Repurposing Irosustat for Malaria: Host-Targeted Antiplasmodial Activity via Cholesterol Sulfate Modulation Against Drug-Resistant Plasmodium falciparum

Background The urgent global need for novel antimalarial drugs targeting Plasmodium falciparum has intensified due to rising mortality and drug resistance. This study examines a host-directed strategy targeting lipid metabolism by evaluating the antiplasmodial activity of cholesterol sulfate (CS) and Irosustat, a steroid sulfatase inhibitor designed to elevate circulating CS concentrations. Methods The antimalarial efficacy of CS was evaluated in vitro against chloroquine-sensitive (3D7 and CamWT), chloroquine-resistant (K1 and Dd2), and artemisinin-resistant (CamWTC580Y(+) and Dd2R539T(+)) strains of P. falciparum . In vivo antimalarial activity of Irosustat was further confirmed using a modified single-dose 4-day test via oral route (PO) in a mouse model against P. yoelii (CQ-resistant strain), both as monotherapy and in combination therapy with chloroquine (CQ). Results CS effectively inhibited the growth of P. falciparum strains, including both drug-sensitive and drug-resistant strains. In vitro assays revealed moderate nanomolar IC ₅₀ values for sensitive strains and low micromolar IC ₅₀ values for resistant strains. The compound exhibited slow speed clearance and a synergistic effect with artemisinin in vitro . In vivo , Irosustat achieved more than 80% suppression as monotherapy (40 mg/kg, PO) and more than 90% efficacy in combination with CQ (40/10 mg/kg, PO) against P. yoelii , significantly improved survival rates, mean survival days (MSD), body weight, and clinical outcomes. Irosustat exhibits promising antimalarial activity with a favorable oral pharmacokinetic profile. Conclusions Future optimization of Irosustat may enhance its antiplasmodial activity, positioning it as a promising candidate for antimalarial drug development.