Chemotherapy-Free Induction with Venetoclax and Azacitidine, Followed By Tandem CD19/CD22 CAR-T Cell Therapy As First-Line Treatment in Newly Diagnosed High-Risk Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia: A Prospective, Single-Center, Single-Arm, Phase 2 Trial

Background:

The high-risk genetic subsets of acute lymphoblastic leukemia (ALL) were associated with higher rates of induction failure, persistent measurable residual disease (MRD), and dismal prognosis (Nicola Gökbuget, Blood. 2012 Aug 30;120(9):1868-76.). Anti-apoptotic Bcl-2 family proteins have been identified as crucial pro-survival factors across multiple high-risk ALL subtypes, including KMT2A-rearranged, Ph-like, and hypodiploid B-ALL (Felix Seyfried, Leukemia. 2022 Apr;36(4):901-912.). Venetoclax, a selective Bcl-2 inhibitor, has shown anti-leukemic effects in combination with hypomethylating or conventional chemotherapy in both preclinical and clinical studies in ALL (Laurence C Cheung, Leukemia. 2023 Jan;37(1):61-71.). Chimeric antigen receptor T (CAR-T) cell therapies targeting CD19/CD22 have demonstrated manageable safety profiles and significant efficacy in relapsed/refractory (R/R) B-ALL, achieving high rates of MRD negativity (Wei Cui, Am J Hematol . 2023 Nov;98(11):E338-E340. ). This study aimed to assess the feasibility of a chemotherapy-free induction regimen using the combination of venetoclax and azacitidine (VA), and to evaluate the integration of autologous tandem CD19/CD22 CAR-T cell therapy as a first-line treatment option for high-risk B-ALL patients.

Design:

In this single-center, single-arm, phase 2 trial (NCT06078306) conducted in the First Affiliated Hospital of Soochow University, newly diagnosed high-risk Ph-negative B-ALL patients aged 15–65 years were enrolled. VA consisted of 21-day courses of venetoclax (100mg on day 1, 200mg on day 2, 400mg/day on days 3-21), 7-day courses of azacitidine (75 mg/m²/day on days 1-7). Following induction of VA, patients received autologous tandem CD19/CD22 CAR-T cell therapy as a single infusion (target dose 2.0×10⁷CAR-positive viable T cells per kg) 2 days after completion of lymphodepletion. The primary endpoint was the MRD-negativity after induction treatment. Secondary endpoints were adverse events (AEs), and survival.

Results:

As of July 2024, among the 12 patients enrolled, 50% were adolescents and young adults (15-39 years), with the remaining 50% being older adults (40-65 years). High-risk cytogenetic or molecular factors were detected in 100% patients. Specifically, four patients had a detectable KMT2A rearrangement, two had Ph-like ALL characteristics (one with CRLF2 overexpression and one with EBF1::CSF1R rearrangement),, and three had TP53 mutations (two with TCF3::PBX1 rearrangement and concomitant deletions in CDKN2A/B and PAX5, and one with hypodiploidy). Additionally, there was one patient each with ZNF384 rearrangement, MEF2D rearrangement, and IKZF1-IK6.

CR was achieved in 7(63.6%) patients after the initial induction therapy of VA, and MRD negativity was achieved in 5 patients (45.5%). Among those who did not achieve CR, a median reduction of 93% in bone marrow blasts and hematopoietic recovery was observed. Post CD19/CD22 CAR-T cell infusion, the CR rate was 91%, and MRD negativity was 81.8%. During VA induction, grade ≥3 AEs included neutropenia (72.7%) and thrombocytopenia (51%), with median recovery times of 14 and 2 days, respectively. Non-haematological grade 3 AEs were sepsis in one (9.1%), and laboratory tumor lysis syndrome was documented in 27.3% of patients. Grade 1-2 CRS occurred in 63.6% (7/11) of patients during CAR-T cell infusion, and only one patient experienced grade 3 CRS. No cases of ICANS or neurotoxicity was observed. There were no treatment-related deaths during induction. With a median follow-up of 17 months (range 10-22), the estimated 1-year overall survival rate (OS) was 81.8% (95% CI: 44.7–95.1, and the 1-year leukemia-free survival rate (LFS) was 68.2% (95% CI: 28.6– 89.1).

Conclusion:

The chemotherapy-free induction with the combination of venetoclax and azacitidine, followed by tandem CD19/CD22 CAR T-cell therapy demonstrated profound responses in patients with newly diagnosed high-risk Ph-negative ALL. The lower incidence and severity of CRS showed a more favorable safety profile than in R/R ALL. These results support a favorable clinical benefit-risk profile of this regimen as a first-line treatment option in newly diagnosed, high-risk Ph-negative ALL patients.