Arena Pharmaceuticals Reports Favorable Results from Phase 1 Single-Ascending Dose Clinical Trial of APD371

-- Results support advancement of the novel, oral drug candidate to the next stage of development --

SAN DIEGO, April 29, 2015  -- Arena Pharmaceuticals, Inc. (ARNA) today announced favorable results from a Phase 1 single-ascending dose clinical trial of APD371, a highly selective and potent agonist of the cannabinoid 2 (CB2) receptor currently in development for the treatment of pain and potentially fibrotic diseases.

The randomized, double-blind and placebo-controlled Phase 1 clinical trial enrolled 56 healthy adults to evaluate the safety, tolerability and pharmacokinetics of single-ascending doses of APD371. Dose responsive exposure was observed over the explored dose range of 10-400 mg with good tolerability at all doses administered.

"In this trial, APD371 was well tolerated, as evidenced by the lack of dose-limiting adverse events, at drug levels greatly exceeding those anticipated as needed for activating the CB2 receptor," said William R. Shanahan, Jr., M.D., Arena's Senior Vice President and Chief Medical Officer. "We believe that the intrinsic properties of this compound could offer advantages over currently marketed treatments for pain."

About APD371

APD371, an orally available agonist of the CB2 receptor, is Arena's internally discovered investigational drug candidate for several potential indications, including pain and fibrotic diseases. This compound, through its high level of observed selectivity for the CB2 receptor versus the CB1 receptor, is designed to provide pain relief without psychotropic effects or the potential for dependence or abuse. Preclinical efficacy with APD371 has been shown in animal models of osteoarthritic and neuropathic pain.

About Arena Pharmaceuticals

Arena is embracing the challenge of improving health by seeking to bring innovative medicines targeting G protein-coupled receptors to patients. Arena's focus is discovering, developing and commercializing drugs to address unmet medical needs, and BELVIQ® (lorcaserin HCl) is Arena's first internally discovered drug approved for marketing. 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, safety, efficacy and mechanism of action of APD371; the potential of APD371, including as a treatment for several potential indications, as compared to currently marketed treatments, and in providing pain relief without psychotropic effects or the potential for dependence or abuse; the preliminary results of the Phase 1 clinical trial of APD371, including their significance and support for advancing the drug candidate; embracing the challenge of improving health; seeking to bring innovative medicines to patients; 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: the results are not comprehensive and are based on a preliminary analysis of then available data, and findings and conclusions related to the trial are subject to change following a more comprehensive review of the data; APD371 may not be further advanced, approved for marketing or commercialized for any disease or condition; risks related to commercializing drugs, including regulatory, manufacturing, supply and marketing issues and the availability and use of BELVIQ; cash and revenues generated from BELVIQ, including the impact of competition; the risk that Arena's revenues are based in part on estimates, judgment and accounting policies, and incorrect estimates or disagreement regarding 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 in combination with another drug, for another indication or using a different formulation or in any other territory for any indication; regulatory decisions in one territory may impact other regulatory decisions and Arena's business prospects; 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 regulatory requirements or otherwise be sufficient for (or Arena or a collaborator may not pursue) further research and development, regulatory review or approval or continued marketing; Arena's and third parties' intellectual property rights; the timing, success and cost of Arena's research and development; 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.