Fig. 5: ‘Maintenance’ therapy with ruxolitinib following TSLPRCART-induced ALL clearance prevents in vivo leukemia relapse.
A Luciferase-transduced IGH::CRLF2/JAK2R683G-mutant ALL121 PDX model cells (1e6) were injected IV in NSG mice. Once engraftment was documented by BLI, all mice (n = 10) were treated IV with 2.5e6 TSLPRCART and followed by weekly BLI measurements. After documentation of TSLPRCART-induced leukemia clearance, mice were rechallenged IV with 1e7 ALL121 cells, and cohorts of 5 mice were randomized at day 21 to continued receipt of control chow (orange) or new administration of ruxolitinib chow (green) ad libitum for 2 weeks (horizontal green bar). Mice co-treated with ruxolitinib at ALL121 rechallenge remained in remission, while control chow-fed mice experienced leukemia progression, as assessed by BLI. B Weekly flow cytometric quantification of human CD3+/CD45+ T cells in murine peripheral blood showed no reduction of TSLPRCART numbers in ruxolitinib- (green) versus control-treated (orange) mice or in (C) the CD4:CD8 ratio of T cells harvested from end-study murine spleens at day 36. D Ruxolitinib treatment significantly decreased surface expression of the exhaustion marker PD-1 in CD4+ and CD8+ T cell subsets is reported as median fluorescence intensity (MFI) measured by flow cytometric analyses. PD-1 expression on TSLPRCART is decreased with late ruxolitinib co-treatment. After data normality assessment, statistical analyses were performed for (A) and (B) by unpaired Mann-Whitney tests at each timepoint, (C) with an unpaired t-test, and (D) with one-way ANOVA and Šidák post-test for multiple comparisons between vehicle and ruxolitinib conditions for CD4+ and CD8+ subpopulations. ns not significant, *p < 0.05, **p < 0.01.
