ABSTRACT Men who have sex with men (MSM) make up 69% of people living with HIV in the US. Among MSM and gender minority individuals who have sex with men living with HIV, substance use disorders (SUDs) are associated with inadequate engagement in HIV care, often leading to episodic unsuppressed viral load (VL) or viral rebound, thus driving the epidemic through elevated HIV transmission risk. Behavioral science identifies that internalized stigmas perpetuated by experienced stigma and structural inequities, influences sub-optimal engagement in HIV care, resultant unsuppressed VL, and transmission among MSM with SUDs. Stigma and related emotions (e.g., shame) compromise health outcomes both directly (e.g., via sub-optimal adherence and appointment attendance) and indirectly (e.g., as barriers to social services engagement). Interventions are needed to address stigma and shame as barriers to viral suppression among MSM and gender minority individuals living with HIV and SUDs. To meet this need, we developed, refined, and conducted a pilot RCT (K23DA043418) to assess the feasibility and acceptability of the MATTER intervention, an evidence- and community- informed psychobehavioral intervention to facilitate viral suppression by reducing the impact of internalized stigma and shame on engagement in HIV care among MSM with SUDs. The MATTER intervention aims to mitigate the negative behavioral consequences of internalized stigma and shame on viral suppression by a) behavioral self-care goal setting skills and related self-efficacy, b) increasing metacognitive awareness (i.e., non-judgmental awareness of cognitions and emotions), and c) compassionate self-restructuring (i.e., self- compassion). It involves 5- one-on-one virtual therapy sessions and bidirectional personalized text messaging to extend the impact of the intervention while using less interventionist time and phone- based resource navigation. The proposed hybrid type 1 efficacy-implementation study will use the RE- AIM framework to assess: 1) the efficacy of the MATTER intervention on viral suppression at the final 12-month follow up visit compared to a time-matched control arm using a fully powered randomized controlled trial (RCT; N=256), 2) the proposed mechanisms of the MATTER intervention to inform future interventions to mitigate the impact of stigma, and 3) facilitators and barriers to the reach, adoption, implementation, and maintenance of the MATTER intervention to be conducted in two priority locations with key differences: the Boston, Massachusetts and Miami, Florida metro areas. Should the intervention be efficacious, and the innovative internalized stigma mitigation approach be confirmed, we will be well- positioned to leverage the identified facilitators and barriers to implementing this intervention among MSM and gender minority people who have sex with men living with HIV and SUDs in a subsequent hybrid type 2 trial to assess the scalability, including a full cost-effectiveness assessment.

PUBLIC HEALTH NARRATIVE Men who have sex with men (MSM), and gender minority individuals who have sex with men, living with HIV and substance use disorders (SUDs) are less likely to be virally suppressed, which can lead to HIV transmission and negative health outcomes. This hybrid type 1 study will assess the efficacy, mechanisms, as well as facilitators and barriers to implementing the MATTER intervention, a virtually delivered 5-session text- enhanced psychobehavioral intervention designed to facilitate viral suppression by addressing internalized stigma and shame as barriers to engagement in HIV care among MSM and gender minority individuals living with HIV and SUDs in two locations with different levels of HIV resources (i.e., the Boston, Massachusetts and Miami, Florida metro areas). MATTER aims to mitigate the negative behavioral consequences of internalized stigma and shame on viral suppression by a) developing behavioral self-care goal setting skills and related self-efficacy, b) increasing metacognitive awareness (i.e., non-judgmental awareness of emotions and cognitions), and c) teaching and reinforcing compassionate self-restructuring (i.e., self- compassion), in addition to providing access to phone-based resource navigation. Scalable interventions such as MATTER are essential to our efforts to end the HIV epidemic in high priority regions.