Which of the following is NOT one of the nitrogen mustards?

Lomustine is not classified as a nitrogen mustard; instead, it is an alkylating agent that belongs to a different class known as nitrosoureas. While nitrogen mustards function by forming cross-links in DNA, thereby disrupting the replication process, nitrosoureas like Lomustine also alkylate DNA but have distinct structural components and mechanisms of action. On the other hand, cyclophosphamide, chlorambucil, and melphalan are all nitrogen mustards, characterized by their reactive nitrogen atoms that play a crucial role in their ability to attach alkyl groups to DNA, leading to cell death.

This classification helps in understanding the pharmacological profiles, side effects, and clinical uses of these drugs, allowing for more informed treatment planning in oncology.