Background: To date, efficacious interventions to promote and sustain pre-exposure prophylaxis (PrEP) adherence among youth are limited. Smartphone apps provide a platform to address adherence barriers by delivering tailored strategies and culturally-relevant content in an engaging format. App-based interventions that also allow for intensified interactions through direct communication with adherence counselors may improve outcomes among nonresponsive youth. We describe the development and initial testing of a PrEP adherence app for young men who have sex with men (YMSM) and young transgender women who have sex with men (YTWSM) that includes provision of adherence counseling delivered within the app through a provider texting interface.
Methods: P3 (Prepared, Protected, emPowered) is an app built upon an established theory-based, health platform, optimized through our teams'' prior work with HIV+ YMSM and with youth advisory board (YAB) members at 7 Adolescent Trials Network for HIV Interventions (ATN) sites. P3 includes interactive components to encourage peer-to-peer sharing and the development of daily medication self-monitoring behaviors. Game-based elements, including virtual and real-world rewards, based on established behavioral economics principles, incentivize engagement. Strengths-based adherence counseling delivered by a centrally-located adherence counselor via two-way text messaging through the app addresses individuals'' unique barriers to PrEP adherence.
Results: Usability testing was conducted with 12 YMSM/YTWSM (mean age 20.9, 10 male), either PrEP experienced or considering, at 2 ATN sites using a clickable app prototype (screenshots presented in Figure 1). Most (92%) found the app highly acceptable, particularly the tailored medication reminders, the daily medication tracking with corresponding medication history calendar, and the accessibility, comprehensiveness and tone of the information provided. Youth were enthusiastic about connecting directly with an adherence counselor and provided concrete recommendations for rapport building, session duration and explicitly defining the counselors'' role.
Conclusions: P3 represents, to our knowledge, the first theoretically-based PrEP adherence app for YMSM/YTWSM that includes features to increase intervention engagement (e.g. gamification, financial incentives, social connectivity) and provides in-app adherence counseling. Interventions that capitalize on technology-based platforms have great potential to encourage health promotion behaviors. A technical pilot of P3 will be conducted in Summer 2018 followed by an efficacy trial if feasibility/acceptability is achieved.

Screen Shots of the P3 app
[Screen Shots of the P3 app]