It is worth noting that the real challenge in gene therapy at this time is not editing the genes, but in getting sufficient coverage of edited cells (and especially progenitors and stem cells) in an adult individual to achieve the therapeutic goal and make it last.

(Most studies of genetic alterations in the broader sense have bypassed this challenge by working with animal lineages, or animals in which the editing happens in the earliest stages of development, when there are very few cells needing to be changed. The alteration then propagates during embryonic and later development).

There have been a number of very promising studies in the past year or two with regard to gene therapies to apply to adults, such as animal studies that demonstrated a cure for an inherited muscular dystrophy, but in the bigger picture, comprehensive coverage of tissues and cells is still something that the research community is in the midst of getting to grips with.