Mitoguazone is a guanylhydrazone derivative with potential antineoplastic activity. Mitoguazone inhibits S-adenosyl-L-methionine decarboxylase (SAMD), an enzyme involved in the synthesis of polyamines, resulting in a decreased proliferation of tumor cells, antimitochondrial effects, and p53-independent apoptosis. In the 1960s the drug was investigated in clinical trials. Despite the responses in acute leukemia, chronic myelogenous leukemia, lymphoma, multiple myeloma, head and neck cancer, esophageal cancer and other types of cancer, the development of the drug was discontinued because of marked myelosuppression and mucositis. Using a weekly schedule of administration, mitoguazone had minimal toxicity and showed limited activity in patients with lymphoma, esophageal cancer, prostate cancer, and other types of tumors.