Hyperion Therapeutics Receives Special Protocol Assessment Approval From FDA For Pivotal Phase III Trial In Urea Cycle Disorders

Main Category: Pediatrics / Children's Health
Also Included In: Clinical Trials / Drug Trials;  Regulatory Affairs / Drug Approvals;  Blood / Hematology
Article Date: 08 Jul 2009 - 7:00 PST

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Hyperion Therapeutics announced that it has reached agreement with the U.S. Food and Drug Administration (FDA) under the Special Protocol Assessment (SPA) process for the pivotal Phase III trial of investigational product HPN-100 (glycerol phenylbutyrate) in adults with urea cycle disorders (UCD). The SPA is a written agreement between the trial sponsor and the FDA regarding the design, endpoints, and planned statistical analysis of the Phase III trial to be used in support of a New Drug Application (NDA).

The 4-week, multi-center, randomized, double-blind, cross-over, Phase III study in adults with urea cycle disorders is designed to evaluate the non-inferiority of HPN-100 (glycerol phenylbutyrate) to BUPHENYL® (sodium phenylbutyrate). The primary efficacy measure is blood ammonia, assessed as 24-hour area under the curve on Days 14 and 28 (last day of each treatment period). The study will enroll approximately 44 adults, and all subjects completing the study will be eligible to enter a 12-month, open label safety study.

Hyperion will concurrently conduct a 2-3 week open label study of the safety, pharmacokinetics, and pharmacodynamics of glycerol phenylbutyrate compared to sodium phenylbutyrate in approximately 10 children ages 6-17.

Bruce Scharschmidt, MD, Chief Medical Officer of Hyperion Therapeutics, commented, "We appreciate the input from FDA on the pivotal Phase III study protocol and look forward to continuing development of HPN-100 for urea cycle disorder patients, a population with limited treatment options."

About HPN-100 (glycerol phenylbutyrate)

HPN-100 (glycerol phenylbutyrate), an investigational product, is a pre-pro-drug of phenylacetic acid, the active moiety of BUPHENYL®, the only therapy currently FDA-approved as adjunctive therapy for the chronic management of patients with the most prevalent urea cycle disorders: carbamylphosphate synthetase (CPS), ornithine transcarbamylase (OTC), and argininosuccinic acid synthetase (AS) deficiencies. Glycerol phenylbutyrate is administered orally in liquid form. 17.4 mL of glycerol phenylbutyrate (~ 3.5 teaspoons) delivers the same amount of active ingredient as the maximum daily dose of BUPHENYL (forty tablets or 6.67 teaspoons of powder mixed with food or dissolved in liquid). Glycerol phenylbutyrate holds orphan product designation from the FDA for maintenance treatment of patients with enzymes of the urea cycle.

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 BUPHENYL

BUPHENYL is indicated as adjunctive therapy in the chronic management of patients with urea cycle disorders involving deficiencies of carbamylphosphate synthetase (CPS), ornithine transcarbamylase (OTC), or argininosuccinic acid synthetase (AS). BUPHENYL should not be administered to patients with known hypersensitivity to sodium phenylbutyrate or any component of this preparation. The most common adverse reactions associated with BUPHENYL were amenorrhea dysfunction, decreased appetite, body odor (probably caused by its metabolite phenylacetate) and bad taste or taste aversion. Patients with urea cycle disorders should not take valproic acid, haloperidol, or steroids as these drugs have been reported to increase blood ammonia levels, and probenecid may affect the kidneys' excretion. Use with great care, if at all, in patients with congestive heart failure or severe renal insufficiency, and in clinical states where there is sodium retention with edema. Use caution when administering to patients with hepatic or renal insufficiency or inborn errors of beta oxidation. The safety or efficacy of doses in excess of 20 grams (40 tablets) per day has not been established.

Source
Hyperion Therapeutics