At the 2017 Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle, 48-week results from a somewhat small Phase 2 study in people new to treatment showed that the Gilead Science’s experimental integrase inhibitor bictegravir suppressed HIV levels as well as ViiV’s integrase inhibitor dolutegravir (Tivicay). Unlike Gilead’s current integrase inhibitor, elvitegravir, bictegravir does not need to be boosted with cobicistat.
The study enrolled 98 previously untreated people, with twice as many taking bictegravir as dolutegravir (65 vs. 33). Everyone also took emtricitabine + tenofovir (Truvada) with or without food. Average viral load was around 30,000, with 15% and 21% of the bictegravir and dolutegravir starting with viral loads above 100,000 respectively. The average CD4 count was roughly 450 for both groups. Nearly all participants were male, and roughly 40% were non-white in both arms. No one with hepatitis B or C was enrolled.
At week 24, 97% of those on bictegravir had suppressed HIV below 50 copies compared to 94% of those on dolutegravir. By week 48, 97% and 91% were suppressed. Though the percentage of participants with full suppression on bictegravir was numerically higher, the difference was not statistically significant. As for changes in CD4 counts, those who took bictegravir saw an average increase of 258 cells compared to 192 for those on dolutegravir — this was also not statistically significant, despite the large numerical difference.
No integrase inhibitor or NRTI mutations developed in either group.
Both regimens were safe and well tolerated and no serious side effects were seen. Diarrhea and nausea were the most reported mild side effects across both groups (8–12%). Lab abnormalities were similar as well between the groups and occurred in fewer than 10% of the participants. Additionally, decreasing levels in eGFR (a measure of liver health) were similar with -7.0 mL/min in those on bictegravir vs. -11.3 mL/min on dolutegravir.
Larger groups of people will need to be compared in further studies to draw stronger conclusions about meaningful differences in viral suppression, CD4 increases or adverse events. Bictegravir + emtricitabine + tenofovir is being studied as a single tablet regimen in two Phase III studies and as separate pills in two other studies.
P Sax, et al. Randomized Trial of Bictegravir or Dolutegravir with FTC/TAF for initial HIV therapy. 2017 CROI, Seattle. Abstract 41.