Honokiol enhances the cyotoxicity of fludarabine, cladribine, and chlorambucil. B-CLL cells were incubated with the indicated concentrations of fludarabine, cladribine, or chlorambucil in the presence or absence of 25 μM honokiol for 24 hours, at which time cell viability was assessed. The assay was performed in duplicate, and each sample was normalized to untreated cells. Data from 6 patients' samples (patients 1, 4, 6, 9, 11, and 17) are represented as mean ± SEM. ^*P < .05 when cells incubated with the combination of honokiol and nucleoside analog or chlorambucil were compared with cells incubated with nucleoside analog or chlorambucil alone.