Cell cycle-specific chemotherapeutic drugs exert their action on cells traversing the cell cycle. Which of the following is not a cell cycle-specific chemotherapeutic drug?

• A. Capecitabine
• B. Paclitaxel
• C. Bleomycin
• D. Cisplatin

Answer: (D)

The idea being tested is that some drugs only work when cells are in a particular phase of the cycle, while others can affect cells in any phase. Capecitabine turns into 5-fluorouracil, which disrupts DNA synthesis by inhibiting thymidylate synthase, so it mainly hits cells actively in the S phase. Paclitaxel prevents mitosis by stabilizing microtubules, blocking cells as they attempt to divide, so it is specific to the M phase. Bleomycin induces DNA strand breaks most effectively when cells are preparing for division, particularly in G2/M, making it a G2/M phase–specific agent. In contrast, cisplatin forms DNA crosslinks that impede replication and transcription across many phases of the cycle, so its action is not confined to a single phase. Therefore, cisplatin is not a cell cycle–specific drug.