Gilead and Merck said their once-weekly pill to treat HIV resulted in a comparable level of viral suppression compared to a daily regimen in a 48-week study.
In a rare partnership between large pharmas, the companies are now starting two Phase 3 studies for the weekly pill, which is a combination of Merck’s islatravir and Gilead’s lenacapavir, which is marketed as Sunlenca for certain patients with HIV.
The currently available pills have to be taken every day, but Gilead and Merck hope their experimental drug can provide a long-acting oral option for people with HIV. There is one complete long-acting option on the US market in ViiV’s Cabenuva, which is a once-monthly or every-other-month shot.
Jared Baeten“The treatment options that exist — for some people — are not completely workable in people’s lives,” Jared Baeten, Gilead’s virology therapeutic area head, said in an interview with Endpoints News before the data were released. “And that is, in spite of, for the rest of individuals, the once-a-day therapy is particularly well-tolerated.”
In the Phase 2 open-label study, 104 adults on Gilead’s Biktarvy were randomized to receive either Merck and Gilead’s experimental treatment regimen or continue Biktarvy, which is a daily pill combining three HIV medications. At 48 weeks, those who received the experimental combo saw 94.2% HIV suppression, while those who continued on Biktarvy saw 92.3% HIV suppression. No participants at week 48 had a viral load of 50 copies/mL or more, which is often used as a threshold for viral load on HIV tests.
The drugs provide two different mechanisms to stop the virus from making more copies of itself. Lenacapavir tackles the virus’ protective shell, while islatravir inhibits the reverse transcriptase, which is needed for the virus to replicate.
The data build on primary 24-week results that were presented earlier this year and set up the companies to move the combo into pivotal trials. One of the Phase 3 studies, like the Phase 2 trial, will be open-label, while the other will be blinded.
“We’ve talked to patients, providers and prescribers, government — people tell us that some people would want a longer-acting pill, so a pill you take less often,” Baeten said, “and some people would want an injection. And actually, when we really break down our market research, it’s about 50/50.”
A key data point from the Phase 2 study showed that there were no differences in immune cell count changes between the Biktarvy and experimental groups. In 2021, Merck paused development of islatravir after it led to a drop in counts of lymphocytes and CD4+ T cells in a different mid-stage study.
Then, in 2022, the pharma company restarted development using a lower dose of islatravir in its combination studies, including this Phase 2 trial, though it stopped work on a once-monthly oral version for HIV prevention.
Lenacapavir is approved as Sunlenca for use in combination with other antiretroviral drugs to treat people with multidrug resistant HIV infection. Gilead is also planning to seek approval for a six-month injection of lenacapavir for HIV prevention after presenting compelling results from two Phase 3 studies. They plan to begin regulatory filings at the end of this year.