CRISPR, the revolutionary gene editing technology, offers tantalising promises of new disease treatments via precise and efficient genome editing. As a consequence the technology has caused widespread interest in the life sciences community and in the imagination of the general public, as well as significant investment in biotech companies that use this approach and legal struggles around the patents on this technology.

A significant development in European chapter of the CRISPR patents wars occurred on 16th and 17th January 2018 when the European Patent Office's (EPO) Opposition Division revoked EP2771468 – one of the key patents on CRISPR gene editing technology held by The Broad Institute Inc, Massachusetts Institute of Technology and the President and Fellows of Harvard College. Why? The key reason was a problem with the priority claim in this patent. Once the priority claim was considered invalid, publications about this technology, including those made by the patentees themselves in the window between the earliest claimed priority date the actual filing date, became citable for the consideration of novelty and inventive step.

The situation for EP2771468 is complex as it claims priority from 12 earlier US patent applications. The European Patent Convention (EPC) sets out requirements for correctly claiming priority (Art 87 to 89 EPC) which includes that the applicant who is able to claim priority must be the same applicant as for the earlier patent application(s) or the successor in title. A number of recent decisions from the EPO reiterate that these requirements are applied strictly (see for example T511/11 or T1201/14). It should be noted that the way the EPO apply these strict requirements is not in step with how US patent practice approaches claiming priority and this mismatch has already been seen to have negative consequences for other patentees in Europe.

In this case the patentee was unable to demonstrate that at the filing date of EP2771468 the named applicants were the true successors in title to all of the applicants of the 12 earlier US patent applications. One of the problems raised was that an inventor/applicant (Luciano Marrafini) named on some of the earlier US applications was not named as an applicant and nor was the institute he worked for (Rockefeller University). It is interesting to note that in the US the Broad Institute and the Rockefeller University were wrangling over whether this person should or should not be named as an inventor. A further problem raised with the priority claim was that some of the inventors had only assigned their rights to applicants named on filing EP2771468 after its filing date.

A take home message is that no matter how revolutionary or high profile the technology, ensuring a valid claim to priority is essential. This patent struggle looks set to continue to run since the patentee filed an appeal against the revocation finding the very next day, on 18 January 2018. The patentee's position is that the EPO case law does not fit with international approaches on claiming priority. These appeal proceedings will be interesting to watch for anyone else with a similar fact pattern of priority related issues.

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