Belzutifan

Brand Name: Welireg

Belzutifan is used to treat:

  1. adult patients with von Hippel-Lindau (VHL) disease-associated renal cell carcinoma (RCC), central nervous system hemangioblastoma, or pancreatic neuroendocrine tumor (pNET).
  2. adult patients with advanced renal cell carcinoma (RCC) following treatment with PD-1 or PD-L1 inhibitor and VEGF-TKI.1

How Does Belzutifan Work?

HIF-2α protein with 2 proline motifs

HIF-2α is a protein that orchestrates cellular response and adaptation to low oxygen levels.2 Notably, it contains multiple proline motifs that are crucial for regulating its activity.3

HIF-2α binds to HIF-1β, resulting in active HIF complex

When oxygen level is low, HIF-2α binds to another protein called HIF-1β to form an active HIF complex.4

HIF complex binds to DNA and activates survival genes

This complex can then seek out specific stretches of DNA, where it activates genes involved in cellular adaptation to low oxygen levels and survival.4

PHD proteins use oxygen to hydroxylate proline motifs on HIF-2α

On the other hand, under normal oxygen levels, a protein called PHD uses the amply available oxygen molecules to modify the proline motifs of HIF-2α. This results in hydroxylated proline motifs.5

VHL proteins bind to hydroxylated proline motifs and induce HIF-2α degradation

Hydroxylated proline motifs are recognized by a protein called VHL, which then marks HIF-2α for degradation. This ensures that the HIF complex-associated genes are not active when oxygen level is normal.3,6,7

Mutated VHL proteins are unable to induce HIF-2α degradation

However, patients with von Hippel-Lindau disease possess mutations in the gene encoding VHL protein that prevent functional VHL proteins from being produced. Therefore, HIF-2α is not degraded under normal oxygen levels, even when its proline motifs are hydroxylated.8

HIF complex, comprised of HIF-2α with hydroxylated proline motifs, activates survival genes

As a result, HIF-2α accumulates and constantly activates survival genes, leading to uncontrolled cellular growth; i.e., cancer.8,9

Belzutifan splits up HIF-2α and HIF-1β, resulting in inactive survival genes

Belzutifan is a drug that disrupts the interaction between HIF-2α and HIF-1β. This turns off the constant expression of survival genes, halting cancer growth.10

Side Effects of Belzutifan

References

1. WELIREG - Label. U.S. Food and Drug Administration (2024).

2. Wiesener, M. S. et al. Induction of Endothelial PAS Domain Protein-1 by Hypoxia: Characterization and Comparison With Hypoxia-Inducible Factor-1α. Blood 92(7), 2260-2268 (1998).

3. Ivan, M. et al. HIFα Targeted for VHL-Mediated Destruction by Proline Hydroxylation: Implications for O2 Sensing. Science 292(5516), 464-468 (2001).

4. Tian, H., McKnight, S. L. & Russell, D. W. Endothelial PAS domain protein 1 (EPAS1), a transcription factor selectively expressed in endothelial cells. Genes & Development 11, 72-82 (1997).

5. Epstein, A. C. R. et al. C. elegans EGL-9 and Mammalian Homologs Define a Family of Dioxygenases that Regulate HIF by Prolyl Hydroxylation. Cell 107(1), 43-54 (2001).

6. Maxwell, P. H. et al. The tumour suppressor protein VHL targets hypoxia-inducible factors for oxygen-dependent proteolysis. Nature 399, 271-275 (1999).

7. Jaakkola, P. et al. Targeting of HIF-α to the von Hippel-Lindau Ubiquitylation Complex by O2-Regulated Prolyl Hydroxylation. Science 292(5516), 468-472 (2001).

8. Richards, F. M. et al. Detailed mapping of germline deletions of the von Hippel-Lindau disease tumour suppressor gene. Human Molecular Genetics 3(4), 595-598 (1994).

9. Lonser, R. R., Glenn, G. M., Walther, M., Chew, E. Y. & Libutti, S. K. von Hippel-Lindau disease. The Lancet 361(9374), 2059-2067 (2003).

10. Xu, R. et al. 3-[(1S,2S,3R)-2,3-Difluoro-1-hydroxy-7-methylsulfonylindan-4-yl]oxy-5-fluorobenzonitrile (PT2977), a Hypoxia-Inducible Factor 2α (HIF-2α) Inhibitor for the Treatment of Clear Cell Renal Cell Carcinoma. Journal of Medicinal Chemistry 62(15), 6876-6893 (2019).