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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of report (Date of earliest event reported): September 18, 2025

NEKTAR THERAPEUTICS

(Exact Name of Registrant as Specified in Charter)

Delaware |  | 0-24006 |  | 94-3134940
(State or Other Jurisdiction of Incorporation) |  | (Commission File Number) |  | (IRS Employer Identification No.)

455 Mission Bay Boulevard South

San Francisco, California 94158

(Address of Principal Executive Offices and Zip Code)

Registrant’s telephone number, including area code: (415) 482-5300

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class |  | Trading symbol(s) |  | Name of each exchange on which registered
Common Stock, $0.0001 par value |  | NKTR |  | Nasdaq Capital Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 7.01 | Regulation FD Disclosure.

On September 18, 2025, Nektar Therapeutics (“Nektar”) posted slides on its website (www.nektar.com) containing additional information related to certain new data from the ongoing REZOLVE-AD Phase 2b study of rezpegaldesleukin, as discussed in Item 8.01 below. A copy of the slides is attached hereto as Exhibit 99.1 and is incorporated herein by reference. Information contained on Nektar’s website is not incorporated by reference into this Current Report on Form 8-K, and you should not consider any information on, or that can be accessed from, Nektar’s website as part of this Current Report on Form 8-K.

The information under this Item 7.01, including Exhibit 99.1 hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing. Nektar undertakes no obligation to update, supplement or amend the material attached hereto as Exhibit 99.1.

Item 8.01 | Other Events.

On September 18, 2025, Nektar announced certain new data from the ongoing REZOLVE-AD Phase 2b study of rezpegaldesleukin. A copy of the press release issued in connection with the announcement is attached hereto as Exhibit 99.2 and is incorporated herein by reference.

Item 9.01 | Financial Statements and Exhibits.

(d) Exhibits

99.1 |  | Slides Titled “Efficacy and Safety of Rezpegaldesleukin, A Selective Regulatory T-Cell-Inducing Interleukin-2 Conjugate, in the Treatment of Atopic Dermatitis: Final Results from the 16-Week Induction of a Randomized Phase 2b Study (REZOLVE AD)”.
99.2 |  | Press Release Titled “Nektar Presents New Data from REZOLVE-AD Phase 2b Study for Rezpegaldesleukin in Late-Breaker Oral Presentation at EADV 2025”.
104 |  | Cover Page Interactive Data File (embedded within the Inline XBRL Document).

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

| NEKTAR THERAPEUTICS
Date: September 18, 2025 | By: | /s/ Mark A. Wilson
|  | Mark A. Wilson
|  | Chief Legal Officer and Secretary

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