(+)-SJ733 is a clinical candidate for malaria which can also inhibit Na+-ATPase PfATP4.
(+)-SJ733 binds to a single receptor site in P. falciparum-infected erythrocytes with equivalent affinity to its growth-inhibitory potency (kd=50 nM). (+)-SJ733 has not exhibited either significant safety liabilities at any dose in extensive profiling in vitro or significant safety or tolerability liabilities in either single- or repeat-dose studies at any dose tested in any preclinical species (no observed adverse effect level and maximum tolerated dose >240 mg/kg from 7-d repeat dosing study in rat). Therefore, (+)-SJ733 is expected to have a safety margin of at least 43-fold[1].
Treatment of P. falciparum-infected NOD-scid IL2Rγnull mice with (+)-SJ733 causes rapid clearance of parasites, which are 80% depleted within the first 24 h and undetectable by 48 h. (+)-SJ733 is highly potent and efficacious against P. falciparum 3D70087/N9 in vivo when administered as four sequential daily oral doses in the NOD-scid IL2Rγnull mouse model, with a 90% effective dose, (ED90 1.9 mg/kg) and exposure [area under the curve at ED90 (AUCED90), 1.5 μM?h] superior to artesunate (11.1 mg/kg; AUCED90 not determined), chloroquine (4.3 mg/kg; AUCED90 3.1 μM?h), and pyrimethamine (0.9 mg/kg; AUCED90 5. μM?h) in the same model. When treated with the ED90 dose, (+)-SJ733 concentrations in blood remain above the average in vitro EC90 for 6 to 10 h after each dose[1].
[1]. Jiménez-Díaz MB, et al. (+)-SJ733, a clinical candidate for malaria that acts through ATP4 to induce rapid host-mediated clearance of Plasmodium. Proc Natl Acad Sci U S A. 2014 Dec 16;111(50):E5455-62.