Ametantrone (AM) is a synthetic 9,10-anthracenedione bearing two (hydroxyethylamino)ethylamino residues at positions 1 and 4; along with other anthraquinones and anthracyclines, it shares a polycyclic intercalating moiety and charged side chains that stabilize DNA binding. Ametantrone is anticancer drug candidate targeting DNA. Ametantrone is a topoisomerase II inhibitor of the anthrapyrazole family. Ametantrone induces interstrand DNA cross-links in HeLa S3 cells. These cross-links were observed only in cellular system suggesting that metabolism of the drugs is a necessary step leading to DNA cross-linking. Ametantrone appeared to be very well tolerated and easy to handle. A dose-schedule of 135 mg/m2 q 2–3 weeks was recommended for phase II studies in solid tumors.

Ethidium is a DNA intercalating agent first discovered as and used as a veterenary trypanocide. A bromide salt is commonly used as a fluorescent tag in molecular biology. The fluorescene of ethidium bromide increased 21 fold upon binding to double-stranded RNA, 25 fold upon binding double stranded DNA. Because of the binding to DNA, ethidium bromide is a powerful inhibitor of DNA polymerase.

Dezaguanine is a broad spectrum guanine antimetabolite. This compound differs from guanine only in the substitution of a carbon for the 3-nitrogen of guanine. Dezaguanine must be converted to its nucleotides to be active. Dezaguanine nucleotides inhibit synthesis of guanine nucleotides, and can be incorporated into nucleic acids in place of guanine nucleotides; incorporation into DNA may be particularly important in the cytotoxicity of this compound. Addition of certain purines or purine nucleosides can prevent dezaguanine cytotoxicity in vitro. It has exhibited sufficient preclinical antitumor activity, particularly against rat and mouse mammary adenocarcinomas, slow and fast growing mammary tumors in mice and the human breast xenograft subrenal capsule implant system. It has completed one phase I trial.

Piroxantrone is one of a series of compounds commonly known as anthrapyrazoles developed in an effort to combine the broad antitumor activity of the anthracyclines with decreased myocardial toxicity. The mechanism of action of piroxantrone and other anthrapyrazoles is incompletely understood but likely involves DNA binding with induction of DNA strand breaks, DNA-protein cross-linking, and inhibition of DNA, RNA, and protein synthesis. Collectively, these findings suggested an interaction with topoisomerase II. Piroxantrone demonstrated antitumor activity in a wide spectrum of experimental systems against breast carcinoma, colon carcinoma, sarcoma, melanoma and leukemia. Piroxantrone is inactive in patients with persistent, progressive, or recurrent ovarian cancer who recently had received a platinum-based regimen. Piroxantrone has detectable but minimal activity against disseminated malignant melanoma. A phase II clinical trial of the piroxantrone administration for the treatment of advanced metastatic or recurrent endometrial cancer was prematurely terminated due to lack of patient accrual.

Nafoxidine is a nonsteroidal antiestrogen available as an investigational agent from the Investigational Drug Branch of the National Cancer Institute. It has been used effectively in the treatment of breast cancer patients. Nafoxidine competes with endogenous estrogen for binding to specific estrogen receptors. This agent also inhibits angiogenesis in some tissues by blocking the effects of fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF); paradoxically, it may enhance angiogenesis in uterine tissue. Nafoxidine also induces oxidative stress, protein kinase C and calcium signaling.

Esorubicin (4'-deoxydoxorubicin, NSC 267469) is a synthetic derivative of the anthracycline antineoplastic antibiotic doxorubicin with potential antineoplastic activity. Esorubicin intercalates into DNA and inhibits topoisomerase II, thereby inhibiting DNA replication and ultimately, interfering with RNA and protein synthesis. This agent exhibits less cardiotoxicity than the parent antibiotic doxorubicin, but may cause more severe myelosupression compared to other compounds within the anthracycline class. Esorubicin was being clinically tested for the treatment of solid tumors as well as lymphomas an leukemias. Esorubicin development has been discontinued.

Crisnatol is a derivative of arylmethylaminopropanediol with significant antineoplastic activity in a variety of murine and human tumor models. Crisnatol functions as a DNA intercalator, with the presence of additional basic amine groups in the sidechain enhancing binding to DNA due to electrostatic interactions. Crisnatol did not show antitumor efficacy in patients with ovarian carcinoma. In another clinical study, 2 of 26 patients with glioma showed complete long-lasting responses to the drug. The dose-limiting side effect was neurotoxicity.

SNX-2112, a novel 2-aminobenzamide inhibitor of heat shock protein 90 (Hsp90) was discovered by Serenex. This drug was investigated for treatment of different cancer cell lines, including hepatocellular carcinoma cells, breast cancer cells and in combination with 5-fluorouracil in esophageal cancer. However, subsequent development has been discontinued due to ocular toxicity as identified in a phase I study.