Infectious diseases caused by trypanosomatids, including African trypanosomiasis (sleeping sickness), Chagas disease, and different forms of leishmaniasis, are Neglected Tropical Diseases affecting millions of people worldwide, mainly in vulnerable territories of tropical and subtropical areas. In general, current treatments against these diseases are old-fashioned, showing adverse effects and loss of efficacy due to misuse or overuse, thus leading to the emergence of resistance. For these reasons, searching for new antitrypanosomatid drugs has become an urgent necessity, and different metabolic pathways have been studied as potential drug targets against these parasites. Considering that trypanosomatids possess a unique redox pathway based on the trypanothione molecule absent in the mammalian host, the key enzymes involved in trypanothione metabolism, trypanothione reductase and trypanothione synthetase, have been studied in detail as druggable targets. In this review, we summarize some of the recent findings on the molecules inhibiting these two essential enzymes for Trypanosoma and Leishmania viability.

The development of new alternative models is essential to overcome the limitations of traditional two-dimensional (2D) cell cultures and animal models. Three-dimensional (3D) models, such as organoids, better mimic the structural and functional complexity of mammalian organs, thereby reducing the ethical and economic issues related to animal experimentation. These systems provide more physiologically relevant environments, improving the accuracy of disease modeling and drug response prediction. In this context, we have developed mouse hepatic organoids from livers of adult BALB/c mice and characterized them by microscopy and transcriptional analysis. This model was applied to a robust and reproducible high-throughput screening (HTS) platform for testing cytotoxicity at the preclinical stage of drug discovery. In addition, mouse hepatic organoids were co-cultured with amastigotes of Leishmania donovani parasites to establish a model of host–parasite interaction, which was characterized by RNA-seq linked to differential expression analysis and cytokine production by the hepatic organoids. The findings provided in this work establish mouse hepatic organoids as an alternative model for drug discovery and pathogenesis studies.

Leishmania infantum is the vector-borne trypanosomatid parasite causing visceral leishmaniasis in the Mediterranean basin. This neglected tropical disease is treated with a limited number of obsolete drugs that are not exempt from adverse effects and whose overuse has promoted the emergence of resistant pathogens. In the search for novel antitrypanosomatid molecules that help overcome these drawbacks, drug repurposing has emerged as a good strategy. Nitroaromatic compounds have been found in drug discovery campaigns as promising antileishmanial molecules. Fexinidazole (recently introduced for the treatment of stages 1 and 2 of African trypanosomiasis), and pretomanid, which share the nitroimidazole nitroaromatic structure, have provided antileishmanial activity in different studies. In this work, we have tested the in vitro efficacy of these two nitroimidazoles to validate our 384-well high-throughput screening (HTS) platform consisting of L. infantum parasites emitting the near-infrared fluorescent protein (iRFP) as a biomarker of cell viability. These molecules showed good efficacy in both axenic and intramacrophage amastigotes and were poorly cytotoxic in RAW 264.7 and HepG2 cultures. Fexinidazole and pretomanid induced the production of ROS in axenic amastigotes but were not able to inhibit trypanothione reductase (TryR), thus suggesting that these compounds may target thiol metabolism through a different mechanism of action.

Visceral leishmaniasis caused by Leishmania donovani is one of the major neglected tropical diseases attributable to parasitic protozoa. In the absence of an effective vaccine, chemotherapy remains the only available therapeutic option. However, current treatments rely on a limited number of drugs that are largely obsolete, highly toxic or require intravenous administration, and their extensive use has led to the emergence of drug resistance. Consequently, the discovery of new antileishmanial agents is an urgent priority. In this study, a commercial library of 449 alkaloids in a high-throughput screening format was evaluated against both axenic bone marrow-derived amastigotes and intramacrophagic amastigotes from mice infected with L. donovani IRFP, a strain engineered to emit infrared fluorescence in its viable form. Six isoquinoline-type alkaloids showed the best antileishmanial efficacy against intramacrophagic amastigotes while exhibiting minimal cytotoxicity toward RAW 264.7 and HepG2 cell lines, with a promising selective index higher than four, and good mouse intestinal tolerance in mouse organoids. Among these compounds, the protoberberine scaffold emerged as the most promising candidate for further drug development.

Visceral leishmaniasis, caused by Leishmania donovani, is characterized by profound alterations in hepatic immune responses that promote parasite persistence. However, the lack of physiologically relevant in vitro systems limits investigation of tissue-level host–pathogen interactions. An immunocompetent three-dimensional hepatic organoid model incorporating bone marrow-derived macrophages was established to investigate liver-stage immune responses to L. donovani infection. Integrated cytokine profiling and transcriptomic analyses were benchmarked against infected mouse liver tissue. Macrophages acquired functional characteristics consistent with a Kupffer cell-like phenotype and contributed to immune homeostasis within the co-culture. Infection induced a conserved immune response characterized by inflammatory and chemotactic activation. This response was accompanied by coordinated suppression of antimicrobial pathways, including the IL-12–IFN-γ axis and interferon-stimulated genes. These immune alterations were largely shared between the organoid model and infected liver tissue, although systemic metabolic reprogramming and multicellular complexity were not fully recapitulated. Our findings identify a conserved pattern of hepatic immune dysregulation in which inflammatory activation is uncoupled from effective antimicrobial signaling, potentially facilitating parasite persistence. This immunocompetent hepatic organoid platform provides a physiologically relevant system for investigating host–pathogen interactions and evaluating host-directed therapeutic strategies for visceral leishmaniasis.