A single pill taken once a week kept HIV suppressed as effectively as the daily regimen that is currently the global standard, according to phase 3 results published in the New England Journal of Medicine.
The trial tested a combination tablet of islatravir 2 mg and lenacapavir 300 mg in adults whose virus had already been suppressed for at least six months on daily therapy. At 48 weeks, the phase 3 ISLEND-1 results met the primary endpoint of noninferiority against once-daily bictegravir, emtricitabine and tenofovir alafenamide.
For people living with HIV, the endpoint being measured is the one that matters most. Sustained viral suppression protects the individual's immune system and, when maintained, means the virus is not sexually transmitted to partners. A regimen that holds suppression while requiring 52 doses a year instead of 365 changes the daily texture of living with the condition without changing the biological goal.
Endpoint That Matters in HIV Care
Noninferiority is a specific claim and worth understanding precisely. The trial did not attempt to show the weekly pill works better. It tested whether it works close enough to the daily standard to be considered an acceptable alternative, using a prespecified margin of 4 percentage points.
The measure was the percentage of participants with an HIV-1 RNA level of 50 copies per milliliter or higher at week 48, assessed by the FDA-defined snapshot algorithm. That threshold is the standard definition of losing suppression.
The results were tight. None of the participants who switched to the weekly regimen reached the 50-copy threshold, compared with 0.3 percent of those who stayed on daily therapy, a single person. Both ISLEND trials met the primary endpoint, and the manufacturers reported no new safety concerns.
CD4 counts are the other number worth watching here, because earlier, higher doses of islatravir had been associated with declines in CD4 cells and lymphocytes. In this trial, the mean change at week 48 was a drop of 10 cells per microliter on the weekly regimen and 18 on daily therapy, a difference that favored neither group meaningfully.
Trial Design and the Population Studied
ISLEND-1 was a phase 3, double-blind, randomized, active-controlled noninferiority trial conducted across 12 countries, enrolling 607 adults. A total of 304 were assigned to switch to the weekly regimen and 303 to continue daily therapy for 96 weeks, with each group receiving a matched placebo for the alternative regimen. The 48-week data represent the halfway point.
The enrolled population was more diverse than many HIV trials: 21 percent of participants were women, 31 percent were Black, 26 percent were Hispanic or Latine, and 15 percent were 65 or older.
A companion trial, ISLEND-2, enrolled adults switching from a range of standard daily regimens rather than one specific comparator, and reached the same noninferiority conclusion at week 48. One design difference matters when weighing the two: ISLEND-2 was open-label rather than blinded, which makes it the weaker of the pair.
The enrolled population also defines the limits of the finding. Everyone was already virologically suppressed for at least six months. Nobody was starting treatment for the first time, and nobody had uncontrolled virus. These results describe switching, not initiating, and they say nothing about people whose HIV is not yet suppressed.
Both trials were funded by Gilead Sciences and Merck, the companies developing the two components. That funding does not invalidate a double-blind randomized design with a prespecified endpoint, but readers deserve to know it.
Safety Signals and Open Questions
Serious adverse events were slightly more common in the weekly group, occurring in 16 participants, or 5.3 percent, compared with 14 participants, or 4.6 percent, on daily therapy. Six participants in the weekly group, 2.0 percent, and five in the daily group, 1.7 percent, discontinued because of adverse events.
Those differences are small and, in a trial of this size, not obviously meaningful in either direction. The manufacturers say the safety profile was generally similar to the comparator regimens and that no new safety concerns emerged.
The unresolved questions are about time and real-world use. Forty-eight weeks is half of the planned follow-up. Longer data will address whether suppression holds and whether resistance emerges. A weekly schedule also introduces a different adherence problem: a missed daily dose is a small gap, while a missed weekly dose is a larger one, and how that plays out outside a trial with study visits and reminders is unknown.
Distance Between a Trial Result and a Prescription
This regimen is not approved and cannot be prescribed. Gilead and Merck have said the data will form the basis of regulatory submissions, which means review has not concluded and no availability date exists. Detailed results were presented at the International AIDS Conference in Rio de Janeiro.
Nobody currently on antiretroviral therapy should change, pause or delay treatment in anticipation. Interrupting a suppressive regimen risks viral rebound and resistance, and any switch belongs in a conversation with an HIV clinician who can weigh resistance history, kidney and bone health, other medications and pregnancy plans.
Investigators framed the appeal in terms of choice rather than superiority. Jürgen Rockstroh of University Hospital Bonn was first author, and Chloe Orkin of Queen Mary University of London was senior author. The case they and others have made is that daily dosing remains a barrier for some patients and that a longer interval without injections would widen the menu.
People for whom this would matter most are those managing pill fatigue after years of daily dosing, people whose privacy is compromised by a daily bottle, and those who want a longer interval without injections. Anyone in that position can raise it now with a clinician so the conversation is already underway if approval comes.
The bottom line: the newest confirmed finding is that a once-weekly pill matched daily therapy on viral suppression at 48 weeks in already-suppressed adults; the drug is not approved, and no one should alter current treatment.
Frequently Asked Questions
What did the trial show? A once-weekly tablet combining islatravir and lenacapavir was noninferior to a once-daily standard regimen for maintaining HIV viral suppression at 48 weeks.
What does noninferior mean? It means the weekly pill performed closely enough to the daily standard to be considered an acceptable alternative, within a prespecified margin of 4 percentage points. It does not mean it works better.
Who was studied? 607 adults across 12 countries whose HIV had been virologically suppressed for at least six months on daily therapy. The trial tested switching, not starting treatment.
Is it available now? No. The manufacturers say the data will support regulatory submissions. It has not been approved and cannot be prescribed.
Were there safety problems? Serious adverse events occurred in 5.3 percent of the weekly group and 4.6 percent of the daily group. Discontinuations for adverse events were 2.0 percent and 1.7 percent. The companies reported no new safety concerns.
What about CD4 counts? Mean CD4 change at week 48 was a decline of 10 cells per microliter on the weekly regimen and 18 cells per microliter on daily therapy, with no meaningful difference between groups.
Should anyone change their current regimen? No. Interrupting suppressive therapy risks rebound and resistance. Any change should be planned with an HIV clinician.
