Aminoquinuride (Surfen) binds to glycosaminoglycans (GAGs) and has been shown to influence their function, and the function of proteoglycans (complexes of GAGs linked to a core protein). Surfen was first described in 1938 as a component of depot insulin; however, subsequent studies have revealed its efficacy in binding to glycosaminoglycans (GAGs). Surfen contains four quinoline rings that contain positively charged amino or methyl groups. Surfen was found to bind with greatest avidity to heparin. There are now a handful of studies on the biological effects of surfen, many of which relate to its ability to block the interaction between GAGs and signaling proteins, including effects on growth factors (fibroblast growth factor and vascular endothelial growth factor) and fibrils associated with the binding of human immunodeficiency virus (HIV)-1 to target cells. Surfen inhibits the action of SEVI (semen-derived enhancer of HIV viral infection). Because SEVI can increase HIV infectivity by several orders of magnitude, supplementing current HIV microbicide candidates with SEVI inhibitors, such as surfen, might greatly increase their potency. Surfen has also been shown to reduce inflammation but inhibits remyelination in murine models of multiple sclerosis.