The purpose of this study is to determine the safety and tolerability of an experimental form of therapy, known as WU-CART-007 ("study drug"). WU-CART-007 uses immune cells, called T cells, that are genetically changed to identify cancer cells. In this study, T cells are collected from a healthy human donor and have been modified in a laboratory. If the genetically changed T cells recognize and attach to cancer cells, they may have the ability to kill those cancer cells.

Patients with T-cell Acute Lymphoblatic Leukemia (T-ALL) or Lymphoblastic Lymphoma (LBL), where the disease has come back (relapsed) or has not responded to treatment (refractory) may be eligible for the study.

This study enrolls patients that have been diagnosed with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), or mixed phenotype acute leukemia (MPAL) that has either come back (relapsed) or does not respond to therapy (refractory). This study involves taking a drug called uproleselan that is not yet approved for use in children or adults. The purpose of the study is to find a safe dose of the study drug in children that can be given with standard chemotherapy without causing severe side effects.