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

Abstract

dVisceral leishmaniasis is an emerging neglected tropical disease (NTD) caused by the protozoan Leishmania infantum in 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 Sb V . 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) from Leishmania spp. 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 with L. 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 in Leishmania promastigotes and in vitro cleaving assays confirmed that these drugs are Top poisons. The inhibitory potency of both indenoisoquinolines on L. infantum recombinant TopIB was assessed in 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.

PEGylated Dendritic Polyglycerol Conjugate Delivers Doxorubicin to the Parasitophorous Vacuole in Leishmania infantum Infections

“…In free DOX treated cells, nuclei showed a 15‐fold higher fluorescence level than PG‐DOX(pH)‐PEG treated cells, confirming that our nanoparticle avoids drug deposition in the nuclei. The accumulation of free DOX in nucleus or mitochondria is a major drawback of this drug as well as of other drugs, such as the topoisomerase‐I poisoning derivatives (camptothecin derivatives and indenoisoquinolines) that have shown to be active against intracellular‐leishmania amastigotes but are highly toxic to host cells …”

Appraisal of a Leishmania major Strain Stably Expressing mCherry Fluorescent Protein for Both In Vitro and In Vivo Studies of Potential Drugs and Vaccine against Cutaneous Leishmaniasis

“…Most of the current multiwell-screening methods involve established-macrophage cell lines since it is quite difficult to scale-up a procedure based on primary macrophages [57], [18], [58], [20], [22], [59]. Accordingly, a well-planned combination of different approaches (promastigote/intracellular; cell line/primary cultures) would help us to identify lead compounds through large-scale drug screening [60], [61].…”

“…Because of the profound influence of the host's immune response on the treatment of leishmaniasis, new approaches should include the whole immunopathological environment found at the host-parasite interaction site. However, only one alternative approach has been used in order to transfer this immunological concept to HTS systems [43], [61].…”

Novel Very Long‐Chain α‐Methoxylated Δ5,9 Fatty Acids from the Sponge Asteropus niger Are Effective Inhibitors of Topoisomerases IB

“…The extent of plasmid DNA relaxation was assessed in 1% agarose gels by electrophoresis in 0.1 M Tris borate EDTA buffer (pH 8.0) at 2 V/cm for 16 h. Gels were visualized with UV illumination after ethidium bromide (0.5 μg/ml) staining. A further electrophoresis was run in the presence of 0.1 μg/ml ethidium bromide in order to separate nicked DNA from relaxed topoisomers [20]. …”