Fig. 1:
examples of metallodrugs presenting in vivo antileishmanial activity as potential drug candidates to tackle leishmaniasis. CL: cutaneous leishmaniasis; VL: visceral leishmaniasis; IP: intra-peritoneal; Ther: therapeutical. Molecular structures were reproduced from.1212. Iniguez E, Varela-Ramirez A, Martínez A, Torres CL, Sánchez-Delgado RA, Maldonado RA. Ruthenium-clotrimazole complex has significant efficacy in the murine model of cutaneous leishmaniasis. Acta Trop. 2016; 164: 402-10.,1515. Sharlow ER, Leimgruber S, Murray S, Lira A, Sciotti RJ, Hickman M, et al. Auranofin is an apoptosis-simulating agent with in vitro and in vivo anti-leishmanial activity. ACS Chem Biol. 2014; 9(3): 663-72.,1717. Tunes LG, Morato RE, Garcia A, Schmitz V, Steindel M, Corrêa-Junior JD, et al. Preclinical gold complexes as oral drug candidates to treat leishmaniasis are potent trypanothione reductase inhibitors. ACS Infect Dis. 2020; 6(5): 1121-39.,1919. Alcolea V, Moreno E, Etxebeste-Mitxeltorena M, Navarro-Blasco I, González-Peñas E, Jiménez-Ruiz A, et al. 3,5-Dimethyl-4-isoxazoyl selenocyanate as promising agent for the treatment of Leishmania infantum-infected mice. Acta Trop. 2021; 215: 105801.,2020. do Nascimento NRF, de Aguiar FLN, Santos CF, Costa AML, Hardoim DJ, Calabrese KS, et al. In vitro and in vivo leishmanicidal activity of a ruthenium nitrosyl complex against Leishmania (Viannia) braziliensis. Acta Trop. 2019; 192: 61-5.
Fig. 2:
antileishmanial drug discovery and development pipeline. Target elucidation is part of fundamental research performed in universities and research centers. Drug target validation can be a result of collaborative work between pharmaceutical industry and academy. This initial step leads to the synthesis of new potential inhibitors that are synthesised and can be optimised after drug screening. Computer-aid strategies are helpful on rational drug design. Drug sensitivity values obtained during phenotypic screening on antileishmanial activity and drug toxicity are used to improve activity and reduce unwanted effects. Antileishmanial in vitro assays should be performed using intracellular amastigote forms. For that, the drug toxicity against the used host cell must be evaluated previously. Murine bone marrow-derived macrophages, murine peritoneal macrophages or human monocyte-derived THP-1 macrophages are commonly used as host-cells. When assaying metal-based drugs, it is important to choose defined or semi-defined culture medium, since reactive metal atom can interact with medium constituents and interfere with drug availability. The selection of resistant parasites by increased step-wise drug pressure can be an indicative of easy drug resistance acquisition. It can be included during in vitro phenotypic screening as an assay of drug-resistance prediction. Before moving forward through in vivo efficacy evaluation, it is strongly recommended to obtain the drug pharmacokinetic profile in a reduced group of golden hamsters. Drug administration preferable route is oral and visceral leishmaniasis model should be the first choice on evaluating systemic antileishmanial effect. If successful, cutaneous leishmaniasis model can be included. Drug combination is encouraged in order to prevent drug resistance emergence, increase efficacy and to reduce toxicity. In vivo efficacy and administration, distribution, metabolism, excretion and toxicity (ADMET) hints can feedback drug design and resynthesis. Predictive ADMET can also be assessed using computational approaches, like pkCSM tool (http://biosig.unimelb.edu.au/pkcsm).3434. Pires DEV, Blundell TL, Ascher DB. pkCSM: predicting small-molecule pharmacokinetic and toxicity properties using graph-based signatures. J Med Chem. 2015; 58(9): 4066-72. The crucial step on antileishmanial drug discovery/ development is to establish partnership with the pharmaceutical industry, especially during scaling up, production and for clinical trials. Consortia with government can afford legal and financial security. The gap between academic research and the industry against neglected tropical diseases (NTDs) will be reduced only after aligning goals and together with the private and public sectors. Parts of Fig. 2 were created with BioRender.com and are licensed under the agreement number: JY23H65VZS.
Fig. 3:
impact of CRISPR/Cas9 in the identification of potential drug targets in Leishmania related to post-translational modification (PTMs). The number of Leishmania genes with published attempts at the creation of a null mutant almost tripled after the establishment of CRISPR/Cas9 technology compared to the period where the main method consisted in the homologous recombination of fragments bearing homology regions alone (upper panel). This is more evident for Leishmania genes belonging to PTM regulatory machinery (upper panel, right data), and especially for those involved in the regulation of phosphorylation (PKs), ubiquitination (UB) and acetylation (BDR) (lower panels).