Cyclosporin A. Clinical pharmacology and therapeutic potential.

Cyclosporin A is a cyclical polypeptide of 11 amino acids, one of which is unique to the cyclosporins. First isolated as an antifungal agent, it has been shown to have marked immunomodulatory properties. These properties have meant that the drug can be used as an immunosuppressant to prevent the rejection of transplants, both of organs and bone marrows, as well as in the control of autoimmune diseases. It has already been shown to have a major clinical impact in the transplantation of kidneys, pancreas, liver, hearts, heart and lung and both compatible and incompatible bone marrow grafts. The drug acts by inhibiting that part of the immune system which relies on T cell proliferation, probably by interference with second signal controls. The clinical results so far achieved with cyclosporin A indicate that it has an important part to play in the future of immunosuppression. With better, more reliable, immunosuppressive controls, the possibility exists that transplantation of immunologically more susceptible organs could become a routine procedure providing a treatment to patient populations whose conditions had previously been considered incurable.