Vadimezan (5,6-dimethyl(xanthenone-4-acetic acid), ASA404, DMXAA) is a fused tricyclic analogue of flavone acetic acid with potential antineoplastic activity. In pre-clinical mouse tumour models it was demonstrated that administration of Vadimezan rapidly leads to disruption of the existing vasculature in the tumour and consequent haemorrhagic necrosis of the tumour. This was consistent with the finding that a single dose of Vadimezan induced a prolonged reduction in the growth of xenografted tumours in animal models. The ability to disrupt the vasculature in these pre-clinical models has been attributed to a rapid induction of cytokines, particularly TNFα (tumour necrosis factor α), serotonin and nitric oxide, resulting in hemorrhagic necrosis and a decrease in angiogenesis. Despite the fact that the molecular targets for the drug remained unknown, the promising pre-clinical results led to Vadimezan being selected for clinical development. Results of Phase I trials showed some restriction of tumour blood flow within 24 h of treatment, although this was not as dramatic as seen in pre-clinical models. Unlike the animal models, there was also very little evidence for the rapid death of blood vessels or for increases in TNFα levels in human tumors. No difference in antitumour activity, cytokine induction or toxicity was observed between two parallel Phase I trials, one dosed weekly and the other dosed every 3 weeks. Therefore the drug proceeded to Phase II clinical trials, dosed every 21 days in combination with chemotherapeutic agents. These trials indicated the drug had small benefits in the treatment of non-small-cell lung cancer and prostate cancer. However, a subsequent Phase III clinical trial was not able to reproduce this response and clinical development was halted.

Alvespimycin (17-desmethoxy-17-N,N-dimethylaminoethylamino-geldanamycin) (17-DMAG; NSC 707545) is an inhibitor of the molecular chaperone heat shock protein HSP90. Alvespimycin is a derivative of antineoplastic benzoquinone antibiotic geldanamycin. Alvespimycin binds to HSP90, a chaperone protein that aids in the assembly, maturation and folding of proteins. Subsequently, the function of Hsp90 is inhibited, leading to the degradation and depletion of its client proteins such as kinases and transcription factors involved with cell cycle regulation and signal transduction. Alvespimycin was studied in clinical trials for the treatment of solid tumors and hematologic malignancies however its development was discontinued.

Ispinesib (SB-715992) is a potent, specific and reversible inhibitor of kinesin spindle protein (KSP). KSP, also known as HsEg5, is a kinesin that plays an essential role in the formation of a bipolar mitotic spindle and is required for cell cycle progression through mitosis. Ispinesib is the highly specific small-molecule inhibitor of KSP tested for the treatment of human disease. It causes mitotic arrest and growth inhibition in several human tumor cell lines and is currently being tested in multiple phase II clinical trials for treatment of the breast cancer and renal cell cancer.

Ombrabulin is an experimental drug candidate discovered by Ajinomoto and further developed by Sanofi-Aventis for cancer treatment. Ombrabulin is a synthetic water-soluble analog of combretastatin A4, derived from the South African willow bush (Combretum caffrum), with potential vascular-disrupting and antineoplastic activities. Ombrabulin binds to the colchicine binding site of endothelial cell tubulin, inhibiting tubulin polymerization and inducing mitotic arrest and apoptosis in endothelial cells. As apoptotic endothelial cells detach from their substrate, tumor blood vessels collapse; the acute disruption of tumor blood flow may result in tumor necrosis. Ombrabulin has been used in trials studying the treatment of Sarcoma, Neoplasms, Solid Tumor, Neoplasms, Malignant, and Advanced Solid Tumors, among others. In January 2013, Sanofi said it discontinued development of Ombrabulin after disappointing results from phase III clinical trials.

Lometrexol, formerly known as DDATHF; LY 264618; T-64 was the first glycinamide ribonucleotide formyl transferase (GARFT) inhibitor to be investigated clinically. Lometrexol had been in phase II clinical trial for the treatment non-small cell lung cancer (NSCLC). However, the studies have been discontinued by Tularik Inc, because Company had suggested, that drug would face competition from other companies in the indication

Nemorubicin, a doxorubicin derivative, is a DNA-intercalator, topoisomerase and RNA synthesis inhibitor that was undergoing development with Nerviano Medical Sciences (Nerviano MS; formerly Pharmacia Italia) for the treatment of solid tumours, specifically, the loco-regional treatment of primary liver tumours (hepatocellular carcinoma). The drug is active on tumors resistant to alkylating agents, topoisomerase II inhibitors and platinum derivatives. It works primarily through topoisomerase I inhibition. Of note, Nemorubicin is active in cells with upregulation of the nucleotide excision repair (NER) pathway, where current therapies fail. Nemorubicin is biotransformed in the liver into cytotoxic metabolites that may further contribute to render this drug highly active against primary liver tumors or liver metastases. Clinical trials were conducted in Europe, US and China with Nemorubicin given at different dose-schedules and by different routes of administration: as single agent by systemic IV route, oral route and by intra-hepatic artery (IHA) infusion alone or in combination with cisplatin.

Veribulin is a novel microtubule destabilizer that both functions as a potent cytotoxin and acts as a vascular disrupting agent (VDA). It binds to the same (or nearby) sites on β-tubulin as colchicine. It is capable of evading multidrug resistance pumps and, thus, achieves high CNS concentrations. It is efficacious in multiple xenograft models without CNS toxicity. Veribulin had previously demonstrated pre-clinical and clinical activity in multiple tumor types. Veribulin is in phase II clinical trial for the treatment of Glioblastoma and Malignant melanoma.

L-778123 is a dual inhibitor of Farnesyl Protein Transferase (FPTase) and Geranylgeranyl Protein Transferase type-I (GGPTase-I), which can completely inhibit Ki-Ras prenylation. L-778123 has been used in phase I clinical trials to determine its effectiveness in treating patients with recurrent or refractory solid tumors. L-778123 was also studied in combination with paclitaxel to determine efficacy as a treatment for both recurrent or refractory solid tumors, and lymphomas.

Fostriecin, an antitumor antibiotic produced by Streptomyces pulveraceus, is a strong inhibitor of serine/threonine protein phosphatases type 2A and type 4, and inhibits the catalytic activity of partially purified Topo II (type II topoisomerase) in a non-competitive manner.

Fosbretabulin (Combretastatin A4 phosphate, CA4P) is the lead compound of a relatively new class of agents termed vascular disrupting agents that target existing tumor blood vessels. Rapid tumor blood flow shutdown has been demonstrated in preclinical models and patients by various techniques such as dynamic contrast-enhanced MRI, perfusion computed tomography and PET scans following CA4P infusion. CA4P typically induces rapid tumor necrosis in the center of the tumor and leaves a rim of viable cells in the periphery. In oncology, CA4P does not appear to be that active by itself, but may be more efficacious when combined with chemotherapy, antiangiogenic therapy and radiation therapy. Combretastatin was initially isolated from the root bark of the South African Bush willow Combretum caffrum in 1982 by Pettit and colleagues at the Arizona State University (AZ, USA). Combretastatin A4 phosphate binds avidly to tubulin at the colchicine-binding site to inhibit microtubule assembly and destabilize the cytoskeleton. CA4P is a tubulin-binding agent that binds at or near the colchicine binding site of β-tubulin (Kd = 0.40 uM), inhibits tubulin assembly with IC50 of 2.4 uM. Fosbretabulin has orphan drug status in the EU and the US for the treatment of ATC (Anaplastic Thyroid Cancer). Later the development of this drug was discontinued.