Altimmune Inc美股招股说明书(2026-01-28版)

12,397,920 Shares of Common StockPre-Funded Warrants to Purchase 4,647,534 Shares of Common Stock We are offering 12,397,920 of shares of our common stock, par value $0.0001 per share and, in lieu ofcommon stock to a certain investor, pre-funded warrants to purchase up to 4,647,534 shares of ourcommon, in a registered direct offering to a limited number of purchasers pursuant to this prospectussupplement and the accompanying prospectus. Each pre-funded warrant is exercisable for one share ofcommon stock. The purchase price of each pre-funded warrant will be equal to the price per share at whichshares of our common stock are being sold to the public in this offering, less $0.001 exercise price of eachpre-funded warrant. The pre-funded warrants do not expire, and each pre-funded warrant will beexercisable at any time after the date of issuance, subject to an ownership limitation. Our common stock is listed on The Nasdaq Global Market under the symbol “ALT.” On January 27, 2026,the closing price for our common stock, as reported on The Nasdaq Global Market, was $6.18 per share.There is no established public trading market for the pre-funded warrants, and we do not expect a marketto develop. We do not intend to list the pre-funded warrants on The Nasdaq Global Market or any othernational securities exchange or nationally recognized trading system. We have engaged Titan Partners Group LLC, a division of American Capital Partners, LLC, to act as oursole placement agent (the “Placement Agent”) in connection with this offering. The Placement Agent is notpurchasing or selling any of the securities offered pursuant to this prospectus supplement and theaccompanying prospectus and the Placement Agent is not required to arrange the purchase or sale of anyspecific number of securities or dollar amount and has agreed to use its reasonable best efforts to sell thesecurities offered by this prospectus supplement and the accompanying prospectus. We are a “smaller reporting company” under U.S. federal securities laws and as such are subject toreduced public company reporting requirements. Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on pageS-7of this prospectus supplement and other similar headings in the documents that are incorporated byreference into this prospectus supplement and the accompanying base prospectus for a discussion ofinformation that should be considered in connection with an investment in our securities. Neither the Securities and Exchange Commission nor any state securities commission has approvedordisapproved of these securities or determined if this prospectus supplement and theaccompanying prospectus is truthful or complete. Any representation to the contrary is a criminaloffense. Deliveryof the shares of common stock and pre-funded warrants is expected to be made on or aboutJanuary 29, 2026. The shares of common stock will be settled via the Depository Trust Company. The pre-funded warrants will be delivered to a purchaser in certificated form. Sole Placement Agent Titan Partners Groupa division of American Capital Partners The date of this prospectus supplement is January 27, 2026. TABLE OF CONTENTS PROSPECTUS SUPPLEMENT MARKET, INDUSTRY AND OTHER DATAS-iiABOUT THIS PROSPECTUS SUPPLEMENTS-iiiPROSPECTUS SUPPLEMENT SUMMARYS-1THE OFFERINGS-5RISK FACTORSS-7SPECIAL STATEMENT REGARDING FORWARD-LOOKING STATEMENTSS-9USE OF PROCEEDSS-11DILUTIONS-12DESCRIPTION OF SECURITIES WE ARE OFFERINGS-14MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS FOR NON-US HOLDERS OFCOMMON STOCK OR PRE-FUNDED WARRANTSS-16PLAN OF DISTRIBUTIONS-20LEGAL MATTERSS-22EXPERTSS-23WHERE YOU CAN FIND MORE INFORMATIONS-24INCORPORATION OF DOCUMENTS BY REFERENCES-25PROSPECTUSABOUT THIS PROSPECTUS1RISK FACTORS2CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS3OUR COMPANY4USE OF PROCEEDS6SECURITIES WE MAY OFFER7DESCRIPTION OF CAPITAL STOCK8DESCRIPTION OF DEBT SECURITIES12DESCRIPTION OF WARRANTS18DESCRIPTION OF UNITS19PLAN OF DISTRIBUTION22LEGAL MATTERS25EXPERTS26WHERE YOU CAN FIND MORE INFORMATION27INCORPORATION BY REFERENCE28 MARKET, INDUSTRY AND OTHER DATA We obtained the industry, market and competitive position data included or incorporated by referencein this prospectus supplement and the accompanying base prospectus from our own internal estimates andresearch, as well as from independent market research, industry and general publications and surveys,governmental agencies and publicly available information in addition to research, surveys and studiesconducted by third parties. Internal estimates are derived from publicly available information released byindustry analysts and third-party sources, our internal research and our industry experience, and are basedon assumptions made by us based on such data and our knowledge of our industry and market, which webelieve to be reasonable. We have not independently verified the accuracy or completeness of the datacontained in the third-