Merck announced that its once‑daily, oral, two‑drug single‑tablet regimen of doravirine and islatravir (DOR/ISL) achieved the primary efficacy endpoint in a pivotal Phase 3 trial of treatment‑naïve adults with HIV‑1 infection. The study, enrolling 537 participants, demonstrated non‑inferiority to the standard of care bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF), with 88.5 % of DOR/ISL patients and 88.9 % of BIC/FTC/TAF patients achieving viral suppression (<50 copies/mL) at week 48.
Safety data mirrored the efficacy profile. The primary safety objective was met, with rates of grade 3 or higher adverse events comparable between the two arms (4.2 % vs 4.5 %). The most common adverse events were mild gastrointestinal symptoms and headache, and no new safety signals emerged. These findings address earlier concerns about islatravir’s lymphocyte count effects, which were mitigated by the lower dose used in the combination.
The U.S. Food and Drug Administration accepted Merck’s New Drug Application for DOR/ISL, setting a target action date of April 28, 2026. Acceptance signals that the agency has confidence in the data set and is moving toward potential approval, positioning Merck to launch a new oral HIV treatment within the next few years.
Merck’s senior vice president and chief medical officer, Dr. Eliav Barr, said the results “confirm that a two‑drug regimen without an integrase inhibitor can match the efficacy and safety of a three‑drug INSTI‑based therapy in treatment‑naïve patients.” He added that the simplified regimen could improve adherence and reduce pill burden for patients, potentially expanding the market share in the competitive HIV treatment landscape.
Analysts noted that the positive data could strengthen Merck’s HIV portfolio, which already includes the once‑weekly oral regimen MK‑8591A‑053 and a once‑monthly oral PrEP candidate. While the company’s stock experienced modest downward pressure on the day of the announcement, the market reaction was tempered by broader sector volatility rather than concerns about the data itself.
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