United States: Federal Circuit Finds Wyeth Restenosis Claims Invalid As Not Enabled

In Wyeth v. Abbott Laboratories, the Federal Circuit affirmed the district court's decision that the claims at issue are invalid for failing to satisfy the enablement requirement of 35 USC § 112. The court took only 10 pages to explain why a specification that describes one specific compound did not enable claims encompassing tens of thousands of compounds.

The Patents at Issue

The patents at issue are U.S. Patent 5,516,781 and U.S. Patent 5,563,146, which are based on the same specification. As summarized by the Federal Circuit, the patents "relate to the use of rapamycin for the treatment and prevention of restenosis, which is the renarrowing of an artery." The claims at issue recite methods of treating or preventing restenosis by "administering an antirestenosis effective amount of rapamycin" to a mammal."

Important to this case, the term "rapamycin" may refer to a class of compounds. However, the patent specifications disclose only one rapamycin species, "sirolimus." The structure of sirolimus includes a macrocyclic triene ring at C-1 to C-36 and a substituent group at and beyond C-37. position. As noted by the Federal Circuit, at the time the patent applications were filed it was known that sirolimus acts in part by binding two proteins at sites within the macrocyclic ring. It also was known that there were four additional compounds with the same macrocyclic ring as sirolimus, but different substituent groups beyond the C–37 position.

The patent specifications discuss the immunosuppressive and antirestenotic properties of sirolimus, and disclose "in vitro test data indicating that sirolimus inhibits rat smooth muscle cell proliferation," and "in vivo test data indicating that intraperitoneal injection of sirolimus in rats reduced the thickening of the arterial wall following vascular injury."

The District Court Proceedings

As summarized by the Federal Circuit, "[t]he defendants market stent products that elute everolimus and zotarolimus, two drugs that have the same macrocyclic ring as sirolimus but different substituents at the C–42 position."

Wyeth urged a claim construction of "rapamycin" as "a compound containing a macrocyclic triene ring structure produced by Streptomyces hygroscopicus, having immunosuppressive and anti-restenotic effects."

The district court adopted Wyeth's construction, but held that the claims were not adequately described or enabled by the patent specifications. In so doing, the court noted that "the only species disclosed is sirolimus," that the chemical arts are unpredictable, that the invention is complex, and that there was limited knowledge of the treatment of restenosis using sirolimus at the time of the invention.

The Federal Circuit Decision

The Federal Circuit addressed only the enablement issue. It's analysis begins with this succinct statement of the law:

A patent's specification must describe the invention and "the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains . . . to make and use the same." 35 U.S.C. § 112(a) (2012). Claims are not enabled when, at the effective filing date of the patent, one of ordinary skill in the art could not practice their full scope without undue experimentation. .... Enablement is a question of law based on underlying facts.

The Federal Circuit agreed with the district court's finding that "practicing the full scope of the claims, measured at the time of filing, would require excessive experimentation" for two main reasons: (1) the scope of the claims in contrast with the guidance provided in the specification and (2) the burden of having to screen potential candidates for the required activity.

On the first point, the court noted that the claims encompass "at least tens of thousands of candidates," but the only example in the specification is sirolimus. Further, "[t]he specification is silent about how to structurally modify sirolimus, let alone in a way that would preserve the recited utility. Indeed, the court noted that "it would be necessary to first synthesize and then screen each candidate compound using the assays disclosed in the specification to determine whether it has immunosuppressive and antirestenotic effects." On this point, the court cited testimony from a Wyeth scientist to the effect that "'until you test [compounds], you really can't tell whether they work or not [i.e., have antirestenotic effects].'" Thus, the court found "no genuine dispute that practicing the full scope of the claims would require synthesizing and screening each of at least tens of thousands of compounds."

On the second point, the court emphasized that even "routine experimentation is 'not without bounds.'" The court characterized the specification as providing "only a starting point for further iterative research in an unpredictable and poorly understood field." The court found that even "[s]ynthesizing candidate compounds derived from sirolimus could ... require a complicated and lengthy series of experiments in synthetic organic chemistry," and cited testimony from Wyeth's expert that "it would take technicians weeks to complete each of these [functional] assays." Thus, the court found "no genuine dispute that practicing the full scope of the claims, measured at the filing date, required undue experimentation."

One Is Not Enough

It is not surprising that the Federal Circuit found that the disclosure of one compound with no other guidance was not enough to enable a broad genus, but this decision provides little guidance as to how many exemplary compounds or how much guidance might have been enough. Further, this decision indicates that even the need to carry out routine screening assays can undermine enablement when identifying compounds within the scope of the claims is akin to finding a needle in a haystack.

The recent change to a first-to-file patent system has placed a new emphasis on filing patent applications "early," but this case warns that filing too early can backfire, particularly when broad claims are pursued.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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

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

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
Check to state you have read and
agree to our Terms and Conditions

Terms & Conditions and Privacy Statement

Mondaq.com (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 www.mondaq.com

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 Mondaq.com’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.

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 by clicking here .

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 unsubscribe@mondaq.com 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 webmaster@mondaq.com.

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 EditorialAdvisor@mondaq.com.

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 enquiries@mondaq.com.

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