The U.S. Food and Drug Administration (FDA) has expanded the approved use of denosumab (Xgeva) to treat adults and some adolescents with giant cell tumor of the bone, a rare and usually noncancerous tumor. Denosumab, which was granted orphan product designation, was reviewed under the FDA’s priority review program. The agent was previously approved in 2010 for the prevention of skeletal-related events in patients with bone metastases from solid tumors.
Giant cell tumor of the bone generally occurs in adults between the ages of 20 and 40 years. In most cases, the tumor does not spread to other parts of the body but destroys normal bone as it grows, causing pain, limited range of motion, and bone fractures. Rarely, giant cell tumor of the bone can transform into a cancerous tumor and spread to the lungs.
Denosumab is a monoclonal antibody that binds to RANKL, a protein essential for maintenance of healthy bone and that is also present in giant cell tumor of the bone. The agent is intended for patients who have unresectable giant cell tumor of the bone or for whom surgery is likely to result in severe morbidity, such as loss of limbs or joint removal. Denosumab should only be used in adolescents whose bones have matured.
“Today’s approval of [denosumab] provides a needed treatment option for patients with giant cell tumor of the bone who are not surgical candidates or who would otherwise have to undergo extensive, life-altering surgery,” said Richard Pazdur, MD, Director of the Office of Hematology and Oncology Products in FDA’s Center for Drug Evaluation and Research.
Safety and Effectiveness
The safety and effectiveness of denosumab for giant cell tumor of the bone were established in two clinical trials that enrolled a total of 305 adult or adolescent patients. All patients had confirmed cases of giant cell tumor of the bone that were recurrent, unresectable, or where surgery would result in severe morbidity.
Of the 187 patients whose tumors could be measured, 47 patients had their tumors reduce in size after an average of 3 months. Over an average follow-up duration of 20 months, regrowth of giant cell tumor of the bone occurred in three patients whose tumors originally became smaller during treatment.
Common side effects included arthralgia, headache, nausea, fatigue, back pain, and extremity pain. The most common serious side effects were osteonecrosis of the jaw and osteomyelitis. Women of reproductive potential should use highly effective contraception while taking denosumab because of potential fetal harm. ■