Activating mutations in the interleukin 7 receptor alpha chain (IL7R), Janus kinases, JAK1 or JAK3, or the Signal transducer and activator of transcription 5B (STAT5B) cause constitutive activation of JAK-STAT signaling observed in one-third of T-ALL patients (177–179).There are several ongoing clinical trials targeting the JAK/STAT pathway in T cell malignancies, which include NCT03613428, a phase I/II study combining ruxolitinib with the combination of vincristine, prednisone, and asparaginase in relapsed and refractory T-ALL (180). Here, STAT5B is linked to acute lymphoblastic leukemia.