Preclinical characterization of NEO-811, a novel molecular glue degrader of ARNT for the treatment of clear cell renal cell carcinoma

A hallmark of clear cell renal cell carcinoma (ccRCC) is inactivation of the von Hippel-Lindau tumor suppressor gene (VHL). Deficiency in VHL results in aberrant stabilization and activation of hypoxia-inducible factors 1alpha and 2alpha (HIF-1alpha/2alpha) promoting cancer cell survival, metastasis, and angiogenesis. The therapeutic value of targeting hypoxia signaling in ccRCC has been clinically validated by the development of small molecule inhibitors of HIF-2alpha. However, subsequent studies have also uncovered susceptibility to the onset of resistance conferred by mutations in the small molecule binding pocket. As class I basic helix-loop-helix PER/ARNT/SIM (bHLH-PAS) proteins, HIF-1alpha/2alpha require heterodimerization with aryl hydrocarbon nuclear translocator (ARNT, also known as HIF-1beta, a class II bHLH-PAS protein) to exert their transcriptional activity. Consequently, ARNT represents a viable alternative target for disrupting oncogenic HIF activity. While traditionally regarded as undruggable, here we highlight the preclinical characterization of NEO-811, a potent, selective, and orally bioavailable molecular glue degrader of ARNT. Consistent with its mechanism of action, NEO-811 induced rapid, cereblon (CRBN)-dependent ARNT depletion in multiple ccRCC cell lines in vitro and in vivo. Global proteomics analysis confirmed that NEO-811 was highly selective and did not degrade well-known neosubstrates. Transcriptomic profiling of NEO-811 activity across several VHL-deficient ccRCC cell lines confirmed suppression of HIF-2alpha target genes, including cyclin D and vascular endothelial growth factor (VEGF). NEO-811 also uniquely suppressed expression of target genes regulated by other Class I bHLH-PAS transcription factors, including HIF-1alpha and aryl hydrocarbon receptor (AHR). Critically, NEO-811 retained activity in HIF-2alpha inhibitor-resistant cells that harbored previously described mutations. In conclusion, our findings highlight the potential of ARNT degradation as a promising therapeutic modality for the treatment of VHL-deficient ccRCC.