Temsirolimus: a safety and efficacy review

Introduction: The vascular endothelial growth factor (VEGF) pathway and the mammalian Target of Rapamycin (mTOR) represent the most frequently exploited targets in renal cell carcinoma (RCC). Temsirolimus is an inhibitor of mTOR, and is a unique ester derivative of sirolimus, a macrocyclic lactone, with improved pharmaceutical properties, including stability and solubility. Temsirolimus binds to the cytoplasmic protein FKBP-12, and the complex binds and inhibits mTOR. Areas covered: This review summarizes the clinical findings and safety of temsirolimus in RCC patients. Expert opinion: A Phase III clinical trial has demonstrated that temsirolimus has statistically significant advantages over treatment with IFN-alpha in RCC patients with poor prognosis, in terms of OS (overall survival), PFS (progression-free survival), and tumor response. Median OS was improved 49% compared to IFN-alpha, and median PFS was approximately doubled. It is now considered the standard for RCC patients with poor prognostic features. The possibility that this agent is useful in metastatic non-clear cell carcinoma patients has also been suggested by a subset analysis of the pivotal Phase III trial. Studies in untreated favorable and intermediate risk clear cell and refractory mRCC patients are required.