The purpose of this study is to determine whether a combination of naltrexone SR and bupropion SR is safe and effective in the treatment of nicotine-dependence in overweight and obese subjects.

Key Inclusion Criteria:

1. Female and male subjects must be 18 to 65 years of age;
2. Have body mass index (BMI) greater than or equal to 27 and less than or equal to 45kg/m2;
3. Have smoked an average of at least 10 cigarettes/day in the preceding year, with < 3 month total abstinence period;
4. Self-reported level of motivation to stop smoking ≥ 7, on a scale of 1-to-10;
5. At least moderately concerned about gaining weight after quitting smoking
6. Women of child-bearing potential, must be non-lactating and agree to use effective contraception throughout the study period and 30 days after discontinuation of study drug;
7. Able to comply with all required study procedures and schedule;
8. Able to speak and read English;
9. Willing and able to give written informed consent.

Key Exclusion Criteria:

1. Obesity of known endocrine origin
2. Serious medical condition
3. History of drug or alcohol abuse or dependence
4. Use of excluded concomitant medications
5. History of surgical or device (e.g. gastric banding) intervention for obesity;
6. History or predisposition to seizures
7. Pregnant or breast-feeding women or planning to become pregnant during the study period or within 30 days of discontinuing study drug;
8. Planned surgical procedure that can impact the conduct of the study;
9. Use of investigational drug, device or procedure within 30 days prior to Screening;
10. Participation in any previous clinical trial conducted by Orexigen Therapeutics;
11. Any condition which in the opinion of the investigator makes the subject unsuitable for inclusion in the study.