This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chemotherapy, Subject name: Pharmacology
[{'content': "Which of the following anti-cancer drug is NOT 's'-phase specific: \nSelect and explain. \nA. Methotrexate, B. Mercaptopurine, C. Ifosfamide, D. Thioguanine", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Cytotoxic drugs are either cell cycle specific (CCS) or cell cycle nonspecific (CCNS). (a) Cell cycle nonspecific Kill resting as well as dividing cells, e.g. nitrogen mustard, cyclophosphamide, chlorambucil, carmustine, dacarbazine, busulfan, L-asparaginase, cisplatin, procarbazine, actinomycin D. (b) Cell cycle specific Kill only actively dividing cells. Their toxicity is generally expressed in S phase. However, these drugs may show considerable phase selectivity, e.g.- G1: Vinblastine. S : Mtx, cytarabine, 6-TG, 6-MP, 5-FU, hydroxyurea, mitomycin C, doxorubicin, daunorubicin. G2: Daunorubicin, bleomycin, etoposide, topotecan. M: Vincristine, vinblastine, paclitaxel, docetaxel ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:830', 'role': 'assistant'}]