PROJECT SUMMARY Transgender and gender diverse (TGD) people, who have a gender identity that differs from their assigned birth sex and who may use hormones to affirm their gender, are disproportionately affected by HIV. Antiretroviral therapy (ART) greatly reduces HIV-related morbidity and mortality for those who are adherent and able to achieve viral suppression. However, many TGD people with HIV face barriers to ART adherence, including the inability to pay for medications. This study seeks to examine the health and economic impact of Medicaid prescription caps for TGD people living with HIV–an NIH priority population. Prescription caps represent a cost- containment strategy employed by some state Medicaid programs that limit the number of brand name drugs or total number of prescriptions that may be filled in a given time window, typically per month. Though a few outdated studies have used Medicaid data to evaluate the impact of prescription caps on the health of members of the general population, until now, this has not been studied among TGD people. Relative to cisgender (non- TGD) people, TGD people are not only at greater risk for HIV and other chronic conditions but also face economic constraints and competing gender affirmation needs, including the necessary use of gender-affirming hormones to alleviate psychological distress.35,39 In the face of prescription caps, people with HIV have to make tradeoffs between which medications to use and we hypothesize that this tradeoff will lead to lower ART adherence, health complications, and additional medical costs for both TGD and cisgender people with HIV. However, given the documented health comorbidities, economic constraints, and gender affirmation needs that TGD people disproportionately experience, we hypothesize that when faced with prescription caps, TGD people with HIV will have lower levels of medication adherence and worst health outcomes than their cisgender counterparts. Health services research involving Medicaid claims data has not historically accounted for TGD people as Medicaid data does not include a reliable indicator of TGD status. In response to the NIH’s expressed interest to conduct feasible, efficient, and rigorous research, we aim to apply novel algorithms developed by our team to identify TGD and cisgender people with HIV in Medicaid data and study the impact of medication caps on the health of these populations. Specifically, will build off the parent grant by using Medicaid data to explore the differential impact of prescription caps on ART adherence for TGD and cisgender adults with HIV; evaluate whether hormone use moderates the relationship between prescription caps and ART adherence among TGD people alone; and estimate the potentially avoidable health and economic effects of medication caps and ART non- adherence for TGD and cisgender people with HIV. We will engage TGD researchers and community members throughout all stages of the study to ensure the cultural re...