Adaphostin synergizes with fludarabine to induce cell death in CLL B cells. (A-B) Sample dose response curves for lymphocytes isolated from a patient with CLL cultured with increasing doses of adaphostin alone (A; and solid line), the active component of fludarabine alone (B; and solid line), or fixed 2:1 ratio of adaphostin plus the active component of fludarabine (A-B; ▪ and dashed line) for 24 hours. Percent viable cells relative to control (vehicle alone) is expressed on the y-axis. (C) Combination index (CI) calculated from data for the patient in panels A and B under assumption agents are mutually nonexclusive (solid line) or mutually exclusive (dashed line). (D) Combination index 50 (50% cell kill) and combination index 90 (90% cell kill) values for adaphostin and fludarabine (constant ratio, 2:1) for CLL B cells from 10 patients (calculated using Calcusyn software). Value less than 1 implies synergy. The dark dashed line indicates CLL sample highlighted in Figure 5A-B.