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.

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.

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.

Cemadotin (LU103793) is a cytotoxic water-soluble pentapeptide analogue of dolastatin 15. The dolastatin peptides were originally isolated from the shell-less mollusc Dolabella auricularia. Cemadotin blocks cells at mitosis. It exerts its antitumor activity by suppressing spindle microtubule dynamics through a distinct molecular mechanism by binding at a novel site in tubulin. Cemadotin was in phase II clinical trials as a promising cancer chemotherapeutic agent. However, this agent appears to be inactive in the treatment of advanced non-small-cell lung cancer and other tumors and this research has been discontinued.

gamma-sitosterol is a naturally occurring plant steroid isolatable from plants of the genus Lagerstroemia. Gamma-sitosterol is a potent inhibitor of the complement component C1 complex, and it has demonstrated potential as a diabetic treatment in rats. Gamma-sitosterol is a stereoisomer of beta-sitosterol, which sees wide use as an over the counter natural supplement. However, plant extracts containing gamma-sitosterol have demonstrated toxicity on in-vitro human cell assays; which may discourage use as a natural supplement.

Thiabendazole (TBZ, trade names Mintezol, Tresaderm, and Arbotect) was first introduced in 1962. This drug is a fungicide and parasiticide and is indicated for the treatment of: strongyloidiasis (threadworm), cutaneous larva migrans (creeping eruption), visceral larva migrans, trichinosis: relief of symptoms and fever and a reduction of eosinophilia have followed the use of this drug during the invasion stage of the disease. But usage of this drug was discontinued. The precise mode of action of thiabendazole on the parasite is unknown, but it may inhibit the helminthspecific enzyme fumarate reductase. It was shown, also that thiabendazole reversibly disassembles newly established blood vessels, marking it as vascular disrupting agent (VDA) and thus as a potential complementary therapeutic for use in combination with current anti-angiogenic therapies. Was shown, that vascular disruption by TBZ results from reduced tubulin levels and hyper-active Rho signaling. In addition, was confirmed, that thiabendazole slowed tumor growth and decreased vascular density in preclinical fibrosarcoma xenografts and thus, it could lead directly to the identification of a potential new therapeutic application for an inexpensive drug that is already approved for clinical use in humans.

Thiabendazole (TBZ, trade names Mintezol, Tresaderm, and Arbotect) was first introduced in 1962. This drug is a fungicide and parasiticide and is indicated for the treatment of: strongyloidiasis (threadworm), cutaneous larva migrans (creeping eruption), visceral larva migrans, trichinosis: relief of symptoms and fever and a reduction of eosinophilia have followed the use of this drug during the invasion stage of the disease. But usage of this drug was discontinued. The precise mode of action of thiabendazole on the parasite is unknown, but it may inhibit the helminthspecific enzyme fumarate reductase. It was shown, also that thiabendazole reversibly disassembles newly established blood vessels, marking it as vascular disrupting agent (VDA) and thus as a potential complementary therapeutic for use in combination with current anti-angiogenic therapies. Was shown, that vascular disruption by TBZ results from reduced tubulin levels and hyper-active Rho signaling. In addition, was confirmed, that thiabendazole slowed tumor growth and decreased vascular density in preclinical fibrosarcoma xenografts and thus, it could lead directly to the identification of a potential new therapeutic application for an inexpensive drug that is already approved for clinical use in humans.

Apramycin is a broad-spectrum aminocyclitol antibiotic produced by a strain of Streptomyces tenebrarius. It has a bactericidal action against many gram-negative bacteria. Apramycin is a structurally unique antibiotic that contains a bicyclic sugar moiety and a monosubstituted deoxystreptamine. It is not approved for use in humans. Apramycin is registered for use in more than twenty countries in cattle, pigs and chickens. The drug exerts its antibacterial effect by inhibiting protein synthesis at the level of peptidyl translocation. It is mostly used for treating gastrointestinal infections. Apramycin is available in soluble powder and feed premix formulations.

Vinflunine (Javlor) is the first fluorinated microtubule inhibitor belonging to the Vinca alkaloids family. Vinflunine, at the lowest effective concentrations, interacts with the Vinca alkaloid binding site on tubulin, suppresses microtubule dynamics (switching at microtubule ends between phases of slow growth and rapid shortening) and microtubule treadmilling (growth at the plus end and shortening at the minus end of the microtubule), causes cell cycle arrest which appears on fluorescence-activated cell sorting analysis as a G2 + M phase arrest, and is associated with an accumulation of cells in mitosis leading to cell death via apoptosis. Vinflunine has been been approved for advanced or metastatic transitional cell carcinoma of the urothelial tract. Pierre Fabre submitted an extension to the EU authorisation to add treatment of advanced breast cancer.