The purpose of this study is to determine the effect of nasal PYY3-36 on weight loss post 24 weeks of treatment.

This is a multi-center, Phase 2 double-blind, randomized, placebo-controlled trial in healthy obese patients. The primary objective of the study is to evaluate the effect of increasing nasal PYY3-36 dosing on weight loss post 24 weeks of treatment.

Secondary Objectives:

• To evaluate the safety of three nasal PYY3 36 dose groups compared to nasal placebo
• To compare the weight loss post 12 and 24 weeks of treatment for each of the three nasal PYY3 36 dose groups versus the nasal placebo group
• To compare the proportion of patients who lose at least 5% and 10% of the baseline body weight post 12 and 24 weeks of therapy for each of the three nasal PYY3 36 dose groups versus the nasal placebo group
• To compare the weight loss and proportion of patients who lose at least 5% of the baseline body weight post 12 and 24 weeks of treatment with sibutramine versus capsule placebo
• To compare the weight loss and proportion of patients who lose at least 5% of the baseline body weight post 12 and 24 weeks of treatment with nasal placebo versus capsule placebo
• To compare the weight loss and proportion of patients who lose at least 5% of the baseline body weight post 12 and 24 weeks of treatment with sibutramine versus the nasal PYY3 36 dose groups
• To evaluate the effect of 12 and 24 weeks of treatment with nasal PYY3 36 and sibutramine on fasting lipid profile, plasma glucose, insulin, blood pressure and pulse, waist circumference and BMI
• To evaluate the effect of 24 weeks of treatment with nasal PYY3 36 and sibutramine on HbA1c levels

Inclusion Criteria:

• Male or Female patients 18 and 65 years, inclusive;
• BMI 30-43 kg/m2, inclusive;
• In good health, determined by medical history and physical examination, as well as normal 12-lead ECG and vital signs;
• Non-smoker and no use of tobacco or nicotine products for at least 3 months;
• Females will be non-pregnant, non-lactating, and either post-menopausal for at least 1 year, surgically sterile (including tubal ligation, hysterectomy) for at least 3 months, until 30 days following Study Completion be willing to use an approved method of contraception;
• Has normal nasal mucosa.

Exclusion Criteria:

• Previous surgical treatment for obesity;
• Serious Medical Condition
• Serious Psychiatric illness
• Organic causes of obesity (e.g. untreated hypothyroidism)
• Type 1 or Type 2 Diabetes;
• Presence of uncontrolled hypertension
• On prohibited concomitant medication