Schweinfurthins and their analogues are highly selective cellular probes for oxysterol-binding protein (OSBP)

Schweinfurthins (SWs) are natural products isolated from the plant genus <i>Macaranga</i> which display a unique cytotoxicity profile in human cancer cell lines with low nanomolar potency. Their known target is the sterol transport protein (STP) oxysterol-binding protein (OSBP), a key mediator and regulator of lipid transport between the endoplasmic reticulum (ER) and the trans-Golgi network (TGN). However, until now the underlying structure-activity relationships (SAR), as well as the cellular toxicity-target engagement relationships of SWs towards OSBP have not been well-studied. In this study, we present the first comprehensive SAR and selectivity study by characterizing 59 SW analogues utilizing our STP screening panel. Complementary detailed docking studies shine light on the SW-OSBP interactions and unravel amino acid residues critical for potent binding to OSBP. Additionally, we demonstrate cellular target engagement and correlate cancer cell cytotoxicity with Golgi fragmentation as a phenotypic consequence of OSBP inhibition by selected SW analogues. Therefore, this study will pave the way for more focused investigations and therapeutic applications of OSBP inhibitors.