called "Guide-Seq" to track instances of unintended DNA cuts. And as for delivering these treatments, Editas "isn't trying to reinvent the wheel," Bosley says. Rather, it's looking to proven delivery methods—at least initially. For the LCA program, it's delivering a CRISPR/Cas9 using adeno-associated

has become the first of the group not only to attract crossover backers, but to begin discussing the diseases that its targeting. Its first program, Bosley says, is a potential treatment for a form of leber congenital amaurosis (LCA), a genetically driven blindness. It's a different form of the LCA than