NGS-MRD Assessment of Combination Immunotherapies Targeting B-ALL

Minimal residual disease (MRD) monitoring is currently performed in B-ALL patients to evaluate treatment response and define risk stratification. Patients with good prognosis have undetectable MRD levels after treatment, while persistent MRD defines high relapse-risk patients. A standardized flow cytometry assay detects MRD reliably in bone marrow or peripheral blood at levels ≥0.01% mononuclear cells. More sensitive MRD assay detecting specific immunoglobulin heavy (IgH) chain rearrangement by next-generation sequencing (NGS) can approach reliably detectable blast level at ≤10-6 cells. Given the high sensitivity, the NGS-MRD approach improves distinction between deeply negative and very low positive cases. Recent studies also demonstrate that NGS-MRD assessment of the bone marrow with undetectable blast cells is a strong predictive factor, indicating patients with possible long-term response after CAR-T cell therapy.

In the past decade, adoptively transferred T cells modified with chimeric antigen receptors (CARs) have demonstrated high effectiveness and changed the treatment paradigm for B-ALL. More than 80% B-ALL patients achieved complete remission due to CAR-T treatment, but some patients with CR still have MRD that ultimately leads to relapse, which indicates the importance for further combination therapy to enhance anti-tumor immunity and to eradicate all malignant cells. Therefore, this protocol includes multi-target CAR-T cell infusions followed by cytotoxic T lymphocyte (CTL)-based immunotherapy, which react with B-ALL tumor antigens, and then followed by injection of immune-modified dendritic cells fused with leukemic cells (DCvac). In addition to the significant success of CAR-T cell therapy, various clinical studies also reported the importance and potential benefits of using engineered tumor-specific T cells in different types of cancer. Moreover, DC-based vaccine as another agent of immunotherapy has proven to prevent or delay relapse in leukemia patients achieving remission. In this study, we propose to combine those strategies to augment anti-tumor immunity in patients and expect undetectable NGS-MRD remission to prevent disease recurrence.

We propose a novel protocol which combines multiple CAR-T cell therapy, engineered immune effector CTLs and DCvac against B-ALL. The aim of this study is to evaluate the feasibility, safety, and efficacy of the NGS-MRD analysis-based combinational immunotherapy.