<p><em>Leishmania donovani</em> Growth Inhibitors from Pathogen Box Compounds of Medicine for Malaria Venture</p>

Abstract

Introduction: Leishmaniasis is a collective term used to describe various pathological conditions caused by an obligate intracellular protozoan of the genus Leishmania. It is one of the neglected diseases and has been given minimal attention by drug discovery and development stakeholders to narrow the safety and efficacy gaps of the drugs currently used to treat leishmaniasis. The challenge is further exacerbated by the emergence of drug resistance by the parasites. Methods: Aiming to look for potential anti-leishmanial hits and leads, we screened Medicines for Malaria Venture (MMV) Pathogen Box compounds against clinically isolated Leishmania donovani strain. In this medium-throughput primary screening assay, the compounds were screened against promastigotes, and then against amastigote stages. Results: From the total 400 compounds screened, 35 compounds showed >50% inhibitory activity on promastigotes in the initial screen (1 μM). Out of these compounds, nine showed >70% inhibition, with median inhibitory concentration (IC 50 ) ranging from 12 to 491 nM using the anti-promastigote assay, and from 53 to 704 nM using the intracellular amastigote assay. Identified compounds demonstrated acceptable safety profiles on THP-1 cell lines and sheep red blood cells, and had appropriate physicochemical properties suitable for further drug development. Two compounds (MMV690102 and MMV688262) were identified as leads. The anti-tubercular agent MMV688262 (delamanid) showed a synergistic effect with amphotericin B, indicating the prospect of using this compound for combination therapy. Conclusion: The current study indicates the presence of additional hits which may hold promise as starting points for anti-leishmanial drug discovery and in-depth structure-activity relationship studies.

Preclinical Studies in Anti-Trypanosomatidae Drug Development

“…This variation in strain susceptibility is consistent with previous observations [ 19 ]. The underlying reason as to why the two L. infantum strains display different susceptibilities towards an array of unrelated chemotypes has yet to be established but given the adaptable nature of Leishmania we postulate that life cycle selection processes have helped shape the parasite’s genome leading to the strains with contrasting gene/protein expression profiles and the observed phenotypic variations [ 20 , 21 , 22 ]. This highlights that when screening for novel chemotherapeutics targeting a trypanosomatid parasite, multiple strains of the same species obtained from different sources should be tested.…”

In vitro growth inhibitory activity of Medicines for Malaria Venture pathogen box compounds against Leishmania aethiopica

“…This finding is consistent with the reports of Berry et al [ 25 ] and Duffy et al [ 24 ] which used L. Mexicana and L. donovani strains, respectively. We previously reported MMV690102 as one of the potent growth inhibitors of L. donovani promastigotes and amastigotes [ 19 ]. This indicates the potentials of this compound for the treatment of infections caused by more than one Leishmania species types.…”

“…Macrophages were collected from Swiss albino mice as described briefly in our previous work [ 19 ]. Young mice (6–8 weeks old) were injected into the peritoneal cavity with 2% freshly prepared starch (Sigma-Aldrich, Co., St. Louis, USA) and 10 mL of sterile ice-cold phosphate-buffered saline (PBS) (Sigma, Co., St. Louis, USA) supplemented with 3% HINBCS after 2 days, and 6–8 mL exudates were recovered.…”

“…Intracellular amastigote assay was conducted according to the method described elsewhere [ 19 , 22 ] with modifications. Approximately 3 × 10 5 peritoneal macrophages were seeded in 24-well plates and allowed to adhere for 12 h at 33 °C in 5% CO 2 .…”

“…The PB contains 400 pure compounds active against various neglected tropical diseases. It has been previously screened for Trypanosoma brucei [ 15 ], Giardia lamblia [ 16 ] Cryptosporidium parvum and Plasmodium falciparum [ 17 ], Toxoplasma gondii [ 18 ], and recently against L. donovani [ 19 ] to uncover new starting points for antiprotozoal drug discovery. In this study, we screened the MMV PB to expand the pool of antileishmanial drugs active against clinical L. aethiopica promastigote and intracellular amastigote in vitro.…”