Antiretroviral treatment consisting of integrase strand inhibitors (INSTI) in combination with two nucleoside reverse transcriptase inhibitors (NRTIs) has become the standard of therapy for HIV-1 infected patients (2017 DHHS Guidelines). The development and advancement of such therapy have resulted in improved prognosis, allowing a larger proportion of patients in United States (\> 50%) with HIV-1 infection to be 50 years of age or older, which is defined by the CDC as "older adults". A novel INSTI, bictegravir (BIC), has been recently approved by FDA, available in a fixed dose combination with emtricitabine (FTC) and tenofovir alafenamide (TAF) as a novel single-tablet regimen (STR), BIKTARVY®. Similar to other INSTI, BIC prevents HIV replication by inhibiting HIV integration into the host cell. In vitro studies have shown its selectivity against HIV-1 infected cells with a low cytotoxic profile.

Elvitegravir, boosted with cobicistat, is currently available as part of a single-tablet formulation with FTC and TAF (GenvoyaTM) or with FTC and TDF (StribildTM). Unlike ritonavir, cobicistat has no antiretroviral activity, but has potent inhibitory effects on CYP3A44. Elvitegravir is primarily metabolized by CYP3A4 and its co-administration with cobicistat boosts elvitegravir plasma concentration and prolongs its half-life4. Concurrent use of a potent CYP3A4 inhibitor, e.g., cobicistat, with medications that are metabolized by CYP3A4 can significantly increase the risk of drug-drug interactions. With an increase in the average survivability age of HIV-infected patients, chances of polypharmacy due to multimorbidity, a term used to define the presence of two or more concurrent chronic medical conditions, increases. Two studies have demonstrated that older HIV+ individuals engaged in polypharmacy are more likely to experience potential drug-drug interactions (PDDI). Many chronic medications such as antidepressants, HMG-CoA reductase inhibitors (statins), and cardiovascular medications are metabolized by CYP3A4. Concurrent administration of these medications with GenvoyaTM and StribildTMcan lead to increases in PDDI. Such interactions can result in more adverse drug reactions, drug-related toxicity of narrow therapeutic index drugs, and variations in the efficacy of concurrent medications. However, unlike elvitegravir, BIC does not require a booster such as cobicistat for pharmacokinetic enhancement. Its use can result in reductions in PDDI caused by cobicistat in adults with polypharmacy. This can improve quality of life in general, adherence and can directly avoid DDI-related adverse effects.

Although antiretroviral therapy (ART), when used concurrently with certain medications, has an increased risk of PDDI, studies have suggested a low DDI profile of BIC. In this study, such benefits of bictegravir will be assessed through the evaluation of polypharmacy, PDDI, health-related quality of life, and adherence of HIV-infected subjects.

BIC/FTC/TAF related adverse drug events are possible in the study. Due to BIC's recent FDA approval, a comprehensive list on the possible adverse drug events has become available. Common side effects reported in clinical phase II and phase III studies include diarrhea, nausea, and headache. Serious adverse events, including lactic acidosis, severe hepatomegaly have been reported with nucleoside reverse transcriptase inhibitors, but are uncommon. The standard regimen of BIC/FTC/TAF will be used; if a regimen change occurs, participation in the study will be discontinued. Participants will be carefully screened and those with pre-conditions, such as morbid obesity, hepatitis B virus, hepatitis C virus co-infection will be documented in the study.