Development of chiral praziquantel analogues as potential drug candidates with activity to juvenile Schistosoma japonicum

A series of chiral praziquantel analogues were synthesized and evaluated against Schistosoma japonicum both in vitro and in vivo. All compounds exhibited low to considerable good activity in vivo. Remarkably, worm reduction rate of R-3 was 60.0% at a single oral dose of 200 mg/kg against juvenile stage of Schistosoma japonicum. The target compounds displayed in vivo antischistosomal activity against both Schistosoma japonicum and Schistosoma mansoni. Furthermore, all R-isomers displayed stronger antischistosomal activity than S-isomers in vivo, indicating R-isomers were the active enantiomers, while S-isomers were less active ones. This structure activity relationship (SAR) could have important implications in further drug development for schistosomiasis.