内克塔治疗美股招股说明书(2026-04-23版)

3,532,609 Shares of Common Stock We are offering 3,532,609 shares of our common stock, par value $0.0001 per share, or common stock, pursuant to this prospectus supplement and the Our common stock is listed on the Nasdaq Capital Market under the symbol “NKTR”. On April21, 2026, the last reported sale price for our common stock on theNasdaq Capital Market was $98.16 per share. We are a “smaller reporting company” under the federal securities laws and, as such, we have elected to comply with certain reduced public company reportingrequirements for this prospectus supplement and for future filings. See “Prospectus Supplement Summary—Implications of Being a Smaller Reporting Company.” Public offering price (1)See “Underwriting” for a description of the compensation payable to the underwriters. We have granted the underwriters an option for a period of 30 days to purchase an additional 529,891 shares of our common stock from us, at the public offeringprice, less the underwriting discounts and commissions. Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on page S-11 of this prospectussupplement and page 6 of the accompanying prospectus, and in the documents incorporated by reference herein. You should readthe entire prospectus supplement and the accompanying prospectus, including any information incorporated by reference,carefully, before investing in our securities. 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 underwriters expect to deliver the shares of common stock to purchasers on or about April 23, 2026. Piper Sandler Table of Contents TABLE OF CONTENTSPROSPECTUS SUPPLEMENT ABOUT THIS PROSPECTUS SUPPLEMENTSPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTSPROSPECTUS SUPPLEMENT SUMMARYRISK FACTORSUSE OF PROCEEDSDILUTIONDIVIDEND POLICYMATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS FOR NON-U.S. HOLDERSUNDERWRITINGLEGAL MATTERSEXPERTSWHERE YOU CAN FIND MORE INFORMATIONINCORPORATION OF CERTAIN INFORMATION BY REFERENCE PROSPECTUS ABOUT THIS PROSPECTUSSPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTSABOUT THE COMPANYRISK FACTORSUSE OF PROCEEDSDIVIDEND POLICYGENERAL DESCRIPTION OF SECURITIES Table of Contents ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering of common stockand also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference into this prospectussupplement and the accompanying prospectus. The second part is the accompanying prospectus dated November12, 2025, included in our registrationstatement on Form S-3 (File No.333-291466), along with the documents incorporated by reference therein, which provides more general information,some of which may not apply to this offering. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between the information contained in this prospectus supplement and the information contained in theaccompanying prospectus or in any document incorporated by reference that was filed with the Securities and Exchange Commission, or the SEC,before the date of this prospectus supplement, you should rely on the information in this prospectus supplement. If any statement in one of thesedocuments is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in theaccompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement. This prospectus supplement and the accompanying prospectus are part of a “shelf” registration statement that we filed with the SEC. Under theshelf registration process, we may offer from time to time various securities, of which this offering of shares of our common stock is a part. Suchregistration statement also includes exhibits that provide more detail on the matters discussed in this prospectus supplement and the accompanyingprospectus. You should read this prospectus supplement, the accompanying prospectus, including the information incorporated by reference, the exhibitsfiled with the SEC, and any free writing prospectus that we have authorized for use in connection with this offering, in their entirety before making aninvestment decision. You should rely only on the information contained or incorporated by reference in this prospectus supplement, the accompanyingprospectus and any free writing prospectus prepared by us or on our behalf. We have not, and the underwriters have not, authorized any otherperson to provide you with information different from that contained in this prospectus supp