Fluorouracil is an antineoplastic anti-metabolite. Anti-metabolites masquerade as purine or pyrimidine - which become the building blocks of DNA. They prevent these substances from becoming incorporated into DNA during the "S" phase (of the cell cycle), stopping normal development and division. Fluorouracil blocks an enzyme which converts the cytosine nucleotide into the deoxy derivative. In addition, DNA synthesis is further inhibited because Fluorouracil blocks the incorporation of the thymidine nucleotide into the DNA strand. Fluorouracil is used for the topical treatment of multiple actinic or solar keratoses. In the 5% strength it is also useful in the treatment of superficial basal cell carcinomas when conventional methods are impractical, such as with multiple lesions or difficult treatment sites. Fluorouracil injection is indicated in the palliative management of some types of cancer, including colon, esophageal, gastric, rectum, breast, biliary tract, stomach, head and neck, cervical, pancreas, renal cell, and carcinoid.

Mannomustine is a substance synthesized as one of a series of compounds linking the actively cytotoxic chemical group beta-chlorethylamine with a naturally occurring substance, mannitol. Mannomustine is an alkylating agent with antineoplastic properties. It was being studied in the treatment of hematologic malignancies.

The D-isomer of melphalan, known as medphalan, is less active against certain animal tumors and the dose needed to produce effects on chromosomes is larger than that required with the L-isomer.