GS-1179

GS-1179, formerly ABI-1179, is an experimental long-acting oral antiviral for recurrent genital herpes. In a small Phase 1b analysis, weekly doses were associated with much less HSV-2 shedding than placebo during a short swabbing period.

Gilead selected GS-1179 to advance from a two-candidate helicase-primase inhibitor program and expected to start Phase 2 by the end of 2026. As of September 1, 2026, the Phase 1 study was complete, but no registered or initiated Phase 2 study had been identified.

GS-1179 blocks the HSV helicase-primase complex, which the virus uses during replication. Its pharmacokinetic profile is being developed around oral dosing once a week rather than the daily dosing used for existing suppressive antivirals.

The candidate came from Gilead and was contributed to the company's 2023 collaboration with Assembly Biosciences. Assembly ran the first human study under the name ABI-1179. After Gilead exercised its option, the candidate became GS-1179 and Gilead took control of further development.

The first study tested single doses in healthy adults and weekly doses in adults with recurrent genital HSV-2. It measured safety, drug exposure, HSV-2 shedding from twice-daily genital swabs, and several lesion outcomes.

NCT06698575 began in December 2024, enrolled 103 people across its Phase 1a and Phase 1b parts, and completed in January 2026. The detailed public antiviral analysis covers two Phase 1b cohorts rather than all 103 participants.

In that analysis, 20 participants received 20 mg once weekly, 20 received 50 mg once weekly, and nine evaluable participants received pooled placebo. Swabs and symptom reports were collected twice daily from day 8 through day 35.

HSV-2 was detected on 16.9% of assessed swabs in the placebo group, 1.4% in the 20 mg group, and 0.4% in the 50 mg group. The reported relative reductions versus placebo were 92% and 98%, with p<0.01 for both weekly doses.

Overall genital-lesion rates were numerically lower with both doses, but those comparisons had p values of 0.06 and 0.09. A narrower measure counting lesions with HSV-2 detected showed larger reported reductions, including 91% at 50 mg. Keeping those two lesion measures separate matters.

The poster reported no serious adverse events or adverse-event-related discontinuations in the disclosed analysis. This was a small, short Phase 1 study and cannot establish long-term safety or tolerability.

The most defensible evidence-maturity label is early human evidence. The controlled shedding result is a meaningful signal that the drug affected HSV-2 replication, but the small cohorts and short study do not establish durable recurrence control, long-term weekly use, or prevention of transmission.

GS-1179 suppresses viral replication. The checked evidence does not show removal of latent HSV or a cure.

Gilead has the exclusive license and controls further development. Its June 2026 plan selected GS-1179 for Phase 2 and said it did not intend to advance GS-5366 further at that time. That is a current portfolio decision, not proof that GS-5366 permanently failed.

The reported next step was a Phase 2 study in recurrent genital herpes expected to begin by the end of 2026. The timing was forward-looking, and the study had not been verified as started as of September 1, 2026.