Standard versus double dose dolutegravir in patients with HIV-associated tuberculosis: a phase 2 non-comparative randomised controlled (RADIANT-TB) trial

Dolutegravir, a second-generation integrase strand transfer inhibitor (InSTI), is replacing efavirenz as first-line antiretroviral therapy (ART) in low middle-income countries (LMICs). Tuberculosis remains the leading cause of HIV-related morbidity and mortality in LMICs. Rifampicin is a key agent in the treatment of tuberculosis but induces genes involved in dolutegravir metabolism and efflux. The resulting drug-drug interaction (DDI) reduces the exposure of dolutegravir. However, this can be overcome by supplying a supplemental dose of 50 mg dolutegravir 12 hours after the standard daily dose, which is difficult to implement in LMICs. Four lines of evidence suggest that the supplemental dose may not be necessary: 1) a phase 2 study showed 10 mg of dolutegravir as effective as 50 mg; 2) the prolonged dissociative half-life of dolutegravir after binding to its receptor; 3) a DDI study reported dolutegravir trough concentrations were maintained above its minimum effective concentration when using 50 mg dolutegravir with rifampicin; and 4) virologic outcomes were similar between standard and double dose of raltegravir (a first-generation InSTI) in participants with HIV-associated tuberculosis treated with rifampicin. We hypothesise that virologic outcomes with standard dose dolutegravir-based ART will be acceptable in patients on rifampicin-based antituberculosis therapy. Here we outline the protocol for a phase 2, non-comparative, randomised, double-blind, placebo-controlled trial of standard versus double dose dolutegravir among adults living with HIV (ART naïve or first-line interrupted) on rifampicin-based antituberculosis therapy. A total of 108 participants will be enrolled from Khayelitsha in Cape Town, South Africa. Follow up will occur over 48 weeks. The primary objective is to assess proportion virological suppression at 24 weeks between groups analysed by modified intention to treat. Participant safety and the emergence of antiretroviral resistance mutations among those with virologic failure will be assessed throughout. Trial registrations: clinicaltrials.gov NCT03851588 (22/02/2019), SANCTR DOH-27-072020-8159 (03/07/2020).