Moxetumomab Pasudotox (CAT-8015, HA22) in Children With B-lineage Acute Lymphoblastic Leukemia and Minimal Residual Disease Prior to Allogeneic Hematopoietic Stem Cell Transplantation

This is a Phase 2 study designed to assess safety, feasibility and clinical activity of pre-HCT moxetumomab pasudotox for patients with ALL in morphologic CR but with MRD. It is hypothesized that subjects in a morphologic complete remission with proven minimal residual disease (MRD) after chemotherapy for ALL planned for allogeneic HCT who receive a course of moxetumomab pasudotox prior to the start of conditioning will show a marked reduction or elimination of detectable MRD after moxetumomab pasudotox treatment without adverse impact on the feasibility or safety of allogeneic HCT. The primary objective of this study is to determine if treatment with moxetumomab pasudotox in the MRD positive setting is able to lead to MRD negativity (\< 0.01% by flow cytometry) or at least a 1-log10 reduction in MRD prior to allogeneic HCT. Secondary objectives to be studied include: toxicity profile (including safety and feasibility of administration in the pre-HCT setting and ability to proceed to transplant, incidence of capillary leak syndrome, hemolytic uremic syndrome and other post-HCT toxicities), comparison of quantitative MRD assessments, progression-free survival, overall survival, pharmacokinetic profiles, immunogenicity to moxetumomab pasudotox, transplant-related mortality, acute and chronic graft-versus-host disease (GVHD), and relapse.