Hyperion Therapeutics Receives Orphan Drug Exclusivity From FDA

Hyperion Therapeutics Receives Orphan Drug Exclusivity From FDA

SOUTH SAN FRANCISCO, Calif., May 2, 2013 (GLOBE NEWSWIRE) -- Hyperion
Therapeutics, Inc. (Nasdaq:HPTX) today announced that the U.S. Food and Drug
Administration (FDA) yesterday notified the company that RAVICTI™ (glycerol
phenylbutyrate) Liquid has qualified for orphan drug exclusivity. The orphan
exclusivity is for seven years from the date of the approval on February 1,

According to Donald J. Santel, president and chief executive officer, "Orphan
drug exclusivity further strengthens the protections for RAVICTI.
Additionally, as we recently announced, we were issued a patent that relates
to use of RAVICTI with optimal measurement timing and target levels for blood
ammonia in urea cycle disorder (UCD) patients. It has a term that expires in
March 2032 and is now listed in the FDA's Approved Drug Products with
Therapeutic Equivalence Evaluations, known as the Orange Book."

RAVICTI Indications, Usage and Safety Information

RAVICTI is indicated for use as a nitrogen-binding agent for chronic
management of adult and pediatric patients ≥ two years of age with UCD that
cannot be managed by dietary protein restriction and/or amino acid
supplementation alone. RAVICTI must be used with dietary protein restriction
and in some cases, dietary supplements (e.g. essential amino acids, arginine,
citrulline, protein-free calorie supplements).

Limitations of Use:

  *RAVICTI is not indicated for the treatment of acute hyperammonemia (HA) in
    patients with UCD because more rapidly acting interventions are essential
    to reduce plasma ammonia levels.
  *The safety and efficacy of RAVICTI for the treatment of N-acetylglutamate
    synthase (NAGS) deficiency has not been established.

RAVICTI is Contraindicated in Patients:

  *Less than two months of age. Children less than two months of age may have
    immature pancreatic exocrine function which could impair hydrolysis of
    RAVICTI, leading to impaired absorption of phenylbutyrate and HA.
  *With known hypersensitivity to phenylbutyrate. Signs of hypersensitivity
    include wheezing, shortness of breath, coughing, low blood pressure,
    flushing, nausea and rash.

The major metabolite of RAVICTI, PAA, is associated with neurotoxicity at
levels ≥ 500 μg/mL. If symptoms of vomiting, nausea, headache, drowsiness, or
confusion are present in the absence of high ammonia or other intercurrent
illnesses, reduce the RAVICTI dosage.

Pancreatic insufficiency or intestinal malabsorption may result in reduced or
absent digestion of RAVICTI and/or absorption of phenylbutyrate and reduced
control of plasma ammonia. Monitor ammonia levels closely in these patients.

Most common adverse reactions in 10% or more of patients are: diarrhea,
flatulence, headache, nausea, vomiting, fatigue, decreased appetite, HA,
dizziness, headache, upper abdominal (stomach) pain and rash.

Corticosteroids, valproic acid, or haloperidol may increase plasma ammonia
levels; monitor ammonia levels closely when used concomitantly with RAVICTI.
Probenecid may affect renal excretion of metabolites of RAVICTI including PAGN
and PAA.

The use of RAVICTI in pregnant women may cause fetal harm. Breastfeeding is
not recommended during RAVICTI treatment.

Please see full Prescribing Information for RAVICTI at www.hyperiontx.com.

About Hyperion Therapeutics

Hyperion Therapeutics, Inc. is a commercial stage biopharmaceutical company
committed to developing and delivering life-changing treatments for orphan
diseases and hepatology.

CONTACT: Shari Annes, Investor Relations
         (650) 888-0902
         Kristie Kuhl, Media Relations
         (203) 556-7417
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