PAK inhibitor FRAX486 induces remission of ALL and prolongs survival in combination with midostaurin. (A) In vivo bioluminescent imaging of G-Luc transgenic ALL22089 xenografted in NSG mice on days 0 and 6 of a treatment course with FRAX486 (20 mg/kg daily). Control animals were treated with solvent in buffer. Color bar represents photon emission per second (also see supplemental Figure 11A). (B) In analogy to panel A in vivo imaging of G-Luc ALL22089 xenografted NSG mice on days 0, 7, and 14 of PKC412 monotherapy vs combined PKC412 and FRAX486 treatment compared with vehicle-treated controls. (C) Photon emissions per cohort and day of treatment are presented as mean plus or minus SD of photons per second in a dot plot. Mann-Whitney U test, 2-tailed; **P < .01; ***P < .001 (for day 21 imaging data refer to supplemental Figure 11B-C). (D) Kaplan-Meier analysis of leukemia progression-free survival of G-Luc ALL22089 xenografted NSG mice treated with midostaurin vs midostaurin in combination with FRAX486 compared with vehicle control. Rectangular boxes: red, combined treatment; green, PKC412 monotherapy. Note dose reduction and treatment pause due to gastrointestinal toxicity. Three mice were lost in the combined regimen arm due to gastrointestinal toxicity and 1 mouse in the control arm died during imaging under general anesthesia. Log-rank test; **P < .01; ****P < .0001. EOI, end of induction treatment; ns, not significant.