Assembly Biosciences, Inc. (ASMB) has announced positive interim results from two phase 1b clinical studies of its experimental oral drugs, ABI-1179 and ABI-5366, in recurrent genital herpes.
ABI-5366 and ABI-1179 are two potent, long-acting helicase primase inhibitors for the treatment of recurrent genital herpes, a serious condition that leads to painful genital sores, emotional and social challenges, and raises the risk of HIV infection. Epidemiologic data suggest that more than four million people across the U.S., France, Germany, Italy, Spain, and the U.K. live with recurrent genital herpes.
The interim findings announced yesterday are the first Phase 1b data for ABI-1179, evaluating weekly oral dosing. For ABI-5366, the reported data reflect a monthly oral dosing regimen, following the positive interim results for weekly oral dosing reported earlier this year.
ABI-1179-101 and Key Findings
ABI-1179 is under a Phase 1a/b clinical study in healthy subjects and in subjects who are seropositive for herpes simplex virus type 2 with recurrent genital herpes, dubbed ABI-1179-101.
Positive interim data have been previously reported for Phase 1a, which evaluated the safety, tolerability and pharmacokinetics of ABI-1179 following single dose administration in healthy participants.
The Phase 1b interim analysis included data from cohort B1 (50 mg weekly oral dose) and cohort B2 (20 mg weekly oral dose) of ABI-1179 in subjects seropositive for HSV-2 with recurrent genital herpes, through the data cutoff date of November 25, 2025.
According to the findings, highly potent antiviral activity was observed, with a 98% reduction in the HSV-2 shedding rate compared with placebo over the 29-day evaluation period in the 50 mg weekly-dose cohort. This reduction exceeds Assembly Bio's mark for the study of an 80%-85% reduction in HSV-2 shedding rate. Further, data revealed a 91% reduction in virologically confirmed genital lesion rate compared to placebo with the 50 mg weekly dose.
ABI-1179 was observed to be well-tolerated, and the pharmacokinetic profile supported once-weekly oral dosing across the 50 mg and 20 mg cohorts.
ABI-5366-101 and Key Findings
ABI-5366 is under a phase 1a/1b trial in healthy subjects and in subjects who are seropositive for herpes simplex virus type 2 with recurrent genital herpes, dubbed ABI-5366-101.
Positive interim data have been previously reported for the Phase 1a part of the trial, which evaluated the safety, tolerability and pharmacokinetics of ABI-5366 following single dose administration in healthy participants.
The Phase 1b interim monthly dosing cohort analysis, reported yesterday, includes data from cohort B3, evaluating five loading doses of 350 mg given over seven days (the monthly cohort) in participants seropositive for HSV-2 with recurrent genital herpes, through the data cutoff date of November 25, 2025.
In the ABI-5366 monthly dose cohort, potent antiviral activity was observed, with a 76% reduction in HSV-2 shedding rate compared to placebo over the 29-day evaluation period. An 88% reduction in virologically confirmed genital lesion rate, along with an 81% reduction in the number of samples with high viral load compared to placebo, was observed.
Earlier, for the 350 mg weekly dose cohort, a 94% reduction in HSV-2 shedding rate and a 97% reduction in virologically confirmed genital lesion rate compared to placebo were observed.
ABI-5366 remained well tolerated across all evaluated oral dosing regimens up to 350 mg weekly, and the PK profile supports both once-weekly and potentially once-monthly dosing regimens.
In parallel, the company plans to start Phase 2 clinical trials of ABI 5366 (a once-weekly regimen) around mid-2026.
ASMB closed Monday's trade at $35.38, up 1.06% In premarket trading, ASMB is up 3.17% at $36.50.
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