(A) Human CML CD34⁺ cells were treated with PJ-68, IM, or a combination for 24 hours, and Western blot analysis of protein levels of PRMT5 and its arginine methylation mark H2AR3SDM was performed. (B) Representative flow cytometry plots for apoptosis in human CML CD34⁺ cells. (C) CML CD34⁺ cells (n = 4) were treated with PJ-68 alone and in combination with IM (2.5 μM) for 24 hours, and apoptosis was analyzed by flow cytometry after staining with annexin V–FITC and anti-CD38–PE. (D) Sorted human CML CD34⁺CD38^– cells (n = 3) were labeled with CFSE, then cultured with PJ-68 ± IM for 96 hours, and apoptotic cells were analyzed by flow cytometry after labeling with annexin V–PE. (E) Pharmacological inhibition of PRMT5 lessened the serial replating capacity of CML LSCs. Human CML CD34⁺ cells (n = 3) were treated with 2 different concentrations of PJ-68 for 24 hours, washed with PBS, and counted; 1,000 cells were plated in methylcellulose medium. Colonies were counted on day 14. The cells were harvested and counted, 1,000 cells were replated for the second and third rounds, and colonies were counted on day 14 after each round. (F) Pharmacological inhibition of PRMT5 activity lessened the LTC-IC capacity of CML LSCs. 2 × 10⁶ human CML cells (n = 3) were seeded in LTC-IC medium onto irradiated M2-10B4 cells and treated with PJ-68 (25.0 μM) with or without IM (2.5 μM) for 1 week, and cells were cultured for 5 more weeks in LTC-IC medium with weekly half drug-free medium changes. After 6 weeks, cells were harvested and plated into MethoCult H4435. LTC-IC–derived colonies were counted after 14 days. *P < 0.05, ***P < 0.0001, 1-way ANOVA, post hoc intergroup comparisons, Tukey’s test.