A Study of the Drug IMGN632 in Children With Leukemia That Has Come Back After Treatment or is Difficult to Treat

This phase I/II trial finds the highest safe dose of IMGN632 that can be given with other chemotherapy without causing severe side effects, studies what kind of side effects IMGN632 may cause, and determines whether IMGN632 is a beneficial treatment for leukemia in children that has come back after treatment or is difficult to treat. IMGN632 is a monoclonal antibody linked to a chemotherapy drug. IMGN632 is a form of targeted therapy because it attaches to specific molecules (receptors) on the surface of cancer cells, known as CD123 receptors, and delivers the chemotherapy drug to kill them. Giving IMGN632 with other chemotherapy may cause the leukemia to stop growing or to shrink for a period of time.

PRIMARY OBJECTIVES: I. To determine the recommended phase 2 dose (RP2D) of anti-CD123 ADC IMGN632 (IMGN632) monotherapy in pediatric patients with second or greater relapse of CD123 positive leukemia or CD123 positive leukemia refractory to relapse therapy. (Cohort 1 \[Monotherapy Phase 1\]) II. To assess the flow-based overall response rate (complete remission \[CR\]/CR with incomplete blood count recovery \[CRi\]/CR with partial recovery of platelet count \[CRp\]) in patients with acute myeloid leukemia (AML) treated with IMGN632. (Cohort 1 \[Monotherapy Phase 1\]) III. To determine the safety, feasibility, and RP2D of IMGN632 in combination with liposome-encapsulated daunorubicin-cytarabine (DAUNOrubicin and cytarabine liposome) in pediatric patients with first relapse of CD123 positive AML. (Cohort 2 \[Combination Therapy Dose Finding\]) IV. To compare the minimal residual disease (MRD) negative flow-based overall response rate (CR/CRi/CRp) in pediatric patients with first relapse of CD123 positive AML randomized to two cycles of therapy including DAUNOrubicin and cytarabine liposome followed by fludarabine phosphate (fludarabine)/cytarabine with or without IMGN632. (Cohort 3 \[Randomized Phase 2\]) SECONDARY OBJECTIVE: I. To characterize the pharmacokinetics of IMGN632 in a pediatric population. (Cohort 1 \[Monotherapy Phase 1\]) EXPLORATORY OBJECTIVES: I. To describe the anti-leukemic activity (morphologic and flow-based CR/CRp/CRi after up to two cycles, rates of MRD negative response after up to 2 cycles, event free survival \[EFS\] and overall survival \[OS\]) of IMGN632 in patients with multiply relapsed or refractory relapsed pediatric leukemia including AML, B-cell acute lymphoblastic leukemia \[ALL\], T-cell ALL and mixed phenotype acute leukemia (MPAL). (Cohort 1) II. To describe the EFS, OS, cumulative incidence of relapse, and rate of subsequent stem cell transplant for patients with first relapse of AML randomized to treatment with up to two cycles of chemotherapy with or without IMGN632. (Cohort 3) III. To determine if CD123 expression on leukemic blasts (assessed by flow cytometry) correlates with clinical response to IMGN632. (All Cohorts) IV. To determine the cumulative incidence of left ventricular systolic dysfunction (LVSD), defined as an absolute decline in EF by \>= 10% to an ejection fraction (EF) value of \< 50%, or an absolute decline in shortening fraction (SF) by \>= 4% to an SF value of \< 25%, within 1 year of initiation of DAUNOrubicin and cytarabine liposome based therapy for relapsed pediatric AML. V. To describe safety (adverse events) in pediatric leukemia patients treated with IMGN632 including long-term safety events related to treatment for up to 5 years. (All Cohorts) OUTLINE: This is a phase I, dose-escalation study of IMGN632 followed by a phase II study. In phase I, patients with second or greater relapse or refractory relapsed disease of AML, B-ALL, T-ALL or MPAL with CD123 expression are assigned to Cohort I, while patients with CD123 positive AML in first relapse are assigned to Cohort II. In phase II, patients with first relapse of CD123 positive AML are assigned to Cohort III. COHORT 1: Patients receive IMGN632 intravenously (IV) on days 1 and 22. Treatment repeats every 42 days for up to 6 cycles in the absence of disease progression or unacceptable toxicity. COHORT 2: CYCLE 1: Patients receive IMGN632 IV on days 1 and 22 and liposome-encapsulated daunorubicin-cytarabine (CPX-351) IV over 90 minutes on days 1, 3, and 5 in the absence of disease progression or unacceptable toxicity. Patients with CNS1 also receive intrathecal triple therapy (ITT) consisting of methotrexate intrathecally (IT), hydrocortisone or prednisolone IT, and cytarabine IT on day 0 of cycle 1 (NOTE: Patients who received IT cytarabine or ITT at time of diagnostic lumbar puncture \[LP\] do not need to repeat ITT on day 0 if given within 7 days of starting protocol therapy). Patients with CNS2 receive ITT once weekly (QW) until the cerebrospinal fluid (CSF) is clear for a maximum of 6 ITT treatments in the absence of disease progression or unacceptable toxicity. CYCLE 2: Patients receive ITT on day 0, IMGN632 IV on days 1 and 22, fludarabine IV over 30 minutes once daily (QD) on days 1-5, and cytarabine IV over 1-3 hours QD on days 1-5 in the absence of disease progression or unacceptable toxicity. COHORT 3: Patients are randomized to 1 of 2 arms. ARM A: Patients receive CPX-351 IV over 90 minutes on days 1, 3, and 5 of cycle 1 in the absence of disease progression or unacceptable toxicity. Patients then receive fludarabine IV over 30 minutes QD on days 1-5 of cycle 2 and cytarabine IV over 1-3 hours QD on days 1-5 of cycle 2 in the absence of disease progression or unacceptable toxicity. ARM B: Patients receive CPX-351 IV over 90 minutes on days 1, 3, and 5 of cycle 1 and IMGN632 IV on days 1 and 22 of cycle 1 in the absence of disease progression or unacceptable toxicity. Patients then receive fludarabine IV over 30 minutes QD on days 1-5 of cycle 2, cytarabine IV over 1-3 hours QD on days 1-5 of cycle 2, and IMGN632 IV on days 1 and 22 of cycle 2 in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed every 3 months for the first year, twice a year for year two and yearly visits until five years from enrollment.