Cyclosporine is an immunosuppressant drug most significantly used in post-operative organ transplants to reduce the chance of rejection of donor organs by decreasing the activity of the patient’s immune system. Subsequent to an organ transplant, patients are tested at regular intervals for the presence of very low levels of the compound. Cyclosporine is a cyclic non-ribosomal peptide of 11 amino acids and contains a single D-amino acid.