# EDGAR Filing Document

**Accession Number:** 0001426800
**File Stem:** 0000950170-25-104020
**Filing Date:** 2025-8
**Character Count:** 29280
**Document Hash:** dabdf184f0777cb871df192ce92e75d2
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000950170-25-104020.hdr.sgml**: 20250806

**ACCESSION NUMBER**: 0000950170-25-104020

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 12

**CONFORMED PERIOD OF REPORT**: 20250806

**ITEM INFORMATION**: Results of Operations and Financial Condition

**ITEM INFORMATION**: Other Events

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20250806

**DATE AS OF CHANGE**: 20250806

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** ASSEMBLY BIOSCIENCES, INC.
- **CENTRAL INDEX KEY:** 0001426800
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-35005
- **FILM NUMBER:** 251189646

**BUSINESS ADDRESS:**
- **STREET 1:** TWO TOWER PLACE
- **STREET 2:** 7TH FLOOR
- **CITY:** SOUTH SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94080
- **BUSINESS PHONE:** (833) 409-4583

**MAIL ADDRESS:**
- **STREET 1:** TWO TOWER PLACE
- **STREET 2:** 7TH FLOOR
- **CITY:** SOUTH SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94080

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** VENTRUS BIOSCIENCES INC
- **DATE OF NAME CHANGE:** 20080211

?xml version='1.0' encoding='ASCII'? 8-K

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**WASHINGTON, D.C. 20549** 

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**FORM** 8-K

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**CURRENT REPORT**

**Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934**

**Date of Report (Date of earliest event reported):** August 6, 2025

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Assembly Biosciences, Inc.

 **(Exact name of Registrant as Specified in Its Charter)**

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| | | |
|:---|:---|:---|
| Delaware | 001-35005 | 20-8729264 |
| **(State or Other Jurisdiction**<br>**of Incorporation)** | **(Commission File Number)** | **(IRS Employer**<br>**Identification No.)** |
| Two Tower Place**,** 7th Floor**,**<br>South San Francisco**,** California |  | 94080 |
| **(Address of Principal Executive Offices)** |  | **(Zip Code)** |

---

**Registrant's Telephone Number, Including Area Code:** (833) 509-4583

**Not Applicable**

**(Former Name or Former Address, if Changed Since Last Report)**

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Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) 

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) 

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) 

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) 

Securities registered pursuant to Section 12(b) of the Act:

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| | | |
|:---|:---|:---|
| **Title of each class** | **Trading**<br>**Symbol(s)** | **Name of each exchange on which registered** |
| Common Stock, par value $0.001 | ASMB | The Nasdaq Global Select Market |

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Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

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**Item 2.02 Results of Operations and Financial Condition.**

On August 6, 2025, Assembly Biosciences, Inc. (the "Company") issued a press release announcing its financial results for the quarter ended June 30, 2025. A copy of the press release is attached hereto as Exhibit 99.1.

The information furnished with this Item 2.02, including Exhibit 99.1, shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.

**Item 8.01 Other Events.**

On August 6, 2025, the Company issued a press release announcing interim results from the Phase 1a clinical study evaluating ABI-6250, an investigational orally bioavailable, small molecule hepatitis delta virus (HDV) entry inhibitor candidate.

A copy of the press release is attached as Exhibit 99.2 and is incorporated herein by reference.

**Item 9.01 Financial Statements and Exhibits.**

(d) <u>Exhibits</u>. The exhibits shall be deemed to be filed or furnished, depending on the relevant item requiring such exhibit, in accordance with the provisions of Item 601 of Regulation S-K (17 CFR 229.601)and Instruction B.2 to this form.

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| | |
|:---|:---|
| **Exhibit**<br>**Number** | **Description** |
| 99.1 | [<u>Press Release dated August 6, 2025.</u>](asmb-ex99_1.htm) |
| 99.2 | [<u>Press Release dated August 6, 2025.</u>](asmb-ex99_2.htm) |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) |

---

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**SIGNATURES**

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

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| | | |
|:---|:---|:---|
|  | Assembly Biosciences, Inc. | Assembly Biosciences, Inc. |
| Date: August 6, 2025 | By: | /s/ John O. Gunderson |
|  |  | John O. Gunderson |
|  |  | VP, General Counsel and Corporate Secretary |

---

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## Exhibit 99.1

**Exhibit 99.1**

**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**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•Initiated dosing in the Phase 1b portion of the ongoing Phase 1a/b trial for ABI-1179 and received clearance for an Investigational New Drug application to support expansion of this study to sites in the United States

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•Released positive topline Phase 1b results for ABI-4334 that met Assembly Bio's target clinical profile for the study, including strong antiviral activity in participants with chronic HBV infection

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•Shared interim data from a Phase 1a study of ABI-6250 in healthy volunteers, including pharmacokinetics (PK) supportive of a once-daily oral dosing profile and biomarker data indicating engagement of its target, sodium taurocholate cotransporting polypeptide (NTCP), the receptor used by HDV to infect hepatocytes

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•Presented four posters, including one late-breaker, highlighting Phase 1a clinical data for ABI-5366 and ABI-1179, preclinical data for ABI-5366, and claims data estimating U.S. genital herpes prevalence and treatment patterns at the STI & HIV 2025 World Congress, July 26-30, 2025

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•Presented one oral and one poster presentation describing the Phase 1a clinical and preclinical profiles for ABI-5366 and ABI-1179 at the 49th Annual International Herpesvirus Workshop, July 26-30, 2025

**Anticipated Milestones and Events**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**ABI-5366 and ABI-1179:** In fall 2025, interim efficacy, safety and PK data from Phase 1b studies for ABI-5366 and ABI-1179

oAssembly Bio is running both studies concurrently and plans to evaluate weekly (and, for ABI-5366, monthly) oral dosing in participants with recurrent genital herpes over a 28-day dosing period

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**ABI-6250:** Abstract describing preclinical profiling of ABI-6250 accepted for oral presentation at the International HBV Meeting, September 8-12, 2025

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**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**Cash, cash equivalents and marketable securities** were $75.0 million as of June 30, 2025, compared to $91.0 million as of March 31, 2025. Assembly Bio's cash position is projected to fund operations into mid-2026.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**Revenue** from collaborative research with Gilead was $9.6 million for the three months ended June 30, 2025, compared to $8.5 million in the same period in 2024. The change reflects the increase in research and development incurred under the collaboration as well as an increase in collaboration funding from amending the agreement in December 2024.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**Research and development expenses** were $16.1 million for the three months ended June 30, 2025, compared to $16.3 million for the same period in 2024. The decrease is most largely due to a decrease in spending on ABI-6250, which we had incurred significant preclinical and start-up activities for the Phase 1a study in 2024.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**General and administrative expenses** were $4.6 million for the three months ended June 30, 2025, compared to $4.5 million for the same period in 2024, remaining essentially flat.

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**Net loss attributable to common stockholders** was $10.2 million, or $1.33 per basic and diluted share, for the three months ended June 30, 2025, compared to $11.2 million, or $1.98 per basic and diluted share, for the same period in 2024.

**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.

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**Contacts**

**Investor and Corporate:**<br>Shannon Ryan<br>SVP, Investor Relations, Corporate Affairs and Alliance Management<br>(415) 738-2992<br>investor_relations@assemblybio.com

**Media:**<br>Sam Brown Healthcare Communications<br>Alyssa Kuciunas

(331) 481-3751<br>ASMBMedia@sambrown.com

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**ASSEMBLY BIOSCIENCES, INC.**

**CONDENSED CONSOLIDATED BALANCE SHEETS**

(In thousands except for share amounts and par value)

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| | | |
|:---|:---|:---|
|  | **June 30,** | **December 31,** |
|  | **2025** | **2024** |
|  | **(Unaudited)** |  |
| **ASSETS** |  |  |
| Current assets |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Cash and cash equivalents | $24006 | $38344 |
| &nbsp;&nbsp;&nbsp;&nbsp;Marketable securities | 50974 | 73735 |
| &nbsp;&nbsp;&nbsp;&nbsp;Prepaid expenses and other current assets | 2487 | 3424 |
| Total current assets | 77467 | 115503 |
| &nbsp;&nbsp;&nbsp;&nbsp;Property and equipment, net | 219 | 284 |
| &nbsp;&nbsp;&nbsp;&nbsp;Operating lease right-of-use assets | 2782 | 3069 |
| &nbsp;&nbsp;&nbsp;&nbsp;Other assets | 312 | 312 |
| **Total assets** | $**80780** | $**119168** |
| **LIABILITIES AND STOCKHOLDERS' EQUITY** |  |  |
| Current liabilities |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Accounts payable | $743 | $585 |
| &nbsp;&nbsp;&nbsp;&nbsp;Accrued research and development expenses | 1691 | 2273 |
| &nbsp;&nbsp;&nbsp;&nbsp;Other accrued expenses | 3407 | 6862 |
| &nbsp;&nbsp;&nbsp;&nbsp;Deferred revenue from a related party - short-term | 40917 | 37622 |
| &nbsp;&nbsp;&nbsp;&nbsp;Operating lease liabilities - short-term | 533 | 461 |
| Total current liabilities | 47291 | 47803 |
| &nbsp;&nbsp;&nbsp;&nbsp;Deferred revenue from a related party - long-term | 13038 | 35378 |
| &nbsp;&nbsp;&nbsp;&nbsp;Operating lease liabilities - long-term | 2351 | 2628 |
| **Total liabilities** | **62680** | **85809** |
| **Commitments and contingencies** |  |  |
| **Stockholders' equity** |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued or outstanding |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Common stock, $0.001 par value; 150,000,000 shares authorized as of June 30, 2025 and December 31, 2024; 7,672,249 and 7,457,240 shares issued and outstanding as of June 30, 2025 and December 31, 2024, respectively | 8 | 7 |
| &nbsp;&nbsp;&nbsp;&nbsp;Additional paid-in capital | 863312 | 859488 |
| &nbsp;&nbsp;&nbsp;&nbsp;Accumulated other comprehensive loss | (279) | (211) |
| &nbsp;&nbsp;&nbsp;&nbsp;Accumulated deficit | (844941) | (825925) |
| &nbsp;&nbsp;&nbsp;&nbsp;Total stockholders' equity | 18100 | 33359 |
| **Total liabilities and stockholders' equity** | $**80780** | $**119168** |

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**ASSEMBLY BIOSCIENCES, INC.**

**CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS**

(In thousands except for share and per share amounts)

(Unaudited)

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| | | | | |
|:---|:---|:---|:---|:---|
|  | **Three Months Ended<br>June 30,** | **Three Months Ended<br>June 30,** | **Six Months Ended<br>June 30,** | **Six Months Ended<br>June 30,** |
|  | **2025** | **2024** | **2025** | **2024** |
| **Collaboration revenue from a related party** | $9626 | $8533 | $19045 | $14318 |
| **Operating expenses** |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Research and development | 16125 | 16259 | 30976 | 28138 |
| &nbsp;&nbsp;&nbsp;&nbsp;General and administrative | 4594 | 4477 | 9103 | 9112 |
| Total operating expenses | 20719 | 20736 | 40079 | 37250 |
| **Loss from operations** | **(11093)** | **(12203)** | **(21034)** | **(22932)** |
| **Other income** |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Interest and other income, net | 895 | 1457 | 2018 | 3109 |
| Total other income | 895 | 1457 | 2018 | 3109 |
| **Loss before income taxes** | **(10198)** | **(10746)** | **(19016)** | **(19823)** |
| Income tax expense |  | 406 |  | 406 |
| **Net loss** | $**(10198)** | $**(11152)** | $**(19016)** | $**(20229)** |
| **Other comprehensive loss** |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Unrealized loss on marketable securities | 26 | 54 | 68 | 212 |
| **Comprehensive loss** | $**(10224)** | $**(11206)** | $**(19084)** | $**(20441)** |
| Net loss per share, basic and diluted | $(1.33) | $(1.98) | $(2.51) | $(3.64) |
| Weighted average common shares outstanding, basic and diluted | 7655854 | 5642752 | 7581501 | 5563033 |

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## Exhibit 99.2

**Exhibit 99.2**

**Assembly Biosciences Reports Interim Phase 1a Data from Clinical Study of Oral Entry Inhibitor Candidate ABI-6250 for Hepatitis Delta Virus**

*– Data to date in single- and multiple-ascending dose cohorts of healthy participants demonstrate a four-day half-life for ABI-6250, supporting target daily oral dosing profile and dose-dependent elevations in biomarker of target engagement –*

*– Further pharmacological assessment to be conducted in parallel with Phase 2 preparation –*

SOUTH SAN FRANCISCO, Calif., August 6, 2025 (GLOBE NEWSWIRE) -- Assembly Biosciences, Inc. (Nasdaq: ASMB), a biotechnology company developing innovative therapeutics targeting serious viral diseases, today announced interim data from several cohorts from the ongoing Phase 1a clinical trial of ABI-6250, the company's orally bioavailable, small molecule hepatitis delta virus (HDV) entry inhibitor candidate.

In the cohorts evaluated to date, a mean half-life of four days was observed for ABI-6250 when dosed orally, supporting the target daily oral dosing profile. Additionally, dose-dependent elevations of total serum bile acids (TBA) were seen over both single- and multiple-dose cohorts. These biomarker data indicate ABI-6250's potent engagement of the sodium taurocholate cotransporting polypeptide (NTCP) target, the receptor used by HDV to infect hepatocytes, and inform the potential dose range for evaluation of antiviral activity in further studies in participants with chronic HDV (cHDV) infection.

As the study remains blinded, combined safety data for ABI-6250 and placebo recipients are reported. A grade 2 alanine transaminase (ALT) elevation was observed in the cohort evaluating the highest single-dose level, and grade 1 elevations were seen at a low frequency in the other cohorts. All were self-limited and none were accompanied by bilirubin elevations or other markers of liver injury. Additional studies are planned to explore potential factors associated with these elevations given the role of ABI-6250's target as a bile acid transporter. This assessment is expected to include further pharmacological characterization of ABI-6250 and may incorporate additional cohorts in this Phase 1a study. Assembly Bio expects to conduct these activities in parallel with preparations for Phase 2 clinical studies and the completion of ongoing chronic toxicology studies.

"In this first clinical study of ABI-6250, we are encouraged by the observed half-life supportive of once-daily oral dosing and bile acid elevations indicative of NTCP target engagement," said Anuj Gaggar, MD, PhD, chief medical officer of Assembly Bio. "As we continue to evaluate these Phase 1a clinical data, we plan to further explore ABI-6250's pharmacologic and biologic profile in preparation for proceeding to further clinical studies in participants with cHDV infection. With just one approved therapy for cHDV in the European Union and none in the U.S., the need for new treatment options for this underserved patient

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population remains critical – a need we believe ABI-6250 could have an important role in addressing given its potential to be the first oral therapy."

ABI-6250 is an investigational product candidate that has not been approved anywhere globally, and its safety and efficacy have not been established.

**Study ABI-6250-101 – Phase 1a Interim Results**

**Study Overview** 

ABI-6250-101 is an ongoing randomized, blinded and placebo-controlled Phase 1a clinical study evaluating the safety, tolerability and pharmacokinetics (PK) of ABI-6250 following single- and multiple-ascending oral dose administration in healthy participants. Changes in TBAs are also evaluated as a biomarker for NTCP engagement. Dosing is complete in two single-dose cohorts evaluating doses of 5 mg and 25 mg and three multiple-dose cohorts evaluating doses of 0.05 mg, 0.2 mg and 1 mg, each randomized 6:2 between ABI-6250 and placebo. Multiple-dose cohorts evaluated repeat daily dosing over 10 days.

Data are reported here for all cohorts dosed to date through completion of the study follow-up period of 10 days after dosing. As the study remains blinded, combined safety data for ABI-6250 and placebo recipients are reported.

**Results**

**PK:** Across the cohorts evaluated to date, a mean half-life of approximately four days was observed for ABI-6250 when dosed orally, supporting the once-daily oral dosing profile target. Given this half-life, accumulation was observed in the multiple-dose cohorts with exposures on the last day of dosing generally reaching 6- to 7-fold higher than the exposure seen after the first dose.

**Biomarkers**: Dose-dependent elevations of TBAs were observed for both the 5 mg and 25 mg single-dose cohorts, indicative of NTCP target engagement. In the highest single-dose cohort of 25 mg, coproporphyrin I (CP-1), a biomarker for off-target engagement of the organic anion transporters, OATP1B1 and/or OATP1B3, was also elevated.

Given the predicted ABI-6250 accumulation driven by the long half-life and the observed elevations in TBAs for the single-dose cohorts, doses at and below 1 mg daily were selected for the multiple-dose cohorts to characterize the lower end of the dose-response curve. Elevation of TBAs was observed for both the 0.2 mg and 1 mg daily multiple-dose cohorts, consistent with the respective ABI-6250 exposures. Minimal TBA elevation was observed in the 0.05 mg daily multiple-dose cohort.

**Safety:** Treatment-emergent adverse events (AEs) and laboratory abnormalities were all grade 1 or 2 in severity with the majority being grade 1. There were no serious AEs in any dose cohort.

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No protocol defined stopping criteria were met. There were no clinically significant electrocardiogram abnormalities or patterns of AEs noted.

One grade 2 ALT elevation was observed in the cohort evaluating the highest single-dose level of 25 mg. In this cohort, off-target engagement of other liver transporters was also seen as indicated by elevated CP-1 levels. Grade 1 ALT elevations were observed at a low frequency across the other cohorts. All ALT elevations were self-limited, and none were accompanied with elevations in bilirubin or other markers of liver injury.

Additional information about the Phase 1a trial is available at clinicaltrials.gov using the identifier NCT06740474. Assembly Bio expects to submit complete data from the trial for presentation at future scientific meetings.

**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 Sciences, Inc. (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:**<br>Shannon Ryan<br>SVP, Investor Relations, Corporate Affairs and Alliance Management<br>(415) 738-2992<br>investor_relations@assemblybio.com

**Media:**<br>Sam Brown Healthcare Communications<br>Alyssa Kuciunas

(331) 481-3751<br>ASMBMedia@sambrown.com

------