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Getting Priority Right

By Jay Erstling

The European Patent Office Board of Appeal recently handed down a decision on the requirements for validly claiming the right of priority of a first-filed patent application. The decision, which upheld the ruling of the EPO Opposition Division to revoke a crucial CRISPR patent, has important implications for US filers.

Patterson Thuente IP’s Jay Erstling served as an expert witness for George Schlich, the UK patent attorney who represented Opponent #1in the EPO opposition proceedings. The basis of the opposition challenge, and the core of the EPO’s decision, was that the owners of the CRISPR patent did not correctly claim the priority of their US provisional applications; although the priority claim was in accordance with US practice, it was inconsistent with, and ran afoul of, European filing requirements.  As a result, the seminal European patent for the CRISPR gene-editing technique lost its priority filing date, and the patent was revoked for lack of novelty because of the presence of intervening prior art.

The EPO has long held that all applicants who are named in a priority application, or their successors in title, must be named as applicants in any subsequent application that claims priority to the first application. The CRISPR case affirmed that requirement. In contrast, US law requires only that there be one inventor in common.

The EPO’s requirement is known as the “all applicants approach,” and failure to respect it, as the CRISPR case demonstrates, can have dire effects. Under the all applicants approach, if there is a lack of complete identity between the applications, in other words, if any applicant listed in the priority application (or the applicant’s assignee) is not included in the subsequent application, the application’s priority claim will fail and the application will lose the benefit of the priority right. Consequently, the application’s effective filing date will no longer be considered the date on which the first application was filed, but rather it will be the filing date – usually twelve months later – of the subsequent application. As in the case of the CRISPR patent, a patent’s life or death can depend on the right of priority. Loss of priority can result in the loss of the patent and all the exclusive rights that go with it if the invention was disclosed in the intervening period.

The CRISPR European patent (EP2771468) was derived from a PCT application. The patent was issued in the names of the Broad Institute, MIT, and Harvard College, and it listed a number of inventors, all of whom were named on the PCT application. The PCT application, however, did not name one of the inventors (Dr. Maraffini) or that inventor’s assignee (Rockefeller University) although Dr. Maraffini was named in the provisional applications to which the PCT application claimed priority. The PCT application and the applications that formed the basis of the priority claim thus lacked complete identity, rendering the priority claim invalid. Two intervening publications, which became fatal prior art, dealt the patent its final blow.

To avoid the same fate as the owners of the CRISPR patent, it is important to remember that European and US practice differ, particularly with respect to getting priority right. To ensure the validity of a priority claim, all applicants (or inventors in the case of provisional applications) named in the priority filing, or their assignees, should be named in the subsequent application claiming priority. Moreover, the chain of title needs to be complete. All assignments from applicants or inventors named in the priority application to their assignees should be completed before filing the subsequent application claiming priority. If there is any gap in the chain of title because an applicant or inventor has not yet assigned rights, that applicant should be named in the subsequent application pending completion of the assignment.


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