IN8bio Inc. 美股招股说明书（2026年6月1日版）

PROSPECTUS SUPPLEMENTTo Prospectus dated May19, 2026 We have entered into a Capital on DemandTMSales Agreement, or the Sales Agreement, with JonesTrading Institutional Services LLC, referred to herein as theSales Agent or Jones, relating to shares of our common stock, par value $0.0001 per share, offered by this prospectus supplement. In accordance with the terms of theSales Agreement, we may offer and sell shares of our common stock having an aggregate offering price of up to $2,800,000 from time to time through or to the Sales Our common stock is listed on the Nasdaq Capital Market under the trading symbol “INAB.” On May29, 2026, the last reported sale price of our common stockwas $1.87 per share. Sales of our common stock, if any, under this prospectus supplement will be made in sales deemed to be an “at the market offering” as defined in Rule 415(a)(4)promulgated under the Securities Act of 1933, as amended, or the Securities Act. The Sales Agent is not required to sell any specific amount of securities, but will act asour sales agent using commercially reasonable efforts consistent with its normal trading and sales practices, on mutually agreed terms between the Sales Agent and us. The compensation to the Sales Agent for sales of common stock sold pursuant to the Sales Agreement will be equal to 3.0% of the gross proceeds of any shares ofcommon stock sold under the Sales Agreement. In connection with the sale of the common stock on our behalf, the Sales Agent will be deemed to be an “underwriter”within the meaning of the Securities Act and the compensation of the Sales Agent will be deemed to be underwriting commissions or discounts. We have also agreed to We are an “emerging growth company” and a “smaller reporting company” as defined under the federal securities laws and, as such, have elected to comply withcertain reduced public company reporting requirements for this prospectus supplement and the documents incorporated by reference herein and may elect to comply with The aggregate market value of our common stock held by non-affiliates as of June 1, 2026 pursuant to General InstructionI.B.6 of FormS-3 is $17,932,668,which was calculated based on 9,589,662 shares of our common stock outstandingheld by non-affiliates and at a price of $1.87 per share, the closing price of ourcommon stock on May29, 2026. Asof the date hereof, we have offered and sold $3,113,883 of securities pursuant to General Instruction I.B.6 of Form S-3 during theprior 12calendar month period that ends on and includes the date hereof. As a result of the limitations of General Instruction I.B.6 of FormS-3, and in accordance with Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertaintiesdescribed under the section titled “Risk Factors” in this prospectus supplement, the accompanying prospectus andunder similar headings in the documents that are incorporated by reference herein and therein before making a Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined ifthis prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense. The date of this prospectus supplement is June 1, 2026. Prospectus Supplement ABOUT THIS PROSPECTUSPROSPECTUS SUMMARYRISK FACTORSSPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTSUSE OF PROCEEDSDESCRIPTION OF CAPITAL STOCKDESCRIPTION OF DEBT SECURITIESDESCRIPTION OF WARRANTSDESCRIPTION OF RIGHTSDESCRIPTION OF UNITSLEGAL OWNERSHIP OF SECURITIESPLAN OF DISTRIBUTIONLEGAL MATTERSEXPERTSWHERE YOU CAN FIND ADDITIONAL INFORMATIONINCORPORATION OF CERTAIN INFORMATION BY REFERENCES-i Table of Contents ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplement is part of a shelf registration statement on FormS-3that we filed with the Securities and ExchangeCommission, or the SEC. This document is in two parts. This first part is this prospectus supplement, which describes the specific terms of the commonstock we are offering and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by referencetherein. The second part is the accompanying prospectus, which provides more general information about securities we may offer from time to time,some of which does not apply to this offering. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. Tothe extent there is a conflict between the information contained in this prospectus supplement and the information contained in the accompanying You should rely only on the information contained in, or incorporated by reference into, this prospectus supplement, the accompanyingprospectus or in any other prospectus supplement or free writing prospectus that we may authorize for use in connection with this offering. We have not,and the Sales Agent have not,