Which of the following is an alkylating chemotherapy agent?

• A. Cisplatin
• B. Vincristine
• C. Bevacizumab
• D. Temozolomide

Answer: (D)

Temozolomide is the alkylating chemotherapy agent. Alkylating drugs work by adding alkyl groups to DNA, causing cross-links and other damage that prevent replication and trigger cell death. Temozolomide is a prodrug that becomes the active metabolite MTIC, which methylates DNA at the O6 and N7 positions of guanine. This DNA methylation disrupts replication in rapidly dividing tumor cells, leading to cell death. By contrast, the other agents work through different mechanisms: cisplatin causes DNA crosslinks via platinum chemistry (not alkylation), vincristine disrupts microtubule dynamics, and bevacizumab is a monoclonal antibody that inhibits VEGF. Therefore, temozolomide fits the alkylating category.