Bictegravir versus Dolutegravir: Phase 2 Results of New Integrase Inhibitor

Bictegravir (formerly GS-9883) is a once-daily integrase inhibitor (INI) that has in vitro activity against many INI-resistant viruses and a plasma half-life of 18 hours. Bictegravir does not require boosting or to be taken with food.

The top-line results were presented at a press conference before the full data presentations.1 More detailed results are due to be presented tomorrow by Paul Sax from Brigham and Women's Hospital in Boston, after which this report will be updated accordingly.2

This was a phase 2 randomised double-blind, placebo controlled, double blind, 48-week study. The study randomised 98 treatment naive participants 2:1 to either bictegravir 75 mg (n=75) or dolutegravir 50 mg (n=33), both taken once daily with FTC/TAF as background NRTIs. This was a non-inferiority study with the primary endpoint of viral suppression at week 24 and secondary efficacy and safety endpoints at week 48.

Limited baseline characteristics included that this was a largely male study, with further details expected tomorrow.

At week 24, viral suppression to <50 copies/mL was achieved by 97% vs 94% in the bictegravir vs dolutegravir groups respectively (95% CI: -8.5% to +14.2%, p=0.50).

For the secondary endpoint at week 48, these rate were 97% vs 91% (95%CI: -6.0% to 18.8%, p=0.17), with no statistical difference between groups. No patients discontinued to lack of viral efficacy and only one person in each arm discontinuing for other reasons, while viral load was above 50 copies/mL.

Tolerability in both groups was also good with no discontinuations due to treatment-related side effects or deaths -- and no significant other differences between groups -- though the study number were small.

The most common side events were diarrhoea (12% in each group) and nausea (8% vs 12%). One participant in the bictegravir group discontinued due to urticaria (hives) after week 24.


These early results show the potential for bictegravir to be an important ARV and several phase 3 studies are already underway using a fixed dose combination coformulated with FTC/TAF.


  1. Press conference. Discussion of oral abstract session 4 -- New drugs, formulations, combinations and resistance. (Webcast)
  2. Sax PE et al. Randomized trial of bictegravir or dolutegravir with FTC/TAF for initial HIV therapy. Oral abstract 41.