This is a nonrandomized study of ruxolitinib in combination with a standard multi-agent
chemotherapy regimen for the treatment of B-cell acute lymphoblastic leukemia. Part 1 of the
study will optimize the dose of study drug (ruxolitinib) in combination with the chemotherapy
regimen. Part 2 will evaluate the efficacy of combination chemotherapy and ruxolitinib at the
recommended dose determined in Part 1.