ABSTRACT HIF2a is a transcription factor induced by hypoxia and tumor associated mutations. HIF2a is a nodal regulator of cancer angiogenesis and cancer metabolism, stem cell development and inflammation and it is validated as a therapeutic target in von Hippel-Lindau (VHL)-deficient clear cell renal cell carcinoma (ccRCC). HIF2a had also been implicated in other diseases, beyond ccRCC, such as glioblastoma and prostate cancer. We identified specific HIF2a inhibitors and, by using them as chemical biology tools, we discovered that these small molecules activate Iron Regulatory Protein 1 (IRP1) to suppress HIF2a translation. In this application we propose to validate IRP1 as a target for HIF2a inhibition in xenograft and transgenic animal models of ccRCC and VHL disease. In addition, we propose to gain further insights into the complexity of IRP1-HIF signaling by identifying the direct protein target of HIF2a inhibitors. Finally, we propose to synthesize a series of derivatives of HIF2a inhibitors to further improve their potency and physicochemical properties in order to generate compounds suitable for in vivo preclinical studies and/or tools for further in vivo dissection of HIF2a biology.