The invention provides extracts and compositions derived from Tripterygium wilfordii for overcoming drug resistance in cancer therapy. This invention relates to organic solvent extracts of T. wilfordii and their use in cancer treatment, particularly in the treatment of cancers which have exhibited resistance to treatment by chemotherapeutic drugs. Methods of treating a cancer are disclosed. The method administers to a patient in need thereof a combination of (a) an organic solvent extract of T. wilfordii and (b) a chemotherapeutic drug. The organic solvent extract of T. wilfordii (a) and chemotherapeutic drug (b) are administered in a combined amount effective to treat the cancer. The cancer being treated is at least in part resistant to treatment by the chemotherapeutic drug (b) alone. Also disclosed are chemotherapeutic compositions comprising a combination of (a) an organic solvent extract of T. wilfordii and (b) a chemotherapeutic drug, wherein (a) and (b) are administered in a combined amount effective to treat the cancer； and a pharmaceutically acceptable carrier.
