Assembly Biosciences presents interim Phase 1b data for ABI-5366

Assembly Biosciences (ASMB) announced that interim Phase 1b clinical data for its long-acting herpes simplex virus helicase-primase inhibitor candidate ABI-5366 are featured in a late-breaking oral presentation during the 38th Congress of the International Union Against Sexually Transmitted Infections- Europe, taking place October 9-11, 2025, in Athens, Greece. The late-breaking oral presentation titled “Safety, pharmacokinetics and antiviral activity of ABI-5366, a novel, oral, long-acting HSV helicase-primase inhibitor in subjects with recurrent genital herpes: interim data from a phase 1b study” highlights positive interim data from the first two cohorts of participants with recurrent genital herpes. In the 350 mg weekly dosing cohort, statistically significant reductions were observed compared to placebo for HSV type 2 shedding rate, which decreased by 94%, high viral load shedding rate, which decreased by 98%, and genital lesion rate, which decreased by 94%. The observed pharmacokinetic profile continues to support weekly and potentially monthly dosing of ABI-5366. A monthly oral dosing regimen of ABI-5366 is currently being evaluated in the ongoing Phase 1b study. In addition, a Phase 1b study evaluating weekly dosing of ABI-1179, another long-acting HSV helicase-primase inhibitor candidate, is being conducted concurrently. Assembly Bio anticipates sharing interim data from both studies later this fall and expects to initiate Phase 2 clinical studies of ABI-5366 in mid-2026.