Epothilones: a novel class of microtubule-stabilizing drugs for the treatment of cancer

Microtubule-targeted anticancer drugs are effective in treating various cancers but are limited in use due to development of resistance and unacceptable toxicities. The epothilones are a novel class of microtubule-stabilizing anticancer drugs and may have a role in treating taxane-resistant cancers. Revised and updated data from several clinical studies for ixabepilone were recently published and subsequently resulted in ixabepilone becoming the first epothilone approved as monotherapy or in combination for treatment of locally advanced or metastatic breast cancer. BMS-310705, patupilone, KOS-862, KOS-1584 and ZK-EPO are epothilones that have been developed. Although peripheral sensory neuropathy and neutropenia are the dose-limiting toxicities for ixabepilone, these dose-limiting toxicities are ixabepilone specific. This review will discuss the current preclinical, clinical pharmacokinetic and pharmacodynamic, efficacy and toxicity data of the epothilones.

Potential clinical applications of epothilones: a review of phase II studies

BACKGROUND

Epothilones are cytotoxic macrolides that share a similar mechanism of action with the taxanes but demonstrate antitumor activity in taxane-resistant settings. Six epothilones are in early clinical trials for cancer treatment.

DESIGN

This review summarizes data from phase II clinical studies of the epothilones ixabepilone (BMS-247550), patupilone (EPO906), and KOS-862. Data were identified by searches of PubMed and of the proceedings of the American Society of Clinical Oncology annual meetings and the Federation of European Cancer Societies biennial conference for the period 2000-2006. Studies were included if safety and efficacy data were available for at least 10 patients with a given tumor type in a standard phase II design.

RESULTS

Epothilones have demonstrated activity in lung, ovarian, breast, prostate, and renal carcinomas and in non-Hodgkin's lymphoma in phase II studies. Little or no evidence of clinical activity has been reported in studies of epothilones in other tumor types. Preliminary data indicate that epothilones can be combined safely with other cytotoxic agents such as carboplatin.

CONCLUSIONS

The epothilones may play a role as an alternative to taxanes if activity in resistant settings can be confirmed together with an acceptable toxicity profile. Randomized studies are awaited to investigate the utility of epothilones in single-agent and combination regimens.