Hyperion Therapeutics Exercises Option to Acquire Rights to BUPHENYL(R) and AMMONUL(R)

Hyperion Therapeutics Exercises Option to Acquire Rights to BUPHENYL(R) and

SOUTH SAN FRANCISCO, Calif., May 2, 2013 (GLOBE NEWSWIRE) -- Hyperion
Therapeutics, Inc. (Nasdaq:HPTX) today announced the exercise of its option to
acquire BUPHENYL®(sodium phenylbutyrate) Tablets and Powder, an FDA approved
therapy for the chronic management of the most prevalent urea cycle disorders
(UCD), and AMMONUL® (sodium phenylacetate and sodium benzoate) Injection
10%/10%, a hospital based product used to treat UCD patients in hyperammonemic
crisis, from Valeant Pharmaceuticals International, Inc. (NYSE:VRX) (TSX:VRX).

As a result of a March 2012 agreement between Hyperion and Medicis
Pharmaceutical Corporation, now a subsidiary of Valeant, Valeant has 20 days
to formally notify Hyperion whether it intends to retain rights to AMMONUL.
If Valeant elects not to retain AMMONUL, Hyperion is obligated to pay $22
million to Valeant; if Valeant elects to retain AMMONUL, Valeant must pay
Hyperion $13 million. The transaction is expected to close by May 29, 2013
subject to satisfaction of any closing conditions.

According to Donald J. Santel, Hyperion's chief executive officer, "RAVICTI™
remains the cornerstone of our commercial plan.We are confident that either
one or both of these therapies represent important opportunities for Hyperion
to serve the UCD community. "

Please see full Prescribing Information for:

BUPHENYL at http://ureacycle.com/buphenyl.aspx

AMMONUL at http://www.ureacycle.com/ammonul.aspx

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.

Forward-Looking Statements

To the extent that statements contained in this press release are not
descriptions of historical facts regarding Hyperion, they are forward-looking
statements reflecting the current beliefs and expectations of management 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. Forward-looking statements
contained in this press release include statements regarding expectations
about Valeant's intention to retain AMMONUL as well as the timing of the
closing of the transaction. Hyperion undertakes no obligation to update or
revise any forward-looking statements. For a further description of the risks
and uncertainties relating to the business of the company in general, see
Hyperion's Annual Report on Form 10-K/A filed with the Securities and Exchange
Commission on February 26, 2013, and any subsequent filings with the
Securities and Exchange Commission.

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