Merck’s HIV drug rivals Gilead’s blockbuster in key trial

Merck & Co.’s (MSD) HIV combo (doravirine + islatravir) matched Gilead’s market-leading Biktarvy in a Phase 3 trial, hitting its main goal in treatment-naive patients and showing non-inferiority to Biktarvy at 48 weeks.

Why it matters: This success positions Merck to compete in the $5B+ HIV market, offering an alternative for patients seeking better tolerability, fewer drug interactions, and strategic options for long-term care.

Backstory: Integrase strand transfer inhibitors (INSTIs) like Gilead’s bictegravir (Biktarvy) are the cornerstone of HIV treatment but carry risks of resistance and side effects. Merck has been developing islatravir as a new treatment backbone, particularly for patients switching regimens or those needing simpler, safer options.

Big picture: With potential FDA approval by April 2026 and EU filings ahead, Merck aims to challenge Gilead’s dominance and grab hold of the 20% of HIV patients who change regimens yearly. The company even sees a chance to expand use beyond switching regimens to first-line treatment and weekly dosing regimens, which could reshape HIV therapy.