Nocodazole is an anti-mitotic drug that has long been used as an experimental tool in cell biology. Nocodazole is known to bind with high affinity to tubulin and to inhibit microtubule assembly. The tubulin molecule is a α/β heterodimer; both α and β exist as various isotypes whose distribution and drug-binding properties are significantly different. Nocodazole has the highest affinity for αβIV and the lowest affinity for αβIII. In addition, nocodazole was investigated as an anticancer drug on xenografts model and it was revealed, that nocodazole possessed a high-affinity for the cancer-related kinases ABL, c-KIT, BRAF, and MEK, and inhibited Abl, Abl(E255K) and Abl(T315I).

Sardomozide (previously known as SAM486A or CGP-48664) was developed as an inhibitor of S-adenosyl-methionine-decarboxylase, a key enzyme for polyamine biosynthesis. Sardomozide possessed the broad-spectrum antiproliferative and antitumor activity. The drug participated in a phase II clinical trial as a monotherapy in patients with refractory or relapsed non-Hodgkin's lymphoma. In Phase II clinical trial in patients with metastatic melanoma, the drug didn’t have significant therapeutic potential. The further development of this drug was discontinued.

Elvucitabine (ACH-126443 or beta-L-Fd4C) is a reverse transcriptase inhibitor exerting antiviral properties. Elvucitabine, an L-cytosine nucleoside analog, is intracellularly phosphorylated to its active 5′-triphosphate metabolite, which has an intracellular half-life of at least 20 hours. Elvucitabine triphosphate inhibits the activity of HIV reverse transcriptase by competing with natural substrates and by causing DNA chain termination after incorporation into viral DNA. Elvucitabine has also demonstrated in vitro and in vivo activity against HBV. Achillion, under license from Vion is developing elvucitabine for the potential treatment of HIV and hepatitis B virus (HBV) infection.

Palifosfamide or ZIO-201 (isophosphoramide mustard; IPM), a bi-functional DNA alkylator, is the active metabolite of ifosfamide (IFOS). IFOS and the related drug cyclophosphamide (CPA) are widely used anti-cancer drugs. Both are pro-drugs and need to be metabolized to be active. Their clinical use is limited by the toxicity associated with some of their metabolites. Palifosfamide has shown efficacy in diverse cancer models. ZIOPHARM Oncology Inc, under license from Dekk-Tec Inc, was developing palifosfamide, a formulation of isophosphoramide mustard with tris(hydroxymethyl)aminomethane salt-stabilization (palifosfamide-tris) and previously with lysine-stabilization (palifosfamide-lys). Preclinical studies and phase I and I/II clinical trials demonstrated that palifosfamide-tris had an antitumor efficiency comparable or superior to that of ifosfamide. To date ZIO-201 is not present in ZIOPHARM pipeline.

Losoxantrone is an anthrapyrazole that induces both single and double strand breaks in DNA and is a potent inhibitor of DNA synthesis. The drug is in clinical trials for the treatment of breast cancer and of prostate cancer that is refractory to androgen ablation. Acute toxicity is negligible. Losoxantrone may be less cardiotoxic than doxorubicin. Up to 40% of patients encounter alopecia. 3% of patients develop congestive heart failure. Losoxantrone had been in phase II clinical trial for the treatment of breast and prostate cancer. However, this development was discontinued.

Fazarabine (Arabinofuranosyl-5-azacytosine) is a synthetic pyrimidine nucleoside which combines the arabinose sugar of cytosine arabinoside with the triazine base of 5-azacytidine. It has demonstrated activity against a variety of human solid tumor xenografts including colon, lung and breast cancers. It has been selected by the Division of Cancer Treatment, National Cancer Institute for clinical development as an antineoplastic agent based on its high degree of activity against a broad range of tumor types in preclinical studies. Therapeutic activity has been observed against murine and human leukemias, transplantable murine solid tumors, and human tumor xenografts. Arabinosyl-5-azacytosine exhibited a broader spectrum of activity against human solid tumors than cytosine arabinoside. The mode of action of fazarabine is mediated through its incorporation into DNA and inhibition of DNA synthesis.

Gimatecan is a topoisomerase I inhibitor that is presently tested in phase II of clinical trials for the treatment of different cancers: glioma, glioblastoma, epithelial ovarian cancer, fallopian tube or peritoneal cancer. The drug recieved orphan designation for the treatment of glioma.

Pelitrexol (also known as AG2037) was developed by Pfizer as a glycinamide ribonucleotide formyltransferase inhibitor. This drug was studied in phase II clinical trials in patients with metastatic non-small cell lung cancer and in patients with metastatic colorectal cancer who failed treatment. In addition, the drug participated in a phase I clinical trial in treating patients who have advanced, metastatic, or recurrent solid tumors. Information about the further development of pelitrexol is not available.

Topixantrone (BBR 3576) is a hetero-analog of the anthrapyrazole class of compounds. The mechanism of action of BBR 3576 is similar to that of mitoxantrone in terms of DNA intercalation, DNA affinity, topoisomerase II interaction and formation of single-strand breaks. BBR 3576 showed curative antitumor activity at the maximum tolerated dose (MTD) with a number of long-term survivors and showed greater activity than mitoxantrone and doxorubicin in preclinical studies. BBR 3576 retained a high level of activity across a wide range of doses. In human xenograft studies, equivalent antitumor activity was observed when compared with doxorubicin and mitoxantrone. The compound showed reduced cardiotoxicity when repeatedly administered in rodent models. Topixantrone has a manageable toxicity profile on a 4-week schedule.

Nitracrine (Ledakrin, C-283) is an acridine derivative with potential cytostatic and antitumor activities. Nitracrine induces the unwinding of supercoiled DNA and binds to the DNA through intercalation, forming drug-DNA adducts and DNA interstrand crosslinks. This inhibits RNA synthesis, protein production, cell growth, DNA replication and cell proliferation; altogether, this may promote apoptosis. Since cancer cells have increased metabolism and proliferate at an increased rate, nitracrine may induce tumor cell apoptosis. The drug was used in clinics in Poland for the treatment of ovarian, colon, lung and mammary carcinomas. Some undesirable effects observed in clinics: e.g. nausea, vomiting and toxicity and mutagenicity of the drug in S. typhimurium strongly limited the therapeutic use of nitracrine and promoted a search for more suitable analogues.