Assembly Biosciences Presents Positive Phase 1b Data for Next-Generation Capsid Assembly Modulator ABI-4334 at AASLD The Liver Meeting®
Assembly Biosciences (Nasdaq: ASMB) presented positive Phase 1b data for its next‑generation capsid assembly modulator ABI‑4334 at AASLD The Liver Meeting® on Nov 7, 2025.
The randomized, blinded Phase 1b evaluated oral once‑daily 150 mg and 400 mg doses for 28 days in predominantly HBeAg‑negative chronic hepatitis B patients. ABI‑4334 was reported as well tolerated at both doses, produced multi‑log declines in HBV DNA and pgRNA, and achieved exposures multiple‑fold above levels anticipated to inhibit cccDNA formation. As expected for the population and short dosing interval, no reductions in HBsAg were observed. Under a collaboration, Gilead has a post‑study option to obtain an exclusive license for further development of ABI‑4334.
Assembly Biosciences (Nasdaq: ASMB) ha presentato dati positivi di fase 1b per il suo modulatore di assemblaggio capsid di nuova generazione ABI‑4334 all'AASLD The Liver Meeting® il 7 novembre 2025.
Lo studio randomizzato in cieco di fase 1b ha valutato dosi orali una volta al giorno di 150 mg e 400 mg per 28 giorni in pazienti con epatite B cronica prevalentemente HBeAg‑negativa. ABI‑4334 è stato riportato come ben tollerato ad entrambe le dosi, ha prodotto cali multi‑log in HBV DNA e pgRNA, e ha raggiunto esposizioni multipli superiori ai livelli previsti per inibire la formazione di cccDNA. Come previsto per la popolazione e l'intervallo di dosaggio breve, non si sono osservate riduzioni di HBsAg. In base a una collaborazione, Gilead ha un'opzione post‑studio per ottenere una licenza esclusiva per ulteriori sviluppi di ABI‑4334.
Assembly Biosciences (Nasdaq: ASMB) presentó datos positivos de la fase 1b para su modulador de ensamblaje de cápside de nueva generación ABI‑4334 en AASLD The Liver Meeting® el 7 de noviembre de 2025.
El ensayo aleatorizado y ciego de fase 1b evaluó dosis orales de 150 mg y 400 mg una vez al día durante 28 días en pacientes con hepatitis B crónica mayoritariamente HBeAg‑negativa. ABI‑4334 se informó como bien tolerado en ambas dosis, produjo caídas a varios logaritmos en HBV DNA y pgRNA, y alcanzó exposiciones varias veces superiores a los niveles previstos para inhibir la formación de cccDNA. Como era de esperar para la población y el intervalo de dosificación corto, no se observaron reducciones en HBsAg. En virtud de una colaboración, Gilead tiene una opción post‑estudio para obtener una licencia exclusiva para un mayor desarrollo de ABI‑4334.
Assembly Biosciences (Nasdaq: ASMB)는 AASLD The Liver Meeting®에서 차세대 캡시드 어셈블리 모듈레이터 ABI‑4334의 긍정적인 1b상 데이터를 2025년 11월 7일에 발표했습니다.
무작위화되고 맹검된 1b상은 주 1회 또는 매일 복용되는 경구 150 mg 및 400 mg 용량을 28일간 평가했습니다. HBeAg 음성인 만성 B형 간염 환자에서 주로 나타났습니다. ABI‑4334는 두 용량 모두에서 잘 견디는 것으로 보고되었고, HBV DNA 및 pgRNA에서 다중 로그 감소를 일으켰으며, cccDNA 형성을 억제하는 데 예상되는 수준보다 몇 배 높은 노출을 달성했습니다. 짧은 투약 간격과 대상 집단 특성상 HBsAg 감소는 관찰되지 않았습니다. 협력하에 Gilead는 ABI‑4334의 추가 개발을 위한 독점 라이선스를 얻기 위한 연구 후 옵션을 갖고 있습니다.
Assembly Biosciences (Nasdaq: ASMB) a présenté des données positives de phase 1b pour son modulateur d'assemblage de capside de nouvelle génération ABI‑4334 lors de l'AASLD The Liver Meeting® le 7 novembre 2025.
L'essai randomisé en aveugle de phase 1b a évalué des doses orales une fois par jour de 150 mg et 400 mg pendant 28 jours chez des patients atteints d'hépatite B chronique principalement HBeAg‑négative. ABI‑4334 a été rapporté comme bien toléré à ces deux doses, a provoqué des diminutions multilogarithmiques du HBV DNA et pgRNA, et a atteint des expositions plusieurs fois supérieures aux niveaux prévus pour inhiber la formation de cccDNA. Comme prévu pour la population et l'intervalle posologique court, aucune réduction de HBsAg n'a été observée. Dans le cadre d'une collaboration, Gilead dispose d'une option post‑étude pour obtenir une licence exclusive pour un développement ultérieur d'ABI‑4334.
Assembly Biosciences (Nasdaq: ASMB) präsentierte positive Phase-1b-Daten für seinen Next‑Generation Capsid Assembly Modulator ABI‑4334 auf der AASLD The Liver Meeting® am 7. November 2025.
Die randomisierte, verblindete Phase-1b evaluierte orale Dosen von 150 mg und 400 mg einmal täglich über 28 Tage bei überwiegend HBeAg‑negativen Chronische Hepatitis-B‑Patienten. ABI‑4334 wurde bei beiden Dosen als gut verträglich berichtet, verursachte Mehrfach‑Logabnahmen von HBV DNA und pgRNA und erreichte Expositionen, die mehrmals über den erwarteten Werten lagen, um die Bildung von cccDNA zu hemmen. Wie bei der Population und dem kurzen Dosierungsintervall zu erwarten, wurden keine Reduktionen von HBsAg beobachtet. Im Rahmen einer Zusammenarbeit hat Gilead eine Nach‑Studien-Option, um eine exklusive Lizenz für die Weiterentwicklung von ABI‑4334 zu erhalten.
Assembly Biosciences (Nasdaq: ASMB) قدّمت بيانات إيجابية من المرحلة 1b لمُعدِّل تجميع غلاف الفيروس من الجيل التالي ABI‑4334 في اجتماع AASLD The Liver Meeting® في 7 نوفمبر 2025.
قيّم الاختبار العشوائي والأعمى من المرحلة 1b جرعات فموية مرة واحدة يومياً قدرها 150 mg و 400 mg لمدة 28 يوماً في مرضى التهاب الكبد B المزمن سلبيين HBeAg في الغالب. وأفيد أن ABI‑4334 تم تحمله بشكل جيد عند كلا الجرعتين، وأدى إلى انخفاضات متعددة السجلات في HBV DNA و pgRNA، ووصل إلى تعرّضات تفوق بمعدلات متعددة عن المستويات المتوقعة لمنع تشكيل cccDNA. كما هو متوقع للمجموعة ولنافذة الجرعة القصيرة، لم تُلاحظ تخفيضات في HBsAg. وتحت تعاون، لدى جيليد خيار ما بعد الدراسة للحصول على ترخيص حصري لمزيد من التطوير لـ ABI‑4334.
- Multi‑log declines in HBV DNA and pgRNA at 150 mg and 400 mg
- Well tolerated at both 150 mg and 400 mg once‑daily doses over 28 days
- Drug exposures multiple‑fold above levels anticipated to inhibit cccDNA formation
- No reductions in HBsAg observed in predominantly HBeAg‑negative patients
- ABI‑4334 remains investigational with safety and efficacy not established
Insights
Positive Phase 1b safety and strong antiviral activity for ABI-4334 supports continued development and a potential Gilead option review.
Assembly Biosciences's next-generation capsid assembly modulator ABI-4334 showed favorable tolerability and multi-log reductions in HBV DNA and pgRNA at
The key dependencies are explicit: safety in larger or longer studies, demonstration of HBsAg reductions in more suitable populations or combination regimens, and Gilead's decision under the collaboration option. Risks include limited duration (28 days), the patient population (predominantly HBeAg-negative) explaining lack of HBsAg decline, and that clinical benefit beyond virologic markers must be shown. Watch for the option data package review timeline and results of any longer or combination studies within the next 6–18 months for evidence of second-mechanism engagement and antigen declines.
– Phase 1b data demonstrating favorable safety and tolerability profile and potent reductions in viral nucleic acids highlighted in late-breaking poster presentation –
SOUTH SAN FRANCISCO, Calif., Nov. 07, 2025 (GLOBE NEWSWIRE) -- Assembly Biosciences, Inc. (Nasdaq: ASMB), a biotechnology company developing innovative therapeutics targeting serious viral diseases, today announced Phase 1b clinical data for its next-generation investigational capsid assembly modulator (CAM) ABI-4334 featured in a late-breaking poster presentation at the American Association for the Study of Liver Diseases (AASLD), The Liver Meeting®. The conference is taking place November 7-11, 2025, in Washington, D.C.
“We are pleased to highlight positive data from our Phase 1b study for ABI-4334 with the scientific community,” said Anuj Gaggar, MD, PhD, chief medical officer of Assembly Bio. “These data demonstrate the very high potency we set out to achieve for ABI-4334 and support its potential to maximize antiviral activity as a component of multi-drug combination regimens targeting cures for chronic hepatitis B infection.”
The late-breaking poster presentation titled “Safety, pharmacokinetics and antiviral activity of the next-generation hepatitis B capsid assembly modulator ABI-4334 in patients with HBeAg-negative chronic hepatitis B infection not suppressed on nucleoside analogues: results from a randomized, blinded, Phase 1b study” highlights data in individuals with chronic hepatitis B infection treated with ABI-4334. This poster is the first scientific presentation of the complete Phase 1b data announced earlier this year by Assembly Bio.
Two cohorts of predominantly HBeAg-negative subjects were enrolled, evaluating 150 mg and 400 mg oral doses of ABI-4334 given once-daily over 28 days. ABI-4334 was well tolerated at both doses evaluated. Multi-log declines in hepatitis B virus (HBV) DNA and pregenomic RNA (pgRNA) were observed for both doses, consistent with the increased in vitro potency of ABI-4334 compared to first-generation CAMs. These declines in HBV DNA and pgRNA are supportive of full engagement of the first CAM mechanism of action, suppression of viral replication. Exposures multiple folds above levels anticipated to be required for inhibition of cccDNA formation, the second CAM mechanism of action, were also observed at both dose levels. As expected in predominantly HBeAg-negative patients with a short dosing interval, reductions in HBsAg were not observed.
The poster presentation is available on the “Events & Presentations” page in the “Investors” section and on the “Publications” page in the “Pipeline” section of Assembly Bio’s website at www.assemblybio.com.
Under the collaboration agreement between Assembly Bio and Gilead Sciences, Inc. (Gilead), Gilead has the right to opt in to an exclusive license for further development and commercialization of ABI-4334 after reviewing an option data package following completion of this Phase 1b study.
ABI-4334 is an investigational product candidate that has not been approved anywhere globally, and its safety and efficacy have not been established.
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 maintain financial resources and secure additional funding necessary to continue its research activities, clinical studies, and other business operations; 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; potential effects of changes in government regulation, including as a result of the change in U.S. administration in 2025; 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
Investor and Corporate:
Shannon Ryan
SVP, Investor Relations, Corporate Affairs and Alliance Management
(415) 738-2992
investor_relations@assemblybio.com
Media:
Sam Brown LLC
Alyssa Kuciunas
(331) 481-3751
ASMBMedia@sambrown.com
FAQ
What Phase 1b results did Assembly Biosciences report for ABI‑4334 (ASMB) on Nov 7, 2025?
What doses of ABI‑4334 were tested in the Phase 1b study presented at AASLD 2025?
Did ABI‑4334 reduce HBsAg in the Phase 1b AASLD presentation for ASMB?
What safety findings were reported for ABI‑4334 in the Phase 1b data (ASMB)?
How could Gilead's collaboration affect ABI‑4334 development after the Phase 1b study?
Is ABI‑4334 approved and available for patients following the Nov 7, 2025 presentation?
