FDA Approves First Therapy for Tumor-Induced Osteomalacia

Burosumab-twza (Crysvita, Utragenyx Pharmaceutical) injection has been approved as the first therapy for a rare disease that causes low phosphate blood levels and bone softening, according to the FDA.

Tumor- induced osteomalacia (TIO) is a rare disease that is characterized by tumors causing soft and weakened bones. Lower phosphate levels are caused by the tumors releasing a peptide homeo- like substance known as fibroblast growth factor 23 (FGF23), according to the FDA. Usually, treatment for TIO is identifying and removing the tumor. However, when that is not a possible option, burosumab-twza can be used to increase the phosphate in the blood.

Two studies were used to prove the drug’s safety and efficacy, according to FDA. Combined, they enrolled 27 adults living with TIO. Patients were administered burosumab-twza every 4 weeks. Half of participants achieved normal phosphate levels through week 24 and maintained normal or near normal rates through week 144 during the first study. Additionally, bone scans from the first study suggested that bone lesions related to osteomalacia were healing. The second study saw 69% of participants achieving normal phosphate levels through week 24, and maintained normal or near normal rates through week 88, according to the FDA.

Adverse effects associated with burosumab-twza were infection, dizziness, muscle spasms, constipation, injection site reaction, rash, and headaches, according to the FDA. It has been approved for patients aged 2 years and older.

Additionally, burosumab-twza has also been approved to treat individuals aged 6 months and older with X-linked hypophosphatemia. According to FDA, this causes low level of phosphate in the blood and leads to impaired bone growth and development in children and teenagers.

REFERENCE

FDA Approves First Therapy for Rare Disease that Causes Low Phosphate Blood Levels, Bone Softening [news release]. Silver Spring, MD; June 18, 2020; FDA. https://www.fda.gov/news-events/press-announcements/fda-approves-first-therapy-rare-disease-causes-low-phosphate-blood-levels-bone-softening. Accessed June 18, 2020