Study of Sirolimus With PEG-Asparaginase in Acute Lymphoblastic Leukemia (ALL)

The goal of this study is to find a safe dose of sirolimus that can be used with a standard dose of L-asparaginase. To find the safe dose, the investigators will give the first patient a very small dose of sirolimus (smaller than the dose used in organ transplant children) and the standard dose of L-asparaginase. The investigators will then look for side effects. If side effects develop, the investigators will decrease the dose of sirolimus. If they do not, the investigators will increase the dose of sirolimus in the next patient on the study. The investigators will continue this method until fewer than one-third of patients have a side effect that would require stopping the drug or changing the dose. The investigators plan to enroll up to 15 children with relapsed ALL. The enrolled patients must have recovered from other treatment before starting this study. Also, they cannot have severe side effects from their earlier therapy that will possibly make these drugs less safe. The investigators will collect information on whether these drugs help to cure the ALL, but the purpose will be to find a dose of sirolimus that does not cause too many side effects when combined with L-asparaginase. This will be explained to the families and they will sign a written consent. The patients will provide either verbal or written assent when appropriate.