ST-193 hydrochloride is a potent broad-spectrum arenavirus inhibitor. ST-193 hydrochloride inhibits Guanarito, Junin, Lassa and Machupo virus with IC50s of 0.44, 0.62, 1.4 and 3.1 nM, respectively.

ST-193 effectively inhibits LASV pseudotypes, demonstrating potent activity with an IC50 value of 1.6 nM. It similarly inhibits pseudotypes from other arenaviruses associated with hemorrhagic fever, showing efficacy against Junín, Machupo, Guanarito, and Sabiá with IC50 values ranging from 0.2 to 12 nM. However, ST-193 does not exhibit antiviral activity against pseudotypes that incorporate the GP from the LASV-related arenavirus lymphocytic choriomeningitis virus or the unrelated G protein from vesicular stomatitis virus, even at concentrations up to 10 μM [2].

ST-193 is well-tolerated following daily intraperitoneal injections of either 25 or 100 mg/kg/day over a 14-day period. Animals treated with ST-193 show fewer disease symptoms and improved survival rates compared to those in the ribavirin or vehicle groups. Although body temperatures increase by day 9 across all groups, they normalize by day 19 in most animals treated with ST-193. Furthermore, ST-193 treatment results in a significant 2- to 3-log reduction in viremia levels compared to vehicle-treated controls. Remarkably, the survival rate for ST-193-treated guinea pigs stands at 62.5% (10/16), starkly contrasting with 0% survival in both the ribavirin (0/8) and vehicle (0/7) groups.