Hyperion Therapeutics Receives FDA Fast Track Designation for Glycerol Phenylbutyrate for the Treatment of Urea Cycle Disorders

SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE)-- Hyperion Therapeutics, Inc. announced today that its investigational compound glycerol phenylbutyrate (HPN-100) has been granted Fast Track Designation by the U.S. Food and Drug Administration (FDA) as adjunctive therapy for the chronic management of urea cycle disorders. Hyperion recently completed its phase III trial which was conducted under a Special Protocol Assessment (SPA) agreement with the FDA. The Company plans to announce results from that trial later this year.

The FDA Fast Track Development Program is designed to facilitate the development and expedite the review of new drugs that are intended to treat serious or life-threatening conditions and that demonstrate the potential to address unmet medical needs. Fast Track designation enables Hyperion to communicate frequently with the FDA through meetings and written correspondence. The Company is also eligible to submit its New Drug Application (NDA) on a rolling basis, which allows the FDA to review sections of the document in advance of receiving the complete submission. Fast Track designated drugs typically qualify for priority review.

"We are very pleased to receive this Fast Track designation and acknowledgement by the FDA of the potential importance of glycerol phenylbutyrate for patients with urea cycle disorders," said Donald J. Santel, Chief Executive Officer of Hyperion Therapeutics. "We look forward to continuing to work closely with the FDA as we unblind our phase III study later this year and prepare our NDA submission."

Glycerol phenylbutyrate holds orphan product designation from the FDA for maintenance treatment of patients with deficiencies in enzymes of the urea cycle. The 4-week, multi-center, randomized, double-blind, cross-over, Phase III study, conducted in adults with urea cycle disorders, was designed to evaluate the non-inferiority of glycerol phenylbutyrate to BUPHENYL® (sodium phenylbutyrate).

About Urea Cycle Disorders

Urea cycle disorders are inherited, inborn errors of metabolism present in an estimated 1 in 10,000 births in the United States. Patients with urea cycle disorders are deficient in one of the key enzymes that comprise the urea cycle, the body’s primary vehicle for removing ammonia, a potent neurotoxin, from the bloodstream. Onset may occur at any age depending on the severity of the disorder. Left untreated, urea cycle disorders can cause dangerously heightened levels of ammonia in the bloodstream (hyperammonemia) resulting in brain damage, coma, and/or death.

About Glycerol Phenylbutyrate

Glycerol phenylbutyrate, an investigational product, is a pre-pro-drug of phenylacetic acid, the active moiety of BUPHENYL®. Glycerol phenylbutyrate holds orphan product designation from the FDA for maintenance treatment of patients with deficiencies in enzymes of the urea cycle.

About Hyperion Therapeutics

Hyperion Therapeutics is a privately held specialty therapeutics company focused on the development of therapies that address critical unmet needs in the areas of gastroenterology and hepatology. Hyperion and Ucyclyd Pharma, Inc., a subsidiary of Medicis Pharmaceutical Corporation, entered into a collaboration agreement for glycerol phenylbutyrate in August 2007. Under the terms of the agreement, Hyperion is conducting ongoing research and development of glycerol phenylbutyrate for urea cycle disorders, hepatic encephalopathy, and other forms of hyperammonemia. Hyperion is headquartered in South San Francisco, CA. For additional information, visit www.hyperiontx.com.

BUPHENYL® is a registered trademark of Ucyclyd Pharma, Inc.

Full Prescribing Information for BUPHENYL® is available at www.Buphenyl.com or by contacting Ucyclyd Pharma, Inc.