FDA approves new orphan drug to treat very rare autosomal recessive disorder

The US Food and Drug Administration on Friday approved Xuriden (uridine triacetate), the first FDA-approved treatment for patients with hereditary orotic aciduria, developed and to be marketed by privately-held US firm Wellstat Therapeutics.

Wellstat was also granted a rare pediatric disease priority review voucher, which can be used by the company for another drug to be given a priority review. The review voucher is also a valuable and sellable asset, as recently seen when United Therapeutics sold its priority review voucher to AbbVie for $350 million (The Pharma Letter August 19). Also, Retrophin sold its priority review voucher to Sanofi for $245 million.

Hereditary orotic aciduria is a rare metabolic disorder, which has been reported in around 20 patients worldwide. The disease is due to a defective or deficient enzyme, which results in the body being unable to normally synthesize uridine, a necessary component of ribonucleic acid (RNA). Signs and symptoms of the disease include blood abnormalities (anemia, decreased white blood cell count, decreased neutrophil count), urinary tract obstruction due to the formation of orotic acid crystals in the urinary tract, failure to thrive, and developmental delays.