The goal of the TAIL-PrEP study is to understand how to support the safe discontinuation of injectable long-acting cabotegravir (cab-LA) and lenacapavir (LEN) while maximizing the public health impact of biomedical HIV prevention interventions. In Aim 1, the study will pilot test and assess the acceptability and feasibility of the TAIL-PrEP intervention: for participants discontinuing cab-LA, this will consist of monthly cabotegravir drug level monitoring to provide personalized HIV prevention coaching, for participants considering discontinuing cab-LA or LEN, this will consist of a one-time personalized HIV prevention coaching session. In Aim 2, the study will refine the TAIL-PrEP intervention and implementation strategy based on findings from the pilot study.

Oral PrEP is highly effective but underutilized, with only 25% of individuals eligible for PrEP in the US having a prescription. Recent approval of cabotegravir-LA (cab-LA), a long-acting injectable integrase inhibitor and the first long-acting injectable PrEP, and lenacapavir (LEN), a long-acting class capsid inhibitor presents an opportunity to increase uptake. However, the long and variable half-life of cab-LA across different individuals after discontinuation (called the "tail") poses an implementation challenge. During the tail, cabotegravir levels are sub-therapeutic but could select for integrase-inhibitor resistance if the patient were to acquire HIV. This concern about the tail presents a barrier to providers prescribing cab-LA, potentially limiting the contribution of cab-LA to achieving End the HIV Epidemic targets and PrEP uptake and HIV infection. Currently, to mitigate this risk, individuals are advised to use oral PrEP for up to and beyond 12 months after stopping cab-LA injections if they have an ongoing risk of becoming infected with HIV. However, a risk mitigation strategy that requires daily oral PrEP may not be feasible or acceptable to many patients who started injectable PrEP precisely because they were unable or unwilling to adhere to a daily medication. LEN does not pose the same issue with a drug tail during discontinuation, but patients discontinuing LEN may need guidance on how to switch to other HIV prevention strategies rather than discontinuing HIV prevention altogether. In Aim 1, the study will pilot test and assess the acceptability and feasibility of the TAIL-PrEP intervention: for participants discontinuing cab-LA, this will consist of monthly cabotegravir drug level monitoring to provide personalized HIV prevention coaching, for participants considering discontinuing cab-LA or LEN, this will consist of a one-time personalized HIV prevention coaching session. In Aim 2, the study will refine the TAIL-PrEP intervention and implementation strategy based on findings from the pilot study.

Inclusion criteria:

• At least 18 years of age
• HIV-negative (self-report)
• Able to speak and read in English
• Have access to an internet-connected device capable of running the online video conferencing platform
• Have a private location at which to take online conference calls

Participants considering discontinuing cab-LA or LEN have the following additional inclusion criteria:

- Considering discontinuing cab-LA or LEN

Participants discontinuing cab-LA have the following additional inclusion criteria:

• Have discontinued cab-LA injections within the last three months
• Not currently on cab-LA injections
• Able to receive and send monthly packages
• The study period will end for patient participants once the monthly blood draw result indicates that cab-LA levels are not detectable (estimated average of 6 months across all patients) or after 6 months of the study, whichever comes first. If at 6 months of study participation, cab-LA levels are still detectable and participants adhered to at least 50% of study activities (self-collecting and mailing monthly blood samples, completing monthly surveys, attending monthly coaching sessions), participants will be invited to participate in the study for an additional 6 months, for a total of up to 12 study visits.