Weekly Herpes Pill Update: Gilead Takes Over, GS-1179 Heads to Phase 2

A once-a-week pill for genital herpes is now in the hands of Gilead Sciences, the company behind most of the world's HIV drugs. Gilead licensed the program from Assembly Biosciences in December 2025 and, in August 2026, picked one of the two candidates, GS-1179 (formerly ABI-1179), to move into a Phase 2 trial expected to start by the end of 2026.

No weekly pill is available yet. If Phase 2 and a later Phase 3 both succeed, a realistic approval date is several years away, likely around 2030 at the earliest.

Both drugs are helicase-primase inhibitors. They block the enzyme the herpes virus uses to unwind and copy its DNA, which is a different target from acyclovir and valacyclovir. That matters for people whose outbreaks don't respond well to current drugs, and for anyone tired of taking a pill every day.

The first trial cut viral shedding by 94% on a weekly dose

The original news came on August 8, 2025, when Assembly released interim Phase 1b results for ABI-5366 in people with recurrent HSV-2. Over a 29-day study, a 350 mg weekly oral dose produced:

• a 94% reduction in viral shedding compared with placebo
• a 98% reduction in high viral load shedding, the kind most linked to transmission
• a 94% reduction in genital lesion rate

Viral shedding is the main way herpes passes to partners, often when there are no symptoms. A drug that suppresses it this strongly could lower transmission risk as well as outbreaks.

Current suppressive therapy with valacyclovir (Valtrex) reduces shedding by roughly 70% and has to be taken every day. ABI-5366 stays in the body long enough to support weekly dosing, and the study also tested a once-monthly regimen.

The second candidate, ABI-1179, did even better at a lower dose

In December 2025 Assembly reported Phase 1b data for its second drug, ABI-1179, alongside updated ABI-5366 results. At just 50 mg once a week, ABI-1179 showed:

• a 98% reduction in HSV-2 shedding versus placebo
• more than a 99% reduction in high viral load shedding
• a 91% reduction in virologically confirmed genital lesions

At 350 mg weekly, ABI-1179 cut shedding by 94% and confirmed lesions by 97%.

A lower effective dose usually means a smaller pill, lower manufacturing cost and fewer side effects. That is likely why Gilead chose ABI-1179, now renamed GS-1179, as the candidate to take forward.

Gilead now controls development and the Phase 2 timeline

Gilead paid Assembly $35 million to exercise its option in December 2025 and took over sole responsibility for clinical development and commercialization of both drugs. Assembly can earn up to $330 million in milestones plus royalties, and had the right to share 40% of US costs and profits.

In its August 13, 2026 update, Assembly confirmed that GS-1179 was selected to advance, with a Phase 2 trial in people with recurrent genital herpes expected to begin by year-end 2026. ABI-5366 was not mentioned as moving forward.

This is a typical path for a large drug company. Phase 2 will test the drug in a few hundred people over months rather than weeks, which is where most candidates either confirm their promise or stall.

Early results come with real limits

The Phase 1b studies were small and ran for only 29 days. They can show that a drug suppresses the virus, but not whether it stays safe over years of use, whether resistance develops, or how well it prevents transmission between partners.

Helicase-primase inhibitors are not new. Pritelivir, from AiCuris, belongs to the same class and is the furthest along: the FDA granted it priority review in 2026 for herpes that no longer responds to standard drugs, with a decision due in late 2026. Amenamevir is already approved in Japan for shingles and cold sores. These drugs show the class works in people, which raises confidence in GS-1179.

None of these drugs cures herpes. They stop the virus from replicating, but the latent virus in nerve cells stays in place.

What to do while you wait

If you have frequent outbreaks today, daily suppressive therapy with valacyclovir, acyclovir or famciclovir is still the standard and works well for most people. Ask your doctor about it, especially if you have a partner who is HSV-negative.

Clinical trials for GS-1179 will be listed on ClinicalTrials.gov once Phase 2 opens. Search for "GS-1179" or "recurrent genital herpes" to check whether a site near you is recruiting.

For the wider picture of what is in development, see our herpes cure research tracker and our page on pritelivir.