A "problem" with this treatment is that, for most patients, the current standard of care works. To the extent that this treatment is effective, it is likely effective for most leukaemia patients, including those who would respond well to current treatments. It is very plausible that this treatment (or a refined version of it) will eventually be shown to be superior to the current standard of care, in which case it would become the standard of care, and the current treatment will be relegated to the niche patient that does not respond to gene edited t-cells.

More broadly, the technique of precisely editing DNA of select cells to perform specific engineered tasks is very broadly applicable. But that is a technique for developing treatments, not a treatment itself.