FDA approves drug for rare bone condition

An immune-boosting biologic therapy already used to prevent fractures in patients with bone metastases has won the FDA’s approval as a treatment for a rare but painful condition called giant cell tumor of the bone.

The FDA gave an expedited review to Xgeva as an orphan therapy, because its use is expected to benefit a small population of patients. Xgeva is marketed by Thousand Oaks-based Amgen.

Giant cell tumor of the bone most often affects younger adults -- those between 20 and 40 years old -- and is infrequently cancerous. But it can cause unusual fractures and progressive pain, and most commonly occurs in the long bones of the body--the distal femur, proximal tibia and distal radius. In cases in which it is cancerous, it can travel to the lungs.

The FDA’s approval allows Xgeva to be marketed for use in adults and adolescents whose bones have matured and whose giant cell tumors cannot be surgically removed. In a clinical trial involving 187 patients in whom giant cell tumor of the bone could be measured and could not readily be removed by surgery, 47 patients taking Xgeva had their tumor reduced in size, and growth of the tumor resumed in three of those patients.

Xgeva, also known as denosumab, is a monoclonal antibody that binds to a protein essential to healthy bones but also present in giant cell tumor of the bone. The therapy’s most common serious side effects are osteonecrosis of the jaw and osteomyelitis, or inflammation or infection of the bone.