Effective Tumor Debulking with Ibrutinib Before Initiation of Venetoclax: Results from the CAPTIVATE Minimal Residual Disease and Fixed-Duration Cohorts

Purpose: The phase II CAPTIVATE study investigated firstline treatment with ibrutinib plus venetoclax for chronic lymphocytic leukemia in two cohorts: minimal residual disease (MRD)-guided randomized treatment discontinuation (MRD cohort) and fixed duration (FD cohort). We report tumor debulking and tumor lysis syndrome (TLS) risk category reduction with three cycles of single-agent ibrutinib lead-in before initiation of venetoclax using pooled data from the MRD and FD cohorts. Patients and Methods: In both cohorts, patients initially received three cycles of ibrutinib 420 mg/day then 12 cycles of ibrutinib plus venetoclax (5-week ramp-up to 400 mg/day). Results: In the total population (N = 323), the following decreases from baseline to after ibrutinib lead-in were observed: percentage of patients with a lymph node diameter ≥5 cm decreased from 31% to 4%, with absolute lymphocyte count ≥25 × 109/L from 76% to 65%, with high tumor burden category for TLS risk from 23% to 2%, and with an indication for hospitalization (high TLS risk, or medium TLS risk and creatinine clearance <80 mL/minute) from 43% to 18%. Laboratory TLS perHoward criteria occurred in one patient; no clinicalTLS was observed. Conclusions: Three cycles of ibrutinib lead-in before venetoclax initiation provides effective tumor debulking, decreases the TLS risk category and reduces the need for hospitalization for intensive monitoring for TLS.