MARLBOROUGH, Mass., July 30, 2026
Sumitomo Pharma America announced that the U.S. Food and Drug Administration (FDA) has granted Orphan Drug Designation (ODD) to enzomenib (DSP-5336) for the treatment of acute lymphoblastic leukemia (ALL). The designation marks another regulatory milestone for the investigational oral therapy, which previously received FDA Orphan Drug Designation for acute myeloid leukemia (AML) in June 2022. Enzomenib is currently being evaluated in an ongoing Phase 1/2 dose-escalation and dose-expansion trial involving patients with relapsed or refractory acute leukemia, as well as the registrational Phase 2 Horizen-1 study targeting KMT2A-rearranged (KMT2Ar) and NPM1-mutated (NPM1m) AML and ALL. The latest designation reinforces the therapy’s potential to address significant unmet needs in rare and aggressive forms of leukemia..
FDA Orphan Drug Designation Strengthens Enzomenib’s Development Path
The FDA’s Orphan Drug Designation is awarded to investigational therapies intended to treat rare diseases or conditions, providing development incentives such as regulatory support, tax credits, and potential market exclusivity upon approval. According to Sumitomo Pharma America, the designation recognizes the urgent need for innovative therapies in acute lymphoblastic leukemia, a rapidly progressing blood cancer characterized by the uncontrolled production of abnormal lymphocytes in the bone marrow. If left untreated, ALL can quickly spread to the brain, spinal cord, and other organs, increasing the risks of severe infections, anemia, and bleeding complications. The company stated that it will continue working closely with the FDA to advance the clinical development of enzomenib and expand treatment options for patients with relapsed or refractory disease.
Menin Inhibitor Targets Key Genetic Drivers of Acute Leukemia
Enzomenib (DSP-5336) is an investigational oral small-molecule menin inhibitor designed to block the interaction between menin and KMT2A (lysine-specific methyltransferase 2A), a molecular pathway known to drive the growth and survival of certain leukemia cells. Preclinical studies have demonstrated that the therapy selectively inhibits leukemia cell lines harboring KMT2A rearrangements or NPM1 mutations, while reducing the expression of leukemia-associated genes HOXA9 and MEIS1 and promoting cellular differentiation through increased CD11b expression. These findings provide the scientific rationale for the ongoing clinical studies evaluating enzomenib in genetically defined subsets of AML and ALL, where targeted therapies may improve outcomes compared with conventional treatment approaches.
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Clinical Development Advances Across Multiple Regulatory Programs
The investigational therapy is currently being studied in the Phase 1/2 NCT04988555 trial involving patients with relapsed or refractory acute leukemia, alongside the registrational Phase 2 Horizen-1 trial evaluating patients with KMT2Ar-positive and NPM1-mutated AML and ALL. Beyond the newly granted Orphan Drug Designation for ALL, enzomenib previously received FDA Fast Track Designation in June 2024 for relapsed or refractory AML with KMT2Ar or NPM1 mutations, as well as Orphan Drug Designation from Japan’s Ministry of Health, Labour and Welfare in September 2024 for the same AML indication. Together, these regulatory milestones underscore Sumitomo Pharma’s commitment to advancing precision oncology therapies aimed at improving treatment options for patients with difficult-to-treat acute leukemias.
Source:Sumitomo Pharma ,press release
