The purpose of this study is to determine the efficacy, safety and tolerability of two approved medicines, dolutegravir (DTG) plus lamivudine (3TC) taken together, compared with subjects taking their current tenofovir alafenamide (TAF)-based regimen (TBR) for the treatment of HIV-1 infected adults in whom the HIV-1 virus is currently suppressed. You have been asked to take part in the study because you have HIV and the virus in your body currently is suppressed. The two drug regimen of DTG and 3TC is considered experimental and is not yet approved for doctors to treat patients with HIV.

Everyone entering the study must be on a HIV treatment regimen consisting of TAF, emtricitabine (FTC) and a third agent, which must be an integrase inhibitor (INI), protease inhibitor (PI) or non-nucleoside reverse transcriptase inhibitor (NNRTI). A fourth agent that acts as a booster is also allowed. At Day 1, one group of about 275 participants will change their current TBR HIV treatment and take the study drugs, DTG + 3TC, for 100 weeks. A second group of about 275 participants will continue to take their current TBR HIV treatment for up to 52 weeks, and if their HIV is suppressed at Week 48 (or upon retest by Week 52), they will be switched to take DTG + 3TC for 48 more weeks. A computer will put people into treatment groups by chance (like flipping a coin). Neither you nor the study doctor can choose a group. You have a 50% chance of being placed in either group. The study doctor, staff and you will know to which group you are assigned. If you are assigned to take DTG + 3TC, you will take one tablet each day at approximately the same time, with or without food (the DTG + 3TC regimen does not have to be taken with a meal). If you are assigned to continue your current HIV treatment regimen, you will continue to take these medications as prescribed. Information about how the study drug that you get affects your body and your health will be collected through a number of tests, procedures and questions. The effects of the drugs will be compared after the study is complete. After 100 weeks, you may choose to stay on DTG + 3TC FDC (fixed dose combination) and come into the clinic for visits every 12 weeks until this drug (the combination of DTG + 3TC) becomes available from your pharmacist, or the drug no longer works for you, or ViiV Healthcare/GSK are no longer developing the DTG + 3TC combination medicine.