Burosumab is in clinical development for the treatment of adults with tumour-induced osteomalacia (TIO). TIO is a rare disease where an overproduction of FGF23 leads to renal phosphate wasting and low levels of phosphate and vitamin D in the body. This causes weakening (or softening) of bones. Main symptoms include bone pain, muscle weakness/fatigue and fractures and without a timely diagnosis, TIO can lead to a significant decrease in quality of life, severe functional impairment and even prostration.
Burosumab is administered by subcutaneous injection. Burosumab is designed to recognise and attach to a protein called FGF23. By attaching to the FGF23 protein, burosumab blocks its activity, thus restoring phosphate and vitamin D levels by achieving phosphate homeostasis. If licensed, burosumab will provide a treatment option for TIO.
Belzutifan is in clinical development for the treatment of von Hippel-Lindau (VHL) disease-associated clear cell renal cell carcinoma (ccRCC). VHL is a hereditary disease that results in the body producing an increased amount of the protein hypoxia inducible factor (HIF) – 2α. This leads to an increased risk of tumours developing in various parts of the body including the kidney. Renal cell carcinoma (RCC) is the most common type of kidney cancer. ccRCC is named as such because when this type of tumour is viewed under a microscope the cells appear clear. Currently patients with VHL disease have limited treatment options which focus on surgically removing tumours once they have developed.