We will not receive any of the proceeds from the sale by the Selling Stockholders of the Common Stock covered bythis prospectus. Upon any exercise of the Warrants by payment of cash, however, we will receive the exercise priceof the Warrants, which, if exercised in cash with respect to the 5,930,016 shares of Common Stock offered hereby,would result in gross proceeds to us of approximately $17.5 million. However, we cannot predict when and in whatamounts or if the Warrants will be exercised by payments of cash and it is possible that the Warrants may expire andnever be exercised, in which case we would not receive any cash proceeds. The Selling Stockholders may sell or otherwise dispose of the Common Stock covered by this prospectus in anumber of different ways and at varying prices. We provide more information about how the Selling Stockholdersmay sell or otherwise dispose of the Common Stock covered by this prospectus in the section entitled “Plan ofDistribution” on page 50. Discounts, concessions, commissions and similar selling expenses attributable to the saleof Common Stock covered by this prospectus will be borne by the Selling Stockholders. We will pay all expenses(other than discounts, concessions, commissions and similar selling expenses) relating to the registration of theCommon Stock with the Securities and Exchange Commission (the “SEC”). Our Common Stock is listed on The Nasdaq Capital Market under the symbol “PHIO.” On January 27, 2025, thelast reported sale price of our Common Stock on The Nasdaq Capital Market was $2.02 per share. Investing in our securities involves a high degree of risk. Before making any investment in these securities,you should consider carefully the risks and uncertainties described in the section entitled “Risk Factors”beginning on page 10 of this prospectus. Neither the Securities and Exchange Commission nor any state securities commission has approved ordisapproved of these securities or determined if this prospectus is truthful or complete. Any representation tothe contrary is a criminal offense. The date of this prospectus is January 28, 2025 TABLE OF CONTENTS PAGE ABOUT THIS PROSPECTUS1CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS2PROSPECTUS SUMMARY3THE OFFERING8RISK FACTORS10USE OF PROCEEDS21DIVIDEND POLICY21DETERMINATION OF OFFERING PRICE21MARKET INFORMATION21HOLDERS21BUSINESS22MANAGEMENT’S DISCUSSION AND ANALYSIS29MANAGEMENT39DIRECTOR AND EXECUTIVE OFFICER COMPENSATION42SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT46SELLING STOCKHOLDERS47PLAN OF DISTRIBUTION49DESCRIPTION OF SECURITIES TO BE REGISTERED51LEGAL MATTERS53EXPERTS53WHERE YOU CAN FIND MORE INFORMATION53INDEX TO FINANCIAL STATEMENTS54 ABOUT THIS PROSPECTUS This prospectus relates to the resale by the Selling Stockholders identified in this prospectus under the caption“Selling Stockholders,” from time to time, of up to an aggregate of 5,930,016 shares of Common Stock. We are notselling any shares of Common Stock under this prospectus, and we will not receive any proceeds from the sale ofshares of Common Stock offered hereby by the Selling Stockholders, although we may receive cash from theexercise of the Warrants. You should rely only on the information provided in this prospectus. We have not authorized anyone to provide youwith any other information and we take no responsibility for, and can provide no assurances as to the reliability of,any other information that others may give you. The information contained in this prospectus speaks only as of thedate set forth on the cover page and may not reflect subsequent changes in our business, financial condition, resultsof operations and prospects. We are not, and the Selling Stockholders are not, making offers to sell these securities in any jurisdiction in whichan offer or solicitation is not authorized or permitted or in which the person making such offer or solicitation is notqualified to do so or to any person to whom it is unlawful to make such an offer or solicitation. You should read thisprospectus in its entirety before making an investment decision. You should also read and consider the informationin the documents to which we have referred you in the section entitled “Where You Can Find More Information”below, including the registration statement and the other reports we file with the SEC. In this prospectus, unless otherwise noted, (1) the term “Phio” refers to Phio Pharmaceuticals Corp. and oursubsidiary, MirImmune, LLC and (2) the terms “Company,” “we,” “us” and “our” refer to the ongoing businessoperations of Phio and MirImmune, LLC, whether conducted through Phio or MirImmune, LLC. CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS This prospectus contains forward-looking statements within the meaning of the Private Securities Litigation ReformAct of 1995. Forward-looking statements can be identified by words such as “intends,” “believes,” “anticipates,”“indicates,”“plans,”“expects,”“suggests,”“may,”“




