BTK occupancy in lymph node and marrow. (A) Individual BTK occupancy in the lymph node and marrow. The median values are represented by the horizontal lines. (B) BTK occupancy over time in lymph node during the acalabrutinib withholding period, shown as mean ± SEM. Linear regression was used to calculate slopes for the return of free BTK. (C-D) Correlation of BTK occupancy in paired samples of PBMC and lymph node and marrow. Shapes represent collection time since the last dose of acalabrutinib: 4 hours (●), 12 hours (▪), 24 hours (♦), and 36 hours (▲).