Assembly Biosciences, Inc., a biotechnology company developing innovative therapeutics targeting serious viral diseases,  announced data from its herpes simplex virus (HSV) program featured in three poster presentations at the 2025 Congress of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) taking place in Vienna, Austria, on April 11-15, 2025.

“We are encouraged by the data shared from our clinical and preclinical studies of ABI-5366, supporting its potential to be a once-weekly or once-monthly oral treatment option for those with recurrent genital herpes, an underserved disease space,” said Anuj Gaggar, MD, PhD, chief medical officer of Assembly Bio. “Importantly, our analysis of genital herpes prevalence and treatment patterns further underscores the substantial burden of genital herpes in the United States and wide variability in antiviral treatment patterns. This guides our efforts to improve therapeutic options in a field that has seen little innovation for decades.”

ABI-5366: a Long-Acting Helicase-Primase Inhibitor Candidate for Recurrent Genital Herpes
The ePoster entitled “The safety and pharmacokinetics of ABI-5366, a novel, oral, long-acting HSV helicase-primase inhibitor: Interim results from a Phase 1a/1b study in healthy participants” showcases clinical data from a single-dose Phase 1a evaluation of safety and pharmacokinetics (PK) of ABI-5366 in healthy participants. Results demonstrate that ABI-5366 was well tolerated when administered orally up to 350 mg with no Grade 3 or 4 treatment-related laboratory abnormalities or serious adverse events (AEs) reported. Further, an observed half-life of approximately 20 days across all dosing cohorts supports the potential for once-weekly or once-monthly oral administration.

Additionally, the poster entitled “Preclinical profile of ABI-5366, a novel potent HSV helicase-primase inhibitor, with potential for weekly or monthly oral dosing for the treatment of recurrent genital herpes” highlights results from preclinical studies of ABI-5366, in which broad activity against both HSV type 1 (HSV-1) and HSV type 2 (HSV-2) clinical isolates was observed. Preclinical data also reinforce a PK profile supportive of the potential for once-weekly or once-monthly oral dosing and demonstrate distribution of ABI-5366 to tissues relevant to HSV infection.

ABI-5366 is being evaluated in the Phase 1b portion of an ongoing Phase 1a/b study in participants with recurrent genital herpes. Assembly Bio expects to report interim Phase 1b data for both ABI-5366 and ABI-1179, a second long-acting helicase-primase inhibitor candidate, in fall 2025.