Assembly Biosciences Highlights Presentations on Positive Phase 1b Data for ABI-5366 and ABI-1179 in Recurrent Genital Herpes at ESCMID Global 2026
Rhea-AI Summary
Assembly Bio (Nasdaq: ASMB) announced that positive Phase 1b data for two investigational HSV helicase-primase inhibitors, ABI-5366 and ABI-1179, will be presented at ESCMID Global 2026 in Munich, April 17-21, 2026.
ABI-5366 is selected for an oral presentation (April 20, 2026) and two posters (April 18, 2026). ABI-1179 is a late-breaker poster (April 21, 2026). Posters will be posted on the company website. Both candidates are investigational and exclusively licensed to Gilead for further development.
Positive
- ABI-5366 selected for oral presentation on April 20, 2026
- ABI-1179 accepted as a late-breaker poster on April 21, 2026
- Additional data include results from a monthly dosing cohort
- Company will post posters on investor and pipeline web pages
Negative
- ABI-5366 and ABI-1179 remain investigational; safety and efficacy not established
- Gilead holds sole responsibility for further clinical development and commercialization
News Market Reaction – ASMB
On the day this news was published, ASMB gained 1.70%, reflecting a mild positive market reaction.
Data tracked by StockTitan Argus on the day of publication.
Key Figures
Market Reality Check
Peers on Argus
ASMB gained 2.87% while key biotech peers were mixed: LRMR -3.23%, BNTC -2.3%, RCKT -0.83%, TECX +0.91%, YMAB +0.23%, indicating a stock-specific move rather than a sector-wide trend.
Historical Context
| Date | Event | Sentiment | Move | Catalyst |
|---|---|---|---|---|
| Mar 19 | Year-end earnings | Positive | +3.5% | Reported 2025 results with strong cash position and positive pipeline updates. |
| Dec 22 | Gilead option deal | Positive | +2.6% | Gilead exercised option to license ABI-1179 and ABI-5366, triggering $35M payment. |
| Dec 08 | HSV Phase 1b data | Positive | +0.8% | Positive interim Phase 1b HSV data showing large reductions in shedding and lesions. |
| Nov 10 | Q3 earnings & pipeline | Positive | +3.3% | Q3 2025 results plus positive interim HSV data and HDV program progress. |
| Nov 07 | HBV clinical data | Positive | -0.0% | Positive Phase 1b data for HBV capsid modulator ABI‑4334 at a major liver meeting. |
Positive clinical and collaboration updates have typically seen modestly positive next-day price reactions, with only one recent divergence.
Over the last several months, Assembly Biosciences has delivered multiple positive updates across its antiviral pipeline. On Nov 7, 2025, it reported encouraging Phase 1b data for hepatitis B candidate ABI‑4334. Subsequent HSV-focused readouts on Nov 10 and Dec 8, 2025 highlighted strong Phase 1b efficacy for ABI‑5366 and ABI‑1179. Gilead exercised its option on the helicase‑primase programs on Dec 22, 2025, followed by year-end 2025 financials on Mar 19, 2026. Today’s ESCMID presentations extend this ongoing stream of positive HSV data visibility.
Regulatory & Risk Context
An effective S-3 shelf filed on Mar 19, 2026 registers up to $400,000,000 in securities, including an at-the-market program for up to $100,000,000 of common stock via Jefferies LLC, giving the company significant capacity to raise equity capital.
Market Pulse Summary
This announcement highlights broader scientific visibility for ABI‑5366 and ABI‑1179 through multiple Phase 1b presentations at ESCMID 2026, including a late‑breaker poster emphasizing ABI‑1179’s potential as a long‑acting option for recurrent genital herpes. It builds on earlier positive HSV data and Gilead’s exclusive license for these programs. Investors may watch for detailed efficacy and safety metrics from the presentations, subsequent development plans from Gilead, and how these fit alongside Assembly’s broader antiviral pipeline and capital-raising flexibility under its $400,000,000 shelf.
Key Terms
phase 1b medical
helicase-primase inhibitor medical
oral presentation technical
late-breaker technical
AI-generated analysis. Not financial advice.
– Additional Phase 1b data for ABI-5366, including results from monthly dosing cohort, selected for oral presentation –
– Phase 1b data from ABI-1179 accepted for late-breaker poster presentation –
SOUTH SAN FRANCISCO, Calif., April 09, 2026 (GLOBE NEWSWIRE) -- Assembly Biosciences, Inc. (Nasdaq: ASMB), a biotechnology company developing innovative therapeutics targeting serious viral diseases, today announced Phase 1b clinical data for ABI-5366 and ABI-1179, herpes simplex virus (HSV) helicase-primase inhibitor candidates, will be featured in multiple presentations, including one late-breaker, at the 2026 Congress of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) taking place April 17-21, 2026, in Munich, Germany.
“The selection of ABI-5366 for oral presentation at ESCMID underscores the strength and clinical relevance of the data generated to date, including additional results from the monthly dosing cohort,” said Anuj Gaggar, MD, PhD, chief medical officer of Assembly Bio. “We are also pleased to see the first scientific presentation of Phase 1b data for ABI-1179 recognized as a late-breaker presentation, which highlight its potential as a long-acting therapeutic option for patients with recurrent genital herpes.”
Details of the presentations are as follows:
ABI-5366:
- Oral Presentation: ABI-5366-101: a phase 1b study of a novel, oral, long-acting, investigational HSV helicase-primase inhibitor in recurrent genital herpes
Presenter: Mark Bloch, MBBS, Momentum Clinical Research and Kirby Institute, University of New South Wales
Session Date and Time: April 20, 2026, at 5:30 PM CEST - Poster Presentation: Virologic analyses following treatment with ABI-5366, a novel, oral, long-acting HSV helicase-primase inhibitor in participants seropositive for HSV-2 with recurrent genital herpes
Presenter: Kathryn Kitrinos, PhD, Assembly Bio
Session Date and Time: April 18, 2026, at 12:00 PM CEST - Poster Presentation: The safety and tolerability of ABI-5366, a novel, oral, long-acting HSV helicase-primase inhibitor in participants with recurrent genital herpes
Presenter: Cory Sellwood, MBBS, New Zealand Clinical Research
Session Date and Time: April 18, 2026, at 12:00 PM CEST
ABI-1179:
- Poster Presentation (Late-Breaker): The safety and efficacy of ABI-1179, a novel, oral, long-acting HSV helicase-primase inhibitor for recurrent genital herpes: interim results from a phase 1b study
Presenter: Mark Bloch, MBBS, Momentum Clinical Research and Kirby Institute, University of New South Wales
Session Date and Time: April 21, 2026, at 12:00 PM CEST
Assembly Bio intends to make the posters available on the “Events & Presentations” page in the “Investors” section and on the “Publications” page in the “Pipeline” section of its website at www.assemblybio.com.
ABI-5366 and ABI-1179 are investigational product candidates that have not been approved anywhere globally, and their safety and efficacy have not been established. They are exclusively licensed to Gilead Sciences, Inc. (Gilead) under the collaboration between Assembly Bio and Gilead, and Gilead has the sole right and responsibility for further clinical development and commercialization of these programs.
About Assembly Biosciences
Assembly Biosciences is a biotechnology company dedicated to the development of innovative small-molecule therapeutics designed to change the path of serious viral diseases and improve the lives of patients worldwide. Led by an accomplished team of leaders in virologic drug development, Assembly Bio is committed to improving outcomes for patients struggling with the serious, chronic impacts of herpesvirus, hepatitis B virus (HBV) and hepatitis delta virus (HDV) infections. For more information, visit assemblybio.com.
Forward-Looking Statements
The information in this press release contains forward-looking statements that are subject to certain risks and uncertainties that could cause actual results to materially differ. These risks and uncertainties include: Assembly Bio’s ability to realize the potential benefits of its collaboration with Gilead, including all financial aspects of the collaboration and equity investments; Assembly Bio’s ability to initiate and complete clinical studies involving its therapeutic product candidates, including studies contemplated by Assembly Bio’s collaboration with Gilead, in the currently anticipated timeframes or at all; safety and efficacy data from clinical or nonclinical studies may not warrant further development of Assembly Bio’s product candidates; clinical and nonclinical data may not differentiate Assembly Bio’s product candidates from other companies’ candidates; Assembly Bio’s ability to maintain financial resources and secure additional funding necessary to continue its research activities, clinical studies, and other business operations; potential effects of changes in government regulation; results of nonclinical studies may not be representative of disease behavior in a clinical setting and may not be predictive of the outcomes of clinical studies; and other risks identified from time to time in Assembly Bio’s reports filed with the U.S. Securities and Exchange Commission (the SEC). You are urged to consider statements that include the words may, will, would, could, should, might, believes, hopes, estimates, projects, potential, expects, plans, anticipates, intends, continues, forecast, designed, goal or the negative of those words or other comparable words to be uncertain and forward-looking. Assembly Bio intends such forward-looking statements to be covered by the safe harbor provisions contained in Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. More information about Assembly Bio’s risks and uncertainties are more fully detailed under the heading “Risk Factors” in Assembly Bio’s filings with the SEC, including its most recent Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K. Except as required by law, Assembly Bio assumes no obligation to update publicly any forward-looking statements, whether as a result of new information, future events or otherwise.
Contacts:
Investors:
Patrick Till
Meru Advisors
(484) 788-8560
investor_relations@assemblybio.com
Media:
Sam Brown LLC
Alyssa Kuciunas
(331) 481-3751
ASMBMedia@sambrown.com
