Study Background This clinical trial compares blinatumomab and nivolumab combination therapy with single-agent therapy in patients with relapsed B-cell acute lymphoblastic leukemia (B-ALL). Blinatumomab is a bispecific antibody that connects T cells to recognize cancer cells, and nivolumab is a PD-1 inhibitor that enhances the immune response. The hypothesis is that the simultaneous use of the two drugs can create a synergistic effect in immune activation. ## Subjects and Design This is a Phase 2, multi-center, randomized, open-label study, currently recruiting. It includes patients with relapsed B-ALL, especially those with Down syndrome. The primary endpoints are progression-free survival (PFS) and overall survival (OS), and the secondary endpoint is the treatment response rate. The expected completion date has not yet been specified. ## Differentiation from Existing Treatments The current standard treatment for relapsed B-ALL is chemotherapy and CAR-T cell therapy. Blinatumomab has already been approved as a single agent, but the combination with an immune checkpoint inhibitor has not yet been validated. The combination therapy is expected to provide sustained response compared to existing treatments by simultaneously blocking cancer cell evasion mechanisms. ## Clinical Significance and Market Impact If successful, the combination of immune checkpoint inhibitors and bispecific antibodies may present a new treatment paradigm. This is likely to provide significant benefits, especially for high-risk patients, such as those with Down syndrome. Conversely, if ineffectiveness is confirmed, the combination strategy of the two drugs will be re-evaluated, and investors should carefully review the pipeline in this area.