
Up to7,650,764 shares of Common Stock This prospectus relates to the proposed offer and resale or other disposition from time to time by the selling stockholders identified in this prospectus, orcollectively the selling stockholders, of up to an aggregate of7,650,764 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-funded warrants. Thecommon shares and the pre-funded warrants were issued in a private placement, pursuant to a subscription agreement, dated March9, 2026, by andamong us and the purchasers named therein. We are registering the resale of the shares of common stock pursuant to the selling stockholders’ registration rights under a registration rights agreementbetween us and the selling stockholders. Our registration of the resale of the shares of common stock covered by this prospectus does not mean that theselling stockholders will offer or sell all or any of the shares of common stock. The selling stockholders may offer, sell or distribute all or a portion oftheir shares of common stock from time to time directly or indirectly through one or more underwriters, broker-dealers or agents, and in one or morepublic or private transactions. The shares of common stock may be sold in one or more transactions at fixed prices, at prevailing market prices at thetime of the sale, at varying prices determined at the time of sale or at negotiated prices. These sales may be effected in transactions, which may involvecrosses or block transactions. See the section entitled “Plan of Distribution” for more information. We will not receive any proceeds from any sale of common stock by the selling stockholders pursuant to this prospectus (although we will receive thenominal exercise price of $0.001 per share for any pre-funded warrants exercised for cash). We have agreed to bear the expenses in connection with theregistration of the resale of the shares of common stock to be offered by this prospectus by the selling stockholders other than any underwritingdiscounts and commissions or transfer taxes relating to the sale of common stock, which will be borne by the selling stockholders. We may amend or supplement this prospectus from time to time by filing amendments or supplements as required. You should carefully read thisprospectus, as well as any documents incorporated by reference, before you invest in any of the securities being offered. Our common stock is listed on The Nasdaq Capital Market, or Nasdaq, under the symbol “KRRO.” On March19, 2026, the closing price for ourcommon stock, as reported on Nasdaq, was $11.06 per share. Investing in these securities involves certain risks. See “Risk Factors” on page 6of this prospectus as well as thoseincluded in any accompanying prospectus and in the documents incorporated by reference in this prospectus for adiscussion of the factors you should carefully consider before deciding to purchase these securities. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passedupon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense. Table of Contents TABLE OF CONTENTS ABOUT THIS PROSPECTUSCAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSOUR COMPANYRISK FACTORSUSE OF PROCEEDSSELLING STOCKHOLDERS PLAN OF DISTRIBUTION LEGAL MATTERS EXPERTS WHERE YOU CAN FIND MORE INFORMATION INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE Table of Contents ABOUT THIS PROSPECTUS This prospectus is part of a registration statement that we filed with the SEC utilizing a “shelf” registration process. Under this shelf registration process,the selling stockholders may, from time to time, sell the shares of common stock described in this prospectus in one or more offerings. Neither we, nor the selling stockholders, have authorized anyone to give any information or to make any representation other than those contained orincorporated by reference in this prospectus. You must not rely upon any information or representation not contained or incorporated by reference in thisprospectus. The selling stockholders are offering to sell, and seeking offers to buy, shares of our common stock only in jurisdictions where it is lawful todo so. This prospectus does not constitute an offer to sell or the solicitation of an offer to buy any shares other than the registered shares to which itrelates, nor does this prospectus constitute an offer to sell or the solicitation of an offer to buy shares in any jurisdiction to any person to whom it isunlawful to make such offer or solicitation in such jurisdiction. You should not assume that the information contained in this prospectus is accurate onany date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference is c