FDA Approves HIV Tablet with New Molecule Islatravir
The once-daily drug doravirine/islatravir (Merck) received FDA approval for adults with suppressed viral load.
The news of FDA approval for Idvynso (doravirine/islatravir) from Merck is not just an addition to the antiretroviral therapy arsenal. It is a strategic strike delivered precisely at a time of generational shift among HIV patients. I view this FDA decision not as a clinician, but as a market strategy architect, and I see here a multi-layered game by Merck aimed at reshaping a stagnant market.
The Essence: What Is Really Happening
Formally, we have the first complete two-drug regimen without integrase inhibitors (INSTIs) and without tenofovir, proven non-inferior to the "gold standard" Biktarvy. In the double-blind study 052, the rate of virologic failure at 48 weeks was 1% in both groups, and viral load suppression was maintained in 92% of patients on DOR/ISL versus 94% on BIC/FTC/TAF. The numbers are convincing, but they alone do not explain why approval came two weeks before the PDUFA deadline (April 28, 2026), and the drug will be available in pharmacies after May 11. The real essence lies in "defusing" long-term toxicity.
The HIV therapy market has hung for decades on two pillars: tenofovir (nephrotoxicity and bone density loss) and integrase inhibitors (weight gain issues). Idvynso is a response to physicians tired of switching therapy not because of viral load but due to metabolic side effects. Merck has created an "escape therapy" for those who want to move off INSTIs and tenofovir without losing the convenience of a single daily pill.
But the main intrigue is the molecular mechanism of islatravir. It is not just a nucleoside reverse transcriptase inhibitor (NRTI), but the first representative of the NRTTI class — translocation reverse transcriptase inhibitors. The media write about "multiple mechanisms of action" but do not explain the cynical beauty of this molecule. Islatravir causes immediate chain termination and delayed chain termination, meaning it induces structural changes in viral DNA that act like a delayed-action mine. The virus cannot develop resistance through point mutations — the blockade cascade is too complex. This is an evolutionary dead end for HIV.
Timeline and Context
The story of Idvynso is a classic "phoenix rising" narrative. Merck developed islatravir in much higher doses for implants and weekly formulations. In 2021, the FDA paused clinical trials due to unexpected CD4 decline in some patients. Investors wrote off the molecule, and the market cap dropped. However, Merck conducted a brilliant pharmacometric analysis and found that at an ultra-low dose (just 0.25 mg), the immunotoxicity disappears while antiviral activity is fully preserved.
Revival strategy:
- July 2025: FDA accepts the application and sets PDUFA date for April 28, 2026.
- October 2025: Merck publishes data on minimal weight and body composition changes when switching from Biktarvy — a strike at the competitor's most vulnerable point.
- April 20, 2026: FDA approves Idvynso a week ahead of the deadline. The regulator found no issues with efficacy or safety.
- May 11, 2026: Sales begin in the US.
Who Wins and Who Loses
Merck wins. The company gains a platform for an entire family of drugs based on islatravir. Trials are already underway for a combination with ulonivirine (MK-8507) as a weekly pill, as well as with lenacapavir from Gilead for ultra-long-acting therapy. Idvynso is just the first swallow that opens the regulatory path for the entire line.
Aging HIV patients win. Carl Baloney Jr., president of AIDS United, directly stated: people are aging with HIV, accumulating chronic diseases, and are forced to take multiple medications simultaneously. For them, regimens with low potential for drug interactions and metabolic stress are critical.
Gilead Sciences loses. Biktarvy is a blockbuster with annual sales around $10 billion. The direct comparison of Idvynso with Biktarvy in study 052 and the demonstration of non-inferior efficacy is a declaration of war. Merck is entering the territory of the "sacred cow" and promising the same viral suppression quality with lower metabolic risks.
The implicit loser is ViiV Healthcare (GSK). Their drug Dovato (dolutegravir/lamivudine) was the first two-drug regimen, but it contains an INSTI. Now Merck offers a two-drug regimen without any INSTI, making Dovato's positioning as a "simple" regimen vulnerable.
What the Media Are Not Saying
Mainstream coverage focuses on the convenience of a single daily pill and the absence of tenofovir. But no one writes about the pharmacoeconomic time bomb Merck is planting under insurers and government reimbursement programs.
Idvynso is positioned as switch therapy — a drug for replacing the current regimen in patients with already suppressed viral load. It is not a first-line option for treatment-naive patients. The switch market accounts for about 20% of all HIV therapy prescriptions in the US annually. Seemingly a modest niche.
But here the "simplification" factor comes into play. Physicians are increasingly prescribing switches not due to treatment failure but to improve quality of life. Merck is targeting patients tired of rigid regimens or struggling with side effects. And here a conflict arises: insurers (UnitedHealth, Anthem) will resist mass switching to a more expensive drug without virologic reasons. Merck will have to prove pharmacoeconomic benefit through reduced costs for treating kidney failure, osteoporosis, and obesity over 5-10 years.
Non-obvious insight: Merck's real bet is not the current market but the impending collapse of Biktarvy's monopoly. Biktarvy's patent protection expires in the early 2030s. By then, Merck plans to have a ready ecosystem of islatravir: from a daily pill to a long-acting implant. Idvynso is the anchor product that builds physician trust in the platform.
Forecast: Next 30 Days and 90 Days
30 days (by June 13, 2026):
Initial prescriptions will be written in major centers (Boston, San Francisco, New York), where the concentration of patients interested in de-escalating INSTIs is highest. Merck will launch aggressive patient assistance programs to lower access barriers. We will see first physician reports on real-world tolerability outside clinical trials. Merck's stock will get a moderate positive boost, but analysts will await first full-quarter sales data.
90 days (by August 13, 2026):
The key trigger is the publication of 96-week data from the extension phase. At CROI 2026, it was already reported that 96.6% of patients who switched to DOR/ISL maintained suppression at 96 weeks. If these data are formally published in a peer-reviewed journal, it will provide physicians with an evidence base for long-term planning.
Simultaneously, Gilead will ramp up. Expect countermoves: either aggressive marketing of Biktarvy emphasizing longer experience, or acceleration of their own tenofovir-free regimens. Competition will shift to pharmacoeconomics: whose drug is cheaper for the healthcare system over a 10-year horizon.
The main risk for Merck is the emergence of isolated cases of DRESS syndrome or Stevens-Johnson syndrome, which the label already warns about. Any serious skin complication in the post-marketing period will trigger a wave of negative publications and slow adoption. But if the first months go smoothly, Idvynso will carve out a niche as a "clean" therapy for aging patients and become a platform for the next big step — a weekly regimen with lenacapavir. The HIV therapy market is waking up from a long slumber, and Merck has just seized the initiative.
— Editorial Team
