A Trial of the Safety and Tolerability of SEP-363856 in Adults With Generalized Anxiety Disorder

Key Inclusion Criteria 1. Male or female participants at least 18 years of age at the time of informed consent 2. Completed one of the prior GAD Phase 3 studies involving SEP-363856 through Week 8 without discontinuation of trial intervention 3. Able to continue treatment without interruption, and is considered by investigator to potentially benefit from SEP-363856 4. Participant is willing and able to comply with study procedures and visit schedule 5. i) Females of childbearing potential: negative pregnancy test and agreement to use acceptable contraception ii) Males: agreement to follow protocol-defined contraception and reproductive restrictions Key Exclusion Criteria 1. Diagnosis other than GAD that is the primary focus of treatment 2. Clinically significant psychiatric or medical condition that may interfere with study participation 3. Lifetime history of meeting Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for, or was diagnosed during the prior study with, a psychiatric disorder that would compromise accurate assessment of safety and efficacy outcomes 4. Clinically significant abnormal laboratory values or ECG findings 5. Significant suicide risk 6. Substance use/positive drug screen 7. Use of prohibited medications/therapies 8. Known sensitivity to SEP-363856