This treatment is an astonishing example of the power of gene editing technology. Blood diseases are especially suitable for this type of treatment – the relevant cells can be readily obtained from the patient, are already separated (as opposed to being relatively inaccessible in a solid organ), can be modified and amplified, and replaced where they need to be. Time will tell how widely this kind of treatment can be used for diseases affecting other organs.

Genome editing technologies can sometimes cause unintended changes in the DNA in addition to the desired change. A particularly clever aspect of the way this treatment was designed is that some time later, the engineered cells can themselves be removed from the body, virtually eliminating the already small risk that those cells themselves may cause adverse effects