ABSTRACT Post-traumatic stress disorder (PTSD) is a chronic, debilitating health problem that affects 4.7% of adults in the US and has a total economic cost of $232.2 billion, annually. Effective evidence-based treatments exist but are underutilized. Substantial barriers to receiving proven cognitive-behavioral treatments include cost, time, difficulty finding qualified clinicians, and perceived stigma. Thus, it is critical to develop novel therapeutics that overcome these obstacles and increase widespread accessibility to effective treatment for PTSD. To this end, this Fast Track project aims to develop OTX-601, a mobile app, digital therapeutic to treat PTSD. During Phase I, we will develop a usable app, determine the optimal dose, and determine the feasibility, acceptability, and usability of OTX-601. We will also conduct a pilot randomized controlled trial (RCT) to determine the preliminary efficacy of OTX-601 in treating PTSD. During Phase II, we will conduct an RCT to determine the effectiveness of OTX-601 in treating PTSD. Positive results will be the critical initial step for facilitating the widespread implementation and commercialization of the digital therapeutic to enhance access to highly personalized PTSD intervention.