An amino acid derivative with potential antineoplastic activity. NG-monomethyl-L-arginine inhibits the enzyme nitric oxide synthase, resulting in a diminution of nitrous oxide production. This agent may inhibit tumor angiogenesis. Or A form of the amino acid arginine. An amino acid is a protein building block. NG-nitro-L-arginine is being studied in the treatment of cancer and other conditions. In cancer, it may stop the growth of tumor cells by blocking certain proteins needed for tumor cells to grow and by blocking blood flow to the tumor. It is a type of nitric oxide synthase inhibitor and an antiangiogenesis agent. Also called nitroarginine.