PROJECT SUMMARY/ABSTRACT Methamphetamine (MA) use and related morbidity and mortality are rapidly increasing in the United States. MA use disproportionately impacts cisgender men who have sex with men (MSM) and is strongly associated with increased risk for HIV acquisition. MA use is also associated with suboptimal pre-exposure prophylaxis (PrEP) adherence, diminishing the benefit of daily, oral PrEP for HIV prevention among MSM who use MA. Long- acting (LA) PrEP is a promising prevention strategy for MSM who use MA, since its effectiveness does not rely on daily medication adherence. In December 2021, long acting cabotegravir (CAB LA) PrEP received FDA approval, after it was found to be superior to daily, oral Truvada. There are other LA PrEP agents in earlier stages of development, including biannual injections and subdermal implants. To help ensure that populations at highest risk for HIV effectively engage in LA PrEP programs, we will assess interest in different LA PrEP formulations, and facilitators, barriers, and preferences for delivery of CAB LA PrEP among MSM who use MA. We will assess the level of interest and correlates of interest in different LA PrEP formulations among MSM who use MA via the 2023 National HIV Behavioral Surveillance (NHBS) survey at five of the western US sites (San Francisco and San Diego, CA; Portland, OR; Seattle, WA; and Denver, CO) (Aim 1). We will explore multilevel (i.e., on the patient, provider, and system level) barriers to and facilitators of LA PrEP use and important attributes of CAB LA PrEP delivery through in-depth interviews (Aim 2). We will interview up to 40 HIV-negative MSM who use MA (up to 20 who have never taken PrEP and 20 who have) and up to 20 key informants (e.g., clinicians, service providers). We will identify important attributes and levels for LA PrEP delivery across interviews to inform a subsequent discrete choice experiment (DCE). Prior to the DCE we will conduct 10 cognitive interviews to ensure that the DCE inputs accurately capture the perspectives shared during the initial interviews. We will then conduct a DCE (Aim 3) to identify preferences for CAB LA PrEP delivery among MSM who use MA using the final attributes and levels from Aim 2. Our findings will inform engagement of MSM who use MA in LA PrEP programs and the development of an intervention that will be evaluated in a future trial.