In the RADIANT-TB randomised controlled trial carried out in Khayelitsha, researchers found that tuberculosis (TB) patients with HIV taking a double dose of dolutegravir had similar viral suppression to those taking a single dose plus placebo. The findings, published in The Lancet HIV, suggest that a only once-daily dolutegravir is feasible in patients with HIV-associated tuberculosis.
WHO’s preferred first-line antiretroviral therapy (ART) regimen for adults and adolescents with HIV is dolutegravir, combined with tenofovir and lamivudine or emtricitabine. A disadvantage of dolutegravir is substantial drug–drug interaction with rifampicin, which is important as tuberculosis is the most common cause of hospitalisation and mortality among people living with HIV.
The drug–drug interaction between rifampicin and dolutegravir can be overcome by supplemental dolutegravir dosing, but is a challenge in resource-constrained settings. The researchers sought to investigate whether virological outcomes with standard-dose dolutegravir-based ART are acceptable in people with HIV on rifampicin-based antituberculosis therapy.
RADIANT-TB was a phase 2b, randomised, double-blind, non-comparative, placebo-controlled trial in Khayelitsha, Cape Town, South Africa. Participants were aged over 18 years, with plasma HIV-1 RNA >1000 copies/mL, CD4 count > 100 cells/μL, ART-naive or first-line ART interrupted, and on rifampicin-based antituberculosis therapy for less than three months. Participants were assigned (1:1) to receive either tenofovir disoproxil fumarate, lamivudine, and dolutegravir plus supplemental 50mg dolutegravir 12h later or the same drugs but with placebo in place of the supplemental dolutegravir. Participants received standard antituberculosis therapy (rifampicin, isoniazid, pyrazinamide, and ethambutol for the first two months followed by isoniazid and rifampicin for four months). The primary outcome was the proportion of participants with virological suppression (HIV-1 RNA <50 copies/mL) at week 24 analysed in the modified intention-to-treat population.
No treatment-related dolutegravir resistance emerged in the trial, and though not significant, an increase in insomnia was noted in the supplemental dolutegravir arm. In terms of future research, it is questionable whether a phase 3 trial would be needed given the significant time required for a policy change. Limitations included the study not being powered to compare efficacy.
The authors concluded, “Our findings suggest that twice-daily dolutegravir dosing might be unnecessary in people with HIV-associated tuberculosis. More evidence, from cohort studies or possibly a phase 3 trial, might be necessary to change policy on the need for a supplemental dolutegravir dose with rifampicin-based antituberculosis therapy.”
