What happened

Shares of Editas Medicine (EDIT 1.39%) were down as much as 21% at one point on Thursday. The stock closed at $12.25 on Wednesday and opened at only $9.90 on Thursday, falling to as low as $9.61 in early trading. The stock bounced back a bit toward the end of the day but was still down as much as 13.8% by 2 p.m. EST. Editas has a 52-week low of $9.59 and a 52-week high of $37.50, and is down more than 60% so far this year.

So what

The clinical-stage biotech, which seeks therapies through CRISPR gene-editing, paused its Brilliance Phase 1/2 trial for its lead therapy, EDIT-101, to treat the rare eye disease, leber congential amaurosis (LCA) 10, that affects the retina. LCA is a genetic degenerative disease that can be caused by 18 different mutations and LCA10 is just one of those mutations.

There were only 14 patients in the trial. Of that group, only three showed clinically meaningful improvement in their vision after being dosed with EDIT-101. Two of those three patients had the same type of homozygous genetic mutation (when both copies of a gene have the same allele). The company determined that only homozygous patients would respond to the therapy and that was too small a group to make the therapy commercially viable.

Now what

Editas said it would seek a collaborator to continue development of EDIT-101, but there's no guarantee one will come through. In the meantime, the company must hope another one of its pipeline candidates can pay off. It's not making any revenue, and as of the third quarter, said it had $478.5 million in cash, enough to fund operating expenses into 2024. The gene-editing company's next best hope is EDIT-301, which is in trials to treat sickle cell disease and transfusion-dependent beta thalassemia, two genetic blood disorders.