Fixed-duration venetoclax-obinutuzumab for previously untreated patients with chronic lymphocytic leukemia: Follow-up of efficacy and safety results from the multicenter, open-label, randomized, phase III CLL14 trial

8027 Background: The CLL14 trial demonstrated significant improvement of progression-free survival (PFS) with fixed-duration venetoclax-obinutuzumab (VenG) as compared to chlorambucil-obinutuzumab (ClbG) in patients with previously untreated CLL and coexisting conditions. Here, we report follow-up data on safety and efficacy. Methods: Patients with previously untreated CLL and coexisting conditions were randomized 1:1 to receive 12 cycles of venetoclax with 6 cycles of obinutuzumab or 12 cycles of chlorambucil with 6 cycles of obinutuzumab. Primary endpoint was investigator-assessed progression-free survival. Key secondary endpoints were response rates, rates of minimal residual disease (measured every 6 months up to 5 years after last patient enrolment) and overall survival. Follow-up is ongoing but all patients are off study treatment. This trial was registered with ClinicalTrials.gov, number NCT02242942. Results: Of the 432 enrolled patients, 216 were randomly assigned to receive VenG and 216 to receive ClbG. After a median follow-up of 39.6 months (interquartile range 36.75 - 43.04), progression-free survival continued to be superior for VenG as compared to ClbG (median not reached vs 35.6 months; hazard ratio [HR] 0.31 [0.22-0.44], p < 0.001). At 3 years, the estimated progression-free survival rate was 81.9% in the VenG arm and 49.5% in the ClbG arm. This benefit was consistently observed across all clinical and biological risk groups, including patients with TP53 mutation/deletion and unmutated IGHV status. Of note, PFS was also significantly longer for VenG treated patients with mutated IGHV status. Assessment of minimal residual disease 18 months after end of treatment showed that 47.2% of patients in the VenG arm had undetectable (u) uMRD ( < 10−4), 13% had low (L)-MRD (≥ 10−4 and < 10−2) and 7.9% high (H)-MRD (≥ 10−2), compared to 7.4% uMRD, 17.1% L-MRD, 26.9% H-MRD in the ClbG arm. No difference has been observed (HR 1.027, 95% CI 0.602-1.753, p = 0.921) for overall survival; median overall survival has not been reached in either group. Second primary malignancies were reported in 36 (17%) patients in the VenG arm and 22 (10.3%) in the ClbG arm. No new safety signals were observed. Conclusions: The results suggest that the superior efficacy and deep remissions after fixed-duration VenG are maintained during extended follow-up, and show the long-term benefits of 12 cycles of VenG across all known risk categories. Clinical trial information: NCT02242942 .