[New analogues of methotrexate].

New antifolate antimetabolites are currently developed and three analogues of methotrexate (MTX) (Trimetrexate, Edatrexate, TNP-351) are undergoing clinical trials in Japan. Trimetrexate characteristically enters cells primarily by passive transport, which is different from the mechanism of MTX. The increased therapeutic efficacy of Edatrexate is expected, because of the higher concentration of polyglutamates than MTX in tumor cells. TNP-351 is a novel antifolate, which has a different chemical structure from other antifolates. The current state of clinical trials of three antifolates and the indications for chemotherapy of lung cancer are reviewed.