KIT and renal cell carcinoma: In a Phase II trial done by Vuky et al., no or partial response was observed in 12 of 14 patients treated with imatinib in c-kit-positive RCC.[19] As compared with interferon alfa, temsirolimus (a specific inhibitor of the mammalian target of rapamycin kinase), improved overall survival among patients with metastatic RCC.[20] On the other hand, in two separate Phase II studies treated with sunitinib the response rate was approximately 40% in patients who had already failed cytokine therapy.[18]