Animals bearing xenografts of pediatric bone or soft tissue sarcoma were treated with vehicle, prexasertib, chemotherapy, or the combination of prexasertib plus chemotherapy. The specific chemotherapy used is indicated in the key in each panel. A and B, SJCRH30 alveolar RMS CDX, n = 5/arm for each experiment. C, Rh41 alveolar RMS CDX, n = 4/arm. D, CCSARC005 osteosarcoma PDX, n = 5/arm, prexa* = dose reduced from 10 mg/kg to 8 mg/kg only in the combination due to use of SCID animals (this model only). E, A673 Ewing’s sarcoma CDX, n = 5/arm. For B and C, single experiments are displayed in two different graphs with the same vehicle and prexasertib arms but different chemotherapy and combination arms for clearer visualization. Dotted vertical lines: dosing interval; error bars: SEM. Waterfall plots for each model are displayed in Supplementary Fig. S4 and statistical analyses are summarized in Supplementary Table S3.