Lead Optimization of the 5-Phenylpyrazolopyrimidinone NPD-2975 toward Compounds with Improved Antitrypanosomal Efficacy.

Human African trypanosomiasis (HAT) still faces few therapeutic options and emerging drug resistance, stressing an urgency for novel antitrypanosomal drug discovery. Here, we describe lead optimization efforts aiming at improving antitrypanosomal efficacy and better physicochemical properties based on our previously reported optimized hit NPD-2975 (pIC 7.2).

Discovery of 5-Phenylpyrazolopyrimidinone Analogs as Potent Antitrypanosomal Agents with In Vivo Efficacy.

Human African Trypanosomiasis (HAT), caused by , is one of the neglected tropical diseases with a continuing need for new medication. We here describe the discovery of 5-phenylpyrazolopyrimidinone analogs as a novel series of phenotypic antitrypanosomal agents. The most potent compound, (NPD-2975), has an in vitro IC of 70 nM against with no apparent toxicity against human MRC-5 lung fibroblasts.

DNDI-6148: A Novel Benzoxaborole Preclinical Candidate for the Treatment of Visceral Leishmaniasis.

Visceral leishmaniasis (VL) is a parasitic disease endemic across multiple regions of the world and is fatal if untreated. Current therapies are unsuitable, and there is an urgent need for safe, short-course, and low-cost oral treatments to combat this neglected disease. The benzoxaborole chemotype has previously delivered clinical candidates for the treatment of other parasitic diseases.

Miltefosine enhances infectivity of a miltefosine-resistant Leishmania infantum strain by attenuating its innate immune recognition.

Background: Miltefosine (MIL) is currently the only oral drug available to treat visceral leishmaniasis but its use as first-line monotherapy has been compromised by an increasing treatment failure. Despite the scarce number of resistant clinical isolates, MIL-resistance by mutations in a single aminophospholipid transporter gene can easily be selected in a laboratory environment. These mutations result in a reduced survival in the mammalian host, which can partially be restored by exposure to MIL, suggesting a kind of drug-dependency.

Identification of Resistance Determinants for a Promising Antileishmanial Oxaborole Series.

Current treatment options for visceral leishmaniasis have several drawbacks, and clinicians are confronted with an increasing number of treatment failures. To overcome this, the Drugs for Neglected Diseases (DND) has invested in the development of novel antileishmanial leads, including a very promising class of oxaboroles. The mode of action/resistance of this series to is still unknown and may be important for its further development and implementation.

Experimental Strategies to Explore Drug Action and Resistance in Kinetoplastid Parasites.

Kinetoplastids are the causative agents of leishmaniasis, human African trypanosomiasis, and American trypanosomiasis. They are responsible for high mortality and morbidity in (sub)tropical regions. Adequate treatment options are limited and have several drawbacks, such as toxicity, need for parenteral administration, and occurrence of treatment failure and drug resistance.

Interferon Alpha Favors Macrophage Infection by Visceral Species Through Upregulation of Sialoadhesin Expression.

Type I interferons (IFNs) induced by an endogenous RNA virus or exogenous viral infections have been shown to exacerbate infections with New World Cutaneous parasites, however, the impact of type I IFNs in visceral infections and implicated mechanisms remain to be unraveled. This study assessed the impact of type I IFN on macrophage infection with and and the implication of sialoadhesin (Siglec-1/CD169, Sn) as an IFN-inducible surface receptor. Stimulation of bone marrow-derived macrophages with type I IFN (IFN-α) significantly enhanced susceptibility to infection of reference laboratory strains and a set of recent clinical isolates.

Comparative evaluation of nucleic acid stabilizing reagents for RNA- and DNA-based Leishmania detection in blood as proxy for visceral burdens.

Background: Molecular detection techniques using peripheral blood are preferred over invasive tissue aspiration for the diagnosis and post-treatment follow-up of visceral leishmaniasis (VL) patients. This study aims to identify suitable stabilizing reagents to prevent DNA and RNA degradation during storage and transport to specialized laboratories where molecular diagnosis is performed.

Methodology: The stabilizing capacities of different commercially available reagents were compared using promastigote-spiked human blood and peripheral blood of Syrian golden hamsters subjected to experimental infection, treatment (miltefosine or aminopyrazole DNDi-1044) and immunosuppression.

Miltefosine enhances the fitness of a non-virulent drug-resistant Leishmania infantum strain.

Objectives: Miltefosine is currently the only oral drug for visceral leishmaniasis, and although deficiency in an aminophospholipid/miltefosine transporter (MT) is sufficient to elicit drug resistance, very few naturally miltefosine-resistant (MIL-R) strains have yet been isolated. This study aimed to make a detailed analysis of the impact of acquired miltefosine resistance and miltefosine treatment on in vivo infection.

Methods: Bioluminescent versions of a MIL-R strain and its syngeneic parental line were generated by integration of the red-shifted firefly luciferase PpyRE9.

Evaluation of a Pan-Leishmania Spliced-Leader RNA Detection Method in Human Blood and Experimentally Infected Syrian Golden Hamsters.

Several methods have been developed for the detection of Leishmania, mostly targeting the minicircle kinetoplast DNA (kDNA). A new RNA real-time quantitative PCR (qPCR) assay was developed targeting the conserved and highly expressed spliced-leader (SL) mini-exon sequence. This study compared the limits of detection of various real-time PCR assays in hamsters infected with Leishmania infantum, in spiked human blood, and in clinical blood samples from visceral leishmaniasis patients.

Combined treatment of miltefosine and paromomycin delays the onset of experimental drug resistance in Leishmania infantum.

Background: Since miltefosine monotherapy against visceral leishmaniasis (VL) caused by Leishmania donovani has been discontinued in the Indian subcontinent due to an increase in the number of treatment failures, single dose liposomal amphotericin B is now advocated as a treatment option of choice. Paromomycin-miltefosine combination therapy can be used as substitute first-line treatment in regions without cold-chain potential. Previous laboratory studies in the closely related species Leishmania infantum have demonstrated that paromomycin monotherapy fairly rapidly selects for resistance producing a phenotype with increased fitness.

Molecular detection of infection homogeneity and impact of miltefosine treatment in a Syrian golden hamster model of Leishmania donovani and L. infantum visceral leishmaniasis.

Control of visceral leishmaniasis caused by Leishmania infantum and Leishmania donovani primarily relies on chemotherapy using an increasingly compromised repertoire of antileishmanial compounds. For evaluation of novel drugs, the Syrian golden hamster is considered as a clinically relevant laboratory model. In this study, two molecular parasite detection assays were developed targeting cathepsin-like cysteine protease B (CPB) DNA and 18S rRNA to achieve absolute amastigote quantification in the major target organs liver and spleen.