PHOENIX (AP) — Early, partial results from a historic gene editing study give encouraging signs that the treatment may be safe and having at least some of its hoped-for effect, but it's too soon to know whether it ultimately will succeed.

The results announced Wednesday are from the first human test of gene editing in the body, an attempt to permanently change someone's DNA to cure a disease — in this case, a genetic disorder called Hunter syndrome that often kills people in their teens.

In two patients who got a medium dose of the treatment, urine levels of large sugar compounds that are hall...