Burosumab-twza Injection Approved for Treatment of Tumor-Induced Osteomalacia

In a historic move, the US Food and Drug Administration (FDA) has announced the approval of burosumab-twza injection (Crysvita) for the treatment of tumor-induced osteomalacia (TIO) in patients ages 2 and older, the agency announced in a statement. 



The first FDA-approved therapy for TIO, which is a rare disease characterized by the development of tumors that cause weakened and softened bones, burosumab-twza injection is backed by 2 studies evaluation efficacy and safety of the agent in 27 adults with TIO. 



"Treatment for TIO focuses on identifying and removing the tumor that causes the disease. However, when that is not possible, Crysvita can help increase the levels of phosphate in the blood," said Theresa E. Kehoe, MD, acting director of the Division of General Endocrinology in the FDA's Center for Drug Evaluation and Research, in the aforementioned statement. "As the first FDA-approved therapy to treat this debilitating disease, today's action is an important step in finding treatment options for patients living with TIO whose tumor cannot be found or removed."

In the pair of studies backing the approval of burosumab-twza injection, patients received the injection every 4 weeks. In the first study, 50% of patients achieved normal phosphate through 24 and were able to maintain normal or near normal levels through week 144 of the study. In the second study, nearly 70% of patients achieved normal phosphate levels through week 24 and were able to maintain normal or near-normal phosphate levels through week 88.

Additionally, bone scans from patients in the first study indicated healing of the bone lesions related to osteomelacia.

The statement from the FDA pointed out hypersensitivity reactions have been reported in patients who received burosumab-twza injections. The FDA urges patients to stop taking the agent and talk with their health care provider about further medical treatment if hypersensitivity reactions occur.

The most common side effects reported among adults who received burosumab-twza injection were tooth abscess, muscle spasms, dizziness, constipation, injection site reaction, rash, and headaches. The FDA also noted patients taking an oral phosphate or active vitamin D, those with serum phosphate levels within or above normal range for their age, and patients with severe kidney impairment or ESRD should not receive burosumab-twza injection.