Mexico: The Mexican Patent Office Position Regarding The Patentability Of Prodrugs In Terms Of Clarity

Last Updated: 25 May 2007

For about at least three years, the Mexican patent examiners have adopted the practice of issuing official letters in order to reject the term "prodrug", arguing that the meaning thereof is neither restricted nor clearly supported by the patent application description. These rejections are based on the grounds of Article 47 of the Mexican Industrial Property Law (MIPL), wherein Section III states the following:

"The patent applications must be accompanied by:

III.- One or more patent claims, which must be clear and concise and may not exceed the content of the description.

In reference to the particular, it is important to point out that numerous applicants have demonstrated their disagreement with such rejection, saying that the meaning of the term "prodrug" should be well-known and perfectly understood by any person possessing average skill and knowledge in the discipline, especially considering that in several scientific publications the use of the prodrug concept in the design of drugs with improved pharmaceutical, physicochemical and biological properties has already been discussed in detail.

As a reference, applicants mention that Albert1 defined the term prodrug as "a substance which, after being administered and combined with some receptors, is converted in the final substance". This definition includes metabolites of administered drugs that are the original active drug species as well as biologically active compounds, which are chemically modified to alter their absorption, distribution, etc. Harper2, on the other hand, explained the "prodrug" concept by defining the term drug latentation as "the chemical modification of a biologically active compound to form a new compound, which will liberate the parent compound upon in vivo enzymatic attack".

In this sense, it is believed that the rejection of the term "prodrug" does not arise merely from the presumed lack of knowledge about its meaning, but rather from the fact that the chemical nature of the claimed prodrugs, as in Europe, is not clearly defined by the description of the patent in question nor by the examples provided, which, in some cases, do not allow a complete determination of which compounds can be considered within the scope of the invention.

It is important to emphasize that according to the provisions of Article 47 of the MIPL and Article 29 of its Rules and Regulations, the claims must be clear and concise and must not exceed the contents of the description; that is, the claims should clearly and precisely define the matter for which the applicant seeks protection. Therefore, simply mentioning the term "prodrug" in a particular claim does not appear to be sufficient to clearly define the matter to be claimed.

Concerning this particular issue, the Mexican examiners believe that within the pharmaceutical industry the term "prodrug" does not have an accurate meaning that allows an unambiguous determination of whether or not a specific compound falls within the claimed scope and is appropriate for patentability. This opinion prevails even in those cases in which the description of the patent application reveals the definition of "prodrug", by establishing, for example, that "a prodrug is a pharmaceutically acceptable ester and amide derivative, wherein the resulting product, obtained from the biotransformation of the derivative, is the active drug". However, and despite this definition, the examiners claim that the chemical nature of the compound remains undefined; an entirely questionable opinion given that, for many experts on the subject, the above assertion should be interpreted as a clear definition of the chemical nature of the prodrug, so that claiming the ester, amide, etc. of the drug itself should also be perfectly valid.

While it may be true that the position of the Authorities is rather drastic and clearly tends to restrict the scope of the claims, it is also true that should the applicant be able to demonstrate which compounds are those that can be transformed from the original drugs, undoubtedly, it would be possible to argue against it, since once the chemical structure of such prodrugs had been established, the compounds could be defined based on their structural characteristics.

On the other hand, the examiners point out that as the structure of every possible prodrug may vary in relation to its parent compound, it is also very likely that their type of activity differ in relation to the activity of said parent compound as well. Thereby such prodrugs could indeed be considered a distinct invention. In this case, the application would not only be unclear but would also lack of inventive concept, thus infringing that stipulated by both, Article 47, Section III and Article 43 of the Mexican law respectively.

Concerning this specific point, it is worthwhile to emphasize that the essentially unanimous opinion of the Industrial Property agents in Mexico is totally contradictory to that of the authorities, because if it is considered that a prodrug is directly derived from a compound, its essence prevails and the desired activity is certain to take place. Even though the aforementioned activity may be improved, neither indication nor any argument whatsoever exists to establish that for this reason the prodrug lacks of inventive concept. Contrary to what might be believed, that concept is irrevocably evidenced in view of the fact that the compound and its prodrug share a common chemical structure, and also simply because the drug is directly produced from the prodrug.

Likewise, although not recurrently, the term prodrug also tends to be rejected when the patent application neither contains any explanation about which experiments must be carried out in order to obtain the claimed prodrugs, nor explains how the given prodrugs should be tested in order to determine whether or not they are appropriate. Judging by the nature of this type of rejections, it would appear what the examiner aims is a demonstration that an expert in the field has carried out the experiment "in vivo" and that from the results thereof has determined which specific compounds can be considered within the claimed scope. Otherwise, the simple mention of the term prodrug, without any additional substantiation in the application description, would lead to an unclear set of claims and would not allow the aforementioned expert to be able to carry out the claimed invention.

There is no agreement with the authorities concerning this point either. It is assumed that by simply reading the invention description an expert in the field should be able to identify which compounds qualify as prodrugs, bearing in mind that the preparation of the given compounds is independent. Preparing a compound, once the compound is known, is different than determining whether or not it is a prodrug.

In light of the above, and taking the distinct rejections issued by the authorities with respect to the term prodrug into consideration, it is quite evident that if applicant does not have a clear idea of the exact nature of the compounds that fall under this concept, the protection of these compounds would be practically impossible. If the mentioned prodrugs have never been proved or synthesized, there would not be any manner of defining this matter and its rejection would be without doubt eminent, because it would be considered as a clear intention of increasing the scope of the invention, thus contravening the aforementioned Article 47 fraction III of the Mexican Industrial Property Law.

In conclusion, if the applicant would be able to demonstrate which compounds are appropriate to be considered as prodrugs, there would be no apparent reason for which their chemical structure could not be determined or for which the corresponding claims that include the structural characteristics thereof could not be then established, instead of simply defining the matter for which protection is sought based on the result to be obtained by it.

The above implies that if a specific prodrug is claimed and fully supported by the application description, there should not be any obstacle for the given prodrug to be claimed, especially if it is proved that the compound is indeed a prodrug. The application description is precisely what enables and provides support to the matter being claimed, in addition to strengthening the former before any rejection related to the topic in question.


1. A. Albert, "Selective Toxicity", 2nd Ed. New York, NY, 1960.

2. J. Harper, "Absorption and Distribution of Drugs". Ed. Williams.

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

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

Some comments from our readers…
“The articles are extremely timely and highly applicable”
“I often find critical information not available elsewhere”
“As in-house counsel, Mondaq’s service is of great value”

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