<unk>  chemically alters the DNA nucleotide guanine through alkylation, and causes linkages between strands of DNA. This chemical alteration inhibits DNA synthesis and RNA synthesis, functions necessary for cells to survive. These changes cause cytotoxicity in both dividing and non-dividing tumor cells. Tumor cells spend less time in resting phases than normal cells so at any given time, they are more likely to be metabolically active than most normal host cells. The rationale behind incorporating an alkylating function in a molecule resembling a primary cellular metabolite was to get a greater safety margin by fooling tumor cells into taking up the toxin preferentially.
Melphalan
Ifosfamide
Vincristine
Busulfan
Normustine
Carmustine
Lomustine
Bendamustine