New-generation efflux pump inhibitors.

The development of novel efflux pump inhibitors is an emerging and challenging research field. Besides the use of such excipients in cancer therapy, efflux pump inhibitors are gaining increasing interest with regards to drug delivery. In particular, inhibition of efflux pumps located in the intestine and the blood-brain barrier offers promising prospects. Nowadays, third-generation inhibitors, such as elacridar, zosuquidar, laniquidar, OC144-093 and tariquidar, have been evaluated in clinical trials. Apart from these small, molecular inhibitors, which will be discussed within the current review, a focus has been set on polymeric or polymer-based inhibitors, including poly(ethylene glycol) and derivatives, poloxamers and thiomers.