Summary Chromosomal translocations affecting Mixed Lineage Leukemia gene (MLL) result in acute leukemias resistant to therapy. The leukemogenic activity of MLL fusion proteins is dependent on their interaction with menin, providing basis for therapeutic intervention. Here we report development of highly potent and orally bioavailable small molecule inhibitors of the menin-MLL interaction, MI-463 and MI-503, show their profound effects in MLL leukemia cells and substantial survival benefit in mouse models of MLL leukemia. Finally, we demonstrate efficacy of these compounds in primary samples derived from MLL leukemia patients. Overall, we demonstrate that pharmacologic inhibition of the menin-MLL interaction represents an effective treatment for MLL leukemias in vivo and provide advanced molecular scaffold for clinical lead identification.

Summary Translocations involving the Mixed Lineage Leukemia (MLL) gene result in human acute leukemias with very poor prognosis. The leukemogenic activity of MLL fusion proteins is critically dependent on their direct interaction with menin, a product of the MEN1 gene. Here, we present the first small molecule inhibitors of the menin-MLL fusion protein interaction that specifically bind to menin with nanomolar affinities. These compounds effectively reverse MLL fusion protein-mediated leukemic transformation by downregulating the expression of target genes required for MLL fusion protein oncogenic activity. They also selectively block proliferation and induce both apoptosis and differentiation of leukemia cells harboring MLL translocations. Identification of these compounds provides a new tool for better understanding MLL-mediated leukemogenesis and represents a new approach for studying the role of menin as an oncogenic cofactor of MLL fusion proteins. Our findings also highlight a new therapeutic strategy for aggressive leukemias with MLL rearrangements.

Plasmodium falciparum parasites are responsible for the major global disease malaria, which results in >2 million deaths each year. With the rise of drug-resistant malarial parasites, novel drug targets and lead compounds are urgently required for the development of new therapeutic strategies. Here, we address this important problem by targeting the malarial neutral aminopeptidases that are involved in the terminal stages of hemoglobin digestion and essential for the provision of amino acids used for parasite growth and development within the erythrocyte. We characterize the structure and substrate specificity of one such aminopeptidase, PfA-M1, a validated drug target. The X-ray crystal structure of PfA-M1 alone and in complex with the generic inhibitor, bestatin, and a phosphinate dipeptide analogue with potent in vitro and in vivo antimalarial activity, hPheP[CH 2]Phe, reveals features within the protease active site that are critical to its function as an aminopeptidase and can be exploited for drug development. These results set the groundwork for the development of antimalarial therapeutics that target the neutral aminopeptidases of the parasite. drug design ͉ malaria ͉ structural biology ͉ protease T here are 300-500 million cases of clinical malaria annually, and 1.4-2.6 million deaths. Malaria is caused by apicomplexan parasites of the genus Plasmodium, with Plasmodium falciparum the most lethal of the 4 species that infect humans. Clinical manifestations begin when parasites enter erythrocytes, and most antimalaria drugs, such as chloroquine, exert their action by preventing the parasite development within these cells (1). As a result of the rapid spread of drug-resistant parasites, there is a constant need to identify and validate new antimalarial targets.Intraerythrocytic parasites have limited capacity for de novo amino acid synthesis and rely on degradation of host hemoglobin (Hb) to maintain protein metabolism and synthesis, and an osmotically stable environment within the erythrocyte (1-4). Within the erythrocytes, malaria parasites consume as much as 75% of the cellular Hb (1). Hb is initially degraded by the concerted action of cysteine-, aspartyl-, and metalloendoproteases, and a dipeptidase (cathepsin C) within a digestive vacuole (DV) to di-and tripeptide fragments (5, 6). These fragments are suggested to be exported to the parasite cytoplasm, where further hydrolysis to release free amino acids takes place [supporting information (SI) Fig. S1; see refs. 7 and 8].The release of amino acids involves 2 metallo-exopeptidases: an alanyl aminopeptidase, PfA-M1 (9, 10), and a leucine aminopeptidase, PfA-M17 (7,11,12). We have demonstrated that the aminopeptidase inhibitor bestatin, an antibiotic and natural analogue of the dipeptide Phe-Leu derived from the fungus Streptomyces olivoretticul, prevents P. falciparum malaria growth in culture (13,14). More recently, it was shown not only that synthetic phosphinate dipeptide analogues that inhibit metallo-aminopeptidases prevented the growth of wildty...

Menin functions as a critical oncogenic cofactor of mixed lineage leukemia (MLL) fusion proteins in the development of acute leukemias, and inhibition of the menin interaction with MLL fusion proteins represents a very promising strategy to reverse their oncogenic activity. MLL interacts with menin in a bivalent mode involving 2 N-terminal fragments of MLL. In the present study, we reveal the first high-resolution crystal structure of human menin in complex with a smallmolecule inhibitor of the menin-MLL interaction, MI-2. The structure shows that the compound binds to the MLL pocket in menin and mimics the key interactions of MLL with menin. Based on the menin-MI-2 structure, we developed MI-2-2, a compound that binds to menin with low nanomolar affinity (K d ‫؍‬ IntroductionTranslocations of the MLL (mixed lineage leukemia) gene frequently occur in aggressive human acute myeloid and lymphoid leukemias in both children and adults. 1 Fusion of MLL with 1 of more than 60 different genes results in chimeric MLL fusion proteins that enhance proliferation and block hematopoietic differentiation, ultimately leading to acute leukemia. 2 Patients with leukemias harboring MLL translocations have very unfavorable prognoses and respond poorly to currently available treatments. 2,3 The relapse risk is very high using conventional chemotherapy and stem cell transplantation, 2 leading to an overall 5-year survival rate of only approximately 35%. 4 All MLL fusion proteins preserve an N-terminal MLL fragment approximately 1400 amino acids in length fused in-frame with the C-terminus of the fusion partner. 3,[5][6][7] Two regions in this fragment of MLL have been shown to be indispensable for leukemogenic transformation: the N-terminal region, which binds to menin 8 and to lens epithelium-derived growth factor (LEDGF), 9 and the conserved region encompassing the CXXC domain, which mediates binding to nonmethylated CpG DNA [10][11][12] and interacts with the polymerase associated factor complex (PAFc). 13,14 Targeting these interactions provides new opportunities for the development of new therapeutic agents for the MLL leukemias. 15 Menin is a tumor-suppressor protein encoded by the MEN1 (multiple endocrine neoplasia 1) gene. 16 Mutations of MEN1 are associated with tumors of the parathyroid glands, pancreatic islet cells, and anterior pituitary gland. 17 Menin is also a highly specific binding partner for MLL and MLL fusion proteins and is required to regulate the expression of MLL target genes, including HOXA9 and MEIS1. 8 Loss of the ability to bind menin abolishes the oncogenic potential of MLL fusion proteins both in vitro and in vivo. 8 Disruption of the interaction between menin and MLL fusion proteins using genetic methods blocks the development of acute leukemia in mice, 8 indicating that menin functions as a critical oncogenic cofactor of MLL fusion proteins and is required for their leukemogenic activity. The menin-MLL interaction represents an attractive therapeutic target for the development of novel drugs for acut...

MLL (Mixed Lineage Leukemia) is the target of chromosomal translocations which cause leukemias with poor prognosis. All leukemogenic MLL fusion proteins retain the CXXC domain which binds to nonmethylated CpG DNA. We present the solution structure of the MLL CXXC domain in complex with DNA, showing for the first time how the CXXC domain distinguishes nonmethylated from methylated CpG DNA. Based on the structure, we designed point mutations which disrupt DNA binding. Introduction of these mutations into MLL-AF9 results in increased DNA methylation of specific CpG nucleotides in Hoxa9, increased H3K9 methylation, decreased expression of Hoxa9 locus transcripts, loss of immortalization potential, and inability to induce leukemia in mice. These results establish that DNA binding by the CXXC domain and protection against DNA methylation is essential for MLL fusion leukemia. They also provide support for this interaction as a potential target for therapeutic intervention.