SAN DIEGO, CA, USA I April 5, 2013 I Arena Pharmaceuticals, Inc. (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 (S1P1) 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 S1P1 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 target healthy 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 S1P1 receptor for the potential treatment of a number of conditions related to autoimmune diseases, including multiple sclerosis, psoriasis and rheumatoid arthritis. S1P1 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 S1P1 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.

SOURCE: Arena Pharmaceuticals