Indotecan (LMP400) and AM13-55: Two Novel Indenoisoquinolines Show Potential for Treating Visceral Leishmaniasis

Abstract

ABSTRACTVisceral leishmaniasis is an emerging neglected tropical disease (NTD) caused by the protozoanLeishmania infantumin the countries bordering the Mediterranean Basin. Currently there is no effective vaccine against this disease, and the therapeutic approach is based on toxic derivatives of SbV. Therefore, the discovery of new therapeutic targets and the development of drugs designed to inhibit them comprise an extremely important approach to fighting this disease. DNA topoisomerases (Top) have been identified as promising targets for therapy against leishmaniasis. These enzymes are involved in solving topological problems generated during replication, transcription, and recombination of DNA. Being unlike that of the mammalian host, type IB DNA topoisomerase (TopIB) fromLeishmaniaspp. is a unique bisubunit protein, which makes it very interesting as a selective drug target. In the present investigation, we studied the effect of two TopIB poisons with indenoisoquinoline structure, indotecan and AM13-55, on a murine BALB/c model of infected splenocytes withL. infantum, comparing their effectiveness with that of the clinically tested leishmanicidal drug paromomycin. Both compounds have high selectivity indexes compared with uninfected splenocytes. SDS-KCl-precipitable DNA-protein complexes inLeishmaniapromastigotes andin vitrocleaving assays confirmed that these drugs are Top poisons. The inhibitory potency of both indenoisoquinolines onL. infantumrecombinant TopIB was assessedin vitro, with results showing that indotecan was the most active compound, preventing the relaxation of supercoiled DNA. Experimental infections in susceptible BALB/c mice treated with 2.5 mg/kg body weight/day once every other day for a total of 15 days showed that indotecan cleared more than 80% of the parasite burden of the spleen and liver, indicating promising activity against visceral leishmaniasis.