The intravenous to oral switch of taxanes: strategies and current clinical developments

The taxanes paclitaxel, docetaxel and cabazitaxel are important anticancer agents that are widely used as intravenous treatment for several solid tumor types. Switching from intravenous to oral treatment can be more convenient for patients, improve cost-effectiveness and reduce the demands of chemotherapy treatment on hospital care. However, oral treatment with taxanes is challenging because of pharmaceutical and pharmacological factors that lead to low oral bioavailability. This review summarizes the current clinical developments in oral taxane treatment. Intravenous parent drugs, strategies in the oral switch, individual agents in clinical trials, challenges and further perspectives on treatment with oral taxanes are subsequently discussed.

Taxanes – The Backbone of Medical Oncology

Drug development in oncology has witnessed a revolutionary growth from its humble beginning with nitrogen mustard in 1940 to immunotherapy in 1986 (Interferon alpha). The arsenal of cytotoxics is ever increasing, contributing to better survival outcomes and improved quality of life. Over the years, many cytotoxics have fallen out of favor too, due to its side effects and availability of drugs with better efficacy and toxicity profile. Taxane, a microtubule stabilizing agent extracted from the poisonous Yew tree, was discovered in 1964 and came into clinical use in 1992 with its approval for ovarian cancer. This group has grown into a cornerstone of many treatment protocols, spanning multiple tumor types. This review discusses in brief the salient features of cytotoxic agents in this drug group, its history, physico-chemical properties, mechanism of action, pharmacodynamics, and pharmacokinetics. Though the benefits of taxanes are well understood, there are unique problems associated with the use of taxanes and there is an expanding literature on taxane resistance. We briefly look at the resistance mechanisms. There have been significant efforts to circumvent the problems related to conventional taxanes, with an attempt at creating newer carrier molecules and adjunct drugs with taxanes, which is slowly gaining traction in clinical practice.

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.