Fig. 7: Acquired venetoclax resistance can be overcome by ibrutinib addition in vivo.

a RIVA cells immunomagnetically isolated from five different donors (that had been exposed during weeks three and four, and again during weeks seven and eight to venetoclax as single agent) were exposed to 40 nM venetoclax for 48 h and subjected to viability testing by CellTiter-Blue assay; the original cell line is shown as control. b–d Venetoclax-resistant RIVA cells isolated from donor mouse M21 were re-transplanted into MISTRG recipients. IVIS images were recorded on the indicated days (b) and the radiance was plotted longitudinally as means ± SD (c); p values for the relevant comparisons (as determined by one-way ANOVA of AUC) are shown below the curves. Mice received twice-weekly doses of 40 mg/kg venetoclax, 25 mg/kg ibrutinib, or the combination via oral gavage, initiated once lymphomas were clearly detectable in all mice of the cohort (after 2 weeks of growth; indicated by gray shading in c). All mice were subjected to the quantification of their lymphoma burden in the spleen and bone marrow at the study endpoint by flow cytometric staining for hCD45 and mouse CD45 (d). Both the frequencies and absolute counts are shown. Data in c and d are pooled from three independent experiments (the ibrutinib-only group was included only once); representative images from one study are shown in (b). e–g 1 × 10⁶ human primary DLBCL cells were transplanted into MISTRG6 mice, which were treated from week four post transplantation onwards with either venetoclax, ibrutinib or the combination as described for b-d. Images of the spleens, and their weights are shown in e and f; the human lymphoma burden in the spleen and bone marrow at the study endpoint (eight weeks post transplantation) is shown in g. Data in e–g are pooled from two independent studies. *p < 0.05, **p < 0.01, ***p < 0.005, as determined by one-way ANOVA throughout.