A phase I/II study of the Janus kinase (JAK)1 and 2 inhibitor ruxolitinib in patients with relapsed or refractory acute myeloid leukemia

Background Ruxolitinib is a potent and specific JAK1/JAK2 inhibitor recently approved for the treatment of myelofibrosis. Patients and Methods We conducted a single-center phase I/II clinical study testing 3 dose levels (50 mg b.i.d. [n = 4], 100 mg b.i.d. [n = 5], and 200 mg b.i.d. [n = 18]). We enrolled 27 patients older than 14 years with relapsed or refractory acute myeloid leukemia (n = 26) or acute lymphoid leukemia (n = 1). Results The median age was 66 (range, 25-88) years. Thirteen patients were evaluable for dose-limiting toxicities. The most common Grade 3 or 4 nonhematologic event was infection (n = 26 events; most frequently pneumonia; 15 of 26; 58%). One patient with multiple relapses after 7 lines of therapy had a CRp at a ruxolitinib dose of 200 mg b.i.d. Conclusion In this cohort of heavily pretreated patients with relapsed or refractory acute leukemias, ruxolitinib was overall reasonably well tolerated, with 1 patient achieving CRp.