ART838 synergized strongly with BCL2 inhibitors to inhibit growth and induce death of human leukemia cells. (A) Top 5 hits from the artemisinin synergy screen; BCL2 inhibitors are shown in bold. Synergy scores >0 indicate drug synergy, 0 additivity, and <0 antagonism. (B) Antileukemic synergy between ART838 and VEN against KOPN8 ALL, and ML2 and MV4;11 AML cell growth was validated by alamarBlue assays following 48-hour culture with ART838, VEN, or ART838 plus VEN.^18,52,53  Data points represent means of 3 independent experiments performed with triplicate samples plus or minus SEM, normalized to vehicle (dimethyl sulfoxide [DMSO])-treated controls set to 1. Combination indices (CIs) were determined using CompuSyn software based on Chou-Talalay principles^52,53 ; CI < 1 indicates synergy; CI = 1, additivity; CI > 1, antagonism. CI at each drug’s IC₅₀ is shown in bold. (C) Percentage of viable cells was quantitated by flow cytometry after Annexin V/7AAD staining of KOPN8 ALL, ML2, and MV4;11 AML cells following short (18-hour) treatment with either DMSO (○; colored symbols are as shown in the key in panel A), ART838 (200 nM), VEN (50 nM), or ART838 (200 nM) plus VEN (50 nM), with and without preincubation with 10 nM pan-caspase inhibitor QVD.⁵⁴  Data points represent the percentage of viable (Annexin V⁻/7AAD⁻) cells averaged from 3 independent experiments. Statistical comparisons were performed for combination treatments vs single-drug treatments, at each drug dose (B), or for drug treatment groups vs DMSO control (C). *P < .05; **P < .01; ***P < .001; no asterisk if P > .05.