Phase II Pharmacokinetics Study of CAM2038

Inclusion Criteria: 1. Subject must provide written informed consent prior to the conduct of any study related procedures. 2. Male or non pregnant, non lactating female subject, aged 19 to 65 years, inclusive. 3. Body mass index between 19 and 35 kg/m2, inclusive. 4. Current diagnosis of moderate to severe opioid use disorder (according to the DSM 5) or past medical history of opioid use disorder currently being treated with SL BPN. 5. Subject must be taking SL BPN (Subutex® equivalent) 24 mg (Group 1 and Group 2) or ≥24 mg (Group 3) daily for at least 30 days prior to Screening. 6. Subject has a history of moderate to severe chronic non cancer pain. 7. Male and female subjects of childbearing potential must be willing to use a reliable method of contraception during the entire study (Screening visit to Follow-up phone call). 8. Subject must be willing and able to comply with all study procedures and requirements. Exclusion Criteria: 1. Individuals meeting DSM-V substance use disorder criteria for alcohol, benzodiazepines, central nervous system (CNS) stimulants, or other drugs of abuse (excluding caffeine, tobacco or THC/marijuana). 2. Any clinically significant abnormality on the basis of medical history, vital signs, physical examination, 12-lead electrocardiogram (ECG; Fridericia's corrected QT interval \[QTcF\] ≥450 msec. for males or ≥470 msec. for females), and laboratory evaluations (including hematology, clinical chemistry, urinalysis at Screening), in the opinion of the Investigator. 3. Significant symptoms, medical conditions, or other circumstances which, in the opinion of the Investigator, would preclude compliance with the protocol, adequate cooperation in the study or obtaining informed consent, or may prevent the subject from safely participating in study, including subjects who are at a risk for gastrointestinal obstruction or paralytic ileus or who have severe respiratory insufficiency, respiratory depression, airway obstruction, gastrointestinal motility disorders, biliary tract disease, severe hepatic insufficiency, planned surgery and prior treatment with monoamine oxidase inhibitors. 4. Use (therapeutic or non-therapeutic) of opioids other than SL BPN. 5. Aspartate aminotransferase (AST) levels \> 3 X the upper limit of normal, alanine aminotransferase (ALT), levels \> 3 X the upper limit of normal, total bilirubin \> 1.5 X the upper limit of normal, or creatinine \> 1.5 X upper limit of normal on the Screening laboratory assessments,…