FLT1 and renal cell carcinoma: Sorafenib can inhibit a number of receptor tyrosine kinases (RTKs) including VEGFR-1/2/3, c-Kit, FLT3, RET, PDGFRβ, and RAF, and is the first approved anti-angiogenic inhibitor.147 It was initially approved for the treatment of advanced RCC in 2005.