In the ongoing worldwide patent battle over the CRISPR Cas9 gene-editing technology between the Broad Institute/MIT (Zhang, et al.), and the University of California/University of Vienna (Doudna/Charpentier, et al.), Broad suffered a stunning blow at the European Patent Office (EPO) last week.

In an EPO opposition proceeding challenging several of Broad’s European patents, the EPO’s Opposition Division revoked Broad’s foundational CRISPR patent, EP2771468. This EPO decision will likely lead to the revocation of several more – but not all – of Broad’s European patents.

The EPO’s decision was based on a procedural defect in Broad’s European patent application that ultimately became the EP ’468 patent. This procedural defect is unique to European patent law for patent priority dates. In particular, Broad’s earliest U.S. priority applications included Rockefeller University researcher Dr. Luciano Marraffini as a named inventor. But Broad did not list Dr. Marraffini as an inventor on the later European patent application that claimed priority to Broad’s earlier U.S. patent applications. Nor did Broad submit any evidence that Dr. Marraffini had assigned his “right of priority” to Broad before Broad filed its corresponding European application.  Thus, under European patent law, Broad’s chain of priority was defective, leaving Broad with a significantly later effective filing date for its European patent application.

Because the EPO rejected Broad’s priority benefit to its earliest filing dates (namely, December 12, 2012, and January 2, 2013), the EPO found that intervening prior art describing aspects of the CRISPR Cas9 technology rendered all of Broad’s patent claims unpatentable. This EPO decision undermines several other Broad European patents that have the same procedural defect. However, not all of Broad’s CRISPR Cas9 gene-editing patent applications have that defect, so Broad may still obtain some European patent protection, albeit of potentially narrower scope.

In a press release, Broad vowed to appeal the EPO’s decision to the EPO’s Technical Board of Appeal. Not surprisingly, ERS Genomics, a licensee of the CRISPR Cas9 technology from the University of Vienna, issued a press release endorsing the EPO’s decision. While the merits of Broad’s promised appeal will be hotly debated, there can be little dispute that this new European development adds more uncertainty in predicting the ultimate outcome of the ongoing CRISPR patent saga.

The EPO result comes as a contrast to the success in the U.S. that Broad has thus far enjoyed in the CRISPR dispute.

In the U.S., the dispute culminated in a patent interference proceeding before the U.S. Patent and Trademark Office (USPTO). In that proceeding, there was no “right of priority” issue, so the USPTO did not evaluate the priority chain issues considered by the EPO. Instead, the issue decided by the USPTO was whether University of California/University of Vienna’s earlier CRISPR invention, shown to work in bacterial cells but claimed more broadly, prevented Broad/MIT from obtaining later patents on CRISPR in the cells of higher organisms like humans (called “eukaryotic cells”).

The USPTO determined that Broad’s narrower patent claims directed to CRISPR Cas9 gene-editing in eukaryotic cells were distinct from, and independently patentable over, the University of California’s/University of Vienna’s more generic claims, which did not specify the particular cellular environment. Accordingly, the USPTO permitted Broad/MIT to pursue patents on their CRISPR technology, despite having a later priority date than University of California/University of Vienna. University of California/University of Vienna have appealed the USPTO’s decision to the United States Court of Appeals for the Federal Circuit. A decision in that case is not expected until the second half of 2018.

In both the EPO and USPTO battlegrounds, the parties have invoked unique requirements of different jurisdictions to gain a significant tactical advantage. Whether those advantages will be permanent remains to be seen. In any event, as this landmark dispute continues worldwide, it would not be surprising to see the parties continue to exploit the idiosyncrasies of national patent laws, leading to additional significant shifts in the parties’ respective patent rights.

So stay tuned. The fight is far from over.