MI-538

MI-538 is an inhibitor of the interaction between menin and MLL fusion proteins with an IC₅₀ of 21 nM. IC50 & Target: IC50 : 21 nM (menin and MLL interaction); Kd: 6.5 nM (menin)^[1] In Vitro: MI-538 inhibits the proliferation of MLL leukemia cells with a GI₅₀ of 83 nM. MI-538 shows no effect (up to 6 μM) on growth of the control cell lines HL-60 and HM-2, which do not harbor MLL translocations, demonstrating good selectivity toward MLL fusion protein transformed cells. MI-538 binds to menin with low nanomolar affinity (K_d=6.5 nM). Its potent cellular activity originates from the improved binding affinity to menin and possibly increased cell membrane permeability. Treatment with MI-538 results in strong down regulation of expression of Hoxa9 and Meis1 genes. About 100 nM 27 was sufficient to reduce by ~50% Hoxa9 expression in MLL-AF9 cells, and even more pronounced effect was seen on Meis1 expression^[1]. In Vivo: Treatment with MI-538 results in a pronounced, about 80%, reduction in the MV4;11 tumor volume, without causing substantial signs of toxicity reflected by less than 10% reduction of the body weight. MI-538 demonstrates markedly improved exposure (area under the curve, AUC, values), Cmax (maximum compound concentration) in the blood plasma, and the lowest value of clearance. The half-life of MI-538 is about 1.6 h. MI-538 has also high oral bioavailability (~50%)^[1].