Early investigational tubulin inhibitors as novel cancer therapeutics

INTRODUCTION

Microtubules represent one of the most logical and strategic molecular targets amongst the current targets for chemotherapy, alongside DNA. In the past decade, tubulin inhibitors as cancer therapeutics have been an area of focus due to the improved understanding and biological relevance of microtubules in cellular functions. Fueled by the objective of developing novel chemotherapeutics and with the aim of establishing the benefits of tubulin inhibition, several clinical trials have been conducted with others ongoing.

AREA COVERED

At present, the antitubulin development pipeline contains an armful of agents under clinical investigation. This review focuses on novel tubulin inhibitors as cancer therapeutics. The article covers the agents which have completed the phase II studies along with the agents demonstrating promising results in phase I studies.

EXPERT OPINION

Countless clinical trials evaluating the efficacy, safety and pharmacokinetics of novel tubulin inhibitors highlights the scientific efforts being paid to establish their candidature as cancer therapeutics. Colchicine binding site inhibitors as vascular disrupting agents (VDAs) and new taxanes appear to be the most likely agents for future clinical interest. Numerous agents have demonstrated clinical benefits in terms of efficacy and survival in phase I and II studies. However conclusive benefits can only be ascertained on the basis of phase III studies.

A phase II study of milataxel: a novel taxane analogue in previously treated patients with advanced colorectal cancer

BACKGROUND

Milataxel is a novel taxane analog, with evidence of enhanced preclinical activity compared to paclitaxel and docetaxel, especially in cell lines that over express P-glycoprotein. Based on preclinical data that milataxel may be active in colorectal cancer (CRC), a phase II study was performed in patients with advanced previously treated CRC.

PATIENTS AND RESULTS

Forty-four eligible patients were entered. Milataxel was administered intravenously every 3 weeks at the dose of 35 mg/m(2). No objective responses were noted, stable disease was seen in three patients. The median time to progression was 1.4 months (95% CI of 1.2-2.4 months). Three subjects developed neutropenic sepsis and two died. The most frequent grade 3/4 adverse events were neutropenia (57%), leukopenia (27%), dehydration (14%), neuropathy (16%), diarrhea (14%) and thrombocytopenia (14%). The pharmacokinetics of milataxel was assessed in five subjects. The mean milataxel elimination half-life was 64 h and the mean area under the plasma concentration-time curve was 1,708 ng h/ml.

CONCLUSIONS

A syndrome of neutropenic sepsis and diarrhea can be life threatening and close surveillance is needed in patients treated with milataxel at the dose of 35 mg/m(2) every 3 weeks. Clinical activity was not demonstrated in patients with advanced previously treated CRC.