[Pemetrexed: from preclinic to clinic].

The pemetrexed (Alimta) is a new generation antifolate prescribed in the treatment of mesothelioma in association with cisplatin and in the 2nd line treatment of locally advanced or metastatic non-small lung cancer. Pemetrexed is an original molecule, different from the other antifolates. On the opposite methotrexate, pemetrexed inhibits several enzymes involved in the synthesis of purines and pyrimidines, in particular thymidylate synthase, dihydrofolate reductase, glycinamide ribonucleotide formyltransferase and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase. Pemetrexed is transported in cells by three receptors, which make easier its cellular penetration. On the other hand, the polyglutamation of the product by the folylpolyglutamate synthetase increases considerably its activity notably towards the thymidylate synthase. Finally, unlike methotrexate, pemetrexed presents an atypical effect on cellular synchronisation. The wide spectre of activity of pemetrexed confers it a therapeutic advantage with regard to the other antifolates specific of one or other one enzymes. The clinical results show an anti-tumoral activity against non-small lung cancer and in mesothelioma and recently towards other solid tumours, in particular in head an neck, colon and mammary cancers.