Analysis of BTK mutations in patients with R/R CLL who progressed during acalabrutinib treatment. (A) Summary of mutations detected in BTK across 2 different platforms. Text in parentheses indicates limits of mutation allele frequency (AF) detection. Each triangle represents a sample assessed at pretreatment baseline (left) or at progression (right); gray indicates wild-type BTK and green indicates BTK C481X mutation. (B) AF of BTK mutations in 6 patients with mutations at progression. Three time points are shown as a line plot for each patient and for each BTK mutation. The inset shows raw next-generation sequencing data from the integrated genome viewer of the BTK mutation at the progression time point. If 2 mutations coexisted in a single patient sample, separate reads are provided for each independent clone. Raw variant allele frequency (VAF) in Integrative Genomics Viewer (IGV) inset where filtered VAF plotted in line charts. PtID, patient identifier; WES, whole-exome sequencing.