CYT997 (Lexibulin) is a wholly synthetic compound that possesses highly potent cytotoxic activity in vitro through inhibition of microtubule polymerization. CYT997 (Lexibulin) is a potent microtubule polymerization inhibitor with IC50 of 10-100 nM in cancer cell lines. CYT997 (Lexibulin) blocks the cell cycle at the G(2)-M boundary, and Western blot analysis indicates an increase in phosphorylated Bcl-2, along with increased expression of cyclin B1. Caspase-3 activation is also observed in cells treated with CYT997 (Lexibulin) along with the generation of poly(ADP-ribose) polymerase. The compound possesses favorable pharmacokinetic properties, is orally bioavailable, and is efficacious per os in a range of in vivo cancer models, including some refractory to paclitaxel treatment. CYT997 (Lexibulin) exhibits vascular disrupting activity as measured in vitro by effects on the permeability of human umbilical vein endothelial cell monolayers, and in vivo by effects on tumor blood flow. CYT997 (Lexibulin) possesses a useful combination of pharmacologic and pharmacokinetic properties having considerable potential as a novel anticancer agent. Lexibulin was being developed by YM BioSciences as a vascular-disrupting agent (VDA) for the potential treatment of cancer, it was in phase II development on YM BioSciences ' pipeline. It appears that the development of lexibulin has been discontinued.

Denibulin is a novel antineoplastic agent. Denibulin selectively targets and reversibly binds to the colchicine-binding site on tubulin and inhibits microtubule assembly. This results in the disruption of the cytoskeleton of tumor endothelial cells, ultimately leading to cell cycle arrest, blockage of cell division and apoptosis. This causes inadequate blood flow to the tumor and eventually leads to a decrease in tumor cell proliferation. Denibulin hydrochloride had been in phase I clinical trials for the treatment of solid tumours. It was generally well tolerated and showed decrease in tumor vascular parameters. However, no recent development has been reported.

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.

LAROTAXEL is a taxoid with potential antineoplastic activity. It prevents microtubule depolymerization, thereby inhibiting cell proliferation. It displays a broad spectrum of antitumor activity in vitro and in vivo, including activity against P-glycoprotein expressing tumors. LAROTAXEL was in phase III clinical trials for the treatment of breast cancer, pancreatic cancer, and bladder cancer. However, its development was discontinued.

Efatutazone (CS-7017 or RS-5444) is a peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist with antineoplastic properties. Mediated through activation of PPAR-gamma, this agent is capable of inducing cell differentiation and apoptosis, thereby leading to a reduction in cellular proliferation. Efatutazone was in clinical trials for the treatment of solid tumors however; its development has been discontinued.

Linifanib (ABT-869) is a structurally novel, receptor tyrosine kinase (RTK) inhibitor that is a potent inhibitor of members of the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) receptor families, but has much less activity against unrelated RTKs, soluble tyrosine kinases, or serine/threonine kinases. Linifanib (ABT-869) does not have a general antiproliferative effect due to its high dose requirement. However, it may exhibit potent antiproliferative and apoptotic effects on tumor cells whose proliferation is dependent on mutant kinases, such as FMS-related tyrosine kinase receptor-3 (FLT3). Linifanib (ABT-869) was in phase III clinical trial for the treatment of hepatocellular carcinoma, but the study failed to meet the primary end point.

Menogaril is a semisynthetic derivative of the anthracycline antineoplastic antibiotic nogalamycin. Biochemical studies indicated that, in comparison to doxorubicin, menogaril is bound weakly to DNA, inhibits RNA synthesis less, and has different cell cycle phase-specific cytotoxicity. Menogaril acts as a cleavable complex-stabilizing topoisomerase II inhibitor. Menogaril has been studied in the treatment of various cancers.

Cilengitide is a cyclized Arg-Gly-Glu (RGD)-containing pentapeptide that selectively blocks activation of the αvβ3 and αvβ5 integrins. Its precursor was first synthesized in 1995 as c(RGDfV), and later modified by the incorporation of N-methyl Val c(RGDfMetV), generating the current form of the drug. Cilengitide displays subnanomolar antagonistic activity for αvβ3 and αvβ5, and is the first integrin antagonist evaluated in clinical phase I and II trials for treatment of glioblastoma and several other tumor types. Cilengitide-induced glioma cell death and inhibition of blood vessel formation may use different molecular mechanisms, including regulation of tumor hypoxia and activation of apoptotic pathways. Cilengitide inhibits cell signaling through FAK-Src-Akt and Erk mediated pathways in endothelial and tumor cells and attenuates the effect of VEGF stimulation on growth factor signaling. Cilengitide has shown encouraging activity in patients with glioblastoma as single agent, and in association with standard RT and temozolomide.

Batabulin or T138067 (2-fluoro-1-methoxy-4-pentafluorophenylsulfonamidobenzene) covalently and selectively modifies the beta1, beta2, and beta4 isotypes of beta-tubulin at a conserved cysteine residue, thereby disrupting microtubule polymerization. Cells exposed to batabulin become altered in shape, indicating a collapse of the cytoskeleton, and show an increase in chromosomal ploidy. Batabulin is equally efficacious in inhibiting the growth of sensitive and multidrug-resistant human tumor xenografts in athymic nude mice. Batabulin has been in clinical trials for the treatment of cancers (breast cancer, colorectal cancer, glioma, hepatocellular carcinoma, non-small cell lung cancer). It does not have clinical activity in the treatment of colorectal cancer and glioma. Batabulin development was discontinued.

Amsilarotene (TAC-101) is a retinobenzoic acid (RAR) derivative with high affinity to the RAR-alpha receptor. It is a Retinoic acid receptor alpha antagonist. Amsilarotene is an orally absorbed synthetic retinoid. This analogue of vitamin A (retinol) binds to nuclear retinoic acid receptor-a (RAR-a), activates RAR-a transcriptional activity, and has shown antitumor activity in primary and metastatic preclinical models of liver cancer. Amsilarotene inhibits retinoblastoma-gene product (RB) phosphorylation and increases the presence of 2 cyclin-dependent kinase (CDK) inhibitors, resulting in cell cycle arrest. This agent also causes a cytotoxic decline in cyclin A and thymidylate synthase expression.Amsilarotene inhibits tumor growth in the liver with low toxicity and markedly improves survival in both primary HCC and metastatic colon cancer models. It was in phase II clinical development with Taiho Pharmaceutical for liver cancer, however it was discontinued.