include technical inaccuracies or typographical errors. Changes are periodically added to the information herein. Mondaq Ltd and/or its respective suppliers may make improvements and/or changes in the product(s) and/or the program(s) described herein at any time.


    Mondaq Ltd requires you to register and provide information that personally identifies you, including what sort of information you are interested in, for three primary purposes:

    • To allow you to personalize the Mondaq websites you are visiting.
    • To enable features such as password reminder, newsletter alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
    • To produce demographic feedback for our information providers who provide information free for your use.

    Mondaq (and its affiliate sites) do not sell or provide your details to third parties other than information providers. The reason we provide our information providers with this information is so that they can measure the response their articles are receiving and provide you with information about their products and services.

    Information Collection and Use

    We require site users to register with Mondaq (and its affiliate sites) to view the free information on the site. We also collect information from our users at several different points on the websites: this is so that we can customise the sites according to individual usage, provide 'session-aware' functionality, and ensure that content is acquired and developed appropriately. This gives us an overall picture of our user profiles, which in turn shows to our Editorial Contributors the type of person they are reaching by posting articles on Mondaq (and its affiliate sites) – meaning more free content for registered users.

    We are only able to provide the material on the Mondaq (and its affiliate sites) site free to site visitors because we can pass on information about the pages that users are viewing and the personal information users provide to us (e.g. email addresses) to reputable contributing firms such as law firms who author those pages. We do not sell or rent information to anyone else other than the authors of those pages, who may change from time to time. Should you wish us not to disclose your details to any of these parties, please tick the box above or tick the box marked "Opt out of Registration Information Disclosure" on the Your Profile page. We and our author organisations may only contact you via email or other means if you allow us to do so. Users can opt out of contact when they register on the site, or send an email to with “no disclosure” in the subject heading

    Mondaq News Alerts

    In order to receive Mondaq News Alerts, users have to complete a separate registration form. This is a personalised service where users choose regions and topics of interest and we send it only to those users who have requested it. Users can stop receiving these Alerts by going to the Mondaq News Alerts page and deselecting all interest areas. In the same way users can amend their personal preferences to add or remove subject areas.


    A cookie is a small text file written to a user’s hard drive that contains an identifying user number. The cookies do not contain any personal information about users. We use the cookie so users do not have to log in every time they use the service and the cookie will automatically expire if you do not visit the Mondaq website (or its affiliate sites) for 12 months. We also use the cookie to personalise a user's experience of the site (for example to show information specific to a user's region). As the Mondaq sites are fully personalised and cookies are essential to its core technology the site will function unpredictably with browsers that do not support cookies - or where cookies are disabled (in these circumstances we advise you to attempt to locate the information you require elsewhere on the web). However if you are concerned about the presence of a Mondaq cookie on your machine you can also choose to expire the cookie immediately (remove it) by selecting the 'Log Off' menu option as the last thing you do when you use the site.

    Some of our business partners may use cookies on our site (for example, advertisers). However, we have no access to or control over these cookies and we are not aware of any at present that do so.

    Log Files

    We use IP addresses to analyse trends, administer the site, track movement, and gather broad demographic information for aggregate use. IP addresses are not linked to personally identifiable information.


    This web site contains links to other sites. Please be aware that Mondaq (or its affiliate sites) are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of these third party sites. This privacy statement applies solely to information collected by this Web site.

    Surveys & Contests

    From time-to-time our site requests information from users via surveys or contests. Participation in these surveys or contests is completely voluntary and the user therefore has a choice whether or not to disclose any information requested. Information requested may include contact information (such as name and delivery address), and demographic information (such as postcode, age level). Contact information will be used to notify the winners and award prizes. Survey information will be used for purposes of monitoring or improving the functionality of the site.


    If a user elects to use our referral service for informing a friend about our site, we ask them for the friend’s name and email address. Mondaq stores this information and may contact the friend to invite them to register with Mondaq, but they will not be contacted more than once. The friend may contact Mondaq to request the removal of this information from our database.


    From time to time Mondaq may send you emails promoting Mondaq services including new services. You may opt out of receiving such emails by clicking below.

    *** If you do not wish to receive any future announcements of services offered by Mondaq you may opt out by clicking here .


    This website takes every reasonable precaution to protect our users’ information. When users submit sensitive information via the website, your information is protected using firewalls and other security technology. If you have any questions about the security at our website, you can send an email to

    Correcting/Updating Personal Information

    If a user’s personally identifiable information changes (such as postcode), or if a user no longer desires our service, we will endeavour to provide a way to correct, update or remove that user’s personal data provided to us. This can usually be done at the “Your Profile” page or by sending an email to

    Notification of Changes

    If we decide to change our Terms & Conditions or Privacy Policy, we will post those changes on our site so our users are always aware of what information we collect, how we use it, and under what circumstances, if any, we disclose it. If at any point we decide to use personally identifiable information in a manner different from that stated at the time it was collected, we will notify users by way of an email. Users will have a choice as to whether or not we use their information in this different manner. We will use information in accordance with the privacy policy under which the information was collected.

    How to contact Mondaq

    You can contact us with comments or queries at

    If for some reason you believe Mondaq Ltd. has not adhered to these principles, please notify us by e-mail at and we will use commercially reasonable efforts to determine and correct the problem promptly.

    By clicking Register you state you have read and agree to our Terms and Conditions