Cyclosporine U is a cytostatic drug that is used to treat various types of cancers, including leukemia and lymphoma. It is also used to prevent rejection of transplanted organs. Cyclosporine U is available as a prescription drug and can be administered orally. The preparation of cyclosporine U involves the following steps: (1) the removal of l-norvaline from cyclosporine A; (2) the conversion of the resulting cyclosporine A to an ester with hplc analysis; and (3) the conversion of this ester to cyclosporine U by conjugation with phosphate derivatives. Cyclosporine U is not active against viruses or bacteria but has been shown to suppress the immune system by preventing T-cell activation and proliferation. Cyclosporine U binds specifically to T-lymphocytes, which are responsible for cell-mediated immunity, and prevents their activation. This binding inhibits production of interleuk