Cyclosporin A-d12 (Cyclosporine A-d12) is deuterium labeled Cyclosporin A. Cyclosporin A (Cyclosporine A) is an immunosuppressant which binds to the cyclophilin and inhibits phosphatase activity of protein phosphatase 2B (PP2B/calcineurin) with an IC50 of 5 nM[3]. Cyclosporin A also inhibits CD11a/CD18 adhesion[8].