Atara Biotherapeutics Inc美股招股说明书(2026-03-25版)

This prospectus relates to the resale, from time to time by HCR Molag Fund, L.P., the selling stockholder named in this prospectus, which we referto as HCR or the selling stockholder, of up to 400,000 shares of our common stock, or the Shares, issuable upon the exercise of a warrant held by theselling stockholder, or the Warrant. Our registration of shares of common stock covered by this prospectus does not mean that the selling stockholder will offer or sell any suchshares. We issued the Warrant pursuant to an amendment, dated as of February20, 2026, to that certain Purchase and Sale Agreement, datedDecember20, 2022, by and between us and HCR, pursuant to which HCR agreed to amend the due date of the one-time $9.0million cash paymentassociated with the achievement of a certain milestone related to that certain Amended and Restated Commercialization Agreement, dated October31,2023, by and between us and Pierre Fabre Medicament, as amended, from June30, 2026 to January1, 2028. We are registering the offer and resale ofthe Shares to satisfy a covenant set forth in the Warrant. We will not receive any of the proceeds from the sale of our common stock by the selling stockholder. Any shares of our common stock subject to resale hereunder will have been issued by us and received by the selling stockholder prior to anyresale of such shares pursuant to this prospectus. The selling stockholder, or its donees, pledgees, transferees or other successors-in-interest may offer or resell the Shares from time to time throughpublic or private transactions at prevailing market prices, at prices related to prevailing market prices or at privately negotiated prices. The sellingstockholder will bear all commissions and discounts and similar selling expenses, if any, attributable to the sale of Shares. We will bear all costs,expenses and fees (other than commissions and discounts and similar selling expenses) in connection with the registration of the Shares. For additionalinformation on the methods of sale that may be used by the selling stockholder, see “Plan of Distribution” beginning on page 11 of this prospectus. Our common stock is listed on the Nasdaq Global Select Market under the symbol “ATRA.” On March13, 2026, the last reported sale price of ourcommon stock was $6.50. We are a “smaller reporting company” under the U.S. securities laws and as such, have elected to comply with reduced public company reportingrequirements for this prospectus and the documents incorporated by reference herein and may elect to comply with reduced public company reportingrequirements in future filings. See “Summary — Implications of Being a Smaller Reporting Company.” Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertaintiesdescribed under the heading “Risk Factors” beginning on page5 of this prospectus and contained in any applicableprospectus supplement and in any free writing prospectuses we have authorized for use in connection with a specificoffering, and under similar headings in the documents that are incorporated by reference into this prospectus and anyprospectus supplement from our filings with the Securities and Exchange Commission, before investing in any of oursecurities. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed uponthe adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense. Table of Contents TABLE OF CONTENTS ABOUT THIS PROSPECTUSSUMMARYTHE OFFERINGRISK FACTORSFORWARD-LOOKING STATEMENTSUSE OF PROCEEDSSELLING STOCKHOLDER Table of Contents ABOUT THIS PROSPECTUS This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or SEC, utilizing a“shelf” registration process. Under this shelf registration process, the selling stockholder may resell, from time to time, in one or more offerings, sharesof our common stock offered by this prospectus. Information about the selling stockholder may change over time. When the selling stockholder sellsshares of our common stock under this prospectus, we will, if necessary and required by law, provide a prospectus supplement that will contain morespecific information about the terms of that offering. Any prospectus supplement may also add or change any of the information contained in thisprospectus. If a prospectus supplement is provided and the description of the offering in the prospectus supplement varies from the information in thisprospectus, you should rely on the information in the prospectus supplement. You should carefully read this prospectus and the accompanyingprospectus supplement, if any, along with all of the information or in the documents that we have incorporated by reference herein and therein, beforemaking an investment decision. We have not authorized anyone to provide you any information other than th