A phase I study of recombinant human interleukin-21 (rIL-21) in combination with sunitinib in patients with metastatic renal cell carcinoma (RCC).

sunitinib induces partial responses in 47% of patients with metastatic renal cell carcinoma (mRCC). However, the achievement of complete responses remains scarce and all patients will eventually develop progressive disease. Recombinant interleukin-21 (rIL-21) is a novel cytokine, which is believed to deliver sustained cellular anti-tumor response and the combination of both agents may work synergistically.