Results of a phase II multicenter study of obinutuzumab plus bendamustine in pts with previously untreated chronic lymphocytic leukemia (CLL)

7523 Background: Bendamustine (B) + rituximab (R; BR) is a commonly used 1L treatment for CLL. The CLL10 study reported an ORR of 96% and CR of 31% with BR. Obinutuzumab (GA101; G) is a glycoengineered, type II anti-CD20 monoclonal antibody. A randomized Phase III trial in 1L CLL pts showed that G significantly improved PFS and CR rate compared with R, when used in combination with chlorambucil (Goede 2014). B + G (BG) was evaluated in a subgroup of CLL pts in the GREEN study (Stilgenbauer 2015). We present results of a Phase II study (NCT02320487) evaluating the efficacy and safety of BG as 1L treatment for CLL pts. Methods: 102 pts with previously untreated CLL received BG, consisting of 6 cycles of G (cycle [C] 1: 100mg day (D) 1, 900mg D2, 1000mg D8 and D15; C2–6: 1000mg D1) and B (90mg/m2: C1, D2 and D3; C2–6, D1 and D2). Each cycle was 28 days. Primary endpoint was CR assessed using iwCLL criteria. Secondary endpoints included ORR, PFS, OS, and MRD. Median follow-up at the time of analysis was 11.0 months. Results: Median pt age was 61 yrs (range 35–90); 68.6% were male; 44.1% had Rai stage 3–4. For evaluated pts, IgVH status was 32.9% mutated and 67.1% unmutated. The incidences of trisomy 12, normal cytogenetics, and deletions of 13q, 11q, and 17p were 23.4%, 37.5%, 17.2%, 15.6%, and 6.3%, respectively. Investigator-assessed CR rate was 49.0% (95% CI 39.0–59.1) and ORR was 89.2% (95% CI 81.5–94.5) after 6 cycles. MRD negativity (MRD-) in blood, as measured by 4-color flow cytometry, was achieved in 42.7% of pts at the end of induction response assessment and in 75.5% of pts at any time following treatment. MRD- in bone marrow (BM) was 60.8% in pts with BM samples. The most common AEs (all grades [Gr]) were infusion reactions (72.5%), nausea (52.0%), pyrexia (36.3%), neutropenia (34.3%), fatigue (34.3%), constipation (26.5%), and rash (26.5%). The most common Gr 3–4 AE was neutropenia (26.5%). Incidence of Gr 3–4 infections was 11.8%. Incidence of TLS was 4.9% (all Gr 3). Three pts died; none were deemed related to study treatment or CLL by investigators. Conclusions: BG is an effective regimen for 1L treatment of CLL pts, inducing a high CR rate after 6 cycles of therapy. No unexpected safety signals were observed. Clinical trial information: NCT02320487.