By quelling a mutant enzyme that can induce bone marrow cells to proliferate wildly, four new drugs stop a deadly form of leukemia in mice. Three of the drugs are now being tested in people who have acute myeloid leukemia, a lethal blood cancer, and plans are under way to start a trial of the fourth.
In this leukemia, bone marrow stem cells multiply out of control and fail to mature into red blood cells or other blood components. The disease carries a grim prognosis–only 14 percent of patients survive 5 years. Roughly two-fifths of people with the leukemia harbor a mutation in a gene encoding an enzyme called FMS-like tyrosine kinase 3 (FLT3), and this mutation further decreases patients' survival rates.