Korro Bio, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)

For the quarterly period ended June 30,2025

OR

For the transition period from_____________________ to_____________________

Commission File Number:001-39062

(Exact name of registrant as specified in its charter)

(617) 468-1999

(Registrant’s telephone number, including area code)

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

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, 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 is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes☐ No☒

As of August 8, 2025, the registrant had 9,390,903 shares of common stock, $0.001 par value per share, outstanding.

Table of Contents

Unless the context otherwise indicates, references in this Quarterly Report on 10-Q to the “Company,” the "combined company," “we,” “our” and “us” refer, collectively, to Korro Bio, Inc., a Delaware corporation, and its consolidated subsidiaries (including Legacy Korro) after completion of our November 2023 business combination. The term “Legacy Korro” refers to privately held Korro Bio Ops, Inc. (formerly known as Korro Bio, Inc.), which we acquired in the November 2023 business combination.

We use various trademarks and trade names in our business, including without limitation our corporate name and logo. All other trademarks or trade names referred to in this Quarterly Report on Form 10-Q are the property of their respective owners. Solely for convenience, the trademarks and trade names in this Quarterly Report on Form 10-Q may be referred to without the ® and ™ symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This Quarterly Report on Form 10-Q, or this Quarterly Report, includes statements that are not historical facts and are considered forward-looking within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. Our forward-looking statements include, but are not limited to, statements regarding our or our management team’s expectations, hopes, beliefs, intentions or strategies regarding the future. In addition, any statements that refer to projections, forecasts or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. The words “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intends,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “will,” “would” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. Forward-looking statements in this Quarterly Report may include, for example, statements about:

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the timing, progress, results, and cost of our Phase 1/2a REWRITE clinical trial of KRRO-110, including our ability to complete the Phase 1/2a clinical trial and KRRO-110’s best-in-class potential for the treatment of Alpha-1 Antitrypsin Deficiency, or AATD;

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the initiation, timing, progress, results, cost of and other statements regarding our research and development programs and our current and future preclinical studies and clinical trials, including statements regarding the timing of announcement of our rare metabolic disorder program, initiation and completion of studies or trials and related preparatory work, and the period during which the results of the trials will become available;

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our cash runway and ability to reach meaningful clinical data readouts and data inflection points;

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the effects of our organizational streamlining and workforce reduction;

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the therapeutic and commercial potential of our product candidates;

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our research and development and other expenses;

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our 3-2-1 strategy and other strategic objectives;

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our collaboration arrangement with Novo Nordisk A/S, or Novo Nordisk, and any future collaboration or licensing arrangements;

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our ability to comply with, and the impact of, regulatory requirements, obligations and restrictions on our business and operations;

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our ability to protect our intellectual property and operate our business without infringing upon the intellectual property rights of others, including our ability to obtain and maintain rights to the technologies required to develop and commercialize our product candidates;

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competitive developments, including the impact on our competitive position of competing products and product candidates and our ability to meet such competition; and

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our ability to manage the growth of our business.

These forward-looking statements are subject to known and unknown risks, uncertainties and assumptions about us that may cause our actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by such forward-looking statements, including those set forth under the heading “Risk Factors” in Part II, Item 1A of this Quarterly Report. Given these risks and uncertainties, you should not place undue reliance on these forward-looking statements. Should one or more of the risks or uncertainties described in this Quarterly Report, or should underlying assumptions prove incorrect, actual results and plans could differ materially from those expressed in any forward-looking statements. Except as otherwise required by applicable law, we disclaim any duty to update any forward-looking statements, all of which are expressly qualified by the statements in this section, to reflect events or circumstances after the date of this Quarterly Report. We qualify all of our forward-looking statements by these cautionary statements.

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SUMMARY OF RISK FACTORS

Our business involves significant risks. Below is a summary of the material risks that our business faces, which makes an investment in our securities speculative and risky. This summary does not address all these risks. These risks are more fully described below under the heading “Risk Factors” in Part II, Item 1A of this Quarterly Report. Before making investment decisions regarding our securities, you should carefully consider these risks. The occurrence of any of the events or developments described below could have a material adverse effect on our business, results of operations, financial condition, prospects and stock price. In such event, the market price of our securities could decline, and you could lose all or part of your investment. Further, there are additional risks not described below that are either not currently known to us or that we currently deem immaterial, and these additional risks could also materially impair our business, operations or market price of our securities.

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

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We have never generated revenue from product sales and may never become profitable.

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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 development programs or future commercialization efforts.

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We have dosed very few participants in our Phase 1/2a REWRITE clinical trial of KRRO-110 for AATD, and have not completed any clinical trials nor reported any clinical trial results for any of our proposed delivery methods or RNA editing approaches. Any favorable results we may have may not be predictive of results that may be observed in later preclinical studies or clinical trials.

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If preclinical studies or clinical trials of any product candidates we may identify and develop fail to demonstrate safety and efficacy to the satisfaction of regulatory authorities or do not otherwise produce positive results, we may incur additional costs or experience delays in completing, or ultimately be unable to complete, the development and commercialization of such product candidates.

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If we experience delays or difficulties in the enrollment of patients in clinical trials, or other delays in our clinical trials, our receipt of necessary regulatory approvals could be delayed or prevented.

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We may not realize the anticipated benefits of our organizational streamlining and workforce reduction.

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The gene editing field and RNA editing in particular is relatively new and is evolving rapidly. We are very early in our research and development efforts and may not be successful in identifying and developing product candidates. It will be many years before we or our collaborators commercialize a product candidate or generate any revenues, if ever. Additionally, other gene editing technologies may be discovered that provide significant advantages over RNA editing, which could materially harm our business.

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RNA editing is a novel technology with limited clinical validation for human therapeutic use. The approaches we take to discover and develop novel therapeutics are unproven and may never lead to marketable products.

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We are very early in our development efforts, and our preclinical studies and clinical trials may not be successful. If we are unable to commercialize our product candidates or experience significant delays in doing so, our business will be materially harmed.

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Any product candidates we develop may fail in preclinical or clinical development or be delayed to a point where they do not become commercially viable.

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Because we are developing oligonucleotides, which are considered a relatively new class of drugs, there is increased risk that the outcome of our clinical trials will not be sufficient to obtain regulatory approval.

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If we are not able to obtain or protect intellectual property rights related to any of our product candidates, development and commercialization of our product candidates may be adversely affected.

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We may not be successful in finding strategic collaborators for continuing development of certain of our product candidates or successfully commercializing or competing in the market for certain indications; and we may not see any benefit from our collaboration agreement with Novo Nordisk.

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The price of our common stock is volatile and fluctuates substantially, which could result in substantial losses for our stockholders.

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Our certificate of incorporation and bylaws and provisions under Delaware law could make an acquisition of us more difficult and may prevent attempts by our stockholders to replace or remove our management.

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Our executive officers, directors and principal stockholders have the ability to control or significantly influence all matters submitted to our stockholders for approval.

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Unfavorable global economic conditions could adversely affect our business, financial condition, results of operations or cash flow.

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Our business may be impacted by macroeconomic conditions, including fears concerning inflation, rising interest rates and volatile market conditions (including as a result of announced tariffs or other policy changes by the current U.S. administration), and other uncertainties beyond our control.

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