Switch to fixed-dose doravirine (100 mg) with islatravir (0·75 mg) once daily in virologically suppressed adults with HIV-1 on antiretroviral therapy: 48-week results of a phase 3, randomised, open-label, non-inferiority trial.

Background: Doravirine and islatravir is an investigational, once-daily, single-tablet regimen with high antiviral potency, favourable safety and tolerability, and low propensity for resistance. We report week 48 results from a phase 3 trial evaluating switch from stable, oral antiretroviral therapy (ART) to the fixed combination of doravirine (100 mg) and islatravir (0·75 mg).

Methods: This phase 3, multicentre, randomised, active-controlled, open-label, non-inferiority trial was conducted at 77 research, community, and hospital-based clinics in 15 countries. Adults aged 18 years or older with fewer than 50 HIV-1 RNA copies per mL on any oral, two-drug or three-drug ART regimen for at least 3 months, and no history of previous virological failure on any past or current regimen were randomly assigned (1:1) by a computer-generated randomisation schedule to switch to doravirine (100 mg) and islatravir (0·75 mg) or to continue their baseline ART regimen. Block randomisation was based on a block size of four, and randomisation was stratified by baseline regimen (ie, protease inhibitor, integrase inhibitor, or other). Participants in the doravirine and islatravir group were instructed to take one tablet at approximately the same time each day, and participants in the baseline ART group continued to take the medication according to the locally approved label. HIV-1 RNA and safety evaluations were done at baseline and weeks 4, 12, 24, 36, and 48. CD4 cell counts were measured at baseline, week 24, and week 48. The primary endpoint was proportion of participants with greater than or equal to 50 HIV-1 RNA copies per mL at week 48 in the full analysis set (ie, all participants who received at least one dose of study drug) using the US Food and Drug Administration snapshot approach and prespecified non-inferiority margin of 4%. This study is registered with ClinicalTrials.gov (NCT04223778) and is completed.

Findings: Between Feb 18 and Oct 2, 2020, 740 individuals were screened for eligibility, of whom 672 (90·8%) participants (249 [37·1%] women and 423 [62·9%] men; median CD4 count of 678 cells per μL [IQR 496-868]) were randomly assigned to doravirine (100 mg) and islatravir (0·75 mg; n=336) or to continue baseline ART (n=336). The last follow-up visit occurred on Sept 8, 2021. At week 48, zero of 336 participants in the doravirine and islatravir group versus five (1·5%) of 336 participants in the baseline ART group had greater than or equal to 50 HIV-1 RNA copies per mL (difference -1·5, 95% CI -3·4 to -0·3). The per-protocol analysis showed consistent results. Headache was the most common adverse event in both groups (35 [10·4%] of 336 participants in the doravirine and islatravir group, 16 [4·8%] of 336 in the baseline ART group), infection rates were similar (113 [33·6%] in both groups), and discontinuations due to adverse events were low (seven [2·1%] vs one [0·3%]). 66 (19·6%) of 336 participants had treatment-related adverse events in the doravirine and islatravir group compared with 30 (8·9%) of 336 in the baseline ART group. In the islatravir and doravirine group, CD4 cell counts (mean change -30·3 cells per μL) and total lymphocyte counts (mean change -0·26 × 10⁹/L) were decreased at 48 weeks.

Interpretation: Switching to single-tablet doravirine (100 mg) and islatravir (0·75 mg) maintained viral suppression up to week 48 and was non-inferior to antiretroviral combinations used in clinical practice for adults with HIV-1; however, decreases in CD4 cell and total lymphocyte counts do not support further development of once-daily doravirine (100 mg) and islatravir (0·75 mg).

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