GlobeNewswire Inc | Aug 18, 2021 08:00AM EDT

August 18, 2021

SOUTH SAN FRANCISCO, Calif., Aug. 18, 2021 (GLOBE NEWSWIRE) -- Assembly Biosciences, Inc. (Nasdaq: ASMB), a clinical-stage biotechnology company developing innovative therapeutics targeting hepatitis B virus (HBV), today announced it has selected a fourth core inhibitor candidate, ABI-4334 (4334), that has been optimized for potency, to advance into clinical development. The company is conducting preclinical work, with the aim of completing regulatory filings and initiating clinical studies as soon as possible in 2022.

In our mission to deliver finite and curative therapies to individuals with HBV, we have always been committed to developing the most promising candidates, specifically those with the profile to achieve greater, and potentially complete, viral suppression in patients, said William Delaney, PhD, chief scientific officer of Assembly Bio. We believe ABI-4334 has a best-in-class preclinical profile with single-digit nanomolar potency against the production of new virus and also the formation of cccDNA. Were excited to further evaluate this compound and its potential, as we plan for the start of clinical studies next year.

Assembly Bio selected 4334 based on a preclinical target drug profile that indicates enhanced target coverage and potency to prevent both formation of new virus and covalently closed circular DNA (cccDNA), which is responsible for maintaining the HBV viral reservoir. Preclinically to date, the candidate has also demonstrated pan-genotypic activity, an improved resistance profile, pharmacokinetics (PK) predicting once-daily dosing and a favorable safety profile. A comparison of Assembly Bios core inhibitor candidates can be found in the table below.

Assembly Bio Core Inhibitors HBV DNA C[min] Total/ cccDNA C[min] Total/ EC[50] Protein EC[50 ] Protein (nM) adjusted HBV DNA (nM) adjusted cccDNA EC EC[50] [50]Vebicorvir 300 mg 154 3 2210 0.22158 300 mg 41 19 204 43733 300 mg 12 28^1 62 6^14334 (projected at 0.5 196^2 2.4 42^2300 mg)

1 Based on preliminary PK in healthy volunteers2 Projected values using modeled human PK based on preclinical species

AboutAssembly BiosciencesAssembly Bio is a clinical-stage biotechnology company committed to bringing finite and curative therapies to the 270 million people living with hepatitis B virus (HBV) worldwide. A pioneer in the development of a new class of potent, oral core inhibitor drug candidates, Assembly Bios approach aims to break the complex viral replication cycle of HBV to free patients from a lifetime of therapy. Assembly Bios strategy toward cure includes a leading portfolio of more potent, next-generation core inhibitors, proof-of-concept combination studies and a research program focused on the discovery of novel HBV targets. For more information, visitassemblybio.com.

Forward-Looking StatementsThe 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 Bios ability to initiate and complete clinical studies involving its HBV therapeutic product candidates, including studies contemplated by Assembly Bios clinical collaboration agreements, in the currently anticipated timeframes; safety and efficacy data from clinical studies may not warrant further development of Assembly Bios product candidates; clinical and nonclinical data presented at conferences may not differentiate Assembly Bios product candidates from other companies candidates; 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; continued development and commercialization of Assembly Bios HBV product candidates, if successful, in the China territory will be dependent on, and subject to, Assembly Bios collaboration agreement governing its activity in the China territory; Assembly Bios ability to maintain financial resources necessary to continue its clinical studies and fund business operations; any impact that the COVID-19 pandemic may have on Assembly Bios business and operations, including initiation and continuation of its clinical studies or timing of discussions with regulatory authorities; and other risks identified from time to time in Assembly Bios reports filed with theU.S. Securities and Exchange Commission(theSEC). 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 Bios risks and uncertainties are more fully detailed under the heading Risk Factors in Assembly Bios filings with theSEC, 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:Lauren GlaserSenior Vice President, Investor Relations and Corporate Affairs(415) 521-3828lglaser@assemblybio.com

Media:Sam Brown Inc.Audra Friis(917) 519-9577ASMBMedia@sambrown.com