['smoking']
['cerc-501', 'placebo']

        Inclusion Criteria:

          1. Provides written informed consent and agrees to complete required clinic visits

          2. Male or female 21 to 60 years of age inclusive

          3. Body mass index (BMI) 18.5 to 40 kg/m2 inclusive

          4. Heavy Smokers

          5. Currently not seeking smoking cessation therapy

          6. In otherwise good general health without any unstable medical conditions (as
             determined by medical history, medication history, physical examination, 12-lead ECG,
             vital signs, and clinical laboratory testing)

          7. Able to read, write, and speak in English

          8. Females must be either:

               -  Post-menopausal (amenorrhea for at least 12 consecutive months), surgically
                  sterile -or-

               -  Women of childbearing potential (WOCBP) must meet the criteria below:

                    -  Uses an acceptable double-barrier method of contraception as determined by
                       the Investigator -and-

                    -  Is not lactating, has a negative serum beta human chorionic gonadotropin
                       pregnancy test at screening and a negative urine pregnancy test prior to
                       dosing on Days 1 and 8 of each treatment period.

          9. Male subjects must agree to use a condom if partner is of childbearing potential

        Exclusion Criteria:

        Subjects meeting the following criteria are not eligible for the study:

          1. Any substance use disorder other than nicotine or caffeine as assessed by the
             Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) substance
             use disorder checklist in addition to the Mini-International Neuropsychiatric
             Interview (MINI) (to capture both DSM-V substance use disorder diagnoses)

          2. Current neurological conditions that interfere with study conduct, assessment or
             treatment in any significant fashion

          3. Any lifetime history of bipolar I, II; schizophrenia or any other psychotic disorders;
             personality disorders, impulse control disorders as assessed by the MINI

          4. Current psychiatric conditions that interfere with study conduct, assessment or
             treatment in any significant fashion, such as major depressive disorder (MDD), eating
             disorders, post-traumatic stress disorder, etc., without permission of the medical
             monitor

          5. Recent active or past history of gastric disease such as peptic ulcer disease,
             gastritis, upper gastrointestinal bleeding, or any gastrointestinal malignancy or
             precancerous condition

          6. Active, comorbid disease that might limit the ability of the subject to participate in
             the study as determined by the Investigator (i.e., poorly controlled diabetes
             mellitus, congestive heart failure, etc.)

          7. Clinically significant clinical laboratory test taken during screening, without
             permission of the Medical Monitor

          8. Elevated AST or ALT ≥ 2 times the upper limit of normal (ULN)

          9. Human immunodeficiency virus (HIV), Hepatitis B or Hepatitis C positive as determined
             by serology testing at Screening

         10. History of severe allergies or multiple adverse drug reactions

         11. Known hypersensitivity to CERC-501

         12. Current use of a proton pump inhibitor or histamine 2 blocker without permission of
             the Medical Monitor

         13. Use of any investigational medication within 2 months prior to the start of this study
             or scheduled to receive an investigational drug other than the study drug during the
             course of this study
      