PROJECT SUMMARY/ABSTRACT Brian Chan MD MPH is an internist and health services researcher passionate about improving health outcomes for vulnerable patients with opioid use disorder (OUD). This career development award will establish Dr. Chan as a clinician-investigator focused on implementing and disseminating novel primary care interventions that target high-risk patients with OUD in safety-net settings. The K23 award provides mentored training to develop expertise in 3 areas: 1) conduct of mixed-methods research to develop deployment-focused interventions; 2) clinical trial design and implementation science; and 3) addiction medicine treatment in federally qualified health center (FQHC) settings. To achieve these goals, Dr. Chan has assembled a multidisciplinary mentoring team with expertise in health services research, addiction medicine, intervention design and implementation science, and FQHC health systems, with success in mentoring faculty to research independence. In 2018, 2.1 million people had an opioid use disorder (OUD) related to heroin or prescription pain relievers. While the recognition of OUD is increasing, few patients receive evidence-based treatment. This is particularly true for medically complex patients with OUD in safety-net settings. OUD complicates management of other chronic medical conditions and is associated with high utilization of healthcare resources. Health systems are interested in risk stratifying complex patients to improve targeting of interventions, like ambulatory intensive care teams (A-ICU); these could be adapted for complex patients with OUD, but scalability limit dissemination. Informed by his clinical experience as an internist and data from his K12 award evaluating an A- ICU for medically complex high-utilizers in an FQHC, Dr. Chan will complete the following 3 aims: 1) Adapt an existing A-ICU intervention to address high complexity patients with OUD using community stakeholder engaged methods; 2) Refine the intervention through an iterative implementation case study, and identify measures of acceptability, feasibility, and implementation strategy; 3) Evaluate and pilot a randomized trial of the intervention to assess feasibility, acceptability, and preliminary efficacy of the refined intervention to improve clinical outcomes, and retention in OUD treatment at a FQHC using implementation and mixed- methods. The results provide preliminary data for a future R01 proposal pragmatic efficacy trial of the refined intervention at multiple FQHC sites. This proposal directly aligns with the priorities of the National Institute on Drug Abuse’s strategic planning workgroup on the “complexity of substance use disorders” and its priority to “develop and test strategies for effectively and sustainably implementing evidence-based treatments.” Completion of these studies will pave the way for implementing scalable primary care interventions to narrow OUD treatment gaps and improve care for high-risk populations.