In the weeks that followed the cell transfer, a miraculous transformation took place in the one-year-old girl; her leukemia began responding to the edited T cells. When her health improved enough, Layla underwent another bone marrow transplant, and within months, the cancer was in complete remission. What had begun as a major gamble—attempting a treatment that had up until that point been tested only in mice—ended up a resounding success and a major endorsement for using gene editing to further immunotherapy.
