Folate pathways are essential in metabolism and macromolecule synthesis. Antifolate drugs that are largely transported via a high capacity folate transporter (i.e. the reduced-folate carrier) and inhibit folate-dependent enzymes include the dihydrofolate reductase inhibitor, methotrexate, and the thymidylate synthase inhibitors, raltitrexed and pemetrexed. Major advances in folate research made within the last decade include (i) the approval of pemetrexed for the treatment of lung cancer and mesothelioma, and (ii) the demonstration that cell membrane-anchored folate receptors (FR) are...