Phase II Results of ECOG-ACRIN EA9152: A multicenter study of liposomal vincristine (L-VCR) or vincristine sulfate (VCR) and venetoclax (VEN) in relapsed or refractory acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LL)

Abstract Background: Relapsed or refractory (R/R) acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LL) remain challenging to treat, particularly in older patients and those with a T-cell phenotype. Venetoclax (VEN), a selective BCL-2 inhibitor, has shown preclinical synergy with vincristine (VCR) in multiple preclinical ALL models. Following the previously reported establishment of the recommended Phase II dose (RP2D), we now report the results of the Phase II (Ph2) portion of EA9152 (VEN 600 mg daily with weekly L-VCR 2.25 mg/m² IV or VCR 1.5 mg/m2 IV capped at 2 mg), evaluating efficacy and safety in this high-risk population. Methods: This open-label, multicenter Phase II study enrolled adults (≥18 years) with R/R B- or T-cell ALL or LL. The phase II portion of this trial was a single-arm, open-label study evaluating the combination of VEN (600 mg po D1–28) with either L-VCR (2.25 mg/m² IV weekly x4) or vincristine sulfate (VCR) (1.4 mg/m² IV weekly x4). Following the market withdrawal of L-VCR in the United States in April 2022, no new patients were initiated on this formulation and patients already receiving L-VCR were transitioned to VCR at the start of their next treatment cycle or sooner if necessitated by drug availability. Prior VCR but not VEN exposure was permitted in Ph2. The primary endpoint was achievement of a complete response or complete response with incomplete count recovery CR + CRi rate by end of cycle 3. Secondary endpoints included measurable residual disease (MRD) response, progression free survival (PFS), overall survival (OS), and safety. The association of phenotype with response and time-to-event were evaluated using Fisher's exact test and the Cox proportional hazards model, respectively. Results: Twenty-one eligible patients were treated (B-cell ALL/LL: n=12; T-cell ALL/LL: n=9). The trial was terminated early after 22/56 patients were accrued on account of withdrawal of sponsor support. Median age was 50 years and 76.2% were male. Performance status was 0–1 in 85.7%. All patients had received prior chemotherapy; 47.6% had undergone prior transplant. Median number of treatment cycles was 1 (2 for B-cell, 1 for T-cell). By end of cycle 3, no patients in the B-cell cohort (0/12; 90% CI, 0.00–0.22) achieved CR or CRi, 8 had stable disease (SD). In the T-cell cohort, 1 of 9 patients (11.1%; 90% CI, 0.01–0.43) achieved CR, 1 achieved PR and 1 had SD. There was no statistically significant difference in CR + CRi rate between phenotypes (p=0.43). None of the patients achieved an MRD-negative CR/CRi by flow cytometry or molecular methods. At the time of this analysis, 16 of 21 patients had died. Median overall survival (OS) was 4.3 months (95% CI, 1.5–22.0) for B-cell and 10.2 months (95% CI, 2.0–16.4) for T-cell patients (HR 1.32, p=0.60). Median PFS was 2.9 months (95% CI, 1.7–3.7) for B-cell and 1.2 months (95% CI, 0.7–4.6) for T-cell cohorts (HR 2.18, p=0.18). Grade 3–5 treatment-related adverse events occurred in most patients. One T-cell patient experienced grade 5 respiratory failure. Among 16 patients enrolled under the revised protocol using VCR, only 1 experienced grade 3 peripheral motor neuropathy, and no peripheral sensory neuropathy was reported (combined AE rate 0.06; 90% CI, 0.00–0.26). Tumor lysis syndrome was not observed in this cohort. Conclusions: The combination of VEN at the established RP2D and L-VCR/VCR was feasible and had an acceptable safety profile in heavily pretreated patients with R/R ALL/LL. However, response rates, including CR/CRi and MRD negativity, were limited, particularly in the B-cell cohort. Median OS and PFS remain poor in both subtypes, highlighting the need for improved strategies in this high-risk population. Venetoclax, in combination with other chemotherapy regimens, has shown encouraging response rates warranting continued exploration of its benefit in ALL.