[{"from": "human", "value": "Describe this molecule. [C][=Branch1][C][=O][Branch1][C][N][N][O]"}, {"from": "gpt", "value": "The molecule is a monohydroxyl-substituted urea (hydroxycarbamate) antimetabolite. Hydroxyurea selectively inhibits ribonucleoside diphosphate reductase, an enzyme required to convert ribonucleoside diphosphates into deoxyribonucleoside diphosphates, thereby preventing cells from leaving the G1/S phase of the cell cycle.  This agent also exhibits radiosensitizing activity by maintaining cells in the radiation-sensitive G1 phase and interfering with DNA repair. (NCI04)"}]