Combined venetoclax and ibrutinib vs single-agent treatment in the Tcl1 mouse model of CLL (A-B) Mice were treated with ibrutinib (0.16 mg/mL in drinking water), venetoclax (once daily 100 mg/kg, intragastric), or a combination of both agents and assessed on a weekly basis for WBC count (A) and percentage of CLL cells (B). Means of WBC counts and percentage of CLL cells ± standard error of the mean (SEM) are presented. The figure is representative of 4 independent experiments, including 5 mice in each arm of the respective experiments. (C) Splenomegaly was partially reversed after 4 weeks of treatment and is more pronounced in the combination treatment. At this time point, WBCs were 1.18 × 10⁸ in untreated, 1.26 × 10⁷ in ibrutinib-treated, 6.2 × 10⁶ in venetoclax-treated, and 1.3 × 10⁷ in combination-treated mice. Photographs showing spleen size are representative of 3 experiments. Means of spleen weights ± SEM are presented; significant differences were determined by 1-way analysis of variance (ANOVA) with Tukey’s multiple-comparisons test. ***P < .001; ****P < .0001. (D) Single-agent and combination treatment decreased CLL cell accumulation in mouse spleen and combination-treatment decreased CLL cell accumulation in bone marrow (BM). Means of the percentage of CLL cells ± SEM are presented. Significant differences were determined by 2-way ANOVA with Tukey’s multiple-comparisons test. *P < .05; **P < .01; ****P < .0001. Reduced percentage of proliferating cells (E) and increase in apoptotic cells measured in PB, spleen, and LN (F) after 4 weeks of the indicated treatments. Mean percentage of Ki67⁺ or of cleaved caspase 3⁺ cells ± standard error of the mean (SEM) are presented; significant differences were determined by 2-way analysis of variance with Tukey’s multiple-comparisons test. *P < .05; **P < .01; ***P < .001; ****P < .0001.