Cyclosporin B is cyclic peptide immunosuppressant that has been used in organ transplantationfor the prevention of graft rejection. A group of nonpolar cyclic oligopeptides with immunosuppressant activity. Cyclosporin B is a analogue of cyclosporin A that exhibits significantly less immunosuppressive activity. Cyclosporin B exhibits antiviral properties, inhibiting entry of hepatitis B into hepatocytes. Cyclosporin B also inhibits RANKL-induced TRAP phosphatase activity, inducing apoptosis in osteoclasts.