Propranolol for Aggression, Self-Injury, and Severe Disruptive Behavior in Adolescents and Adults With Autism

Inclusion Criteria: * Age between 12-40 years. * Clinical best-estimate diagnosis of autism spectrum disorder * Occurrence of severe challenging behaviors, such as aggression, self-injury, and/or severely disruptive or destructive behavior, leading to safety concerns or serious impact of the quality of life, at least weekly over the past 2 months before screening. * Score in the ASD range on the Autism Diagnostic Observation Schedule conducted at the time of study entry or in the past 5 years * Clinical Global Impression Severity scale (CGI-S) score of 4 or above at Baseline * Aberrant Behavior Checklist-2 Irritability/Agitation Subscale Score of 18 or above at Screening. * A resting pulse of greater than 60 and a resting blood pressure of greater than 100/60. * Participant must have a designated study partner who spends a minimum of 5 hours/week with the participant, and can, in the opinion of the investigator, provide a reliable report on the participant's behaviors, symptoms, and complete or supervise at-home safety monitoring and other assessments required during the study * Participants of childbearing potential who are sexually active must agree to practice effective contraception from time of screening through 30 days after their last dose of study drug. Effective contraception is the use of two methods of contraception: hormonal contraceptives or intrauterine device and barrier (i.e., condoms, diaphragm, or cervical cap). * Participant must be able to fully swallow s…