Efficacy and Safety of Treatment Venetoclax Monotherapy or Combined with Rituximab in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia (CLL) in the Real -World Setting in Spain: The Venares Study

Introduction: The BCL-2 inhibitor venetoclax (Ven) has been approved on monotherapy or combined with rituximab in relapsed/refractory CLL patients (pts) and combined with obinutuzumab in previously untreated CLL pts. However, evidence from clinical trials can be difficult to generalize to real-world patient populations. The VENARES study assesses the real-world use of Ven following approval to inform of subpopulations underrepresented in clinical trials.

Methods: This is Spanish non-interventional retrospective, multicenter post-marketing observational study. The main objective was to evaluate the effectiveness of Ven in adult CLL pts by the overall response rate (ORR) at 9 months (mo) after the first Ven dose administration. Secondary objective was to evaluate the effectiveness for the Ven monotherapy and the Ven combined with rituximab subpopulations. Consecutive adult pts with diagnosis of CLL who have initiated Ven at least 9 mo before the inclusion in the study were included. Data of pts are retrospectively reviewed until the date of last follow-up or death.

Results: 125 pts diagnosed with CLL and who met the eligibility criteria were analyzed. The median age was 72 years (67 - 77) with 76.8% being older than 65 years. Most patients were male (68.8%), had a concurrent disease (65.6%). ECOG PS was recorded in 76 pts: 40 pts (32%) had PS 0, 30 pts (24%) PS 1 and 6 pts (4.8%) PS 2. Pts had received a median of 4 prior lines of therapy (range 1-13 lines).

At baseline, among the 92 pts with known Binet stage, 31 (33.7%) had stage C and 38 (41.3%) had stage B; bulky nodes ≥ 5 cm were present in 20 of 87 pts; 49 pts (39.2%) had an absolute lymphocyte count ≥ 25 x 10 ⁹/L and 33 of 54 pts (61%) baseline beta-2 microglobulin value above of 3500 ng/mL. In total, 29 of 90 patients (32%) assessed had Cr 17p deletion, 28 of 86 patients (32%) tested had TP53 mutations, and 46 of 56 patients (82%) who were tested had unmutated immunoglobulin heavy-chain variable (IGHV) status.

Ven was administered as monotherapy in 71 pts (57.6%), combined with rituximab in 36 pts (28.8%), combined with obinutuzumab in 5 pts (4%) and combined with other drugs in 13 pts (10.4%).

83 of 125 patients included were evaluable for the primary objective of the study: the ORR at 9 mo was 84.3% (70 patients): CR/CRi in 44 (53%) pts, PR/nPR in 26 pts (31.3%), SD in 9 pts (10.8%) and PD in 4 pts (4.8%). By treatment, in the evaluable patients, ORR at 9 months were 79.2% (38 of 48 patients) in the Ven monotherapy group, with 45% of CR/CRi, and 92.3% (24 of 26 patients) in the Ven combined with rituximab, with 61% CR/Cri.

The median duration of PFS was not reached at the time of the analysis (1-June-2021). Kaplan-Meier estimates of the probability of PFS at 24 mo was 75.4% (95% CI, 58.2 - 86.3). Disease progression occurred in 21 pts.

Assessment of minimal residual disease (MRD) was available for 32 patients (25.6%) on the basis of peripheral-blood samples, bone marrow or both. Best undetectable MRD was reached in fourteen patients (43.8%). uMRD was more common in pts treated with Ven combined with R (83.3%, 5 of 6 pts) than in pts treated with Ven monotherapy (33.3%, 7 of 21 pts).

Adverse events (AEs) were reported during Ven therapy in all 125 patients, 93 of these pts reported AEs related to Ven. Related to Ven, 67 patients (53.6%) experienced at least one AE: 52 pts (41.6%) had neutropenia being grade 3 and 4 in 22 (42.3%) and 9 (17.3%) pts, respectively. 9 pts (7.2%) had febrile neutropenia. Thrombocytopenia and anemia were less common occurring in 5.6% and 2.4%, respectively.

Tumor lysis syndrome (TLS) occurred in 4 of 125 pts during ramp-up (3 laboratory and 1 clinical), 2 of them were related to Ven both lab TLS. None of the pts discontinued therapy due to TLS. Richter transformation was observed in 6 pts (4.8%). Other common AEs was diarrhea (10.4%), but most cases were mild.

Conclusions: Our first real-world data show that Ven monotherapy or combined with rituximab is effective in highly pre-treated CLL patients, ORR at 9 mo was 84.3% in all population and PFS estimate at 24 mo was 75.4% with similar outcomes to those in the pivotal clinical trials. The safety profile of Ven was consistent with prior experience of Ven in monotherapy or combined with rituximab and no new safety signals were detected.