The goal of HIV treatment is to make sure the HIV virus in the blood remains very low; this is called having an undetectable viral load (virological suppression). If this goal is achieved and sustained life-long, then people with HIV infection can live a healthy life, with a normal life expectancy. However, it is challenging to take medication every single day for life. This may be an even bigger challenge for teenagers living with HIV.

There is now a new way of taking HIV treatment. This is through an injection form of the HIV medicines. Two injections, one of cabotegravir and one of rilpivirine, have to be given in the clinic every 8 weeks. One injection will be given in the left cheek of the buttock and the other in the right cheek of the buttock at the same visit. This is called an intramuscular (IM) injection.

In LATA, two different ways of taking HIV medicines will be compared. Participants will be randomised, with an equal chance that they will either go into the long-acting injectable group or get a daily tablet by mouth. This is what happens depending on which group they are randomised to:

* Long-Acting Injectable Group: In this group, there are 2 options. The first is to stay on current HIV medicines by mouth and then to start the injections around 4 weeks after randomisation. If this is the choice, then at week 4, the first 2 injections will be given, the second two will be given 4 weeks later, and then it's every 8 weeks from then on. The second option is to switch to taking one tablet of cabotegravir and one tablet of rilpivirine for approximately 4-5 weeks before starting the injections. The reason that some people might choose to have the tablet forms first, is to make sure they tolerate them. This is called an oral lead-in (OLI). For the OLI group, and as long as liver test results at 4 weeks are within normal levels, the first two injections will be given at around 5 weeks (about a week after the week 4 visit), the second two are given 4 weeks later, and then it's every 8 weeks from then on.
* Continuous Oral Treatment Group: this group will continue to take HIV medicines every day by mouth. However, to join the trial, some participants will have to change some of their oral medications as the combination being used is dolutegravir with tenofovir plus either lamivudine or emtricitabine as a single tablet taken once a day, called TLD.

The LATA trial will enrol 460 young people living with HIV-1 from Kenya, South Africa, Uganda and Zimbabwe. People taking part need to be 12 to 19 years old, HIV-1-positive, have undetectable HIV-1 viral load (HIV-1 RNA \< 50 c/mL) for at least the last year, on combination ART, and never have switched HIV medication in the past because of treatment failure. In order to join, adolescents who are at least 18 years old will need to sign the consent form for themselves. The consent form describes what the trial is about and what is required of participants. Adolescents aged 12 to 17 years of age will have to sign an assent form - this assent form describes what the trial is about and what is required of participants. The assent form can be signed without a parent or guardian in the same room. The assent form has the same information in it as the consent form that their parent or guardian will also need to sign as well, to agree to them taking part in LATA. Each person taking part will stay in the trial for at least 96 weeks (about 2 years) although it may be longer, between 3-4 years. Young women enrolled in LATA must not be pregnant or breastfeeding when they join and must avoid getting pregnant during their time in the trial. For young women in the long-acting injectables group, they must also avoid getting pregnant for at least 12 months after the last injection is given; this is because not much is known about the safety of these injections in pregnancy. If, however, a young woman does get pregnant while they are on the long-acting injectables, they should immediately contact their clinic for advice and support. More details will be provided in a separate information sheet and consent form about options for HIV treatment during pregnancy, including staying on the long-acting injectables with additional monitoring.

At the beginning of the trial everyone will be screened to make sure they meet the criteria to participate, then they will be randomised - by a computer- to one of the groups in the study. For the long-acting injectable group, there are the 2 options as described above and one or two additional visits around 4-5 weeks after being randomised into the trial. People taking part in the trial will be asked to visit the clinic every 8 weeks until the last participant who joined the trial has been in the trial for 96 weeks. The trial research team will ask questions about health, wellbeing and mood at some of the visits. For girls who have started their periods, a pregnancy test will be done at each visit. Everyone will have their viral load measured approximately every 6 months and they and their doctors will receive the results, which show how much HIV virus is in the blood. At some visits a blood sample will be stored, which may be looked at later for HIV viral load or for changes to the virus that may stop some treatment working as well. An additional blood sample will also be taken at the beginning and then once a year, and urine samples at the beginning and at week 96; these stored samples will be used to look at the health of people's kidneys, bone, heart and other organ systems; they are optional. In addition, to the main trial, there are sub-studies (smaller studies within the main trial), which people taking part may be invited to take part in. Some participants in LATA will be invited to take part in a social science sub-study where there are interviews to find out how people feel about HIV and their medication. In another sub-study, the mood (neuropsychiatric) sub-study, there are additional surveys to find out if young people are having problems with feeling down or worried about HIV, their medication and other things going on in their lives. A small number of participants may be asked to take part in a study that measures the amount of HIV medicine in the blood. These sub-studies require additional consent, so people can decide if they do or don't want to take part in these sub-studies, and it won't affect being in the LATA trial. At selected sites, a further sub-study is about checking the amount of muscle and fat in the body, using a monitor placed on the arm, which doesn't hurt at all. The information for this sub-study is in the main LATA information sheet.

The trial will be able to show whether the injection forms of HIV medicine work as well as taking the daily tablets of HIV medicines in adolescents living with HIV. If the long-acting injectables given every 8 weeks work as well as the daily oral tablet, it is hoped the HIV guidelines will change to recommend this as an option for how adolescents and young people take their HIV medicines.