Long-Term Safety Study of Buprenorphine (CAM2038) in Adult Outpatients With Opioid Use Disorder

Inclusion Criteria: 1. Subject must provide written informed consent prior to the conduct of any study-related procedures. 2. Male or female, 18-65 years of age, inclusive. 3. Female subjects of childbearing potential must be willing to use a highly effective method of contraception during the entire study (Screening Visit to Follow-Up Visit). 4. Current diagnosis of moderate or severe opioid use disorder (DSM-V) or past medical history of opioid use disorder currently being treated with SL BPN. 5. Considered by the Investigator to be a good candidate for BPN treatment, based on medical and psychosocial history. 6. Subjects must meet one of the following criteria for BPN treatment history: * Voluntarily seeking treatment for opioid use disorder (not currently on BPN treatment for at least last 60 days but seeking BPN treatment), or; * Currently on SL BPN treatment. Exclusion Criteria: 1. Current diagnosis of Acquired Immune Deficiency Syndrome (AIDS). 2. Current diagnosis of chronic pain requiring opioids for treatment. 3. Current DSM-V diagnosis for moderate to severe substance use disorder (including alcohol) other than opioids, caffeine or nicotine and currently being treated as the primary substance use disorder. 4. Recent history of or current evidence of suicidal ideation or active suicidal behavior as based on the Columbia Suicide Severity Rating Scale (C-SSRS) ("Yes" responses to questions 4 or 5). 5. Pregnant or lactating or planning to become pregnant during the study. 6. Hypersensitivity or allergy to naloxone (only for subjects receiving the SL BPX test dose), BPN or excipients of CAM2038. 7. Requires chronic use of agents that are strong inhibitors or inducers of cytochrome P450 3A4 (CYP 3A4) such as some azole antifungals (e.g., ketoconazole), macrolide antibiotics (e.g., clarithromycin), or protease inhibitors (e.g., ritonavir, indinavir, and saquinavir). 8. Hepatitis, unless under stable treatment, at the discretion of the Investigator. 9. Any pending legal action that could prohibit participation or compliance in the study. 10. Exposure to any investigational drug within the 4 weeks prior to Screening. 11. 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, or other clinically significant laboratory abnormalities, which in the opinion of the Investigator may prevent the subject from safely participating in study. 12. Participants with a history of risk factors of Torsades de Pointes (e.g., heart failure, hypokalemia, family history of Long QT Syndrome) or an ECG demonstrating a Fridericia's corrected QT interval (QTcF) \>450 msec in males and QTcF \> 470 in females at screening. 13. 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. This includes, but is not limited to, subjects with attention deficit hyperactivity disorder receiving central stimulants (e.g. methylphenidate or other central stimulants), as well as subjects with severe respiratory insufficiency, respiratory depression, airway obstruction, gastrointestinal motility disorders, severe hepatic insufficiency, planned surgery and prior treatment with monoamine oxidase inhibitors. 14. Is an employee of the Investigator or the trial site, with direct involvement in the proposed trial or other studies under the direction of the Investigator or trial site, or is a family member of an employee or of the Investigator.