The orphan nuclear receptor SXR coordinately regulates drug clearance in response to a wide variety ofxenobiotic compounds. The disclosure demonstrates that an HIV protease inhibitor binds SXR and activates its target genes. SXR ligands activate expression of MRP2, a critical regulator of bile flow and biliary drug excretion. Therefore, SXR binding compounds can be used for regulating drug clearance and treatment of hepatic disorders associated with impaired bile flow. The present invention relates to new methods of modifying drug clearance and avoiding multi-drug resistance by modifying SXR activity. SXR is a transcriptional activator of MDR1, cytochrome P40-3A4 and cytochrome P40 2C8. SXR activation can significantly increase the metabolic inactivation and efflux of a wide range of chemotherapeutic agents, for example taxanes. Reducing and/or preventing SXR activation therefore diminishes drug resistance and drug clearance and forms the basis of important therapeutic methods which increase the performance of drugs, such as taxanes. Screening and drug identification methods are described which can identify drugs which are not susceptible to SXR related inactivation and increased efflux. In addition, drugs which can reduce these effects for other agents are provided.
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