The FDA approved Crysvita (burosumab twza), marking the first therapy cleared by the agency for treating X-linked hypophosphatemia (XLH) in adults and children 1 years of age or older.

The antibody therapy treats XLH, a rare and inherited form of rickets, by blocking fibroblast growth factor 23, a hormone that triggers phosphate urinary excretion and stifles the kidney’s active vitamin D production.

The safety and efficacy of the drug was determined through four clinical trials. In the placebo trials, 94 percent of adults receiving the treatment once a month achieved normal phosphorus levels compared to 8 percent receiving the placebo.