Assembly Biosciences Reports Second Quarter 2025 Financial Results and Recent Updates

– On track for proof-of-concept Phase 1b data this no later than this fall in participants with recurrent genital herpes for long-acting herpes simplex virus (HSV) helicase-primase inhibitor candidates, ABI-5366 and ABI-1179 –

– Positive topline data reported for Phase 1b study of ABI-4334, a next-generation highly potent capsid assembly modulator candidate, in participants with chronic hepatitis B virus (HBV) –

– Interim data, including a biomarker for target engagement, reported from Phase 1a study in healthy volunteers of ABI-6250, an orally bioavailable, small molecule viral entry inhibitor candidate in development for chronic hepatitis delta virus (HDV) –

SOUTH SAN FRANCISCO, Calif. – August 6, 2025 – Assembly Biosciences, Inc. (Nasdaq: ASMB), a biotechnology company developing innovative therapeutics targeting serious viral diseases, today reported financial results and recent updates for the second quarter ended June 30, 2025.

“We are advancing toward our goal of generating impactful clinical datasets for four development candidates in 2025,” said Jason Okazaki, chief executive officer and president of Assembly Bio. “We have delivered two important datasets already this year from our hepatitis programs, including positive topline data from our Phase 1b study of our most potent capsid assembly modulator, ABI-4334, in participants with chronic HBV, as well as interim data from a Phase 1a study of ABI-6250, including biomarker data supporting target engagement. Looking ahead, we remain on track to report key proof-of-concept Phase 1b data, including antiviral activity, no later than fall for ABI-5366 and ABI-1179 in participants with recurrent genital herpes, a chronic viral infection that significantly impacts the lives of millions of individuals.”

Second Quarter 2025 and Recent Highlights

Anticipated Milestones and Events

ABI-1179 was contributed by Gilead Sciences, Inc. (Gilead) under the collaboration between Assembly Bio and Gilead. ABI-5366, ABI-1179, ABI-6250 and ABI-4334 are investigational product candidates that have not been approved anywhere globally, and their safety and efficacy have not been established.

Second Quarter 2025 Financial Results

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, other business operations and continue as a going concern; 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 Healthcare Communications
Alyssa Kuciunas

(331) 481-3751
ASMBMedia@sambrown.com 

ASSEMBLY BIOSCIENCES, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(In thousands except for share amounts and par value)

ASSEMBLY BIOSCIENCES, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS

(In thousands except for share and per share amounts)

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