Obinutuzumab plus bendamustine in previously untreated patients with CLL: a subgroup analysis of the GREEN study

Abstract

GREEN (NCT01905943) is a non-randomized, open-label phase IIIb study investigating obinutuzumab alone or plus chemotherapy in chronic lymphocytic leukemia (CLL). We report a preplanned subgroup analysis of 158 previously untreated CLL patients receiving obinutuzumab-bendamustine (G-B). Patients received six 28-day cycles (C) of G-B: obinutuzumab day (D)1/D2 of C1 (25 mg D1/975 mg D2), 1000 mg D8 and D15 of C1, and D1 of C2-6; and bendamustine 70/90 mg/m² D1 and D2 of C1-6. The primary endpoint was safety/tolerability. Grade ≥3 adverse events (AEs) occurred in 82.3% of patients, including neutropenia (49.4%), thrombocytopenia (12.0%) and febrile neutropenia (10.8%). Serious AEs included neutropenia (12.7%), febrile neutropenia (9.5%) and pneumonia (7.6%). Rates of grade ≥3 infections and infusion-related reactions were 20.3% and 17.1%, respectively. Due to tumor lysis syndrome (TLS; 8.2%), including two associated fatalities (one in another study cohort), additional risk-minimization measures were implemented. Overall response rate was 81.0%. After 32.8 months' median observation time, 2-year progression-free survival was 81.8%. Minimal residual disease was undetectable in 59.5% (94/158) and 27.8% (44/158) of patients for blood and bone marrow, respectively. Frontline G-B appears to have manageable toxicity with clinical activity in CLL. Careful TLS risk assessment, pretreatment and monitoring is required.

Fig. 1

Progression-free survival in patients receiving G-B in cohort 1 of GREEN: a in the overall study population; b in fit vs unfit patients; c by genomic aberrations, according to the hierarchical model [29]; d by IGHV mutation status; and e by MRD status at final response assessment in blood (intent-to-treat population). *CIRS ≤6 and CrCl≥ 70 ml/min; ^†CIRS >6 and/or CrCl <70 ml/min; ^‡these data should be interpreted with caution as the subgroups are based on a study outcome, not baseline characteristics. There was also a low number of events (n = 20) and small number of MRD-positive patients (n = 9). The MRD-evaluable subgroup comprised patients who did not progress or die and had an MRD result available at the final response assessment in either blood or bone marrow (n = 105). The time window for MRD assessment was 77 to 168 days after last treatment. The MRD-‘missing’ subgroup included 54 patients. In addition, 1 out of 105 patients had a result available only in bone marrow and therefore came out as ‘missing’ in the blood population (therefore the ‘missing’ group in e is n = 55 and not 54). Reasons for ‘missing’ included sample not taken (n = 20), shipment could not take place within 48 h (n = 18), measurement was outside the time window for the final response assessment (n = 9) or other reason (n = 7). Eleven patients with missing MRD status (in blood and bone marrow) progressed (n = 5) or died (n = 6) within the period since last treatment dose up to 168 days. CIRS Cumulative Illness Rating Scale, CrCl creatinine clearance, G-B obinutuzumab plus bendamustine, IGHV immunoglobulin heavy variable chain, MRD minimal residual disease, PFS progression-free survival