OSW-1 is a saponin that has been found in O. saundersiae and has antiviral and anticancer activities.1 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.2 It induces OSBP translocalization from the cytoplasm to the trans-Golgi network and decreases intracellular levels of OSBP in HEK293 cells.2,3 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.4 It also inhibits replication of hepatitis C virus (HCV) but not mouse hepatitis virus (MHV), a coronavirus.5 It protects against CVA9 and echovirus 2 infection in HeLa cells when used at a concentration of 10 nM.4 OSW-1 inhibits growth of HeLa and HEK293 cells (GI50s = 0.33 and 0.22 nM, respectively).2

|3. Burgett, A.W.G., Poulsen, T.B., Wangkanont, K., et al. Natural products reveal cancer cell dependence on oxysterol-binding proteins. Nat. Chem. Biol. 7(9), 639-647 (2011).|5. Strating, J.R.P.M., van der Linden, L., Albulescu, L., et al. Itraconazole inhibits enterovirus replication by targeting the oxysterol-binding protein. Cell rep. 10(4), 600-615 (2015).