Carboxyamidotriazole (L651582) is a carboxyamide-amino-imidazole compound originally developed as a coccidiostat, an antiprotozoal agent that acts upon Coccidia parasites. Carboxyamidotriazole (L651582) is an orally-active agent with potential antineoplastic activity. Carboxyamidotriazole binds to and inhibits non-voltage-operated Ca2 channels, blocking both Ca2 influx into cells and Ca2 release from intracellular stores and resulting in the disruption of calcium channel-mediated signal transduction and inhibition of vascular endothelial growth factor (VEGF) signaling, endothelial proliferation, and angiogenesis. This agent may also inhibit tumor cell growth, invasion, and metastasis.

Iododoxorubicin is an anthracycline derivative patented by Farmitalia Carlo Erba S.p.A. for cancer treatment. In preclinical studies, Iododoxorubicin has demonstrated significantly reduced levels of cardiotoxicity compared to anthracyclines. Unfortunately, during phase II clinical trials Iododoxorubicin failed to demonstrate efficacy in an advanced breast cancer patient

Lodenosine is the experimental HIV reverse transcriptase inhibitor. It was designed as a chemically and enzymatically stable anti-AIDS drug. A phase II trial of the nucleoside analog lodenosine was suspended after one participant died and others showed signs of liver or kidney damage.

Bristol-Myers Squibb developed BMS-188797 for the potential treatment of solid tumors. BMS-188797 causes G2/M cell cycle arrest and exhibits potent antiproliferative activity against human tumor cell. BMS-188797 in combination with cisplatin successfully has passed phase I clinical and has been recommended for further phase II trials. However, further development has been halted.

Eniluracil (5-ethynyluracil, GW 776, 776C85) is a potent irreversible inhibitor of dihydropyrimidine dehydrogenase, the first enzyme in the catabolic pathway of 5-fluorouracil (5-FU), the most widely used drug in cancer chemotherapy. Eniluracil increases the oral bioavailability of 5-FU to 100%, facilitating uniform absorption and predictable toxicity. Eniluracil was being developed as a novel modulator of 5-FU for the treatment of cancer.

Pumitepa is a purine derivative patented by All-Union Scientific-Research Chemical-Pharmaceutical Institute as cancerolytic. Although the exact mechanism of action of pumitepa has yet to be fully elucidated, this agent appears to work through alkylation, thereby causing DNA damage and cell cycle arrest. In in vitro studies, Pumitepa prolonged the mitotic cycle in human embryo fibroblasts by 2.5-3 hr, primarily by prolonging the start of phase G1. Pumitepa induced similar types of chromosomal aberrations in cells of all phases of the mitotic cycle. Chromosomes in phase S were the most sensitive for Pumitepa, followed by chromosomes in phases G1 and G2.

Tumor hypoxia remains one of the greatest challenges in the treatment of solid tumors, as cancer cells in these regions are resistant to killing by radiation therapy and most anticancer drugs. Tirapazamine (3-Amino-1,2,4-benzotriazine-1,4-dioxide or SR 4233) is a cytotoxic drug with selective toxicity towards hypoxic mammalian cells. Under both aerobic and hypoxic conditions, tirapazamine is reduced by an intracellular reductase to form a highly reactive radical, which can cause DNA single- and double-strand breaks. In addition, tirapazamine under hypoxic conditions reduces the activity of topoisomerase II and stabilizes DNA topoisomerase II cleavable complexes, and these complexes remain bound to DNA. Despite the very promising results obtained in various preclinical studies and early-Phase clinical trials, several Phase III trials have failed to demonstrate any survival benefit of adding tirapazamine to chemotherapy or radiation therapy of cancers.

Pimonidazole (developed as RO 038799) is a derivative of 2-nitroimidazole, which forms adducts (binds to thiol-containing proteins) only at low oxygen tension. Pimonidazole is a novel nontoxic hypoxia marker for the complementary study of tumor hypoxia and cell proliferation in different types of cancer. The drawback of pimonidazole as a hypoxic marker is that it detects only severe hypoxia.

Cevipabulin is a synthetic, water-soluble tubulin-binding agent with potential antineoplastic activity. Cevipabulin appears to bind at the vinca-binding site on tubulin but seems to act more similar to taxane-site binding agents in that it enhances tubulin polymerization and does not induce tubulin depolymerization. The disruption in microtubule dynamics may eventually inhibit cell division and reduce cellular growth.

Taltobulin, also known as HTI-286 and SPA-110, is a fully synthetic analog of the natural tripeptide hemiasterlin, inhibits tubulin polymerization and circumvents transport-based resistance to taxanes. Taltobulin was a potent inhibitor of proliferation (mean IC50 = 4 nm in 18 human tumor cell lines) and had substantially less interaction with multidrug resistance protein (P-glycoprotein) than currently used antimicrotubule agents, including paclitaxel, docetaxel, vinorelbine, or vinblastine. Taltobulin showed strong antitumor activity both in androgen-dependent and androgen- independent tumors and may be a promising agent in second- line treatment strategies for patients suffering from docetaxel- refractory prostate cancer.