ABSTRACT Suicide is one of the top ten causes of death in the US and suicide rates have increased steadily over the last twenty years. Currently, the most effective treatment options are cognitive behavioral therapies for suicide prevention (CBT-SP), which have been shown to reduce both suicide attempt (SA) risk and suicide ideation (SI). However, access to these treatments is limited because there is a shortage of mental healthcare practitioners, especially suicide specialists. Furthermore, face-to-face therapy, which is the standard treatment modality, is costly and logistically prohibitive. As a consequence, most people who experience suicidal thoughts or behavior do not receive treatment. Oui Therapeutics therefore developed Aviva, a digital therapeutic application accessed via smartphone. It is based on two CBT-SP protocols (the Brief Cognitive Behavioral Therapy and Cognitive Therapy for Suicide Prevention protocol), is accessible, less costly than current treatment options, and consistently implements CBT-SP with high fidelity. Ready accessibility is particularly important for patients recently discharged after hospitalization for SA, as they are 40 times more likely to make another SA within 30 days of discharge than the general population. Oui Therapeutics has completed a Phase I SBIR study, creating a beta version of Aviva targeting the general adult population, and testing the usability and feasibility of this version of Aviva in a single-group, open-label trial. During the 8-week open-label trial, Aviva users showed clinically meaningful improvement on the Scale for Suicidal Ideation and the Patient Health Questionnaire. For the proposed Phase II study, we aim to: 1) add capabilities to enhance the usability of Aviva; 2a) determine the efficacy of Aviva in reducing SA and SI in a randomized controlled trial (RCT), and 2b) determine the mechanisms of action in Aviva in the RCT. SAs and SIs will be tested by enrolling 286 patients in a randomized controlled trial, administered at four clinical sites. Half of the participants will receive treatment as usual plus Aviva, and the other half will receive treatment as usual plus a sham app. We will use time-to-event survival analysis at 12 months to assess SAs and evaluate Aviva’s effects on SI at 6 months using a restricted likelihood repeated measures analysis. Aim 2b will be tested using mediation analyses to examine Aviva’s effects on participants' scores on the Monetary Choice Questionnaire and the Cognitive Emotion Regulation Questionnaire at three and six months. Upon successful completion of the phase II study, we expect Aviva to be ready for distribution in the market. To ensure affordability and accelerate the penetration of the product, Oui will also pursue licensing Aviva to a pharmaceutical company(s) that will work with payers to have Aviva included in their formularies. Ultimately, Oui seeks to curtail the multi-billion dollar economic costs associated with SA and SI and save l...