Assembly Biosciences Reports Positive Interim Results from Phase 1b Clinical Studies of Long-Acting Helicase-Primase Inhibitor Candidates ABI-1179 and ABI-5366 Showing Reductions in Viral Shedding Rate and Virologically Confirmed Genital Lesion Rate i...

Assembly Biosciences Reports Positive Interim Results from Phase 1b Clinical Studies of Long-Acting Helicase-Primase Inhibitor Candidates ABI-1179 and ABI-5366 Showing Reductions in Viral Shedding Rate and Virologically Confirmed Genital Lesion Rate in Recurrent Genital Herpes

– 98% reduction in HSV-2 shedding rate, >99% reduction in high viral load shedding rate and 91% reduction in virologically confirmed genital lesion rate observed in 50 mg weekly oral dose of ABI-1179, exceeding expectations for the study –

– 76% reduction in HSV-2 shedding rate, 81% reduction in high viral load shedding rate and 88% reduction in virologically confirmed genital lesion rate observed in proof-of-concept test of monthly oral dose of ABI-5366 –

– Company to hold conference call today at 6 p.m. ET –

SOUTH SAN FRANCISCO, Calif., Dec. 08, 2025 (GLOBE NEWSWIRE) -- Assembly Biosciences, Inc. (Nasdaq: ASMB), a biotechnology company developing innovative therapeutics targeting serious viral diseases, today announced positive interim results from two Phase 1b studies of its investigational long-acting herpes simplex virus (HSV) helicase-primase inhibitors in participants seropositive for HSV type 2 (HSV-2) with recurrent genital herpes. These interim results include the first reported Phase 1b data for ABI-1179, evaluating weekly oral dosing. For ABI-5366, the reported data is for a monthly oral dosing regimen, following the positive interim results for weekly oral dosing reported earlier this year.

“As we saw with ABI-5366, weekly oral dosing of ABI-1179 outperformed our expectations for antiviral efficacy and improvement in clinical outcomes, and we are thrilled with these Phase 1b findings for both highly promising candidates,” said Anuj Gaggar, MD, PhD, chief medical officer of Assembly Bio. “The ABI-5366 monthly oral dosing results are also encouraging and show significant reductions in viral shedding and virologically confirmed genital lesion rate, supporting the continued optimization of exposure to evaluate its potential for monthly oral dosing. We expect to pursue such optimization efforts in parallel with moving once-weekly ABI-5366 regimens into longer-duration Phase 2 clinical studies, which we plan to initiate in mid-2026. In parallel, we are evaluating the potential to also advance ABI-1179 into Phase 2 clinical evaluation and are progressing Phase 2 enabling activities for this candidate.”

In the ABI-1179 study, highly potent antiviral activity was observed with a 98% reduction in HSV-2 shedding rate compared to placebo (p