<prompt> Antifolate cancer drugs are: PGI Nov 2009MethotrexateAzathioprineCyclosporinVincristne  <response>: Ans:A Methotrexate Folate AntagonistMethotrexate-Trimethoprim4Pyrimethamine4PemetrexedMethotrexate MTX It is a folic acid antagonistQ that binds to the active catalytic site of dihydrofolate reductase DHFRQ, interfering with the synthesis of the reduced form that accepts one-carbon units. Lack of this cofactor interrupts the de novo synthesis of thymidylate, purine nucleotides, and the amino acids serine and methionine, thereby interfering with the formation of DNA, RNA, and key cellular proteins.PemetrexedIt is a pyrrolopyrimidine antifolate analogueJwifh activity in the S phase of the cell cycle. As in the case of MTX, it is transported into the cell via the reduced folate carrier and requires activation by the enzyme FPGS to yield higher polyglutamate forms.While this agent targets DHFR and enzymes involved in de novo purine nucleotide synthesis, its main site of action is via inhibition of thymidylate synthase.At present, this anti folate is approved for use in combination with cisplatin in the treatment of mesothelioma - and as a single agent in the second-line therapy of non-small cell lung cancer.Cisplatin Although the precise mechanism of action of cisplati n is still undefined, it is thought to exert its cytotoxic effects in the same manner as alkylating agents.It kills cells in all stages of the cell cycle, binds DNA through the formation of intrastrand and interstrand cross-links, and inhibits DNA synthesis and function. The primary binding site is the iY7 position of guanine1 but covalent interaction with adenine and cytosine also occursDrug Acting Directly on Cells Cytotoxic Drugs1. Alkylating eventsNitrogen mustardQMechlorethamine Mustine HCCyclophosphamideQIfosfamideQChlorambucilMelphalanQ Ethyleninine:Thio-TEPA Alkyl sulfonate:BusulfanQ Nitrosoureas:Carmustine BCNU,Lomustine CCNU Triazine:Dacarbazine DT1C2. AntimetabolitesFolate antagonistMethotrexate Mtx Purine antagonist6-Mercaptopurine 6-MP6-Thioguanine 6-TGAzathioprineQFludarabineQ Pyrimidine antagonist5-FlurouracilQ 5-FU,Cytarabine cytosine arabinoside3. Vinca alkaloidsVincristine Oncovin,Vinblastine4. TaxanesQPaclitaxelQDocetaxei5. Epipodophyllo toxinQEtoposideQ6. Camptothecin analoguesTopotecanQIrinotecanQ7. AntibioticsQActinomycin DQDactinomycinDoxorubicinQDaunorubicinQ RubidomycinMitoxantrone8. MiscellaneousHydroxyureaQProcarbazine,L-Asparaginase,CisplatinQCarboplatinImatinibQ 