Discovering the in vitro potent inhibitors against Babesia and Theileria parasites by repurposing the Malaria Box: A review

Abstract

There is an innovative approach to discovering and developing novel potent and safe anti-Babesia and anti-Theileria agents for the control of animal piroplasmosis. Large-scale screening of 400 compounds from a Malaria Box (a treasure trove of 400 diverse compounds with antimalarial activity has been established by Medicines for Malaria Venture) against the in vitro growth of bovine Babesia and equine Babesia and Theileria parasites was performed, and the data were published in a brief with complete dataset from 236 screens of the Malaria Box compounds. Therefore, in this review, we explored and discussed in detail the in vitro inhibitory effects of 400 antimalarial compounds (200 drug-like and 200 probe-like) from the Malaria Box against Babesia (B.) bovis, B. bigemina, B. caballi, and Theileria (T.) equi. Seventeen hits were the most interesting with regard to bovine Babesia parasites, with mean selectivity indices (SIs) greater than 300 and half maximal inhibitory concentration (IC₅₀s) ranging from 50 to 410 nM. The most interesting compounds with regard to equine Babesia and Theileria parasites were MMV020490 and MMV020275, with mean SIs > 258.68 and >251.55, respectively, and IC₅₀s ranging from 76 to 480 nM. Ten novel anti-B. bovis, anti-B. bigemina, anti-T. equi, and anti-B. caballi hits, MMV666093, MMV396794, MMV006706, MMV665941, MMV085203, MMV396693, MMV006787, MMV073843, MMV007092, and MMV665875, with nanomole levels of IC₅₀ were identified. The most interesting hits were MMV396693, MMV073843, MMV666093, and MMV665875, with mean SIs greater than 307.8 and IC₅₀s ranging from 43 to 630 nM for both bovine Babesia and equine Babesia and Theileria parasites. Screening the Malaria Box against the in vitro growth of Babesia and Theileria parasites helped with the discovery of new drugs than those traditionally used, diminazene aceturate and imidocarb dipropionate, and indicated the potential of the Malaria Box in finding new, potent antibabesial drugs.

Keywords: Babesia; Drug discovery; In vitro; Malaria Box; Theileria.