Surfen dihydrochloride is a potent HS (heparan sulfate) antagonist. Surfen binds to glycosaminoglycans. Surfen neutralizes the anticoagulant activity of both unfractionated and low molecular weight heparins. Surfen affects sulfation of heparin and inhibits degradation by heparin lyases. Surfen inhibits FGF2 binding and signaling. Surfen inhibits cell attachment, and virus infection.