We, therefore, investigated the efficacy of the JAK inhibitor ruxolitinib and the mTOR inhibitor rapamycin in xenograft models of 8 pediatric B-ALL cases with and without CRLF2 and JAK genomic lesions….Three JAK2m/CRLF2R ALL xenografts (I, II, III), including the sample harboring a P2RY8-CRLF2 fusion, exhibited significantly decreased leukemia burden with ruxolitinib treatment compared with vehicle, evidenced by lower peripheral blast count (Figure 1A) and splenic blast count...