After 100 years of chemotherapy with impractical and toxic drugs, an oral cure for human African trypanosomiasis (HAT) is available: Fexinidazole. In this case, we review the history of drug discovery for HAT with special emphasis on the discovery, pre-clinical development, and operational challenges of the clinical trials of fexinidazole. The screening of the Drugs for Neglected Diseases initiative (DNDi) HAT-library by the Swiss TPH had singled out fexinidazole, originally developed by Hoechst (now Sanofi), as the most promising of a series of over 800 nitroimidazoles and related molecules. In cell culture, fexinidazole has an IC50 of around 1 µM against Trypanosoma brucei and is more than 100-fold less toxic to mammalian cells. In the mouse model, fexinidazole cures both the first, haemolymphatic, and the second, meningoencephalitic stage of the infection, the latter at 100 mg/kg twice daily for 5 days. In patients, the clinical trials managed by DNDi and supported by Swiss TPH mainly conducted in the Democratic Republic of the Congo demonstrated that oral fexinidazole is safe and effective for use against first- and early second-stage sleeping sickness. Based on the positive opinion issued by the European Medicines Agency in 2018, the WHO has released new interim guidelines for the treatment of HAT including fexinidazole as the new therapy for first-stage and non-severe second-stage sleeping sickness caused by Trypanosoma brucei gambiense (gHAT). This greatly facilitates the diagnosis and treatment algorithm for gHAT, increasing the attainable coverage and paving the way towards the envisaged goal of zero transmission by 2030.

https://www.mdpi.com/2079-9721/10/4/90/pdf?version=1665996802

Fexinidazole for Human African Trypanosomiasis, the Fruit of a Successful Public-Private Partnership

Chagas disease and Human African Trypanosomiasis, caused by Trypanosoma cruzi and T. brucei, respectively, pose relevant health challenges throughout the world, placing 65 to 70 million people at risk each. Given the limited efficacy and severe side effects associated with current chemotherapy, new drugs are urgently needed for both diseases. Here, we report the screening of the Pathogen Box collection against cruzain and TbrCatL, validated targets for Chagas disease and Human African Trypanosomiasis, respectively. Enzymatic assays were applied to screen 400 compounds, validate hits, determine IC50 values and, when possible, mechanisms of inhibition. In this case, 12 initial hits were obtained and ten were prioritized for follow-up. IC50 values were obtained for six of them (hit rate = 1.5%) and ranged from 0.46 ± 0.03 to 27 ± 3 µM. MMV687246 was found to be a mixed inhibitor of cruzain (Ki = 57 ± 6 µM) while MMV688179 was found to be a competitive inhibitor of cruzain with a nanomolar potency (Ki = 165 ± 63 nM). A putative binding mode for MMV688179 was obtained by docking. The six hits discovered against cruzain and TbrCatL are of great interest for further optimization by the medicinal chemistry community.

/pdf/screening-the-pathogen-box-to-discover-and-characterize-new-1ihooprl.pdf

Screening the Pathogen Box to Discover and Characterize New Cruzain and TbrCatL Inhibitors

Abstract The opportunistic fungal infection cryptococcal meningoencephalitis is a major cause of death among people living with HIV in sub‐Saharan Africa. We report pharmacokinetic (PK) and safety data from a randomized, four‐period crossover phase I trial of three sustained‐release (SR) oral pellet formulations of 5‐flucytosine conducted in South Africa. These formulations were developed to require less frequent administration, to provide a convenient alternative to the current immediate release (IR) formulation, A. Formulations B, C, and D were designed to release 5‐flucytosine as a percentage of the nominal dose in vitro. We assessed their safety and PK profiles in a single dose (1 × 3000 mg at 0 h), relative to commercial IR tablets (Ancotil 500 mg tablets; 3 × 500 mg at 0 h and 3 × 500 mg at 6 h) in healthy, fasted participants. Forty‐two healthy participants were included. All treatments were well‐tolerated. The primary PK parameters, maximum observed plasma concentration (C max) and area under the concentration‐time profiles, were significantly lower for the SR formulations than for the IR tablets, and the geometric mean ratios fell outside the conventional bioequivalence limits. The median maximum time to C max was delayed for the SR pellets. Physiologically‐based PK modeling indicated a twice‐daily 6400 mg dose of SR formulation D in fasted condition would be optimal for further clinical development. This regimen is predicted to result in a rapid steady‐state plasma exposure with effective and safe trough plasma concentration and C max values, within the therapeutic boundaries relative to plasma exposure after four times per day administration of IR tablets (PACTR202201760181404).

Bioavailability of three novel oral, sustained‐release pellets, relative to an immediate‐release tablet containing 500 mg flucytosine: A randomized, open‐label, crossover study in healthy volunteers

The development of new drug modalities has been facilitated recently by the introduction of boron as a component of organic compounds, and specifically within a benzoxaborale scaffold. This has enabled exploration of new chemical space and the development of effective compounds targeting a broad range of morbidities, including infections by protozoa, fungi, worms, and bacteria. Most notable is the recent demonstration of a single oral dose cure using acoziborole against African trypanosomiasis. Common and species-/structure-specific interactions between benzoxaboroles and parasite species have emerged and provide vital insights into the mechanisms of cidality, as well as potential challenges in terms of resistance and/or side effects. Here, we discuss the literature specific to benzoxaborole studies in parasitic protists and consider unanswered questions concerning this important new drug class. 

Pass the boron: benzoxaboroles as antiparasite drugs

Abstract Neglected tropical diseases (NTDs) are a group of at least 20 infectious diseases that primarily affect tropical regions. Despite impacting 1.6 billion people worldwide, these diseases have not received adequate global priority and attention. Currently, NTDs caused by protozoa have limited therapeutic options, and the emergence of drug-resistant strains further exacerbates the situation. In recent years, several antimicrobial peptides (AMPs) have emerged as potential therapeutic candidates against NTDs. This review analyzes the contemporary trends of AMPs, explores their antiparasitic properties, and mechanisms of action against three parasitic protozoan NTDs: Chagas disease, human African trypanosomiasis, and leishmaniasis and one parasitic helminth NTD: lymphatic filariasis. Furthermore, notable drawbacks associated with AMPs are highlighted, and future research directions are proposed. Overall, this review points out the potential of AMPs as therapeutic agents for these three protozoan neglected tropical diseases and one parasitic helminth NTDs as well as emphasizes the imperative need for continued research in this field. 

Nature-derived Peptides as Promising Antiparasitic Agents against Neglected Tropical Diseases

http://www.thelancet.com/article/S2214109X22003382/pdf

Safety and efficacy of oral fexinidazole in children with gambiense human African trypanosomiasis: a multicentre, single-arm, open-label, phase 2–3 trial

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Bioavailability of three novel oral, sustained‐release pellets, relative to an immediate‐release tablet containing 500 mg flucytosine: A randomized, open‐label, crossover study in healthy volunteers

Safety and efficacy of oral fexinidazole in children with gambiense human African trypanosomiasis: a multicentre, single-arm, open-label, phase 2–3 trial