Results of a phase 2, multicenter, single-arm, open-label study of lenalidomide in pediatric patients with relapsed or refractory acute myeloid leukemia

Background Outcomes after relapse remain poor in pediatric patients with acute myeloid leukemia (AML), and new therapeutic approaches are needed. Lenalidomide has demonstrated activity in adults with lower risk myelodysplastic syndromes and older adults with relapsed or refractory (R/R) AML. Methods In this phase 2 study (NCT02538965), pediatric patients with R/R AML who received two or more prior therapies were treated with lenalidomide (starting dose 2 mg/kg/day on days 1-21 of each 28-day cycle) for a maximum of 12 cycles. The primary endpoint was rate of complete response (CR) and CR with incomplete blood count recovery (CRi) within the first four cycles. Results Seventeen patients enrolled and received one or more dose of lenalidomide. Median age was 12 years (range 5-18 years), median white blood cell count was 3.7 x 10(9)/L, and median peripheral blood blast count was 1.0 x 10(9)/L. One patient (5.9%) with a complex karyotype including del(5q) achieved CRi after two cycles of lenalidomide. This responder proceeded to a second hematopoietic stem cell transplantation and has remained without evidence of disease for 3 years. All patients experienced one or more of grades 3-4 treatment-emergent adverse event (TEAE). The most common grades 3-4 TEAEs were thrombocytopenia (58.8%), febrile neutropenia (47.1%), anemia (41.2%), and hypokalemia (41.2%). Conclusions In this population of pediatric patients with R/R AML, safety data were consistent with the known safety profile of lenalidomide. As only one patient responded, further evaluation of lenalidomide at the dose and schedule studied is not warranted in pediatric AML, with the possible exception of patients with del(5q).