A wide range of responses to ABT-737 in primary CLL independent of known prognostic markers. (A) Primary CLL cells derived from 57 patients were incubated with ABT-737 (50nM) for 18 hours. Cell survival was assessed by annexin V/fluorescein isothiocyanate binding, as determined by flow cytometric analysis. Values are normalized to survival of untreated cells, and each data point represents one CLL patient. Based on cell viability data, the response to ABT-737 was classified as: resistant (> 65%), intermediate (40%-65%), and sensitive (< 40%). (B-C) The proportion of CLL patients in the resistant/intermediate and sensitive groups, respectively was examined with regard to the common CLL prognostic markers: (B) Rai stage and (C) Zap-70, CD38 expression. P values are shown for comparison of groups.