This is a research study of an investigational drug, APD356, a novel, selective 5-HT2c receptor agonist, in clinical development as a potential treatment for obesity.

The purpose of this study is to obtain a preliminary assessment of the safety and efficacy of APD356, when administered daily for 12 weeks, in obese subjects who are otherwise healthy. Subjects who are on concomitant medications for control of hypertension or blood lipids may qualify.

This is a double-blind, placebo-controlled, randomized, parallel group study. Three different doses of APD356 or placebo will be administered daily for 12 weeks, to obese, male and nonpregnant, nonlactating, female volunteers, aged 18 to 65 years. Approximately 400 subjects will be enrolled.

Inclusion Criteria:

• Healthy male or nonpregnant, nonlactating females aged 18-65 years (inclusive)
• Body mass index (BMI) of 30-45 kg/m2
• Non-smoker
• No concomitant medications other than hypertension medications (stable > 90 days) and/or statins (stable > 90 days)
• No past treatment with drugs associated with the development of pulmonary hypertension or cardiac valvular insufficiency
• No more than mild mitral valve regurgitation and absence of aortic valve regurgitation upon screening echocardiogram