OSW-1 is a saponin that has been found in O. saundersiae and has antiviral and anticancer activities. It is an inhibitor of oxysterol-binding protein (OSBP) and its paralog OSBP-related protein 4 (ORP4) with Ki values of 16 and 71 nM, respectively, in radioligand binding assays using HEK293T cell lysates. It induces OSBP translocalization from the cytoplasm to the trans-Golgi network and decreases intracellular levels of OSBP in HEK293 cells. OSW-1 inhibits replication of a variety of enteroviruses (IC50s = 2.4-9.4 nM), including replication of coxsackievirus B3 (CVB3) in infected HeLa R19 cells in an OSBP-dependent manner when used at a concentration of 3 nM. It also inhibits replication of hepatitis C virus (HCV) but not mouse hepatitis virus (MHV), a coronavirus. It protects against CVA9 and echovirus 2 infection in HeLa cells when used at a concentration of 10 nM. OSW-1 inhibits growth of HeLa and HEK293 cells (GI50s = 0.33 and 0.22 nM, respectively).
