Switch to fixed-dose doravirine (100 mg) and islatravir (0·25 mg) once daily in virologically suppressed adults with HIV-1 on oral antiretroviral therapy: 48-week results of a phase 3, multicentre, randomised, open-label, non-inferiority trial

Abstract

Background: Doravirine and islatravir is an investigational, once-daily, single-tablet regimen containing two potent antiretrovirals with complementary mechanisms of action and resistance profiles. We aimed to evaluate the efficacy and safety of switching from stable, oral antiretroviral therapy (ART) to the fixed combination of doravirine (100 mg) and islatravir (0·25 mg) in virologically suppressed adults living with HIV-1.

Methods: This phase 3, randomised, active-controlled, open-label, non-inferiority trial was conducted at 53 research, community, and hospital-based clinics in eight countries: Australia, Canada, Colombia, Japan, South Africa, Switzerland, the UK, and the USA. Adults (aged ≥18 years) with a viral load of fewer than 50 copies of HIV-1 RNA per mL on any oral, two-drug or three-drug ART regimen for at least 3 months, with no history of treatment failure, known resistance to doravirine, or active hepatitis B infection, were randomly assigned (2:1) according to a computer-generated randomisation schedule (block size three) to receive oral doravirine (100 mg) and islatravir (0·25 mg) once daily or to continue baseline ART for 48 weeks. Randomisation was stratified by the anchor antiretroviral drug class (integrase strand-transfer inhibitor [INSTI], non-nucleoside reverse transcriptase inhibitor, or protease inhibitor) in the baseline regimen. The primary endpoint (assessed in all treated participants) was the percentage of participants with a viral load of 50 copies per mL or higher at week 48 (analysed according to the US Food and Drug Administration snapshot approach); non-inferiority would be concluded if the upper bound of the multiplicity-adjusted 95% CI for the treatment difference was less than 4%. The safety analysis population included all randomly assigned participants who received at least one dose of study treatment. The trial is registered at ClinicalTrials.gov, NCT05631093, and is ongoing but closed to enrolment.

Findings: Between Feb 20 and Oct 24, 2023, 614 individuals were screened for eligibility, of whom 553 were randomly assigned to receive doravirine and islatravir (n=368) or baseline ART (n=185). 551 participants received at least one dose of allocated medication: 366 in the doravirine and islatravir group and 185 in the baseline ART group. Of these 551 participants, 332 (60%) were assigned male and 219 (40%) were assigned female at birth, and the median age was 51 years (IQR 41-59); 250 (45%) identified as Black or African American and 80 (15%) identified as Hispanic, Latino, or Latina. Doravirine and islatravir showed non-inferiority at week 48, with viral loads of 50 copies per mL or higher in five (1·4%) of 366 participants versus nine (4·9%) of 185 participants on baseline ART (difference -3·6% [multiplicity-adjusted 95% CI -7·8 to -0·8]). Treatment-related adverse events were more common with doravirine and islatravir (44 [12·0%] of 366 participants) than with baseline ART (nine [4·9%] of 185 participants; difference 7·2 [95% CI 2·2 to 11·6]). Rates were similar in the doravirine and islatravir group and the baseline ART group for any adverse event (79·5% [291 of 366 participants] vs 83·8% [155 of 185 participants]; difference -4·3 [-10·7 to 2·8]), serious adverse events (6·3% [23] vs 4·9% [nine]; 1·4 [-3·2 to 5·2]), and discontinuation due to adverse events (0·5% [two] vs 2·2% [four]; -1·6 [-4·9 to 0·2]). One death occurred (in the baseline ART group) and was not considered treatment-related. No participants discontinued treatment as a result of protocol-specified declines in CD4 cell or total lymphocyte counts.

Interpretation: Doravirine and islatravir is efficacious and well tolerated and would represent the first non-INSTI-based, two-drug regimen for HIV-1 treatment. With increasing concern over the potential development of widespread INSTI resistance, this once-daily, oral, single-tablet regimen could be a potential option for people living with HIV-1 requiring a change to their antiretroviral regimen. The safety and efficacy findings support the ongoing development of islatravir, a drug with long-acting potential.

Funding: Merck Sharp & Dohme, a subsidiary of Merck & Co.