Bromebric Acid (Cytembena) is a derivative of bromoacrylic acid with cytostatic and antineoplastic activity. Chemical structure of Bromebric Acid is not related to any previous antineoplastic agent. In animal tumor screens, Jelinek and Semonsky noted antineoplastic activity of Cytembena against sarcoma 180, atlenocarcinoina of the lactic gland in mice, Ehrlich’s ascitic carcinoma, Yoshida’s ascitic sarcoma, and Zojdeln’s heap

Brequinar is a synthetic quinolinecarboxylic acid analogue with antineoplastic properties. Brequinar inhibits the enzyme dihydroorotate dehydrogenase, thereby blocking de novo pyrimidine biosynthesis. This agent may also enhance the in vivo antitumor effect of antineoplastic agents such as 5-FU. Brequinar had been in phase II clinical trials by Bristol-Myers Squibb for the treatment of cancer and transplant rejection. However, this research has been discontinued. Brequinar had been also in preclinical studys for the treatment of cytomegalovirus infections. However, this research has been 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.

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.

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.

Edatrexate (10-ethyl-10-deazaaminopterin or 10-EDAM) is an analog of methotrexate with improved pre-clinical antitumor activity, more selective cellular uptake, and with the more extensive formation of intracellular polyglutamate metabolites. This drug is a new dihydrofolate reductase inhibitor, which was studied in phase II clinical trial for the patients with different cancers. The studies were discontinued, for example, in advanced renal cell carcinoma edatrexate in the investigated dose and schedule had minimal activity and was toxic. In case of non-small-cell lung cancer, the dosing schedule of edatrexate did not appear to be improved compared to other chemotherapeutic regimens. In addition, edatrexate was involved in the experiment for the treatemnt of rheumatoid arthritis, but this study was also discontinued.

Fialuridine, or 1-(2-deoxy-2-fluoro-1-D-arabinofuranosyl)-5-iodouracil (FIAU) is a thymidine nucleoside analog with activity against various herpesviruses and hepatitis B virus (HBV) in vitro and in vivo. Herpes virus thymidine kinase considered to be a target of FIAU. In a Phase II study, fialuridine induced a severe toxic reaction in chronic hepatitis B patients characterized by hepatic failure, lactic acidosis, pancreatitis, neuropathy, and myopathy. These clinical manifestations led to the hypothesis that the toxicity of FIAU was mediated through mitochondrial dysfunction, possibly as a result of the inhibition of mitochondrial DNA polymerase gamma and/or incorporation of FIAU into mitochondrial DNA.

Lobucavir is a new anti-cytomegalovirus infection agent, manufactered by Bristol Myers Squibb, Inc. Lobucavir is a cyclobutyl analog of guanine with broad spectrum antiviral activity against most herpes viruses and Hepatitis B. Lobucavir was shown to inhibit herpes simplex virus (HSV) DNA polymerase after phosphorylation by the HSV thymidine kinase. The drug was well tolerated with few side effects. Lobucavir had been in phase III clinical trial for the treatment of Hepatitis B, Herpes simplex virus infections and in phase II for the treatment of Cytomegalovirus infections. All these studies were discontinued.

CNDAC (TAK-109) is an analog of the nucleoside deoxycytidine with potential antineoplastic activity. CNDAC is incorporated into DNA and induces single-strand breaks, which are converted into double-strand breaks (DSBs) when cells go through a second S phase. This results in the cell cycle arrest in the S and G2/M phases, DNA fragmentation, and tumor cell apoptosis. Sapacitabine, a prodrug of CNDAC, is being developed by the US biotechnology company Cyclacel for the treatment of hemalogical cancers and solid tumors.