Unlike PDX models of CRLF2r/JAK2-mutant ALL, the efficacy of ruxolitinib has also been demonstrated in vivo using PDX models of JAK2r ALL, where ruxolitinib treatment reduced peripheral blood blast counts and tumor burden (Roberts et al., 2012; Roberts et al., 2014a; Roberts KG. This evidence concerns the gene JAK2 and acute lymphoblastic leukemia.