Discovery of novel antischistosomal scaffolds from the open access Pandemic Response Box

Treatment and control of schistosomiasis rely on a single drug, praziquantel. New orally active antischistosomals featuring novel molecular scaffolds are urgently needed to prevent the emergence of resistance. We screened 400 drug-like compounds contained in the open-access Pandemic Response Box (PRB) against newly transformed schistosomula (NTS) at a concentration of 10 µM scoring death, changes in motility, and morphological alterations. Compounds displaying an activity ≥66% at 72 h underwent testing against adult <i>Schistosoma mansoni in vitro</i>. Fast-acting (≥66% at 24 h), nontoxic drugs focusing on late-stage and approved drugs were investigated in the patent <i>S. mansoni</i> mouse model. We identified 26 hits active against NTS, of which 17 elicited ≥66% activity against adult <i>S. mansoni</i> following 24 h of drug exposure. The highest activity against <i>adult S. mansoni</i> was observed with MMV1581558 (EC₅₀ value of 0.18 ± 0.01 µM) and nitazoxanide (0.47 ± 0.07 µM). Of the five compounds tested <i>in vivo</i>, MMV1581558 and the approved drug ozanimod reduced average worm burden versus controls by 42 % and 36 %, respectively, after a single oral dose of 200 mg/kg bodyweight in mice harboring a chronic <i>S. mansoni</i> infection. MMV1581558 discovered from screening the PRB represents a novel antischistosomal scaffold with high <i>in vitro</i> antischistosomal activity amenable to chemical modification for drug development.