credit: Royal Veterinary College, University of London

“Exciting news! Our partner, Dr. Eric Olson and his team at Exonics published their research on increasing dystrophin restoration of 92% in the hearts of dogs. While they have a long way to go, their dramatic research gives hope to all families affected by Duchenne!”. This is how the patient advocacy group CureDuchenne announced the CRISPR breakthrough just published in Science.

Caution is needed of course: the sample size is small (4 dogs), and the duration of the study is short (8 weeks), as Jon Cohen points out in Science news. Olson himself is cautious indeed. “It’s still important to ensure safety and long-term efficacy of this approach. If things continue to go well, perhaps it could move toward a clinical trial in a few years, but it’s too early to know for sure. Lots more work to do”, he told me by email.

Behavioral data are not included in the peer-reviewed paper, however, according to a published quote, the dogs “showed obvious signs of improvement—running, jumping—it was quite dramatic.”

Some excitement is overdue, considering that the only Duchenne treatment currently (and controversially) approved is an injected drug working on RNA, rather than DNA, and requiring continuous delivery. CRISPR is another story, Olson told me: “This approach is different. It corrects the error in the DNA and doesn’t require life-long gene transfer of dystrophin, which is a massive protein. The corrected gene is expressed at the correct time, place and level”.

A marginal note on the CRISPR variant used, in the end: Olson’s lab used Cpf1 in the past, while Cas9 does the job in the latest study, therefore I asked him which is preferable for Duchenne research. He said that “Cas9 works very well for the purposes in this study.  There may be other situations when Cpf1 might work better.”