Identification of a melampomagnolide B analog as a potential lead molecule for treatment of acute myelogenous...

A series of carbamate derivatives of the antileukemic sesquiterpene melampomagnolide B (MMB) has been synthesized utilizing a 1,2,4-triazole carbamate conjugate of MMB as an intermediate synthon. Five imidazole- and benzimidazole-carbamate analogs of MMB (8a-8e) were prepared and evaluated for anti-leukemic activity against cultured M9 ENL1 AML cells. All the analogs exhibited improved anti-leukemic activity (EC₅₀=0.90-3.93μM) when compared to parthenolide and the parent sesquiterpene, MMB (EC₅₀=7.0μM and 15.5μM, respectively). The imidazole carbamate analog, 8a (EC₅₀=0.9μM), was 16 times more potent than MMB. The comparative bioavailabilities of 8a and MMB were determined in BALB/c mice following oral dosing of these compounds. It has been demonstrated that the absolute plasma bioavailabilities of MMB and 8a were 6.7±0.8%, and 45.5±2%, respectively. These results indicate that, compared to MMB, the PK parameters for 8a display significantly improved bioavailability and exposure after oral administration. Analog 8a is considered to be a potential clinical candidate for treatment of acute myelogenous leukemia.