Sequential Phase II Studies of Flavopiridol by 72-Hour Continuous Infusion and 1-Hour Intravenous Bolus for the Treatment of Relapsed B-Cell Chronic Lymphocytic Leukemia: Results from CALGB Study 19805.

Flavopiridol has in vitro activity in CLL and promotes apoptosis independent of p53 function or prior fludarabine exposure. We sought to determine if flavopiridol administered using two different schedules has activity in CLL. Patients with previously treated CLL were enrolled on two sequentially performed phase II studies. Patients in the first trial received flavopiridol (50 mg/m² daily) as a continuous infusion (CI) over 72-hours every 2 weeks. Patients in the second trial received flavopiridol 50 mg/m² as a 1-hour intravenous bolus (IVB) daily for three days repeated every 3 weeks. Patients received up to 6 (CI cohort) or 8 (IVB cohort) cycles of therapy. Fifteen patients enrolled in the 72-hour CI phase II trial; 6 (40%) had intermediate (Rai stage I or II) and 9 (60%) high (Rai stage III and IV) risk stages. No responses were noted in this group with 27% having stable disease (SD) and 73% progressive disease (PD). Thirty-six patients enrolled in the IVB study, with 13 (36%) having intermediate and 23 (64%) having high-risk disease. Four patients (11%) had partial responses, 19 (53%) SD, and 13 (36%) PD. The progression-free survivals for responders in the IVB study were 2.9, 3.2, 8.7, and 19.3 months. The median progression-free survival was 2.1 months (95% confidence interval [CI] 1.8 – 3.8) for patients in the CI study and 3.2 months (95% CI [2.5 – 7.4]) for the IVB study. The median overall survival was 27 months (95% CI [20–42]) for the CI study and 24 months (95% CI [18–31]) for the IVB study. Toxicity was manageable and included mainly myelosuppression (granulocytopenia and thrombocytopenia), infections, diarrhea and fatigue. Grade 3 and 4 toxicities were 20% and 27%, respectively, on the CI study and 39% and 33% on the IVB study. One patient on the IVB study had tumor lysis syndrome that was managed medically and did not require dialysis. There was one on-study death following a myocardial infarction on the IVB study. We conclude that flavopiridol has modest, schedule-dependent clinical activity in relapsed CLL and warrants future investigation utilizing alternative schedules of administration.