PROJECT SUMMARY/ABSTRACT Alcohol use disorder (AUD) is a pervasive and problematic public health concern among populations characterized by homelessness. This health disparity among individuals who are homeless is reflected in the high rates of alcohol-related mortality and morbidity. Racial minorities and women experience disproportionate alcohol-related harm and high rates of alcohol-related mortality and morbidity. This disparity is elevated among racial minorities and women who are homeless. A recent randomized controlled trial (RCT), the Harm Reduction Treatment with Pharmacotherapy study (HaRP; R01AA022309; PI: Dr. Susan Collins), tested the efficacy of harm reduction treatment with extended-release naltrexone (XR-NTX; VIVITROL®) among urban adults experiencing homelessness and AUD. This 4-arm RCT assessed the effects of extended-release naltrexone and harm reduction counseling (XR-NTX + HRC), a placebo medication group and harm reduction counseling (placebo + HRC), and harm reduction counseling alone (HRC), compared to community-based supportive services (TAU). Behavioral harm reduction treatment combined with XR-NTX was shown to improve alcohol and quality of life outcomes, underscoring its utility for people experiencing homelessness and AUD. While behavioral harm reduction treatment combined with XR-NTX has been found to be feasible, acceptable, and efficacious among people experiencing homelessness with AUD, there is a dearth of research on XR-NTX for AUD among NAI and Black adults and women, and no studies of XR-NTX paired with behavioral harm reduction treatment in these historically underrepresented groups for AUD treatment research. Examination of pharmacobehavioral harm reduction treatment for marginalized populations aligns with NIH/NIAAA's recent strategic plan, including their commitment to “supporting studies to better understand health disparities and to develop interventions for at-risk groups.” The proposed study will use content analysis to assess if HaRP is an acceptable treatment across race and sex (Aim 1). Additionally, the study will use invariance testing to assess the efficacy of HaRP across race and sex (Aim 2). Specifically, it will test the hypothesis that the intervention effects of each HaRP treatment group (HRC+XR-NTX, HRC+Placebo, HRC) compared to the TAU are invariant across race (NAI, Black, white) and sex (female and male). Research findings will serve as pilot data to inform future treatment development for underrepresented minorities among a marginalized, transient population. Additionally, the proposed study would provide the Applicant with training experiences that will inform her research program on harm reduction treatment among marginalized populations. Specifically, the proposed training and research would facilitate the acquisition and integration of knowledge on alcohol interventions; RCT methodology and data analysis; alcohol-related health inequities; and treatment development among marginalize...