<p>B-cell acute lymphoblastic leukemia (ALL) with <i>KMT2A</i> rearrangements (<i>KMT2A</i>r B-ALL) represents a distinct, high-risk subtype in adults, characterized by aggressive disease biology, high relapse rates, and inferior long-term survival. Conventional intensive chemotherapy, even when consolidated with allogeneic hematopoietic stem cell transplantation (allo-HSCT), yields suboptimal outcomes, underscoring the need for novel therapeutic approaches. In recent years, substantial progress has been made with the introduction of antibody-based immunotherapies, cellular immunotherapies, and small molecular inhibitors, reshaping the treatment landscape for this challenging subgroup. This review provides a comprehensive overview of current and emerging therapeutic strategies for adult patients with <i>KMT2A</i>r B-ALL. We summarize outcomes associated with pediatric-inspired chemotherapy and allo-HSCT, focus on clinical evidence for antibody-based immunotherapy including blinatumomab and inotuzumab ozogamicin, across frontline, consolidation, and relapsed or refractory settings. Advances in cellular immunotherapy, particularly CD19-directed chimeric antigen receptor T-cell therapy, are discussed, with a focus on unique resistance mechanisms such as antigen loss and lineage switch. In addition, we review the biological rationale, efficacy and emerging resistance mechanisms of menin inhibitors, a promising class of agents specifically targeting the epigenetic dependency of <i>KMT2A</i>-rearranged leukemia. Finally, other molecular approaches, including epigenetic modifiers, apoptosis pathway inhibitors, and signaling pathway inhibitors are discussed. Despite these advances, treatment resistance and disease relapse remain major obstacles. These ongoing challenges highlight the urgent need for multi-center, prospective trials to investigate rational combination strategies to improve outcomes for adults with <i>KMT2A</i>r B-ALL.</p>