Vatalanib a potent oral tyrosine kinase inhibitor with a selective range of molecular targets, has been extensively investigated and has shown promising results in patients with solid tumors in early trials. Vatalanib selectively inhibits the tyrosine kinase domains of vascular endothelial growth factor (VEGF) receptor tyrosine kinases (important enzymes in the formation of new blood vessels that contribute to tumor growth and metastasis), platelet-derived growth factor (PDGF) receptor, and c-KIT. The adverse effects of vatalanib appear similar to those of other VEGF inhibitors. In the CONFIRM trials, the most common side effects were high blood pressure, gastrointestinal upset (diarrhea, nausea, and vomiting), fatigue, and dizziness.

Amiprilose hydrochloride (brand name Therafectin), a novel synthetic carbohydrate with anti-inflammatory properties, which was developed for the treatment of rheumatoid arthritis. In September 1993, FDA informed that this drug could not be approved because there was not adequate data demonstrating the drug’s effectiveness.

Almorexant (ACT-078573) is an orally active dual orexin receptor antagonist that is being developed by Actelion Ltd, in collaboration with GlaxoSmithKline plc, for the treatment of primary insomnia. Almorexant is a first-in-class compound that targets the orexin system, which plays a key role in wake promotion and stabilization; In January 2011, GlaxoSmithKline (GSK) and Actelion Ltd announced that clinical development of Phase III of almorexant has been discontinued. This decision follows a review of data from additional clinical studies, which were conducted to further establish the clinical profile of almorexant, including the tolerability profile.

Andolast is a small molecule activator of Calcium-activated potassium channels and an inhibitor of IgE-mediated anaphylaxis. Andolast is under investigation as an anti-asthmatic and for the treatment of COPD.

Odanacatib is a potent, selective, and neutral cathepsin K inhibitor, an enzyme involved in bone resorption. Merck & Co was developing odanacatib, a once-weekly, oral Odanacatib, for the treatment of postmenopausal osteoporosis and osteoporosis in men. Merck & Co. has discontinued development of its cathepsin K inhibitor odanacatib, citing an increased risk of cardiovascular events for the osteoporosis drug.

Torcetrapib is a CETP inhibitor which was developed by Pfizer for the treatment of diseases associated with elevated level of cholesterol. The drug was tested in phase III (in combination with atorvastatin) of clinical trials in coronary heart disease patients as well as in patients with hyperlipoproteinemia, hypertriglyceridemia, hypercholesterolemia, hyperlipidemia, however its development was terminated due to the high risk of death and heart problems.

Vicriviroc or SCH 417690 is a potent and selective antagonist of the CCR5 receptor. vicriviroc binds specifically to the CCR5 receptor and prevents infection of target cells by CCR5-tropic HIV-1 isolates. In antiviral assays, vicriviroc showed potent, broad-spectrum activity against genetically diverse and drug-resistant HIV-1 isolates and was consistently more active than SCH-C in inhibiting viral replication. This compound demonstrated synergistic anti-HIV activity in combination with drugs from all other classes of approved antiretrovirals. Competition binding assays revealed that vicriviroc binds with higher affinity to CCR5 than SCH-C. Functional assays, including inhibition of calcium flux, guanosine 5'-[35S]triphosphate exchange, and chemotaxis, confirmed that vicriviroc acts as a receptor antagonist by inhibiting signaling of CCR5 by chemokines. Finally, vicriviroc demonstrated diminished affinity for the human ether a-go-go related gene transcript ion channel compared to SCH-C, suggesting a reduced potential for cardiac effects. Vicriviroc represented a promising new candidate for the treatment of HIV-1 infection. Vicriviroc for HIV treatment was previously in Phase III studies but has since been discontinued.

Liarozole is an imidazole-containing compound that inhibits the cytochrome P-450-dependent metabolism of all-trans-retinoic acid (RA). Liarozole, a retinoic acid (RA) metabolism-blocking agent (RAMBA) in clinical development, has been granted orphan drug designation for congenital ichthyosis by the European Commission and the U.S. Food and Drug Administration. Later, based on the mixed results from a phase II/III trial of liarozole for the treatment of ichthyosis, Barrier decided to discontinue the development of liarozole. Liarozole displays antitumor activity against androgen-dependent and independent rat prostate carcinomas.A large phase III international study was completed comparing liarozole 300 mg twice daily with cyproterone acetate (CPA) 100 mg twice daily in a total of 321 patients with metastatic prostate cancer in relapse after first-line endocrine therapy. The results indicate that liarozole might be a possible treatment option for prostate cancer (PCA) following failure of first-line endocrine therapy.

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.

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.