[{"from": "human", "value": "What can you tell me about this molecule? [C][N][C][Branch2][Ring1][Ring1][C][N][C][=C][Ring1][=Branch1][C][=Branch1][C][=O][N][C][=Branch1][Ring2][=N][Ring1][#Branch1][N][C][C][N][C][=C][C][=C][Branch1][Branch1][C][=C][Ring1][=Branch1][C][=Branch1][C][=O][N][C@@H1][Branch1][Branch2][C][C][C][=Branch1][C][=O][O][C][=Branch1][C][=O][O]"}, {"from": "gpt", "value": "The molecule is a folic acid antagonist and mammalian dihydrofolate reductase inhibitor with antineoplastic activity. Ketotrexate inhibits dihydrofolate reductase, an enzyme that reduces dihydrofolic acid to tetrahydrofolic acid which is essential for the synthesis of purine nucleotides and thymidylate. By depleting tetrahydrofolic acid availability, DNA synthesis is halted."}]