Rosabulin (STA 5312) is an antineoplastic compound (inhibiting or halting neoplasm development). This compound was developed for the treatment of drug resistant tumors. By acting as a tubulin inhibitor, rosabulin hinders the microtubule assembly necessary to shape endothelial (vascular) cells, and blocks their cell division. As a result, blood flow to the tumor is reduced and tumor cell proliferation is decreased. Phase I clinical trials in patients with advanced or metastatic tumors, leukemia, lymphoma and hematological malignancies have evaluated the safety and toxicity of rosabulin. Development of rosabulin has been discontinued in 2008.

Bristol-Myers Squibb developed BMS-184476 for the potential treatment of solid tumors. BMS-184476 participated in phase II clinical trials for patients with non-small-cell lung cancer, breast, and ovarian cancers. However, that development has been discontinued.

Dolastatin 10 is an unusual peptide of marine origin which binds to tubulin, inhibits microtubule assembly, resulting in the formation of tubulin aggregates and inhibition of mitosis. Dolastatin 10 has been used in trials phase II studying the treatment of Sarcoma, Leukemia, Lymphoma, Liver Cancer, among others. In case of hormone-refractory prostate cancer, it lacks significant clinical activity as a single agent and also dolastatin-10 is inactive against hepatobiliary and pancreatic carcinomas.

MKC-1 is an orally available cell cycle inhibitor with downstream targets that include tubulin and the importin-β family. MKC-1 has shown broad antitumor activity in preclinical models. MKC-1 and its metabolites inhibit tubulin polymerization, blocking the formation of the mitotic spindle, which may result in cell cycle arrest at the G2/M phase and apoptosis. In addition, this agent has been shown to inhibit the activities of the oncogenic kinase Akt, the mTOR pathway, and importin-beta, a protein essential to the transport of other proteins from the cytosol into the nucleus. MKC-1 had been in phase II clinical trials for the treatment of ovarian cancer, endometrial cancer, pancreatic cancer and breast cancer. This compound was originally discovered by Roche, then licensed to EntreMed (now CASI Pharmaceuticals) the exclusive worldwide rights to develop and commercialize. However, no recent development has been reported.

Maytansine is an ansamycin antibiotic originally isolated from the Ethiopian shrub Maytenus serrata. Maytansine inhibits the assembly of microtubules by binding to tubulin at or near the vinblastine-binding site, decreases microtubule dynamic instability and cause mitotic arrest in cells. It exerts cytotoxicity against a number of tumor cell lines and inhibits tumor growth in vivo. However, in human clinical trials, maytansine showed a small therapeutic window due to its neurotoxicity and harmful effects on the gastrointestinal tract. The potent cell killing ability of maytansine can be used in a targeted delivery approach, such as an antibody-drug conjugate, for the selective delivery of the drug and destruction of cancer cells.

Bristol-Myers Squibb developed BMS-188797 for the potential treatment of solid tumors. BMS-188797 causes G2/M cell cycle arrest and exhibits potent antiproliferative activity against human tumor cell. BMS-188797 in combination with cisplatin successfully has passed phase I clinical and has been recommended for further phase II trials. However, further development has been halted.

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.

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.

Tesetaxel is a taxane derivative patented by Daiichi Pharmaceutical Co., Ltd. as antitumor agent. Preclinical research suggests that tesetaxel may overcome P-glycoprotein-mediated multidrug resistance, thereby facilitating extended intracellular retention and possibly clinical effectiveness. Tesetaxel exhibited potent cytotoxicity against various human and murine cancer cell lines and was particularly potent against cell lines expressing P-glycoprotein. Orally administered tesetaxel showed potent in vivo antitumor activity in murine syngeneic and human xenograft models. The cytotoxic effect of tesetaxel, unlike that of other taxanes, was not influenced by the level of P-glycoprotein expression or by the presence of a P-glycoprotein modulator. In patients with metastatic breast cancer, tesetaxel was shown to have significant, single-agent antitumor activity in two multicenter, Phase 2 studies.

Filanesib is a highly selective, targeted KSP inhibitor with a mechanism of action distinct from currently available myeloma therapies such as immunomodulatory drugs (IMiDs®) and proteasome inhibitors. Across multiple studies, filanesib has demonstrated activity in heavily pretreated multiple myeloma patients, with a consistent safety profile including no drug-induced peripheral neuropathy and limited non-hematologic toxicity. Adverse events are generally limited to transient, non-cumulative and predominantly asymptomatic myelosuppression (decreases in blood counts) when supportive measures are used. Alpha 1-acid glycoprotein (AAG), a plasma protein, is a potential patient selection marker for filanesib. AAG is undergoing further investigation in clinical trials and could represent the first patient selection marker for a myeloma therapy. Filanesib is in Phase II for Multiple myeloma treatment.