The purpose of this study is to determine the safety and tolerability of an experimental form of therapy, known as UCART22 (“study drug”). UCART22 cells are special types of cells called T-cells that have been collected from a donor and then are genetically modified (changed). T-cells are related to your immune system, which helps to fight infection. These T-cells will be changed in a way that will allow the cells to identify and kill your tumor cells.

Patients with B-cell Acute Lymphoblastic Leukemia (B-ALL) whose disease has come back or have not responded to treatment may be eligible for this study.