PROJECT SUMMARY – Pulvinar Neuro LLC, TOWNSEND Substance use disorder (SUD) is a highly prevalent but difficult to treat brain disorder (Wise et al., 2014; McLellan et al., 2000). While clinicians have a range of a range of pharmacologic and behavioral interventions available for the treatment of SUD, unmet need remains high regardless of drug of abuse with 12-month relapse rates of 40-60% (Klein, 2016; McLellan et al., 2000). Transcranial alternating current stimulation (tACS) represents a novel therapeutic approach for the treatment of SUD with a recent study of tACS in SUD showing promising initial results (Daughters et al., 2020). However, shifting from short-term, instantaneous effects of stimulation to long-lasting, therapeutic circuit modulation requires more extensive tACS paradigms than can currently be achieved with existing technology. In the predicate Phase I SBIR project, we address this gap by developing XCSITE HPtACS, a high-powered tACS device based on our existing XCSITE platform that enables gold-standard, double-blind, placebo- controlled study designs. In this project, we will complete modifications to our existing XCSITE 100 device to enable the higher amplitude stimulation required for a durable therapeutic effect. We will evaluate the performance and safety of the device in a preclinical rat study before evaluating feasibility and tolerability of higher amplitude stimulation in a pilot study of patients with SUD. The goal of the predicate Phase 1 grant is to advance product development and testing to prepare the device for further clinical development ahead of seeking FDA clearance for the treatment of SUD. Pulvinar Neuro has successful track-record of developing and commercializing mobile neurophysiology research equipment. In a future Phase 2 study, we plan to perform an initial treatment clinical trial to assess the efficacy of XCSITE HPtACS as a therapeutic for SUD.