Ciclosporin is a cyclic nonribosomal polypeptide of 11 amino acids produced by the fungi Tolypocladium inflatum and Cylindrocarpon lucidum. Ciclosporin is a highly efficient immunosuppressant drug widely used in post-allergenic organ transplant to reduce the activity of the subject's immune system and so the risk of organ rejection. Apart from transplant medicine, ciclosporin is also used in the treatment of autoimmune diseases like psoriasis and infrequently in rheumatoid arthritis and related diseases, although it is only used in severe cases.