A Study to Test the Effects of Nezavist at Different Doses in Healthy Adults

Inclusion Criteria: 1. Healthy male or female volunteer, aged 18-to-55 years-of-age, inclusive. 2. BMI must be between 18 and 32 kg/m\^2 (inclusive) and weigh a minimum of 50 kg (110 lbs). BMI is calculated as weight in kg divided by the square of height measured in meters. 3. A condition of general good health, based upon the results of a medical history, physical examination, vital signs, laboratory profile and a 12-lead electrocardiogram (ECG) at the screening visit. 4. If female, be postmenopausal (at least 2 years prior to dosing) or agree to use an acceptable form of birth control from screening until 1 week after dosing. Subjects who claim postmenopausal status will have status confirmed with a follicle stimulating hormone (FSH) test. Acceptable forms of birth control for females include the following: * Vasectomized partner (at least 6 months prior to dosing) * Surgical sterilization (bilateral tubal ligation, hysterectomy, bilateral oophorectomy) at least 6 months prior to dosing * Non-surgical permanent sterilization (eg, Essure procedure) at least 3 months prior to dosing. * Double barrier (diaphragm with spermicide; condoms with spermicide) * Non-hormonal containing intrauterine device (IUD) * Abstinence (must agree to use a double barrier method if they become sexually active during the study) 5. If male, agree to use an acceptable method of birth control during the study and in the 1 week following dosing. Acceptable forms of birth control for males include the following: * Vasectomy (at least 6 months before dosing) * Partner is surgically sterilized (see methods above for females) * Partner uses oral, injectable, or implantable hormonal contraceptives or IUD * Double barrier (partner uses diaphragm with spermicide; condoms with spermicide) * Abstinence (subject must agree to use a double barrier method if subject becomes sexually active during the study) 6. Be able to verbalize an understanding of the consent form, able to provide written informed consent, verbalize willingness to complete study procedures, able to understand written and oral instructions in English. 7. Complete all assessments required at screening and baseline and be available to stay in the Phase I unit for a period of approximately 4-days and return for follow-up visits. 8. Be someone who in the opinion of the investigator would be expected to complete the study protocol. Exclusion Criteria: 1. History of significant sensitivity to any drug. 2. Requirement for any over-the-counter and/or prescription medication, vitamins and/or herbal supplements on a regular basis or use of any of the above within the 2 weeks or 5 half-lives of the respective medication prior to study drug administration. 3. Not have reported taken any medications known to cause significant GI toxicity. 4. More than moderate alcohol consumption in the past 8 weeks. Moderate alcohol consumption is defined as limiting intake to 2 drinks or less in a day for men and 1 drink or less per day for women. Examples of one drink include: Beer: 12 fluid ounces (355 milliliters); Wine: 5 fluid ounces (148 milliliters); Distilled spirits (80 proof): 1.5 fluid ounces (44 milliliters) 5. Have a urine toxicology screen positive during screening or baseline for any of the following substances: 1. benzodiazepines, 2. cocaine, 3. opioids, 4. amphetamines, 5. buprenorphine, 6. methadone, 7. methamphetamines 8. oxycodone, 9. tetrahydrocannabinol (THC) 10. MDMA 11. Barbiturates 12. ethyl glucuronide for recent alcohol use 6. If female, positive pregnancy test or nursing. 7. Positive test result for hepatitis B surface antigen (HBsAg) or hepatitis C virus antibody (HCV Ab). 8. Positive SARS-CoV-2 antigen test within 72-hours prior to clinic intake. 9. Suspected or known history of Human Immunodeficiency Virus (HIV). 10. History of any clinically significant cardiac, respiratory (except mild asthma), renal, hepatic, GI, hematologic, endocrine, dermatological, metabolic, neurological (nerve injury) or psychiatric disease or disorder, or any uncontrolled medical illness. 11. History of gastric ulcers or known gastric sensitivity to non-steroidal anti-inflammatory drugs. 12. Current symptoms of gastritis or potential GI ulcer complications or screening FOBT positive for blood in the stool. 13. History of head trauma with loss of consciousness, history of epilepsy, seizures or convulsions, including febrile, alcohol or drug withdrawal seizures. 14. Use of any known strong CYP3A4 inhibitors (e.g., ketoconazole) or dual CYP3A4 and 2C9 inhibitor (eg. fluconazole), or dual CYP3A4 and 2C9 inducer (eg. rifampin), or use of any monoamine oxidase inhibitors (MAOIs) within 1 month prior to study drug administration. 15. A clinically notable vital sign abnormality including a history of syncopal or near syncopal events following abrupt change in posture. 16. Have any of the following at screening or baseline: * Blood pressure: systolic greater than140 mmHg, diastolic greater than 90 mmHg at Screening or Day -1. * Heart rate: greater than 100 beats/minute at screening or Day -1 17. Has a clinically significant laboratory test that is greater than 20% of the upper and lower limit of normal. An out of range normal limit laboratory value is clinically significant if associated with one of the following: a) clinical diagnosis; b) systemic signs and symptoms; or c) physical exam finding. 18. History of cardiac disease, including family history of long-QT syndrome, second degree heart block Type II, third degree heart block or unexplained sudden deaths in their family. 19. Has a clinically significant abnormal ECG or an ECG with a QTc interval corrected for heart rate using the Fridericia formula (QTcF) greater than 430 msec. 20. History of gastric surgery, vagotomy, bowel resection or any surgical procedure that might interfere with GI motility, pH or absorption. 21. Donation or loss of 550 mL or more blood volume (including plasmapheresis) or receipt of a transfusion of any blood product within 8 weeks prior to study drug administration. 22. Receipt of any investigational product within 6 weeks prior to study drug administration. 23. Consumption of alcohol within the 1-day period prior to study drug administration 24. Consumption of grapefruit or grapefruit products from 3 days prior to study drug administration to study drug administration. 25. Use of tobacco or nicotine-containing products within the 6-month period preceding study drug administration. 26. Current enrollment in another clinical study. 27. Previous enrollment in this study resulting in administration of nezavist or placebo. 28. Consideration by the investigator, for any reason, that the subject is an unsuitable candidate to receive nezavist.