Discovery of an orally active benzoxaborole prodrug effective in the treatment of Chagas disease in non-human primates

Abstract

Trypanosoma cruzi, the agent of Chagas disease, probably infects tens of millions of people, primarily in Latin America, causing morbidity and mortality. The options for treatment and prevention of Chagas disease are limited and underutilized. Here we describe the discovery of a series of benzoxaborole compounds with nanomolar activity against extra- and intracellular stages of T. cruzi. Leveraging both ongoing drug discovery efforts in related kinetoplastids, and the exceptional models for rapid drug screening and optimization in T. cruzi, we have identified the prodrug AN15368 that is activated by parasite carboxypeptidases to yield a compound that targets the messenger RNA processing pathway in T. cruzi. AN15368 was found to be active in vitro and in vivo against a range of genetically distinct T. cruzi lineages and was uniformly curative in non-human primates (NHPs) with long-term naturally acquired infections. Treatment in NHPs also revealed no detectable acute toxicity or long-term health or reproductive impact. Thus, AN15368 is an extensively validated and apparently safe, clinically ready candidate with promising potential for prevention and treatment of Chagas disease.

Frequency variation and dose modification of benznidazole administration for the treatment ofTrypanosoma cruziinfection in mice, dogs and non-human primates

“…2A and supplemental Table 1)). Multiplex serological screening to assess declines in antibody levels to multiple T. cruzi proteins, an indicator of treatment efficacy in humans [16-19] and non-human primates [20], also showed declining antibody levels in most, but not all animals over this relatively short post-treatment observation period (Fig. 2B).…”

“…The unique mechanisms of action, cytotoxic/cytostatic activities, metabolism and tissue distributions of drugs combine to determine effective treatment regimens. We remain optimistic that shorter treatment courses may be possible using other compounds [20] although amastigote dormancy is likely to negate treatment periods of less than several weeks.…”

“…Declines in anti-parasite antibody levels are highly variable between individuals and are often slow to occur and thus not useful for assessment during or soon after treatment (although they do have utility where longer-term follow-up is possible [18, 19]). Intensive screening for T. cruzi DNA in organ tissues provides solid evidence for cure/not-cure [20] but obviously requires termination of study animals. We took advantage of the culling of several working dogs to obtain tissue samples that solidified the evidence for parasitological cures using the high-dose, weekly BNZ protocol.…”

“…All five animals underwent a final health examination and then were euthanized following a four-week recovery period. Blood samples and fresh, frozen, and paraformaldehyde-fixed tissues were collected from the animals and processed for clinical tests and PCR detection of parasite DNA as previously described [20]…”

Identification of compounds with activity against Trypanosoma cruzi within a collection of synthetic nucleoside analogs

“…Some oxaborole compounds have also been nominated as clinical candidates for the treatment of Chagas disease. For instance, Padilla et al reported that the benzoxaborole prodrug AN15368, which targets the mRNA processing pathway in T. cruzi, was uniformly curative in non-human primates with long-term naturally acquired infections (Padilla et al, 2022). Besides, the oxaborole DNDI-6148 showed high curative rates in mouse models of infection and is currently being evaluated in phase I clinical trials (De Rycker et al, 2022).…”