The European Patent Office (EPO) announced on 23 March its “intention to grant a patent” to the University of California (UC) for its broad-based claims about the genome-editing tool popularly known as CRISPR. UC, on behalf of several parties, has been in a pitched battle with the Broad Institute of Cambridge, Massachusetts, over CRISPR patents, and the new decision marks a sharp departure from the position of the U.S. Patent and Trademark Office (USPTO).

The UC team first reported how to use CRISPR in pieces of circular DNA called plasmids that can invade bacteria, but the Broad won a race to apply the method to human cells, which represents a potential billion-dollar marketplace for medicines. The Broad won the first U.S. patents on CRISPR by paying to have USPTO give them a fast review, but UC’s application is still under review and it filed a so-called “interference” claim against the Broad last year. After a prolonged legal battle, USPTO in February ruled that it wasn’t obvious that UC’s discovery would work in human and other eukaryotic cells, giving the Broad a distinct patent advantage.

But now EPO apparently favors the UC argument that its discovery covers CRISPR use in both prokaryotic and eukaryotic systems. The Scientist first reported this news on 24 March.

Robert Cook-Deegan, a patent expert at Arizona State University in Tempe who is based in Washington, D.C., who has closely followed the CRISPR dispute, says the Broad likely will contest the EPO decision. “This does illustrate that it’s a moving target, and as events unfold the relative strength of the stakeholders will fluctuate,” Cook-Deegan says. “This going to be protracted and complicated.” UC also plans to further challenge USPTO’s decision that favors the Broad.

It’s unclear whether EPO’s actions will have any immediate impact. Companies already pay fees to these warring parties or their affiliates to license CRISPR patents. Some agreements cover international use of CRISPR to make products, and if the UC CRISPR patent stands up to challenges in Europe, companies that banked on the Broad may have to enter more licensing agreements. Companies technically do not need a license until they have a product on the market—that could take a decade for CRISPR-made medicines—but as Cook-Deegan notes, “Licensing is usually smoother and easier while there is still a veil of uncertainty so everyone has a stake in cutting the deal and gets a bit of what they want, even though they don’t know if the license is actually needed in the end.”

Cook-Deegan long has advocated that the public would benefit most if UC and the Broad reached a peace treaty and agreed to share, through what’s known as a cross-license agreement, in the CRISPR spoils. The new decision, he says, “further emphasizes the need for a cross-licensing deal, so folks can have some sense of what they can do and sell without getting sued, and from whom they need to get licenses.”