Hyperion Therapeutics' RAVICTI(TM) (glycerol phenylbutyrate) Liquid Receives FDA Approval for Treatment of Urea Cycle Disorders

Hyperion Therapeutics' RAVICTI(TM) (glycerol phenylbutyrate) Liquid Receives
FDA Approval for Treatment of Urea Cycle Disorders

  *Anticipated market launch by end of April 2013
  *Patent allowance extends coverage to 2032

SOUTH SAN FRANCISCO, Calif., Feb. 1, 2013 (GLOBE NEWSWIRE) -- Hyperion
Therapeutics, Inc. (Nasdaq:HPTX) today announced that the U.S. Food and Drug
Administration (FDA) has approved RAVICTI for the treatment of Urea Cycle
Disorders (UCD) in patients two years of age and older. The drug is expected
to be commercially available by the end of April 2013. 

Separately, Hyperion announced it has received notification from the U.S.
Patent & Trademark Office (USPTO) of the allowance of the claims of patent
application number 13/417,137 entitled, METHODS OF THERAPEUTIC MONITORING OF
NITROGEN SCAVENGING DRUGS, which discloses optimal measurement timing and
target levels for blood ammonia in UCD patients. A Notice of Allowance is
issued after the USPTO makes a determination that a patent can be granted from
an application. The issued patent would have a term that expires in March
2032.After issuance, Hyperion plans to list this patent in FDA's Approved
Drug Products with Therapeutic Equivalence, or Orange Book. 

"With FDA approval of RAVICTI, we are now in a position to commercialize
Hyperion's first product.Furthermore we believe that the allowed claims, once
issued, will provide important protection for the use of RAVICTI to treat
UCD," said Donald J. Santel, Hyperion's chief executive officer. "We thank our
clinical trial patients, their families, our investigators and study
coordinators, the UCD Consortium, and the National Urea Cycle Disorders
Foundation – in particular NUCDF Executive Director Cynthia Le Mons – for
their collaboration and support of our development efforts."

The FDA approval of RAVICTI was based on a New Drug Application (NDA) that
included data from 10 clinical trials, including six in UCD patients, that
involved 23 sites, over 50 investigators and sub-investigators, and
approximately a dozen referring metabolic specialists throughout North
America. As part of FDA approval, Hyperion agreed to post-marketing
requirements that include: studies of RAVICTI safety, ammonia control, and
pharmacokinetics in pediatric UCD patients in the first two months of life and
from two months to two years of age; studies in healthy adults to examine
drug-drug interaction and whether RAVICTI metabolites are present in breast
milk; a randomized controlled clinical trial to assess the safety and efficacy
of RAVICTI in treatment-naïve patients with UCD; and a UCD registry of
approximately 10 years duration.Importantly, the FDA did not require a Risk
Evaluation and Mitigation Strategy (REMS) program.

"We believe the RAVICTI development program has brought not only a promising
new drug to the UCD community, but also a much deeper understanding of UCD
treatment," said Dr. Bruce F. Scharschmidt, M.D., Hyperion's chief medical
officer and senior vice president."The post-marketing studies and registry
represent additional opportunities to expand our knowledge in areas that are
important to the community, particularly in very young children, a population
in which few systematic studies have been done."

Hyperion intends to commercially launch RAVICTI by the end of April.As part
of the commercialization of RAVICTI, Hyperion today announced the launch of a
dedicated call center, Hyperion UCD Support Services, which will serve as an
integrated resource for patients and their physicians in the areas of RAVICTI
prescription intake, reimbursement adjudication, patient financial support,
and ongoing compliance support. Together with distribution via two specialty
pharmacies, the Company believes that its UCD Support Services program will
provide better support to UCD patients, their families and their physicians
and help them better manage their disease.

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 urea cycle
disorders (UCDs) 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 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
    hyperammonemia.
  *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% of patients are: diarrhea, flatulence,
headache, nausea, vomiting, fatigue, decreased appetite, hyperammonemia,
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.

Conference Call and Webcast
Information

Hyperion's senior management team will host a conference call on Monday,
February 4, 2013 to discuss the FDA approval beginning at 5:30 a.m. PT; 8:30
a.m. ET. To access the live teleconference, please dial 877-847-7188 (U.S.) or
408-427-3787 (International) and reference the conference ID# 96938694. To
access the webcast, please go to the Events page on the Investors section of
the Company's web site at www.hyperiontx.com.

A telephone replay will be available approximately two hours after the call
for one week by dialing 855-859-2056 from the (U.S.) or 404-537-3406 for
(International) callers and entering reservation number 96938694. A replay of
the webcast will be available on the Events page on the Company's web site for
30 days.

About Urea Cycle Disorders

Urea cycle disorders, or UCDs, are a collection of inherited metabolic
disorders in which affected patients suffer from high levels of systemic
ammonia, a potent neurotoxin. Ammonia is produced via normal protein
ingestion; the body normally detoxifies it by converting it through a series
of enzymatic steps to urea, which is excreted in urine. Throughout their
lives, UCD patients may experience recurrent hyperammonemic crises in which
ammonia levels rise, and can develop complications ranging from nausea,
vomiting and headache to coma and death.

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. For more information, please visit www.hyperiontx.com

Forward-Looking Statements:

This press release includes forward-looking statements reflecting management's
current beliefs and expectations about future events; these forward-looking
statements are made pursuant to the safe harbor provisions of the Private
Securities Litigation Reform Act of 1995. Words such as "may," "will,"
"expect," "anticipate," "estimate," "intend," and similar expressions (as well
as other words or expressions referencing future events, conditions or
circumstances) are intended to identify forward-looking statements. Examples
of forward-looking statements contained in this press release include, among
others, statements regarding our expectations regarding the timing and
effectiveness of any commercial launch of RAVICTI, the timing of availability
of RAVICTI to physicians and patients, our plans with respect to distribution
of RAVICTI with specialty pharmacies, the launch of a dedicated call center
and our plans with respect to the development of RAVICTI to treat HE.
Forward-looking statements in this release involve substantial risks and
uncertainties that could cause future results, performance or achievements to
differ significantly from those expressed or implied by the forward-looking
statements. Such risks and uncertainties include, among others, risks related
to: the success and timing of commercialization and distribution efforts; the
fact that the patient population suffering from UCD is small and has not been
established with precision; uncertain ability to hire and retain qualified
personnel to assist with those commercialization and distribution efforts;
risks associated with our ability to obtain adequate commercial and clinical
supplies of RAVICTI; uncertainties associated with physician acceptance of
RAVICTI, patient and physician response to pricing of the drug and government
or insurance reimbursement of the drug; and the uncertain ability to raise
sufficient capital to complete the development and commercialization of
RAVICTI in HE.Hyperion undertakes no obligation to update or revise any
forward-looking statements. For a further description of the risks and
uncertainties that could cause actual results to differ from those expressed
in these forward-looking statements, as well as risks relating to the business
of the company in general, see for example Hyperion's Current Report on Form
8-K filed with the Securities and Exchange Commission (the "SEC") on February
1, 2013 as well as Hyperion's Quarterly Report on Form 10-Q filed on November
7, 2012.

CONTACT: Myesha Edwards, Investor Relations
         (650) 745-7829
         myesha.edwards@hyperiontx.com
        
         Kristie Kuhl, Media Relations
         (203) 556-7417
         kkuhl@makovsky.com
 
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