Ultragenyx Phase 3 Success On XLH Drug


Ultragenyx Pharmaceuticals remains on target for a U.S regulatory filing as it gained another win for its rare bone disease drug, burosumab. The biotech revealed positive 48-week data from its phase 3 study of burosumab in adults with X-linked hypophosphatemia (XLH), a rare genetic disease that causes rickets.

During premarket trading, Ultragenyx’s shares were up over 4 percent, while analysts have said that the drug’s approval was “likely.” Its PDUFA date is April 17, 2018.

XLH is normally diagnosed during childhood and is the result of phosphate wasting in the kidneys and low phosphate levels cause rickets. There are several treatments for children, yet the only treatment for adults is centered on pain management.

“This longer term data on symptom improvement and fracture healing support burosumab’s potential value in treating serious disease symptoms and promoting bone healing in adult patients with XLH. The continued clinical improvements in patients and the new data demonstrating a significant decrease in pain medication use after treatment with burosumab provide further support for the potential value in the treatment of adults with XLH.” said Ultragenyx CEO Emil Kakkis, M.D.

The study contained 134 patients, in which half received a 1mg/kg dose of burosumab every four weeks for 24 weeks and the other half received a placebo. At 24 weeks, it was revealed that the drug outperformed placebo in normalizing serum phosphorus levels and improved clinical symptoms of XLH.

Following the 24-week mark, the placebo patients were then placed on burosumab. During the subsequent 24 weeks of treatment, 89% of the patients who had changed from placebo to the drug sustained higher serum phosphorus levels above the lower end of what is normal versus the 84% of those who started taking the drug in the beginning.

Between the 24 and 48-week mark, the crossover patients made positive progression regarding stiffness, physical function, and pain scores all comparable to the results of those treated in the 24-week mark.

The drug is presently in a second phase 3 trial examining its effect on osteomalacia and also being examined in pediatric patients.


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