Kryachok, Iryna

Introduction: The primary analysis of the phase 3 ECHO trial (NCT02972840) demonstrated that acalabrutinib plus bendamustine-rituximab (ABR) significantly improved progression-free survival (PFS) vs placebo plus bendamustine-rituximab (PBR) in older patients (pts) with previously untreated mantle cell lymphoma (MCL) (Wang et al. EHA 2024, Abstract #LB3439). Here we present additional efficacy and safety results from the ECHO trial. Methods: Pts aged ≥65 years (y) with previously untreated MCL and ECOG PS ≤2 were randomly assigned 1:1 to receive ABR or PBR. Acalabrutinib (100 mg twice daily) or placebo was administered until progressive disease (PD) or unacceptable toxicity. Induction with BR was administered for 6 cycles followed by rituximab maintenance (A±R maintenance, cycles 7-30) in pts achieving a partial or complete response (PR or CR). Pts progressing on PBR could cross over to receive acalabrutinib monotherapy. PFS (primary endpoint) was assessed by independent review committee. Minimal residual disease (MRD) negativity rate (10-5) was assessed in peripheral blood (every 24 weeks [wks], at CR, and at PD) and bone marrow (at CR) by NGS-based ClonoSEQ assay (Adaptive Biotechnologies). Results: Among the 598 pts randomized to ABR or PBR (299 in each arm), high-risk baseline characteristics included high-risk simplified MIPI score in 24.1% and 24.4%, blastoid histology in 8.7% and 6.7%, pleomorphic histology in 5.0% and 6.0%, centrally tested Ki-67 ≥30% in 46.5% and 49.2%, and known TP53 mutation in 7.4% and 9.7%, respectively. PFS hazard ratios (HRs) for subgroups were 0.78 (95% confidence interval [CI] 0.51-1.19) in pts with high-risk simplified MIPI score, 0.68 (95% CI 0.29-1.58) in pts with blastoid histology, 0.64 (95% CI 0.25-1.66) in pts with pleomorphic histology, 0.69 (95% CI 0.49-0.98) in pts with Ki-67 ≥30%, and 0.88 (95% CI 0.42-1.78) in pts with known TP53 mutation. In the ABR arm, median PFS was 22.2 months (mo) among pts who discontinued acalabrutinib during induction for reasons other than PD or death, 29.4 mo in pts who discontinued acalabrutinib during A±R maintenance (cycles 7-30) for reasons other than PD or death, and not reached in pts who received acalabrutinib for 31 cycles or more. Among evaluable patients who were MRD negative at the end of induction (24 wks), the rate of conversion to MRD positive during maintenance was lower in the ABR arm (5.85%; n=11/188) than in the PBR arm (15%; n=26/171). Conversely, among evaluable pts who were MRD positive at the end of induction (24 wks), 37.5% (n=3/8) in the ABR arm and 20% (n=3/15) in the PBR arm converted to MRD negative during maintenance. Overall rates of AEs were similar in each arm during induction, but were higher in ABR during A±R maintenance (cycles 7-30) and more so in the monotherapy phase (cycle 31+). Grade ≥3 TEAEs (ABR vs PBR) were 70.0% vs 68.7% during induction, 64.9% vs 62.9% during A±R maintenance (cycles 7-30), and 57.0% vs 45.3% during monotherapy (cycle 31+). Similarly, rates of TEAEs leading to discontinuation of acalabrutinib/placebo were 8.1% vs 8.8% during induction, 23.9% vs 19.0% during A±R maintenance (cycles 7-30), and 25.9% vs 13.7% during monotherapy (cycle 31+). Exposure-adjusted incidence rates per 100 person-years reduced the difference between ABR and PBR for clinically relevant TEAE rates (32.6 vs 29.3 for grade ≥3 serious TEAEs; 4.2 vs 4.0 for grade 5 TEAEs; 15.5 vs 12.4 for TEAEs leading to acalabrutinib/placebo discontinuation), possibly due to longer median exposure to acalabrutinib (28.6 vs 24.6 mo). Conclusion: Acalabrutinib in combination with BR provides a significant PFS benefit in pts with previously untreated MCL, including those with high-risk features. Furthermore, the addition of acalabrutinib to BR provided a greater PFS effect among pts in the ABR arm with the longest exposure to acalabrutinib. The PFS improvement may be partially driven by the contribution of acalabrutinib to sustained MRD-negative status and deepened responses after the end of induction. ABR provides this clinical benefit without excess toxicity as shown by attenuated differences between arms in exposure-adjusted incidence rates, suggesting that higher AE rates in the ABR arm are likely due in part to the longer duration of acalabrutinib treatment vs placebo. These data emphasize the benefits of acalabrutinib in frontline MCL treatment in high-risk pts and the additional benefit of continuous therapy.

Introduction BCL-2 inhibition with venetoclax (ven) was a major advance in CLL treatment, but the 5-week dose ramp-up to mitigate the risk of tumor lysis syndrome and drug-drug interactions (DDIs) challenge treatment optimization. Lisaftoclax is an investigational, oral BCL-2i with a short half-life, allowing it to be ramped-up on a daily schedule. We present updated results of a phase 1b/2 study of lisaftoclax alone or combined with acalabrutinib or rituximab in pts with treatment-naïve (TN; lisaftoclax-acalabrutinib arm), relapsed/refractory, or prior ven-treated CLL/SLL (NCT04215809). Methods Pts were treated with a rapid 4- to 6-day daily ramp-up of lisaftoclax from 20 mg to a target dose of 400, 600, or 800 mg, receiving daily oral lisaftoclax alone or, plus continuous acalabrutinib or 6 cycles of rituximab in 28-day cycles, starting on Cycle 1 Day 8 (C1D8) until disease progression, complete response by C24, or unacceptable toxicity. Intensive blood samples were collected for pharmacokinetic (PK) and exposure-response (E-R) analyses. Results From March 20, 2020, to June 27, 2024, 176 pts were enrolled: 46 in monotherapy and 39 and 91 in rituximab and acalabrutinib combination cohorts, respectively; 154/176 (87.5%) were R/R and 22/176 (12.5%) TN. The median (range) age was 63 (34-80) years; 67% were male; 25.6% had del(17p) and/or TP53 mutation; and 70.6% had unmutated IGHV. Median (range) duration of treatment with lisaftoclax was 16.5 (1-54; monotherapy), 24 (3-39; rituximab), and 27 (1-43; acalabrutinib) months. In R/R pts, the median (range) number of prior lines of therapy was 2 (1-15), and 14 (9%) pts had been treated with ven. Prior ven pts had a median (range) age of 65 (51-78); 79% were male; of evaluable pts, 50% had del(17p), 36% TP53 mut, 64% del(11q), 38% complex karyotype (≥ 3 abnormalities), and 92% unmutated IGHV; 57% were BTKi naïve; and the median (range) number of prior therapies was 3 (1-6). Incidence and severity of TEAEs were similar across cohorts. Common (>10%) any-grade TEAEs in all cohorts combined were neutropenia (59 [33.5%]), diarrhea (38 [21.6%]), anemia (27 [15.3%]), and thrombocytopenia (26 [14.8%]). Grade ≥ 3 TEAEs were neutropenia in 15 (32.6%), 10 (25.6%), and 22 (24%) pts and anemia in 10 (21.7%), 5 (12.8%), and 12 (13.2%) pts in monotherapy, rituximab, and acalabrutinib combination cohorts, respectively. Comprehensive E-R analyses indicated that lisaftoclax had similar systemic exposure as monotherapy or when combined with acalabrutinib or rituximab; lisaftoclax had no DDI when combined with acalabrutinib or rituximab. No discontinuations were attributed to lisaftoclax TRAEs. Forty-four (95.7%) pts in monotherapy discontinued treatment. Most discontinuations were due to progressive disease (n = 41 [23.3%]) and 13 (7.4%), AEs; 9 (5.1%) pts withdrew consent; 7 (4%) achieved complete response or MRD negativity after ≥ 24 cycles; 5 (2.8%) died; and 18 (10.2%) discontinued for other reasons. Clinical (n = 2) and laboratory (n = 3) TLS was observed in 5 (2.8%) pts on lisaftoclax (by Howard/Cairo-Bishop criteria), with cases rapidly resolving to resume lisaftoclax safely. ORR for lisaftoclax plus acalabrutinib in 87 pts was 96.6%, and the median DOR (95% CI, 23-NR) and median PFS (95% CI, 34-NR) were not reached. The 12- and 18-month PFS rates were 89% and 86%, respectively. Fourteen R/R CLL ven-exposed pts received lisaftoclax plus acalabrutinib, of whom 9 had progressed on ven, 3 relapsed after completing ven, and 2 discontinued due to ven intolerance. Median (range) duration of treatment was 16 (3-25) months. Safety profile was similar to that of other study cohorts. ORR was 85.7% (12/14), 100% (8/8), and 66.7% (4/6) in the ven-exposed, ven-exposed but BTKi-naïve, and ven- and BTKi-exposed pts, respectively. The median duration of response (DOR) and progression-free survival (PFS) were not reached. The 12- and 18-month PFS rates were 84% and 73%, respectively. Conclusions Our data suggest that lisaftoclax combined with acalabrutinib is effective for pts with prior ven exposure, including those with progression on ven. In this updated analysis with longer follow-up, no DDIs or new safety findings were observed in TN or R/R CLL/SLL pts treated with lisaftoclax monotherapy/combinations. We continue to accrue pts with prior ven exposure to further evaluate this promising signal. A global registrational phase 3 study GLORA (NCT06104566) is recruiting.