Baseline BCL2:BCL2L1 and BCL2:MCL1 gene expression levels by best response in 44 patients with evaluable bone marrow samples. Quantitation of BCL2, BCL2L1, and MCL1 was performed on CD138-selected BMMCs collected at baseline using droplet digital PCR. Presented are the (A) ratio of BCL2:BCL2L1 and (B) BCL2:MCL1 gene expression levels (log2-transformed copies/µL normalized to housekeeping gene) based on best response (≥PR vs <PR) to venetoclax treatment. Boxes extend from the 25th to the 75th percentile, horizontal bars represent the median, and whiskers extend to the minimum and maximum values. **P < .01; *P < .05 by Wilcoxon rank sum test. (C) Prevalence of high BCL2:BCL2L1 in all patients with evaluable samples (n = 44) and within t(11;14) (n = 24) and non-t(11;14) (n = 20) patients. Bootstrapping and aggregating thresholds from trees (BATTing) was used to estimate a threshold value for the BCL2:BCL2L1 mRNA expression ratio (log2 ≥ 2.3; P < .01) that would provide optimum selection of patients likely to have a response with venetoclax. CD, cluster of differentiation.