RecruitingPhase 1Biological interventionCART123 Cells With or Without Ruxolitinib in Relapsed/Refractory Acute Myeloid LeukemiaThis study is designed to evaluate the safety and effectiveness of CART123 cells either alone or when combined with ruxolitinib in pediatric and young adult subjects with relapsed or refractory AML. Subjects will be enrolled into one of two treatment cohorts: subjects who will receive CART123 alone (Cohort A) or subjects who will receive CART123 in combination with ruxolitinib (Cohort B).