Effectiveness Trial to Support Adoption of Hybrid Closed Loop Therapy in Underserved Adults with Type 1 Diabetes: Impact of System Functionality and Features on Lived Experience - PROJECT SUMMARY/ABSTRACT Minoritized individuals with type 1 diabetes (T1D) have approximately 2% higher average A1c levels and twice the rate of hospitalizations, complications, and mortality as their white counterparts. However, the efficacy trials establishing the benefits of hybrid closed loop (HCL) pump therapy in T1D have been in more socially advantaged and predominantly non-Hispanic white patients. Use of this transformative technology by individuals with T1D from underserved communities remains very low. We plan to conduct a randomized effectiveness trial - with broader eligibility criteria (including markedly elevated A1c) and longer (9 month) follow up than the pivotal HCL efficacy trials - to evaluate the benefits, safety risks and treatment complications of HCL use in underserved adults with T1D (Specific Aim 1). Primary outcome will be % time-in-range 70-180 mg/dL, and secondary outcomes will include % time < 70 mg/dL, DKA events and body weight. The HCL arm in the trial will include three HCL systems (BetaBionics iLet, Insulet OP 5, Tandem Control IQ) that vary in degree of automation and user input required for operation. More automated systems could potentially better match the needs of underserved individuals with competing life demands that limit diabetes self-care; however, the potential benefits of automation are at the cost of less personal control of the system, including adjustments for work-shift changes and activity. Specific Aim 2 incorporates the novel application of Ecological Momentary Assessment to examine the lived experience with HCL (including benefits and burdens, the impact of life stressors impact on HCL use, and how the match between HCL system functionality and the individual’s needs and expectations impacts on user experience). In Specific Aim 3, in collaboration with a user-centered designer, we will apply the learnings from the study to develop: 1) Improved HCL patient education and clinician support tools; and 2) Decision-aids to guide patient selection of the HCL system that is most aligned with personal preferences and needs. These optimized training materials and decision-aids will set the stage for the translation of our research findings into increased adoption of HCL in underserved communities and improved shared decision-making by patients and clinicians in the selection of HCL systems.