In vivo efficacy studies of SJ6986. (A-B) SJ6986 was more effective than CC-90009 in reducing tumor burden in PDX model of ALL (SJBALL047370 and IGH-CRLF2). The yellow shaded area is the dosing period after which dosing was stopped, and mice were monitored by imaging. (C-D) SJ6986 reduced tumor burden and spleen size in PDX model of ALL (SJBALL047370 and IGH-CRLF2). (E-H) SJ6986’s effectiveness in reducing tumor burden and spleen size varies in other PDX models of ALL; effective in SJHYPO123 (near haploid), SJBALL020589 (ATF7IP-JAK2), SJBALL020579 (EPORr); less effective in SJHYPO046 (low hypodiploid); not effective in SJMPAL016856 (PMAL, TCF3-ZNF384).