Trametinib in Treating Patients With Relapsed or Refractory Juvenile Myelomonocytic Leukemia

PRIMARY OBJECTIVE: I. To determine the objective response rate to trametinib in children with recurrent or refractory juvenile myelomonocytic leukemia (JMML). SECONDARY OBJECTIVES: I. To further define and describe the toxicities of single agent trametinib in children with recurrent or refractory JMML. II. To further characterize the pharmacokinetics of trametinib in children with recurrent or refractory JMML. III. To prospectively evaluate mutant allele burden as a marker of disease activity in JMML. IV. To measure the rate of complete responses in children with recurrent or refractory JMML. V. To measure the duration of response among responders. EXPLORATORY OBJECTIVE: I. To describe the distribution of JMML diagnostic criteria in children with recurrent or refractory JMML. OUTLINE: Patients receive trametinib orally (PO) once daily (QD) on days 1-28 of each cycle. Treatment repeats every 28 days for up to 12 cycles in the absence of disease progression or unacceptable toxicity. Patients undergo a bone marrow aspiration or biopsy at baseline, on day 28 of cycles 1 and 2, at all subsequent odd numbered cycles, and at end of treatment. After completion of study treatment, patients are followed up annually for up to 5 years.