Developing a Novel Adolescent Cardiovascular Health Promotion Program (CPP) - PROJECT SUMMARY / ABSTRACT Cardiovascular disease (CVD) risk factors in adolescence are common and robustly associated with adult CVD events. Clinical capacity for intensive behavioral intervention is insufficient to meet demand, and moreover, standard behavioral interventions have had limited efficacy in adolescents. Pediatric guidelines identify critical gaps: we need more effective adolescent interventions, with a greater focus on CVD risk factors beyond BMI, and we need to build lean, effective and scalable treatment packages using the multiphase optimization strategy (MOST). In response, we propose to develop and pilot-test a novel Cardiovascular Health (CVH) Promotion Program (CPP) precisely tailored for adolescents with CVD risk factors. Our preparatory work systematically identified intervention components expected to be effective based on theory, evidence, and user preferences. We propose to overcome efficacy limitations of standard interventions by adding novel components to engage emotion and identity mechanisms of adolescent behavior. These core motivational mechanisms are highly sali- ent in adolescence, which is marked by self-identity formation, heightened emotionality, and emotion regulation difficulties. Concurrently, we propose to overcome scalability issues through protocolized, remote, and largely self-guided delivery methods, based on our successful adult interventions. We will employ the MOST framework to systematically optimize CPP for efficacy while balancing the need for scalability. The current R34 will be the Preparation phase of MOST, yielding refined intervention components and operational guidelines for the Opti- mization-phase RCT. In Aim 1, we will adapt and iteratively refine existing intervention content, including the Diabetes Prevention Program for standard behavioral content, the Unified Protocol for Transdiagnostic Treat- ment of Emotional Disorders in Adolescents for emotion regulation content, and academic interventions for iden- tity content. We will tailor content for the target population and adapt it for remote delivery via self-guided videos and worksheets, brief 1:1 coaching, and group sessions. Our person-centered iterative design process will en- gage adolescents to refine intervention prototypes and protocols via think-aloud/interview sessions, with further input from our Teen and Adult Community Advisory Boards. In Aim 2, we will randomize 42 adolescents with CVD risk factors to 1 of 3 arms in an 8-week pre-post pilot trial. Arms will vary 4 components added to standard behavioral content: emotion content (yes/no), identity content (yes/no), group sessions (yes/no), and coaching dose (high/low). The 3 arms will test conditions with the highest burden (all yes/high), lowest novelty (all no/low), and greatest contamination risk (mixed). Mixed quantitative/qualitative data will establish feasibility, acceptability, and fidelity against predefined benchmarks. This R34 will fully prepare us to conduct the Optimization-phase factorial RCT and assemble ‘active’ components into a lean CPP package for Evaluation-phase effectiveness testing. This work directly responds to NHLBI’s calls (NOT-HL-21-020) and is expected to ultimately produce a scalable, accessible intervention that empowers diverse adolescents to enter adulthood with favorable CVH.