Increase in serum BAFF levels correlates with BCL-2 upregulation in CLL cells in patients undergoing targeted therapies. (A) Schematic representation of the patient groups sampled before or after venetoclax treatment. (B) CLL burden (proportion of lymphocytes) for each patient at collection. (C) Concentration (pg/mL) of serum BAFF. (D) MFI of BCL-2 in CLL cells from each patient. (E) Schematic representation of the study design. PB samples from 3 patients with CLL were collected at screening and during obinutuzumab and venetoclax dose escalation. Patients received IV infusion of obinutuzumab on days 1/2 (first 1000 mg dose divided over 2 days 100/900 mg), 8 (1000 mg), 15 (1000 mg), and 29 (1000 mg). Venetoclax was introduced at 20 mg daily on day 22 and increased weekly (20, 50, 100, 200, 400 mg). (F) Change in lymphocyte concentrations (cells per liter) during obinutuzumab and venetoclax treatment in each patient. (G) Concentration (pg/mL) of BAFF detected in the serum samples of the patients with CLL using a Luminex assay. (H) Histograms (top panel) and MFI (lower panel) of BCL-2 protein expression in CLL cells in each patient at the indicated time points. For panels B-D, the mean ± SEM are shown and each symbol represents a measurement from an individual sample; Student 2-tailed t test was used. ∗P < .05; ∗∗P < .01; ∗∗∗P < .005; ∗∗∗∗P < .001. Obin, obinutuzumab; PBMC, peripheral blood mononuclear cell.