ASSEMBLY BIOSCIENCES, INC.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 10-K

For thefiscal year ended December 31,2024

or

For the Transition Period from __________ to __________

Commission File Number:001-35005

(Exact name of registrant as specified in its charter)

Two Tower Place,7th Floor

South San Francisco, California 94080

(Address of Principal Executive Offices)

Registrant’s telephone number, including area code: (833)509-4583

Securities Registered Pursuant to Section 12(b) of the Exchange Act:

Securities Registered Pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes☐ No ☒

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Exchange Act. Yes☐ No☒

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes☒ No☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes☒ No☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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.☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262 (b)) by the registered public accounting firm that prepared or issued its audit report.☐

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements.☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b).☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes☐ No☒

The aggregate market value of the voting stock held by non-affiliates of the registrant, as of June 30, 2024, was $69.0 million. Such aggregate market value was computed by reference to the closing price of the common stock as reported on the Nasdaq Global Select Market on June 30,2024. For purposes of making this calculation only, the registrant has defined affiliates as including only (1) directors, (2) executive officers and (3) certain stockholders, if any, that hold greater than 10% of the voting stock of the registrant, in each case, as of June 30, 2024. Shares of common stock held by other persons, including certain other holders of more than 10% of the registrant’s outstanding common stock, if any, have not been excluded from the above calculation in that such persons are not deemed to be affiliates. The determination of affiliate status is not necessarily a conclusive determination for other purposes.

As of March 14, 2025, there were 7,503,385 shares of the registrant’s common stock, $0.001 par value per share, outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Part III of this Annual Report on Form 10-K incorporates information by reference to portions of the definitive proxy statement for the Company’s Annual Meeting of Stockholders to be held in 2025, to be filed within 120 days of the registrant’s fiscal year ended December 31, 2024.

TABLE OF CONTENTS

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References to Assembly Biosciences, Inc.

Throughout this Annual Report on Form 10-K, the “Company,” “Assembly Bio,” “Assembly,” “we,” “us,” and “our,” except where the context requires otherwise, refer to Assembly Biosciences, Inc. and its consolidated subsidiaries, and “our board of directors” or “the Board” refers to the board of directors of Assembly Biosciences, Inc.

Forward-Looking Statements

This Annual Report on Form 10-K contains “forward-looking statements” that are subject to certain risks and uncertainties, including, without limitation, those set forth in Part I, Item 1A under the heading “Risk Factors,” that could cause actual results to materially differ. Such risks and uncertainties include, among other things:

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our ability to maintain financial resources necessary to continue our research activities, clinical studies and other business operations;

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our ability to realize the potential benefits of our collaboration with Gilead Sciences, Inc. (Gilead), including all financial aspects of the collaboration and equity investments;

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our ability to initiate and complete clinical studies involving our therapeutic product candidates, including studies contemplated by our collaboration with Gilead, in the currently anticipated timeframes or at all;

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safety and efficacy data from clinical or nonclinical studies may not warrant further development of our product candidates;

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clinical and nonclinical data presented at conferences may not differentiate our product candidates from other companies’ candidates;

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potential effects of changes in government regulation, including as a result of the change in U.S. administration in 2025; and

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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.

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. In particular, forward-looking statements include, but are not limited to, statements regarding the timing of commencement of future clinical studies involving our therapeutic product candidates; and our ability to successfully complete, and receive favorable results in, clinical studies for our product candidates. We intend such forward-looking statements to be covered by the safe harbor provisions contained in Section 27A of the Securities Act of 1933, as amended (the Securities Act), and Section 21E of the Securities Exchange Act of 1934, as amended (the Exchange Act). Except as required by law, we assume no obligation to update publicly any forward-looking statements, whether as a result of new information, future events or otherwise.

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