Objective: To assess the efficacy and safety of AR19 in the treatment of attention-deficit/hyperactivity disorder (ADHD) diagnosed by DSM-5 criteria in adults from 18 through 55 years of age. AR19 is a pellets-in-capsule, immediate-release amphetamine sulfate investigational formulation with physical and chemical barriers designed to resist manipulation to deter snorting, smoking, and intravenous injection.