Hypoxia Inducible Factor-2α (HIF-2α) Pathway Inhibitors.

Abstract

Hypoxia creates a stressful environment for the cells triggering adaptive changes in the transcription factors called hypoxia inducible factors (HIF), which help to meet the metabolic and angiogenic requirements of cells. HIF-2 is one such factor that is implicated in the progression of various cancers, especially the ones associated with Von Hippel-Lindau (VHL) disease. HIF-2 factor has an unstable component alpha and a stable component beta. HIF-2α detects hypoxia and dimerizes with HIF-beta (Aryl hydrocarbon receptor nuclear translocator [ARNT]) through per-ARNT-sim (PAS)-mediated signaling domains. These domain sites are recognized as targets for HIF-2 inhibitors. HIF-2 inhibitors block this heterodimerization and prevent the expression of target genes which are oncogenic, including VEGF, PDGF, CAIX, and Oct4. VHL disease caused by the deficiency of VHL gene product results in decreased degradation of HIF-2α, leading to increased activation of these transcription factors. Tumors driven by the deficiency of VHL gene product are natural candidates for HIF-2 inhibitor therapy. These inhibitors have emerged as a promising class of targeted therapies for renal cell carcinoma (RCC), particularly in cases resistant to conventional treatments. In this review, we explore the role of hypoxia and HIF transcription factors in tumor formation and progression, highlighting the role and development of HIF-2 pathway inhibitors as potential cancer therapies. We discuss the major key inhibitors, with focus on belzutifan and review the various trials investigating its efficacy in monotherapy as well as in combination therapies in RCC. Additionally, we explore its development in pheochromocytoma, hemangioblastoma, and pancreatic neuroendocrine tumors. We also highlight emerging HIF-2α inhibitors currently in clinical trials, namely casdatifan, NKT-2152, and DFF332. Finally, we address the major toxicities and management of these inhibitors.