What was the first drug used for treating cancer as alkylating agent?

• A. Cyclophosphamide
• B. Dacarbazine
• C. Nitrogen mustard
• D. Doxorubicin

Answer: (C)

The main idea here is that nitrogen mustard was the first cancer drug to be used that works as an alkylating agent. This marked the birth of chemotherapy for cancer. In the 1940s, clinicians observed that mustard gas caused tumor responses and bone marrow suppression; from this, nitrogen mustard (mechlorethamine) was developed and used in patients, becoming the first alkylating agent to show clinical activity against cancer. Its action is to transfer alkyl groups to DNA, creating cross-links that block replication and transcription, which is especially lethal to rapidly dividing cancer cells. Other options came later or belong to different mechanisms: cyclophosphamide is another alkylating agent but was developed after nitrogen mustard; dacarbazine is a later alkylating-like agent with a different activation chemistry; doxorubicin is not an alkylating agent at all but an anthracycline that intercalates DNA and generates free radicals.