ST-193 is a potent inhibitor of broad-spectrum arenavirus(Guanarito, Junin, Lassa and Machupo virus with IC50 values of 0.44, 0.62, 1.4 and 3.1 nM, respectively).

LASV pseudotypes(IC50 of 1.6 nM)inhibited by ST-193 . ST-193 inhibits pseudotypes generated with other arenavirus envelopes as well, including the remaining four commonly associated with hemorrhagic fever (IC50s for Junín, Machupo, Guanarito, and Sabiá were in the 0.2 to 12 nM range)[2].

ST-193, exhibits submicromolar antiviral activity in vitro.?To determine the antiviral utility of ST-193 in vivo, Tested the efficacy of this compound in the LASV guinea pig model.?Four groups of strain 13 guinea pigs were administered 25 or 80 mg/kg ST-193, 25 mg/kg of ribavirin, or the vehicle by the intraperitoneal (i.p.) route before infection with a lethal dose of LASV, strain Josiah, and continuing once daily for 14 days.?Control animals exhibited severe disease, becoming moribund between days 10 and 15 postinfection.?ST-193-treated animals exhibited fewer signs of disease and enhanced survival when compared to the ribavirin or vehicle groups.?Body temperatures in all groups were elevated by day 9, but returned to normal by day 19 postinfection in the majority of ST-193-treated animals.?ST-193 treatment mediated a 2-3-log reduction in viremia relative to vehicle-treated controls.?The overall survival rate for the ST-193-treated guinea pigs was 62.5% (10/16) compared with 0% in the ribavirin (0/8) and vehicle (0/7) groups.?These data suggest that ST-193 may serve as an improved candidate for the treatment of Lassa fever[3].