# Repurposing of Inhibitors of Plasmodial Aspartate Transcarbamoylase Toward Trypanosoma Cruzi

## TL;DR

Scientists found that some compounds originally designed to target a specific enzyme in malaria parasites can also inhibit a similar enzyme in a parasite that causes Chagas disease, suggesting a new path for drug development.

## Contribution

A library of Plasmodium falciparum ATC inhibitors was repurposed to identify potent and selective inhibitors of Trypanosoma cruzi ATC.

## Key findings

- 34 compounds from a 70-member library inhibited Trypanosoma cruzi ATC by over 90%.
- Five compounds showed IC50 values below 250 nM, indicating strong inhibitory activity.
- Two compounds demonstrated low micromolar cellular activity but exhibited co-toxicity.

## Abstract

Aspartate transcarbamoylase (ATC) catalyzes the committed and rate‐limiting step in the pyrimidine de novo biosynthesis pathway. While previously suggested to be a potential target for antimalarial, antitubercular, and antioncologic drug discovery, we hypothesized that an existing compound library of ATC inhibitors designed from one scaffold by fragment screening against Plamodium falciparum ATC (PfATC) may also contain inhibitors of Trypanosoma cruzi ATC (TcATC). In this manuscript, we screened the 70‐member library at 35 μM against 50 nM TcATC, and in these initial experiments, 34 compounds showed over 90% inhibition. Of the 34 compounds, 5 compounds demonstrated IC50 values of lower than 250 nM in a follow‐up enzymatic half inhibition concentration analysis. Kinetic studies on one of these compounds indicate that they inhibit TcATC in a noncompetitive manner, and a druggable allosteric pocket is seen in the available crystal structure. While cocrystallization and soaking experiments were unsuccessful, molecular modeling was performed to assess potential binding modes. Two of the best‐performing compounds were selected for a cellular assay, showing EC50s of 7.4 µM and 6.5 µM. However, significant cotoxicity was also observed, demonstrating that further elaboration of the compounds is necessary. These results suggest that this compound library might be a starting point for antitrypanosomatid drug discovery.

Aspartate transcarbamoylase (ATC) catalyzes the committed, rate‐limiting step in pyrimidine de novo biosynthesis and has been proposed as a drug target in several pathogenic contexts. Here, screening a 70‐member ATC inhibitor library originally developed against Plasmodium falciparum ATC identified 34 compounds with ⟩90% inhibition of Trypanosoma cruzi ATC, including five with IC50 values below 250 nM, which likely act via non‐competitive inhibition consistent with a druggable allosteric site. Although selected compounds showed low‐micromolar cellular activity, associated co‐toxicity indicates that further optimization is required, positioning this library as a promising starting point for anti‐trypanosomatid drug discovery.