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16 May 2022

Priority Pitfalls to Avoid at the EPO

The recent consolidated referral to the Enlarged Board of Appeal at the European Patent Office (EPO) (G1/22 and G2/22) will mean another close look at the rules that must be followed for a patent priority claim to be considered valid in Europe. A brief report on the subject of that referral can be found here, but it is likely to be some time before the Enlarged Board’s answers to the referred questions are published.

In the meantime, the case is a reminder of how strict the EPO can be when assessing a priority claim, and how easy it can be to inadvertently lose the benefit of priority. The following provides some important points to consider, and errors to avoid, when the intention is, or may be, to rely on a priority claim in a patent or application at the EPO.

Fixed at the filing date

Article 4A(1) of the Paris Convention is enacted as Article 87(1) in the European Patent Convention (EPC), and provides some bare bones requirements for a valid priority claim. It is important to remember that these more formal requirements are generally assessed as of the filing date of the subsequent (i.e. priority claiming) European application. If it is found during prosecution or opposition proceedings at the EPO, for example, that the priority claim was not validly made because the applicant was not the same as, nor the successor in title to, the applicant for the priority application on the filing date of the European application (see below), then there is often very little, if anything, that can be done to rectify the situation and recover the priority claim. It is therefore vital to make a correct priority claim on the filing date.

Particular pitfalls can arise when the European application or patent is derived from an International application. In such cases, the International application might be filed by an applicant or attorney from a jurisdiction other than Europe, who might be balancing many other concerns and so have given only minimal thought to the possible resultant European application. However, if the requirements for priority are not met when filing the International application, it could be fatal to the eventual European application or patent.

To rectify this, it might be possible to request a correction of the original application documents, but the requirements for a correction can be arduous. A correction is generally required rather than an amendment, because a correction is considered to have effect from the date on which the error was made (“ex tunc”), i.e. the date on which the subsequent application was filed, whereas an amendment is considered to have effect from the date on which the request for the amendment was accepted (“ex nunc”).

Check the applicant details

The priority right to an earlier patent application may only be enjoyed by the applicant of the earlier application or their successor in title. This is one of the strict priority requirements at the EPO. If the applicant of the subsequent European, priority claiming, application is not the same as the applicant for the priority application, then the applicant of the subsequent application must be ready to explain how they have become successor in title for the priority rights. In such cases, the transfer of the priority right can have occurred by any legal means, according to the relevant local law applicable to the priority rights, but if the priority claim is challenged then the onus will be on the owner of the subsequent application or patent to show that the transfer had occurred before the subsequent application was filed.

In addition, if there is more than one applicant for the priority application, then the priority rights of all the applicants must be accounted for.

In other words, either all the same applicants must be listed on the subsequent application as on the priority application when the subsequent application is filed, or the owners of the subsequent application or patent must be able to show how the priority rights of any applicants “missing” from the subsequent application were transferred to an applicant that was listed on the subsequent application.

This can be a particular pitfall when emphasis is placed on indicating correct (or, at least, intended) ownership of the invention rather than the priority rights. For example, there may have been a reassessment of the inventors for the invention, or a parent company may have decided that a different subsidiary company should have ownership of the invention, such that it is felt that different applicants have ownership of the invention in the subsequent application. However, it must be remembered that priority right is a completely separate and severable right to ownership of the invention described in the patent. A priority right may be obtained simply by being listed as an applicant on an application, whereas assessment of the ownership of the invention defined in the priority (and subsequent) application will be determined by inventor contributions and any obligations they have to assign their rights in their invention(s).

The importance of getting the applicants right on the filing date of the subsequent application was perhaps most starkly underscored by the fate of a large part of the portfolio of early CRISPR patents owned by the Broad Institute, Massachusetts Institute of Technology, and Harvard University. With decision T844/18, the Board of Appeal of the EPO revoked the first of many patents in the portfolio for lack of novelty following loss of the earliest priority claims. The priority claims were lost because the Broad Institute, MIT, and Harvard could not show that they owned the priority rights of one of the applicants listed on the priority applications.

Beware intervening disclosures

Of course, loss of a priority claim cannot, on its own, result in the loss of an application or patent. In order for the priority claim to be relevant there must be an intervening disclosure, that is a disclosure citable for novelty and/or inventive step having a date between the filing date of the priority application and the filing date of the subsequent application.

In many instances, such as in the Broad Institute et al. CRISPR case mentioned above, intervening disclosures have been made by third parties, so that there seems to be little that can be done by applicants about them. However, there are two points in particular that are within the control of the applicants and are important in the context of intervening disclosures.

Firstly, the priority claim will only be valid for the subject-matter of the claims that is the same as the subject-matter disclosed in the priority application. The EPO performs a strict analysis as to whether the subject-matter is the same. If the disclosure of the subsequent application is broader than that of the priority application, such that the priority application only discloses some specific embodiments of the claims of the subsequent application, then the priority claim will only be considered valid for those specific embodiments. The priority claim will be considered invalid for any subject-matter encompassed by the claims that was not disclosed in the priority application. This concept of the subject-matter of the claims having only “partial priority” has been affirmed by the Enlarged Board in G1/15.

Secondly, any of the inventor’s own disclosures made between the priority date and the filing date of the subsequent application (i.e. intervening disclosures) will be citable against the subsequent application to the extent that the priority claim is invalid.

These two points can, together, lead to a potential pitfall, particularly when a priority application is filed as a matter of urgency to mitigate the effects of an imminent inventor disclosure. For example, an academic applicant may be about to present their work at a conference, or to have their article published in a journal. In an attempt to mitigate the effects of that disclosure, a simple priority application may be quickly filed including the information about to be disclosed, with the intention of later filing a subsequent application having more details of alternative ways in which the invention may be carried out.

However, if the priority application only really provides the specific embodiments of the inventor’s disclosure, but the intention is to provide a more generalised statement of the invention in the subsequent application, then a “partial priority” situation will arise. The claims of the subsequent application will contain two different groups of subject-matter, the specific embodiments from the priority application, which will have a valid claim to the priority date, and any other embodiments of the generalised disclosure, which will not have the benefit of the priority date.

Any of the more generalised subject-matter not disclosed in the priority application will be susceptible to an attack based on the inventor’s intervening disclosure, because it will not have a valid claim to priority and instead will take the filing date of the subsequent application. The inventor’s intervening disclosure could not, of course, be used for a novelty attack because anything disclosed therein would presumably also be disclosed in the priority application and so fall within the part of the claims having the valid claim to priority.

But, the intervening disclosure would be citable for inventive step purposes against the other embodiments of the generalised disclosure not present in the priority application and, if the generalisation might be considered obvious to try from knowledge of the specific embodiment, the inventive step attack is likely to be successful. It is therefore important to try to avoid this potential pitfall either by including information about the generalisation in the priority application, or by avoiding publication of the intervening disclosure completely. Otherwise, the filing of the priority application might provide false confidence.

Don’t hold back

Finally, a priority application is often filed quite early in the life of an invention. It can be difficult to know at that point exactly what the essential features and information are that are needed to define and work the invention, and inventors can be worried about overstating the requirements or unnecessarily disclosing information. However, applicants should be cautious when withholding information, as a valid priority claim at the EPO requires that the priority application discloses all the features of the invention defined in the subsequent application, and also that it provides an enabling disclosure of the invention.

This means that while the inventors might feel more comfortable keeping some information back, this should only be done knowingly and with caution.

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