Korro Bio Inc — Current Report (Form 8-K)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

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 19, 2026

Korro Bio, Inc.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (617) 468-1999

N/A

(Former name or former address, if changed since last report)

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:

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

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. ☐

Item 8.01. Other Events.

On August 19, 2026, Korro Bio, Inc., or Korro, announced a submission to the Australian Alfred Health Human Ethics Committee to initiate a first-in-human Phase 1/2 clinical trial for KRRO-121, a GalNAc-conjugated RNA editing oligonucleotide in development for the potential treatment of hyperammonemia in patients with Urea Cycle Disorders, or UCDs.

The purpose of the Phase 1/2 clinical trial for KRRO-121 is to determine the safety and tolerability of escalating doses, evaluate its pharmacokinetics, and assess its effect in healthy volunteers and in study participants with UCDs. For additional information, visit ClinicalTrials.gov (NCT 07773246).

Forward-Looking Statements

Certain statements in this current report on Form 8-K may constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements include, but are not limited to, express or implied statements regarding expectations, hopes, beliefs, intentions or strategies of Korro regarding the future including, without limitation, express or implied statements regarding ongoing development of KRRO-121, including approvals to commence a Phase 1/2 clinical trial for UCDs; among others. 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,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “strive,” “would,” “aim,” “target,” “commit,” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that statement is not forward looking. Forward-looking statements are based on current expectations and assumptions that, while considered reasonable, are inherently uncertain. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. Factors that may cause actual results to differ materially from current expectations include, but are not limited to, various factors beyond management’s control including risks of conducting a first-in-human clinical trial; challenges with addressing any regulatory concerns necessary to proceed with enrollment and dosing; risks associated with enrolling sufficient participants and other risks inherent in biopharmaceutical development; risks associated with conducting pre-clinical studies and clinical trials and risks of replicating results from pre-clinical studies in clinical trials; and other risks associated with obtaining regulatory approvals and protecting intellectual property; as well as risks associated with general economic conditions; and other risks and uncertainties indicated from time to time in Korro’s filings with the SEC, including Part II Item 1A. “Risk Factors” in Korro’s Quarterly Report on Form 10-Q filed with the SEC on August 6, 2026, as such may be amended or supplemented by its other filings with the SEC. Nothing in this current report on Form 8-K should be regarded as a representation by any person that the forward-looking statements set forth herein will be achieved or that any of the contemplated results of such forward-looking statements will be achieved. You should not place undue reliance on forward-looking statements in this current report on Form 8-K, which speak only as of the date they are made and are qualified in their entirety by reference to the cautionary statements herein. Except as required by law, Korro does not undertake or accept any duty to release publicly any updates or revisions to any forward-looking statements to reflect any change in its expectations or in the events, conditions or circumstances on which any such statement is based. This current report on Form 8-K does not purport to summarize all of the conditions, risks and other attributes of an investment in Korro.

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 hereunto duly authorized.