Preclinical Evaluation of a Novel Orally Bioavailable Menin-MLL Interaction Inhibitor, DSP-5336, for the Treatment of Acute Leukemia Patients with MLL-Rearrangement or NPM1 Mutation

Background: The 11q23 abnormalities involving mixed lineage leukemia (MLL) gene are frequently found in adult and pediatric patients with acute leukemia. MLL rearrangements (MLL-r) are often associated with a poor prognosis and show poor response to currently available therapies, thus developing more effective therapy is urgently required. The leukemogenic activity of MLL fusion proteins, the products of the chimeric genes of MLL and its fusion partners generated by MLL-r, is critically dependent on direct interaction with MENIN, the product of the MEN1 gene. Interaction of MLL fusion proteins with MENIN plays an important role to enhance the proliferation and to block the differentiation of hematopoietic cells by maintaining high expression of hematopoietic stem cell program genes, such as HOXA9 and MEIS1. It has also been reported that the MENIN interaction with wild-type MLL, is required to induce HOXA9 and MEIS1 expression and also crucial for the development of acute leukemia with nucleophosmin (NPM1) mutations. Therefore, the MENIN-MLL interaction inhibitor is expected to have anti-leukemogenic activity against acute leukemia with MLL-r or NPM1 mutation by suppressing the expression of HOXA9 and MEIS1 and inducing terminal differentiation.

Results: We generated DSP-5336, a novel, potent, and orally bioavailable MENIN-MLL interaction inhibitor for the treatment of acute leukemia patients with MLL-r or NPM1 mutation. DSP-5336 directly bound to the MENIN protein (Kd = 6.0 nM) and inhibited the MENIN-MLL interaction (IC ₅₀ = 1.4 ± 0.058 nM). DSP-5336 selectively inhibited the cell growth of human leukemia cell lines including MV-4-11, MOLM-13, KOPN-8, and OCI-AML3 (IC ₅₀ = 10, 15, 31 and 15 nM, respectively). These DSP-5336-sensitive cell lines possess a MLL-r or NPM1 mutation. On the other hand, DSP-5336 did not affect the cell growth of human leukemia cell lines such as HL-60, MOLT-4, and Reh (IC ₅₀ > 10 μM), which do not have MLL-r or NPM1 mutations. In a mouse xenograft model using MV-4-11 cells, which express MLL-AF4, DSP-5336 exhibited a significant antitumor activity at the doses of 25 mg/kg and 50 mg/kg, administered twice daily (BID) for 20 days. There were no dose related changes in general condition or body weight. The effects of DSP-5336 on the expression of MENIN-MLL-regulated genes and differentiation marker genes were evaluated using MV-4-11 cells as pharmacodynamics markers in vitro and in vivo. In both cases, DSP-5336 significantly reduced the gene expression of MEIS1 and HOXA9, representative leukemic genes regulated by the MENIN-MLL complex. On the contrary, DSP-5336 significantly increased the gene expression level of ITGAM, a terminal differentiation marker.

The efficacy of DSP-5336 was further assessed in acute leukemia patient samples and in mouse AML models. DSP-5336 strongly inhibited blast colony formation and changed the gene expression of the pharmacodynamics markers (HOXA9, MEIS1 and ITGAM ) in an AML patient sample carrying the MLL-AF6 fusion. In patient-derived xenograft (PDX) model with NPM1 mutation, human CD45 positive cells in peripheral blood progressively decreased during and beyond the 28 day period of DSP-5336 administration at doses of 25, 50, and 100 mg/kg BID and achieved a complete remission with no relapse at the doses of 50 and 100 mg/kg BID. At these three dose levels, DSP-5336 also induced a significant prolongation of survival compared to the vehicle control. Similarly, in a PDX model with MLL-AF4, DSP-5336 induced complete remission and significant prolongation of survival at the doses of 100 mg/kg BID compared to the vehicle control. In mouse AML models wherein MLL-ENL- or MLL-AF10-transduced bone marrow cells are transplanted in syngeneic mice, DSP-5336 induced a significant prolongation of survival at the doses of 200 mg/kg once daily (QD) compared to the vehicle control and the standard chemo therapy (cytarabine+daunorubicin) group.

Summary: DSP-5336 has a potential as an antitumor drug that provides survival advantages in acute leukemia patients with MLL rearrangement or NPM1 mutation. Currently, a Phase 1/2 clinical study of DSP-5336 is planned in AML and ALL patients.