Lyell Immunopharma Inc美股招股说明书(2025-12-18版)

1,900,000 Shares of Common Stock This prospectus relates to the proposed resale from time to time by Innovative Cellular Therapeutics Holdings Limited, a Cayman Island exemptedcompany incorporated with limited liability (“ICT Holdings”), as the selling stockholder, of up to 1,900,000 shares of our common stock, par value$0.0001 per share. The shares of common stock registered for resale pursuant to this prospectus were issued as part of the consideration under anExclusive License Agreement, dated as of November6, 2025 (the “License Agreement”), by and among us, ICT Holdings and Innovative CellularTherapeutics, Inc., a Delaware corporation (“ICT” and together with ICT Holdings, the “ICT Group”), pursuant to which the ICT Group granted us anexclusive license to research, develop, manufacture, commercialize and otherwise exploit certain product candidates and products worldwide except inmainland China, Taiwan, Macau and Hong Kong. On November6, 2025, we issued a total of 1,900,000 shares of our common stock to ICT Holdings inconnection with the effectiveness of the License Agreement. We are registering the shares of our common stock on behalf of ICT Holdings, to be offered and sold by ICT Holdings from time to time. We arenot selling any securities under this prospectus and will not receive any of the proceeds from the sale of shares by ICT Holdings. This prospectus provides a general description of the common stock ICT Holdings may offer. ICT Holdings may sell the shares of our commonstock described in this prospectus in a number of different ways and at varying prices. See the section titled “Plan of Distribution for Shares Offered bythe Selling Stockholder”on page21 of this prospectus for more information about how ICT Holdings may sell the shares of common stock beingregistered pursuant to this prospectus. We and ICT Holdings have agreed to each be responsible for 50% of the expenses incurred in registering the shares of common stock, includingcertain legal and accounting fees. ICT Holdings will bear all underwriting discounts, selling commissions and similar fees and arrangements and stocktransfer taxes allocable to its sales of the shares of our common stock and certain additional legal and advisor fees. Our common stock is listed on the Nasdaq Global Select Market under the trading symbol “LYEL.” On December17, 2025, the last reported saleprice of our common stock was $32.07 per share. Investing in our securities involves a high degree of risk. Before making an investment decision, you should reviewcarefully the risks and uncertainties described under the section titled “Risk Factors” contained in this prospectus andunder similar headings in the documents that are incorporated by reference into this prospectus. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities ordetermined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense. Table of Contents TABLE OF CONTENTS ABOUT THIS PROSPECTUSPROSPECTUS SUMMARYRISK FACTORSSPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTSSELECTED FINANCIAL DATA REFLECTING REVERSE STOCK SPLITUSE OF PROCEEDS LEGAL OWNERSHIP OF SECURITIES PLAN OF DISTRIBUTION FOR SHARES OFFERED BY THE SELLING STOCKHOLDER LEGAL MATTERS EXPERTS WHERE YOU CAN FIND MORE INFORMATION INCORPORATION OF CERTAIN INFORMATION BY REFERENCE ABOUT THIS PROSPECTUS This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission (the “SEC”), utilizing a“shelf” registration process under the Securities Act of 1933, as amended (the “Securities Act”). Under this shelf registration process, ICT Holdings, asthe selling stockholder, which as used herein include donees, pledgees, transferees, distributees or other successors-in-interest selling shares of ourcommon stock or interests in our common stock received after the date of this prospectus from the selling stockholder as a gift, pledge, partnershipdistribution or other transfer identified in this prospectus, may offer and sell up to 1,900,000 shares of our common stock. This prospectus provides ageneral description of the shares of our common stock the selling stockholder may offer. We are not selling any securities under this prospectus and willnot receive any of the proceeds from the sale of shares by the selling stockholder. For general information about the distribution of shares of commonstock offered by the selling stockholder, see the section in this prospectus titled “Plan of Distribution for Shares Offered by the Selling Stockholder.” We urge you to read carefully this prospectus, together with the information incorporated herein by reference as described under the sections titled“Where You Can Find More Information” and “Incorporation of Certain Information by Reference,” before buying any of the shares of our commonstock being offered. You should rely only