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 preliminary assessment of the safety and efficacy of APD356, when administered daily for 28 days, in obese subjects who are otherwise healthy.

This is a double-blind, placebo-controlled, randomized, parallel group study. Three different doses of APD356 or placebo will be administered daily for 28 days, to uncomplicated obese, male and nonpregnant, nonlactating, female volunteers, aged 18 to 65 years. Approximately 400 subjects will be enrolled.

• Healthy male or nonpregnant, nonlactating females aged between 18 and 65 years (inclusive)
• Body Mass Index (BMI) of 30-45 Kg/m^2.
• Non-smoker
• No concomitant medications
• No past treatment with drugs associated with the development of pulmonary hypertension or cardiac valvular insufficiency