FDA approves Crysvita for children, adults with rare form of rickets

The FDA has approved Crysvita, a new therapy option for children aged 1 year and older and adults with x-linked hypophosphatemia, or XLH, according to a press release.

Crysvita (burosumab, Ultragenyx Pharmaceutical Inc.) treats this inherited and rare form of rickets by helping patients achieve normal phosphorus levels in the blood. The lack of phosphorus in individuals with XLH may lead to diminished bone growth and development in pediatric and adolescent patients. Those with XLH may have difficulties with bone mineralization as they age.

“XLH differs from other forms of rickets in that vitamin D therapy is not effective,” Julie Beitz, MD, director of the Office of Drug Evaluation III in the FDA’s Center for Drug Evaluation and Research, said in a press release. “This is the first FDA-approved medication for the treatment of XLH and a real breakthrough for those living with this serious disease.”

Crysvita was examined in four clinical trials, including a placebo-controlled trial, according to the release. The drug demonstrated efficacy and safety when administered once a month to adults, with 94% of participants attaining normal phosphorus levels. Only 8% of those in the placebo group were able to achieve normal phosphorus levels. When administered to children every 2 weeks, Crysvita allowed nearly all participants (94%-100%) to achieve normal phosphorus levels.

During the placebo-controlled trial, x-ray studies were performed on both pediatric and adult participants. These images demonstrated that XLH-related bone findings improved with the therapy. When these findings were compared with x-ray studies from those who did not receive the treatment, additional support was provided for this treatment method.

Adverse events were reported by both children and adults treated with Crysvita. The most common reactions for children were headache, injection site reactions, vomiting, decreased vitamin D level and fever. Adults shared some common reactions to the therapy, with reports of back pain, headache, restless leg syndrome, decreased vitamin D level and constipation.

Previously, the FDA granted breakthrough therapy designation and orphan drug designation to Crysvita. Additionally, Ultragenyx Pharmaceutical Inc. has been presented with a rare pediatric disease voucher. This program promotes the creation of new drugs and biologics for both the treatment and prevention of rare diseases. When a sponsor receives a voucher, it has the ability to receive priority review for a product designed at a future date. This marks the 14th voucher presented since the launch of this program.

The FDA estimates that 3,000 children and 12,000 American adults are affected by XLH, and the condition can create lifelong concerns for those with the condition. Children are likely to develop bowed or bent legs, stunted growth and pain in both the bones and teeth. Adults with XLH may also experience joint pain, mobility concerns, dental abscesses and loss of hearing.

Resource: FDA approves first therapy for rare inherited form of rickets, x-linked hypophosphatemia