Prime Medicine, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

(Mark One)

For the fiscal year ended December 31, 2025

OR

For the transition period from ___________________ to ___________________

Commission File Number:001-41536

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code:

(617) 465-0013

Securities registered pursuant to Section 12(b) of the 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 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 Act). Yes ☐ No☑

As of June 30, 2025, the last business day of the registrant’s most recently completed second fiscal quarter, the aggregate market value of the registrant’s common stock held by non-affiliates of the registrant was approximately $238,759,057 based on a closing price of $2.47 per share as quoted by the Nasdaq Global Market as of such date. In determining the market value of non-affiliate common stock, shares of the registrant’s common stock beneficially owned by officers, directors and affiliates have been excluded. This determination of affiliate status is not necessarily a conclusive determination for other purposes.

As of February 20, 2026, there were 180,552,179 shares of Common Stock, $0.00001 par value per share, outstanding.

Table of Contents

i

References to Prime Medicine

Throughout this Annual Report on Form 10-K, “Prime Medicine,” “Prime,” “the Company,” “we,” “us,” and “our,” and similar expressions, except where the context requires otherwise, refer to Prime Medicine, Inc. and its consolidated subsidiaries, and “our board of directors” refers to the board of directors of Prime Medicine, Inc.

From time to time we may use our website, our X, formerly Twitter, account (@PrimeMedicine) or our LinkedIn profile at https://www.linkedin.com/company/prime-medicine to distribute material information. Our financial and other material information is routinely posted to and accessible on the Investors section of our website, available at www.primemedicine.com. Investors are encouraged to review the Investors section of our website because we may post material information on that site that is not otherwise disseminated by us. Information that is contained in and can be accessed through our website or our social media is not incorporated into, and does not form a part of, this Annual Report on Form 10-K.

We intend to apply for various trademarks that we use in connection with the operation of our business. This Annual Report on Form 10-K may also contain trademarks, service marks and trade names of third parties, which are the property of their respective owners. Our use or display of third parties’ trademarks, service marks, trade names or products in this Annual Report on Form 10-K is not intended to, and does not imply a relationship with, or endorsement or sponsorship by us. Solely for convenience, the trademarks, service marks and trade names referred to in this Annual Report on Form 10-K may appear without the ®, SM and ™ symbols, but the omission of such references is not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or the right of the applicable owner of these trademarks, service marks and trade names.

ii

Cautionary Note Regarding Forward-looking Information

This Annual Report on Form 10-K contains forward-looking statements which are made pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. All statements, other than statements of historical facts, contained in this Annual Report on Form 10-K, including statements regarding our strategy, future operations, future financial position, future revenue, projected costs, prospects, plans, and objectives of management, are forward-looking statements. The words “anticipate,” “believe,” “envision,” “estimate,” “expect,” “goal,” “intend,” “may,” “plan,” “predict,” “project,” “strategy,” “target,” “potential,” “will,” “would,” “could,” “should,” “continue,” “contemplate,” “vision” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

Our business and our forward-looking statements in this Annual Report on Form 10-K involve substantial known and unknown risks and uncertainties, including, among other things, the risks and uncertainties inherent in our statements regarding:

•the initiation, timing, progress and results of our research and development programs, product candidates, and ongoing and future preclinical studies and future clinical trials;

•our ability to demonstrate, and the timing of, preclinical proof-of-conceptin vivo for multiple programs;

•our ability to advance any current and future product candidates that we may identify and successfully complete any clinical trials, including the manufacture of any such product candidates;

•our ability to pursue our areas of focus and any other additional programs we may advance;

•our ability to quickly leverage programs within our initial target indications and to progress additional programs to further develop our pipeline;

•the timing of our investigational new drug, or IND, application submissions;

•the ability of our Prime Editing technology to address unmet medical needs in patients;

•the implementation of our strategic plans for our business, programs and technology;

•the scope and duration of protection we are able to establish and maintain for intellectual property rights covering our Prime Editing technology;

•developments related to our competitors and our industry;

•our ability to leverage the clinical, regulatory, and manufacturing advancements made by gene therapy and gene editing programs to accelerate our clinical trials and approval of product candidates;

•our ability to maintain existing collaborations or strategic relationships, to identify and enter into future license agreements and collaborations on favorable terms, if at all, and to realize the intended and potential benefits of such agreements and collaborations;

•developments related to our Prime Editing technology;

•regulatory developments in the United States and foreign countries;

•our ability to attract and retain key scientific and management personnel;

•the accuracy of our estimates regarding our expenses, capital requirements and needs for additional financing;

•our planned regulatory interactions with the U.S. Food and Drug Administration, or FDA, based on the data from our Phase 1/2 trial of PM359 for the treatment of chronic granulomatous disease, or CGD, and the outcomes of any such interactions;

•our ability to maintain an effective system of internal controls;

•the effect of unfavorable macroeconomic conditions or market volatility resulting from national or global economic conditions or geopolitical developments, including high inflation and capital market disruptions,

iii changes in or disruptions of U.S. governmental agencies, whether from a U.S. federal government shutdown or reduced resources, new or increased international tariffs and retaliatory tariffs, trade protection measures, economic sanctions and economic slowdowns or recessions that may result from such developments which could harm our research and development efforts as well as the value of our securities and our ability to access capital markets;

•our expectations regarding the anticipated timeline of our cash runway, future financial performance and our ability to continue as a going concern; and

•other risks and uncertainties, including those listed under the caption “Risk Factors.”

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and these statements may be affected by inaccurate assumptions or by known or unknown risks and uncertainties. You should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have included important factors in this Annual Report on Form 10-K, particularly in the "Summary of the Material Risks Associated with Our Business" and “Risk Factors” sections, that we believe could cause actual results or events to differ materially from the forward-looking statements that we make. Unless otherwise disclosed, our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, collaborations, joint ventures or investments we may make or enter into.

You should read this Annual Report on Form 10-K and the documents that we reference herein and have filed as exhibits to this Annual Report on Form 10-K or other filings with the Securities and Exchange Commission, or the SEC, completely and with the understanding that our actual future results may be materially different from what we expect. The forward-looking statements contained in this Annual Report on Form 10-K are made as of the date hereof, and we do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise after the date of such statements, except as required by applicable law.

This Annual Report on Form 10-K also contains estimates, projections and other information concerning our industry, our business and the markets for our product candidates. Such information is inherently subject to uncertainties and actual events or circumstances may differ materially from events and circumstances that are assumed in this information. Unless otherwise expressly stated, we obtained statistical and other industry and market data from our own internal estimates and research, as well as from reports, industry publications and research, surveys, studies and similar data prepared by third parties, industry, medical and general publications, government data and similar sources. While we are not aware of any misstatements regarding any third-party information presented in this Annual Report on Form 10-K, their estimates, in particular as they relate to projections, involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such data. The industry in which we operate is subject to a high degree of uncertainty and risk due to a variety of important factors, including those described in the sections titled “Summary of the Material Risks Associated with Our Business” and “Risk Factors.”

iv

Summary of the Material Risks Associated with Our Business

Our business is subject to a number of risks that if realized could materially affect our business, financial condition, results of operations, cash flows and access to liquidity. These risks are discussed more fully in the “Risk Factors” section of this Annual Report on Form 10-K. Our principal risks include the following:

•We have incurred significant losses since inception. We expect to incur losses for the foreseeable future and may never achieve or maintain profitability.

•Because our existing cash, cash equivalents, and investments will not be sufficient to fund our operations, as currently planned, for more than one year beyond the filing date of this Annual Report on Form 10-K, we have determined that there is substantial doubt regarding our ability to continue as a going concern.

•We will need substantial additional funding. If we are unable to raise capital when needed, we will be forced to delay, reduce, eliminate or prioritize among our research and product development programs or future commercialization efforts.

•Gene editing, including platforms such as Prime Editing, is a relatively new technology that has not been extensively clinically validated for human therapeutic use. The approach we are taking to discover and develop novel therapeutics is unproven and may never lead to marketable products. We may incur unexpected costs or experience delays in completing, or ultimately be unable to complete, the development and commercialization of any product candidates.

•Clinical drug development involves a lengthy and expensive process, with an uncertain outcome. Because gene editing is novel and the regulatory landscape that will govern our current and future product candidates is uncertain and may change, we cannot predict the time and cost of obtaining regulatory approval, if we receive it at all, for our current and future product candidates.

•We may enter into collaborations with collaborators and strategic partners such as Beam Therapeutics Inc., or Beam, or other third parties for the research, development, delivery, manufacturing and commercialization of Prime Editing technology and certain of the product candidates we may develop. If any such collaborations are not successful, we may not be able to capitalize on the market potential of our Prime Editing platform or product candidates.

•If conflicts arise between us and our collaborators or strategic partners, these parties may act in a manner adverse to us and could limit our ability to implement our strategies.

•If we are unable to obtain and maintain patent and other intellectual property protection for any product candidates we develop and for our Prime Editing technology, or if the scope of the patent and other intellectual property protection obtained is not sufficiently broad, third parties could develop and commercialize products and technology similar or identical to ours and our ability to successfully commercialize any product candidates we may develop and our Prime Editing technology may be adversely affected.

•Our rights to develop and commercialize our Prime Editing platform technology and product candidates are subject to the terms and conditions of licenses granted to us by others. If we fail to comply with our obligations in the agreements under which we license intellectual property rights from third parties or otherwise experience disruptions to our business relationships with our licensors, we could lose license rights that are important to our business.

•Our in-licensed issued patents and owned and in-licensed patent applications may not provide sufficient protection of our Prime Editing technologies and our future product candidates or result in any competitive advantage.

•The intellectual property landscape around the technologies we use or plan to use, including gene editing technology, is highly dynamic, and third parties may initiate legal proceedings alleging that we are infringing, misappropriating, or otherwise violating their intellectual property rights, the outcome of which would be uncertain and may prevent, delay or otherwise interfere with our product discovery and development efforts.

v

•We expect to expand our research, development, delivery, manufacturing, commercialization, regulatory and future sales and marketing capabilities over time, and as a result, we may encounter difficulties in managing our growth, which could disrupt our operations.

•The FDA the European Medicines Agency, or the EMA, and the National Institutes of Health, or NIH, have demonstrated caution as well as concern regarding potential long term impacts in their regulation of gene therapy treatments, and ethical and legal concerns about gene therapy and genetic testing may result in additional regulations or restrictions on the development and commercialization of any product candidates we may develop, which may be difficult to predict.

vi