2-aminobenzimidazoles for leishmaniasis: From initial hit discovery to in vivo profiling

Abstract

Leishmaniasis is a major infectious disease with hundreds of thousands of new cases and over 20,000 deaths each year. The current drugs to treat this life-threatening infection have several drawbacks such as toxicity and long treatment regimens. A library of 1.8 million compounds, from which the hits reported here are publicly available, was screened against Leishmania infantum as part of an optimization program; a compound was found with a 2-aminobenzimidazole functionality presenting moderate potency, low metabolic stability and high lipophilicity. Several rounds of synthesis were performed to incorporate chemical groups capable of reducing lipophilicity and clearance, leading to the identification of compounds that are active against different parasite strains and have improved in vitro properties. As a result of this optimization program, a group of compounds was further tested in anticipation of in vivo evaluation. In vivo tests were carried out with compounds 29 (L. infantum IC50: 4.1 μM) and 39 (L. infantum IC50: 0.5 μM) in an acute L. infantum VL mouse model, which showed problems of poor exposure and lack of efficacy, despite the good in vitro potency.

Zebrafish toxicological screening could aid Leishmaniosis drug discovery

“…The embryo developmental malformations observed, such as the absence of hatching and bradycardia, are directly correlated with prenatal loss in rabbits [6]. These results corroborate with a recent study carried out in rodents for the same compound Ferreira et al [10], the authors observed mortality and distress in the mice that were submitted to efficacy tests, finally, the development of the compound was discontinued. Thus, the use of the zebrafish model could have predicted the acute toxicity of the compound within 4 days (96 h), and tests on rodents could be avoided.…”

“…Thus, the use of the zebrafish model could have predicted the acute toxicity of the compound within 4 days (96 h), and tests on rodents could be avoided. On the other hand, the compounds Carbamazepine and Benzimidazole did not cause changes in the development of the embryos when exposed to concentrations between 6.25 and 100 µM, which demonstrates that the OECD 236 test [10] predicted the safety of these compounds that are currently used in the treatment of human diseases and were previously approved in all preclinical and clinical trials.…”

“…An early in vitro safety assessment was conducted in which 2amnbzl-d showed low inhibition of the hERG channel (IC50 > 30 μM) and the main cytochrome P450 family enzymes (IC50 > 20 μM), similarly, screening against an off-target panel of a panel of 20 marks covering key human enzymes, kinases and receptors showed low interference in the activities (EC50 > 10 µM) as well [10]. On the other hand, 2amnbzl-d compound showed significant hepatotoxic effects at concentrations above 7.5 µM, as well as neurotoxic effect at concentration 15 µM in zebrafish.…”

“…Ferreira et al [10] recently published the results of a hit-to-lead campaign aiming at the identification of new preclinical candidates for the treatment of leishmaniasis, a potentially fatal neglected disease that affects millions of people worldwide and whose current treatment options are limited either by length of treatment or toxic side effects. Starting from a promising 2-aminobendazole hit identified via an in vitro phenotypic screen, hundreds of analogues were synthetized with the aim of finding a molecule capable of killing the parasite and be human safe.…”

“…The aim of this study was to evaluate whether the toxicity identified during the in vivo studies with the new chemical entity 2amnbzl-d published by Ferreira et al [10] could be predicted by tests using the zebrafish model and reduced the time and cost with the tests, as well as the use of mammals in research of drug discovery, thus impacting strongly in the 3Rs principles (replacement, reduction and refinement).…”