Efficacy and Potential Limitation of the Menin Inhibitor Revumenib Outside Clinical Trials: Extramedullary Response with Central Nervous System Escape in a Case of KMT2A-Rearranged Acute Myeloid Leukemia

Acute myeloid leukemia (AML) harboring KMT2A rearrangements (KMT2A-r) accounts for approximately 5–10% of newly diagnosed cases and represents a high-risk AML subtype associated with poor clinical outcomes despite intensive treatment strategies, including allogeneic hematopoietic stem cell transplantation (HSCT). KMT2A-r AML is also characterized by a higher incidence of extramedullary disease compared with other AML subtypes. Therapeutic options for patients with relapsed/refractory (R/R) disease, particularly after post-HSCT relapse, remain extremely limited. In recent years, menin inhibitors have emerged as a promising targeted therapeutic class for KMT2A-r and NPM1-mutated AML by disrupting the aberrant HOX/MEIS1 transcriptional program. Revumenib, a first-in-class menin inhibitor, has shown encouraging efficacy in early-phase clinical trials. Other menin inhibitors, including ziftomenib, bleximenib, and enzomenib, have also demonstrated clinical activity, with distinct pharmacokinetic, pharmacodynamic, and safety profiles. We report the case of a 36-year-old patient with KMT2A-r AML who relapsed after HSCT with both bone marrow and hepatic involvement. Compassionate-use treatment with revumenib (160 mg twice daily on days 1–28 of each 28-day cycle) induced, after two treatment cycles, complete hematologic remission with no detectable abnormal myeloid blast population by multiparameter flow cytometry (MFC) and complete radiological resolution of hepatic lesions. However, despite prior intrathecal CNS-directed therapy and sustained systemic disease control, the patient subsequently developed an isolated central nervous system (CNS) relapse. This case highlights a potential discordance between systemic and CNS disease control during menin inhibitor therapy and emphasizes the need for further investigation into CNS surveillance and disease management in patients achieving deep systemic responses.