Ciclosporin

Ciclosporin is a cyclic peptide immunosuppressant that suppresses T-cell activation by inhibiting calcineurin. It is used to prevent organ transplant rejection and treat selected autoimmune and inflammatory diseases.

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Calcineurin: A calcium- and calmodulin-dependent phosphatase that activates transcription factors involved in immune-cell signaling. Ciclosporin-bound cyclophilin inhibits this enzyme, interrupting T-cell activation.
Organ transplantation: The surgical transfer of an organ from a donor to a recipient to restore organ function. Ciclosporin suppresses immune responses that would otherwise damage a transplanted organ.
Cyclosporins: A family of cyclic peptides, including ciclosporin, with diverse biological activities. Ciclosporin is the best-known immunosuppressive member of this peptide family.
Tolypocladium inflatum: A fungus that produces ciclosporin and was originally isolated from a soil sample. This organism was the natural source from which ciclosporin was discovered.
Transplant immunology: The study of immune responses to transplanted cells, tissues, and organs. Ciclosporin became a major tool for controlling the responses this field investigates.
Cyclophilin: A family of cellular proteins that bind immunosuppressive drugs and catalyze protein folding reactions. Cyclophilin forms the drug–protein complex that inhibits calcineurin.
Graft rejection: An immune response in which a recipient's immune system attacks transplanted tissue. Preventing this response is a central reason for ciclosporin treatment.
Cyclic peptide: A peptide whose amino-acid chain forms a closed ring through covalent bonds. Ciclosporin’s ring structure distinguishes it from many conventional small-molecule drugs.
Sandoz: A Swiss pharmaceutical company that developed ciclosporin for clinical use. Sandoz advanced the compound from fungal product to transplant medicine.
Immunosuppression: The reduction or suppression of immune-system activity by drugs, disease, or other causes. Ciclosporin is a widely used pharmacological means of producing immunosuppression.