Combretastatin is a phenol derivative isolated from the bark of Combretum caffrum, commonly known as South African Bush Willow. Combretastatin is an effective antimitotic agent, and like colchicine, inhibited tubulin polymerization and stimulated tubulin-dependent GTP hydrolysis.

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.

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.

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.

Carbendazim is a broad-spectrum benzimidazole antifungal with potential antimitotic and antineoplastic activities widely used as a fungicide in agriculture and home gardening, and as an antihelminthic in veterinary medicine. As a fungicide, carbendazim used for controls Ascomycetes, Fungi Imperfecti, and Basidiomycetes on a wide variety of crops, including bananas, cereals, cotton, fruits, grapes, mushrooms, ornamentals, peanuts, sugarbeet, soybeans, tobacco, and vegetables. Carbendazim is a chemically stable and relatively persistent fungicide which only metabolizes to a limited extent in plants and in soil. The only detected metabolite is 2-aminobenzimidazole, which constitutes less than 5% of the total residues in leaves. Carbendazim may be anticipated to metabolize in the animal into hydroxylated analogues which may appear in meat and milk products. Carbendazim acts as a mitotic poison by altering tubulin binding and microtubule formation. This has been proposed as a possible mechanism of action for the developmental abnormalities seen in animal studies with high concentrations.

Thiocolchicine is a colchicine-derivative used in the therapy of some diseases and extensively studied in the field of oncological research as antimitotic agent. It is tubulin polymerization and microtubule assembly inhibitor and axonal cytoskeleton modulator; apoptosis inducer. Thiocolchicine-dimers were shown to be potent topoisomerase I inhibitors. Thiocolchicine is a potential antitumor agent.

Trimethylcolchicinic acid (also known as deacetyl colchicine) was used for patients with advanced malignancies. However, these studies were discontinued. Expeiments on rat were shown, that trimethylcolchicinic acid was able to improve normal liver histology, ultrastructure, collagen content and biochemical markers of liver damage in spite of that trimethylcolchicinic acid, didn't bind tubulin.

Demecolcine, also called Colcemid, was isolated from the autumn crocus in 1950 and commercialized by Ciba. Initially, it was explored as a cancer drug due to its low toxicity. Demecolcine depolymerizes microtubules and limits microtubule formation (inactivates spindle fiber formation), thus arresting cells in metaphase and allowing cell harvest and karyotyping to be performed. Today, it is only used as a research tool mainly to overcome limitations of colchicine due to its very slow association and dissociation rate constants. It binds to tubulin at the same site as colchicine, but ~10-fold faster, and it also dissociates faster. Demecolcine main use has been to arrest cells in mitosis for cytogenetic analysis, though to our knowledge it offers no special advantages over other drugs in this application.

Combretastatin A4 is a vascular disrupting agent (VDA) that targets tumor vasculature to inhibit angiogenesis. Combretastatin A4 is a tubulin-binding agent that binds at or near the colchicine binding site of β-tubulin and inhibits tubulin assembly. This tubulin-binding agent was originally isolated from an African shrub, Combretum caffrum. Combretastatin A4 is cytotoxic to umbilical-vein endothelial cells (HUVECs) and to a range of cells derived from primary tumors and these cytotoxicity profiles have been used to assess several novel analogs of the drug for future development. Combretastatin A4 has antitumor activity by inhibiting AKT function. The inhibited AKT activation causes decreased cell proliferation, cell cycle arrest, and reduced in vitro migration/invasiveness and in vivo metastatic ability. Several studies in mice have shown that a single administration of combretastatin A4 (100 mg/kg) does not significantly affect primary tumor growth. However, repeated administration (12.5 – 25.0mg/kg twice daily) for periods of 10 – 20 days resulted in approximately 50% retardation of growth of ectopic Lewis lung carcinoma and substantial growth delay of T138 spontaneous murine breast tumors. In clinical studies, Combretastatin A4 has been well tolerated in patients at doses up to 56 mg/m2, following a protocol of five daily 10-minute intravenous infusions every 21 days. The disodium combretastatin A4 phosphate prodrug is currently undergoing clinical trials in the UK and USA.

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.