Korro Bio Inc. 美股招股说明书（2026年5月12日版）

Up to 7,650,764 shares of Common Stock This Prospectus Supplement No. 1 supplements the prospectus dated March 20, 2026, or the prospectus, relating to the offer andresale or other disposition from time to time by the selling stockholders identified in the prospectus, or collectively the sellingstockholders, of up to an aggregate of 7,650,764 shares of our common stock, par value $0.001 per share, or the common stock,consisting of (i) 4,501,928 shares of our common stock and (ii) 3,148,836 shares of common stock issuable upon exercise of pre- The purpose of this Prospectus Supplement No. 1 is solely to update the information in the table appearing under the caption“Selling Stockholders” commencing on page 8 of the prospectus to reflect in the Selling Stockholder table a transfer of 540,054shares of Common Stock from Point72 Associates, LLC, a selling stockholder previously identified in the prospectus, to SILV Selling Stockholder (11) Shares listed under “Number of Shares Owned Before the Offering” consists of 540,054 shares held by SILV Fund, Ltd.Sirenia Capital Management LP, or Sirenia, serves as the investment manager to SILV Fund, Ltd. and, as a result, maintainsvoting and investment power with respect to the securities held by SILV Fund, Ltd. Sirenia Capital Management GP LLC, orSirenia GP, is the general partner of Sirenia. Alex Silverstein is the managing member of Sirenia GP. Each of SILV Fund, All of the other portions of the prospectus remain unchanged. This Prospectus Supplement No. 1 is not complete without, and may not be utilized except in connection with, the prospectus,including any amendments or supplements thereto. This Prospectus Supplement No. 1 is qualified by reference to the prospectus,except to the extent that the information provided by this Prospectus Supplement No. 1 supersedes information contained in the Our common stock is listed on The Nasdaq Capital Market, or Nasdaq, under the symbol “KRRO.” On May 12, 2026, the closingprice for our common stock, as reported on Nasdaq, was $11.22 per share. Investing in these securities involves certain risks. See “Risk Factors” on page 6 of the prospectus as well as those includedin any accompanying prospectus and in the documents incorporated by reference in this prospectus for a discussion of the Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of thesesecurities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminaloffense. The date of this Prospectus Supplement No. 1 is May 12, 2026.