Flotetuzumab for the Treatment of Pediatric Recurrent or Refractory Acute Myeloid Leukemia

PRIMARY OBJECTIVES: I. To assess the safety and tolerability of flotetuzumab administered by continuous intravenous (IV) infusion to pediatric patients \< 21 years of age with relapsed or refractory acute myeloid leukemia (AML). II. To estimate the maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D) of flotetuzumab administered by continuous IV infusion to pediatric patients \< 21 years of age with relapsed or refractory AML. SECONDARY OBJECTIVES: I. To characterize the pharmacokinetics of flotetuzumab in pediatric patients with relapsed or refractory AML. II. To preliminarily define the anti-tumor activity of flotetuzumab within the confines of a phase 1 study and correlate potential activity with baseline disease burden at study entry. III. To monitor anti-drug antibody (ADA) production and characterize the immunogenicity of flotetuzumab. EXPLORATORY OBJECTIVES: I. To evaluate changes in T-lymphocyte population numbers before and after flotetuzumab treatment. II. To evaluate the tumor microenvironment and cytokine production by immune effector cells before and after flotetuzumab treatment. III. To quantify CD123 surface expression on AML cells at baseline and evaluate expression as a potential biomarker of flotetuzumab response. OUTLINE: This is a dose-escalation/dose de-escalation study of flotetuzumab. Patients receive cytarabine intrathecally (IT) on days -6 to 0 prior to cycle 1. Patients may receive additional doses of cytarabine on day 1 of subsequent cycles per physician discretion. Patients also receive flotetuzumab IV continuously for 28 days. Treatment repeats every 29 days for up to 6 cycles in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed for 30 days.