Arena Pharmaceuticals Initiates Phase 1 Clinical Trial of APD334 for Autoimmune Diseases

     Arena Pharmaceuticals Initiates Phase 1 Clinical Trial of APD334 for
                             Autoimmune Diseases

PR Newswire

SAN DIEGO, April 5, 2013

SAN DIEGO, April 5, 2013 /PRNewswire/ -- Arena Pharmaceuticals, Inc. (NASDAQ:
ARNA) announced today the initiation of dosing in a Phase 1 clinical trial of
APD334, a novel oral drug candidate that targets the sphingosine 1-phosphate
subtype 1 (S1P[1]) receptor for the potential treatment of autoimmune
diseases.

This randomized, double-blind and placebo-controlled Phase 1 trial will
evaluate the safety, tolerability and pharmacokinetics of single-ascending
doses of APD334 in up to 64 healthy adult volunteers.

"We are pleased to expand our clinical-stage pipeline by initiating a Phase 1
trial of APD334, and look forward to advancing this novel compound through our
validated development platform," said William R. Shanahan, M.D., Arena's
Senior Vice President and Chief Medical Officer. "APD334's selectivity for the
S1P[1] receptor has the potential to improve upon the adverse event profile of
currently available treatments for a spectrum of autoimmune diseases."

About Autoimmune Diseases

Autoimmune diseases are characterized by an inappropriate immune response
against substances and tissues that are normally present in the body. In an
autoimmune reaction, a person's antibodies and immune cells targethealthy
tissues, triggering an inflammatory response. Reducing the immune and/or
inflammatory response is an important goal in the treatment of autoimmune
disease.

About APD334

APD334 is an orally available drug candidate discovered by Arena that targets
the S1P[1] receptor for the potential treatment of a number of conditions
related to autoimmune diseases, including multiple sclerosis, psoriasis and
rheumatoid arthritis. S1P[1] receptors have been demonstrated to be involved
in the modulation of several biological responses, including lymphocyte
trafficking from lymph nodes to the peripheral blood. By isolating lymphocytes
in lymph nodes, fewer immune cells are available in the circulating blood to
effect tissue damage. Arena has optimized APD334 as a potent and selective
small molecule S1P[1] receptor agonist that reduces the severity of disease in
preclinical autoimmune disease models.

About Arena Pharmaceuticals

Arena is a biopharmaceutical company focused on discovering, developing and
commercializing novel drugs that target G protein-coupled receptors, or GPCRs,
to address unmet medical needs. BELVIQ^® (lorcaserin HCl), Arena's internally
discovered drug, was approved by the US Food and Drug Administration in June
2012 and is under review for regulatory approval in additional territories.
Arena's US operations are located in San Diego, California, and its operations
outside of the United States, including its commercial manufacturing facility,
are located in Zofingen, Switzerland. For more information, visit Arena's
website at www.arenapharm.com.

Arena Pharmaceuticals^® and Arena^® are registered service marks of Arena
Pharmaceuticals, Inc. BELVIQ^® is a registered trademark of Arena
Pharmaceuticals GmbH.

Forward-Looking Statements

Certain statements in this press release are forward-looking statements that
involve a number of risks and uncertainties. Such forward-looking statements
include statements about the advancement, therapeutic indication and use,
safety, efficacy, tolerability, selectivity and mechanism of action of APD334;
the protocol, design, scope, enrollment and other aspects of the Phase 1
clinical trial of APD334; the potential of APD334 and treatment of autoimmune
diseases in general; the regulatory review of BELVIQ; and Arena's focus,
plans, goals, strategy, expectations, research and development programs, and
ability to discover and develop compounds and commercialize drugs. For such
statements, Arena claims the protection of the Private Securities Litigation
Reform Act of 1995. Actual events or results may differ materially from
Arena's expectations. Factors that could cause actual results to differ
materially from the forward-looking statements include, but are not limited
to, the following: APD334 may not have an adequate safety margin or otherwise
be sufficient for further development or regulatory review or approval; risks
related to commercializing drugs, including regulatory, manufacturing and
supply issues and the pace of market acceptance; cash and revenues generated
from BELVIQ, including the impact of competition; Arena's revenues will be
based in part on management's estimates, judgment and accounting policies, and
incorrect estimates or disagreement regarding Arena's estimates or accounting
policies may result in changes to Arena's guidance or previously reported
results; the timing and outcome of regulatory review is uncertain, and BELVIQ
may not be approved for marketing when expected or ever by any other
regulatory agency; government and commercial reimbursement and pricing
decisions; risks related to relying on collaborative arrangements; the timing
and receipt of payments and fees, if any, from collaborators; the entry into
or modification or termination of collaborative arrangements; unexpected or
unfavorable new data; nonclinical and clinical data is voluminous and
detailed, and regulatory agencies may interpret or weigh the importance of
data differently and reach different conclusions than Arena or others, request
additional information, have additional recommendations or change their
guidance or requirements before or after approval; data and other information
related to any of Arena's research and development may not meet safety,
efficacy or other regulatory requirements or otherwise be sufficient for
further research and development, regulatory review or approval or continued
marketing; Arena's ability to obtain and defend patents; the timing, success
and cost of Arena's research and development programs; results of clinical
trials and other studies are subject to different interpretations and may not
be predictive of future results; clinical trials and other studies may not
proceed at the time or in the manner expected or at all; having adequate
funds; and satisfactory resolution of litigation or other disagreements with
others. Additional factors that could cause actual results to differ
materially from those stated or implied by Arena's forward-looking statements
are disclosed in Arena's filings with the Securities and Exchange Commission.
These forward-looking statements represent Arena's judgment as of the time of
this release. Arena disclaims any intent or obligation to update these
forward-looking statements, other than as may be required under applicable
law.

Contact: Arena Pharmaceuticals, Inc.     Media Contact: Russo Partners
Cindy McGee, Vice President,             David Schull, President
Investor Relations & Alliance Management david.schull@russopartnersllc.com
cmcgee@arenapharm.com                    858.717.2310
858.453.7200, ext. 1479
www.arenapharm.com 

SOURCE Arena Pharmaceuticals, Inc.

Website: http://www.arenapharm.com