FDA Accepts Merck's Filing for Two-Drug, Once-Daily HIV Pill

Merck MRK announced that the FDA has accepted for review the new drug application (“NDA”) seeking approval for its investigational, once-daily, oral, two-drug, single-tablet regimen of doravirine/islatravir (DOR/ISL) for treating virologically suppressed adults with HIV-1 infection.

With the FDA accepting the NDA for review, a decision from the regulatory body is expected on April 28, 2026.

If approved, DOR/ISL would be the first non-integrase inhibitor-based two-drug regimen to show comparable efficacy and safety to the current three-drug standard, BIC/FTC/TAF, in phase III studies.

The NDA was based on data from two pivotal phase III studies, namely – MK-8591A-051 and MK-8591A-052, which investigated DOR/ISL (100 mg/0.25 mg) in adults with HIV-1 infection who are on different antiretroviral therapy regimens, like baseline antiretroviral therapy and bictegravir/emtricitabine/tenofovir alafenamide.

Data from both studies showed that treatment with DOR/ISL demonstrated non-inferiority versus comparator antiretroviral therapies in adults with virologically suppressed HIV-1.

MRK's Stock Performance

Year to date, shares of Merck have plunged 15.5% against the industry’s rise of 0.2%.

MRK's Ongoing Efforts on the HIV-1 Program

Doravirine, in combination with other antiretrovirals and as a single agent, is approved under the trade name Pifeltro for treating adults with HIV-1 in the United States. It is also approved as a component of a single-tablet regimen under the trade name Delstrigo for treating HIV-1.

Besides MK-8591A-051 and MK-8591A-052 studies, two other ongoing phase III studies are evaluating DOR/ISL for the treatment of HIV-1.

The MK-8591A-053 study is evaluating DOR/ISL in treatment-naïve people with HIV. The MK-8591A-054 study is evaluating open-label DOR/ISL in people who participated in earlier phase III studies on the two-drug, single-tablet regimen of DOR/ISL.

Islatravir, an investigational nucleoside reverse transcriptase translocation inhibitor, is currently being evaluated in multiple studies in combination with other antiretroviral therapies for the treatment of HIV-1.

A phase II study is evaluating islatravir in combination with MRK’s investigational non-nucleoside reverse transcriptase inhibitor ulonivirine (MK-8507) as an oral once-weekly treatment for HIV-1.

Merck, in collaboration with Gilead Sciences GILD, is evaluating the investigational combination of islatravir and the latter’s first-in-class HIV-1 capsid inhibitor, lenacapavir, in a phase II study for the treatment of HIV.

Lenacapavir is approved under the brand name Sunlenca in the United States for treating HIV-1 infection in heavily treatment-experienced adults with multidrug-resistant infections.

The FDA recently approved GILD’s lenacapavir for the prevention of HIV under the brand name Yeztugo, the first and only twice-yearly, pre-exposure prophylaxis (PrEP) to reduce the risk of sexually acquired HIV in adults and adolescents weighing at least 35 kg.

GILD also markets Biktarvy, as a once-a-day single tablet, to treat HIV-1 in adults and children.

MRK's Zacks Rank & Stocks to Consider

Merck currently carries a Zacks Rank #3 (Hold).

Some better-ranked stocks from the biotech sector are Amarin Corporation AMRN and Alkermes ALKS, each sporting a Zacks Rank #1 (Strong Buy). You can see the complete list of today’s Zacks #1 Rank stocks here.

In the past 60 days, Amarin's 2025 loss per share estimates have improved from $3.85 to $2.30. Loss per share estimates for 2026 have narrowed from $3.59 to $1.50 during the same period. AMRN stock has surged 78.6% year to date.

AMRN’s earnings beat estimates in two of the trailing four quarters, met the mark once and missed on the other occasion, delivering an average surprise of 29.11%.

In the past 60 days, estimates for Alkermes’ earnings per share have increased from $1.74 to $1.79 for 2025. During the same time, earnings per share estimates for 2026 have risen from $1.79 to $1.91. Year to date, shares of ALKS have gained 5.9%.

ALKS earnings beat estimates in one of the trailing four quarters, while missing the same on the remaining three occasions, the negative average surprise being 8.24%.

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