A Study of Cebranopadol for Opioid Withdrawal Symptoms in Adults With Chronic Pain

Key Inclusion Criteria: * Adults 18-65 years with BMI 18.0-40.0 kg/m² and weight ≥50 kg. * Chronic daily pain for ≥6 months due to chronic low back pain, hip/knee osteoarthritis, or painful peripheral neuropathy. * Prescribed opioid use ≥5 days/week for ≥3 months within the prior 6 months, generally 50-90 MME/day; \>90 MME/day may be allowed with Sponsor/designee approval. * Generally in good health and able to comply with study procedures, including opioid withdrawal and inpatient confinement. * Meet protocol-specified reproductive and contraception requirements. * Able to provide informed consent and complete study assessments in English. * Physical opioid dependence confirmed by protocol-defined COWS and/or SOWS criteria before randomization. Key Exclusion Criteria: * Clinically significant medical or psychiatric condition that could compromise participant safety or study validity. * Protocol-specified excluded pain, neurologic, spinal, infectious, or neoplasm-related conditions. * QTcF \>450 ms in males or \>470 ms in females, other torsade de pointes risk factors, or use of QT-prolonging medications. * Substance use disorder other than opioid, nicotine, or caffeine use disorder, or positive testing for prohibited drugs/alcohol, subject to the protocol-specified cannabinoid exception. * Positive HIV, hepatitis B surface antigen, or hepatitis C antibody test. * Suicidal ideation or active suicidality within the past 2 years. * Use of prohibited medications or inability to meet protocol-specified medication washout requirements. * Pregnant or breastfeeding or planning pregnancy within 30 days after the last study-drug dose. * Significant adverse reaction to naloxone or related opioids/opioid antagonists. * Unable to undergo IV catheter placement or otherwise considered unsuitable or unlikely to comply with the protocol. * Legal, employment, or other circumstances that could interfere with study participation or compliance.