Comparison of Nicotine Plasma Concentrations and Subjective Effects for Three Electronic Cigarettes vs Combustible Cigarettes and Nicotine Gum

Inclusion Criteria: 1. Able to read, understand, and willing to sign an informed consent form and complete questionnaires written in English. 2. Generally healthy male or female, 21 to 60 years of age, inclusive, at Screening. 3. Expired breath carbon monoxide (ECO) level is ≥ 15 ppm and ≤ 100 ppm at the Screening and Randomization Visits, measured between 12 p.m. and 6 p.m. 4. Cigarettes are the only tobacco product used within (≤) 30 days of Screening. 5. Smokes combustible, filtered, non-menthol cigarettes, 83 mm to 100 mm in length. 6. Agrees to smoke usual brand (UB) cigarette throughout the study period. Usual brand cigarette is defined as the cigarette brand style currently smoked most frequently by the subject. 7. Smokes at least 10 cigarettes per day (on average) and inhales the smoke, for at least 6 months prior to Screening. Brief periods of abstinence due to illness, quit attempt (prior to 30 days of Screening), or clinical study participation (prior to 30 days of Screening) will be allowed at the discretion of the Investigator. 8. Response at Screening to Fagerstrom Test for Nicotine Dependence, Question 1 ("How soon after you wake up do you smoke your first cigarette?") is either "Within 5 minutes" or "6 - 30 minutes." 9. Willing to use UB cigarette, the study electronic cigarette brand styles and nicotine gum during the study period. 10. Willing to abstain from tobacco and nicotine use for at least 12 hours prior to check-in at each Test Visit. 11. Willing to not participate for 60 days post-study in donation of blood samples or in any study that requires collection of blood samples. 12. Females of childbearing potential must be willing to use a form of contraception acceptable to the Investigator from the time of signing informed consent until study discharge. Exclusion Criteria: 1. Clinically significant or unstable/uncontrolled acute or chronic medical conditions at Screening, as determined by the Investigator, that would preclude a subject from participating safely in the study (e.g., uncontrolled hypertension, asthma or other lung disease, cardiac disease, neurological disease or psychiatric disorders) based on safety assessments such as clinical laboratory tests, medical history, and physical/oral examinations. 2. Systolic blood pressure of \> 150 mmHg or a diastolic blood pressure of \> 95 mmHg at Screening, measured after being seated for at least 5 minutes. 3. Hemoglobin level is \< 12 g/dL at Screening. 4. Positive test for Human Immunodeficiency Virus (HIV), Hepatitis B surface antigen, or Hepatitis C virus. 5. Postponing a decision to quit smoking (defined as planning a quit attempt within \[≤\] 30 days of Screening) to participate in this study or previous attempt within (≤) 30 days prior to Screening. 6. Employed by a tobacco company, the study site, or handles unprocessed tobacco as part of their job. 7. Use of any medication or supplement that aids smoking cessation, including but not limited to any nicotine replacement therapy (e.g., nicotine gum, lozenge, patch), varenicline (Chantix), bupropion (Wellbutrin, Zyban), or lobelia extract within (≤) 30 days of Screening. 8. Females ≥ 35 years of age currently using systemic, estrogen containing contraception or hormone replacement therapy. 9. A positive urine drug screen without disclosure of corresponding prescribed concomitant medication(s), at Screening or Randomization Visit. A positive alcohol result at Screening, Randomization Visit, or at any Test Visit. 10. A female who is pregnant, lactating, or intends to become pregnant during the course of the study.