Other Events. Filing of Prospectus Supplement On October 30, 2026, Aptevo Therapeutics Inc. (the “Company”) filed with the Securities and Exchange Commission (the “SEC’) a prospectus supplement (the “Prospectus Supplement” and collectively with the Prior Prospectus (as defined below), the “Prospectus”) under the Company’s effective registration statement on Form S-3 (the “Registration Statement”) (File No. 333-284969), relating to the offer and sale of the Company’s shares of common stock, pa…

Material Modification to Rights of Security Holders. The information set forth under “

Entry into a Material Definitive Agreement. On October 23, 2026, Aptevo Therapeutics Inc. (the “Company”) entered into Amendment No. 6 (the “Amendment”) to the Rights Agreement, dated as of November 8, 2020, between the Company and Broadridge Corporate Issuer Solutions, LLC, as rights agent (as amended and/or restated from time to time, the “Rights Agreement”). The Rights Agreement pertains to those certain contingent rights to purchase one one-thousandth of a share of Series A Junior Partici…

Results of Operations and Financial Condition. On August 14, 2026, Aptevo Therapeutics Inc. (the “Company”) issued a press release announcing its financial results for the period ended June 30, 2026. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference. The information in this report, including the exhibit hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Act of 1934, as amended, or otherwise…

Entry into a Material Definitive Agreement. On August 12, 2026, Aptevo Therapeutics Inc. (the “Company”) entered into Warrant Inducement and Reload Letters (the “Inducement Letters”) with certain holders (the “Holders”) of the Company’s common stock purchase warrants, issued on June 20, 2025 (the “June 2025 Warrants”), on April 3, 2025 (the “April 2025 Warrants”) and on December 12, 2024 (the “December 2024 Warrants” and together with the June 2025 Warrants and the April 2025 Warrants, the “E…

Unregistered Sales of Equity Securities. The disclosure required by this Item and included in

Entry into a Material Definitive Agreement. On June 29, 2026, Aptevo Therapeutics Inc. (the “Company”) entered into a Grant Award Agreement (the “Agreement”) with the Andy Hill Cancer Research Endowment (CARE) Fund (the “Grantor”), a Washington State–established public research endowment. Under the Agreement, the Grantor will provide the Company with $1,499,951.00 in funding on a reimbursement basis only to support Investigational New Drug (“IND”) - enabling studies for APVO451, the Company’s…

of this Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of 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 or the Exchange Act, except as expressly set forth by specific reference in such filing. Cautionary Note Regarding Forward Looking Statements This Form 8-K contains forward-looking statem…

Entry into a Material Definitive Agreement. Collaboration Agreement and Supply Agreement with Niowave On May 25, 2026, Aptevo Research and Development LLC (“Aptevo Research”), a subsidiary of Aptevo Therapeutics Inc. (the “Company”), and Niowave, Inc. (“Niowave”) entered into a collaboration agreement (the “Collaboration Agreement”) to collaborate on the development of a potential human therapeutic product incorporating Aptevo’s proprietary molecules (including APVO455) and Niowave’s propriet…

The issuance and sale have not been registered under the Securities Act or any state securities laws. Based in part upon the representations of Niowave in the Stock Purchase Agreement, the Company has relied on the exemption from the registration requirements of the Securities Act under Section 4(a)(2) thereof for a transaction by an issuer not involving any public offering.

Results of Operations and Financial Condition. On May 13, 2026, Aptevo Therapeutics Inc. (the “Company”) issued a press release announcing its financial results for the period ended March 31, 2026. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference. The information in this report, including the exhibit hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Act of 1934, as amended, or otherwise su…

Results of Operations and Financial Condition. On March 26, 2026, Aptevo Therapeutics Inc. (the “Company”) issued a press release announcing its financial results for the period ended December 31, 2025. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference. The information in this report, including the exhibit hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Act of 1934, as amended, or otherwi…

President and Chief Executive Officer — Marvin L. White: Mr. Marvin L. White is retiring as President and CEO, with Jeff Lamothe succeeding him in the role.

Entry into a Material Definitive Agreement. On January 8, 2026, Aptevo Therapeutics Inc. (the “Company”) entered into a Standby Equity Purchase Agreement (the “Purchase Agreement”) with YA II PN, LTD., a Cayman Islands exempt limited company (“Yorkville”). Pursuant to the Purchase Agreement, the Company has the right, but not the obligation, to issue and sell to Yorkville from time to time (each such occurrence, an “Advance”) up to $60.0 million (the “Commitment Amount”) of the Company’s comm…

In the Purchase Agreement, Yorkville represented to the Company, among other things, that it is an “accredited investor” (as such term is defined in Rule 501(a)(3) of Regulation D under the Securities Act). The securities referred to in this current report on Form 8-K are being issued and sold by the Company to Yorkville in reliance upon the exemptions from the registration requirements of the Securities Act afforded by Section 4(a)(2) of the Securities Act.

Results of Operations and Financial Condition. On November 6, 2025, Aptevo Therapeutics Inc. (the “Company”) issued a press release announcing its financial results for the period ended September 30, 2025. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference. The information in this report, including the exhibit hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Act of 1934, as amended, or othe…

Material Modification to Rights of Security Holders. The information set forth under “

Entry into a Material Definitive Agreement. On October 30, 2025, Aptevo Therapeutics Inc. (the “Company”) entered into Amendment No. 5 (the “Amendment”) to the Rights Agreement, dated as of November 8, 2020, between the Company and Broadridge Corporate Issuer Solutions, LLC, as rights agent (as amended and/or restated from time to time, the “Rights Agreement”). The Rights Agreement pertains to those certain contingent rights to purchase one one-thousandth of a share of Series A Junior Partici…

Results of Operations and Financial Condition. On August 11, 2025, Aptevo Therapeutics Inc. (the “Company”) issued a press release announcing its financial results for the period ended June 30, 2025. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference. The information in this report, including the exhibit hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Act of 1934, as amended, or otherwise…

Other Events. As previously disclosed, Aptevo Therapeutics Inc. (the “Company”) received a letter from the Listing Qualifications Staff of The Nasdaq Stock Market LLC (“Nasdaq”) indicating that, for the quarter ended March 31, 2025, the Company was not in compliance with Nasdaq Listing Rule 5550(b)(1) (the “Rule”), which requires the Company to maintain a minimum of $2,500,000 in stockholders’ equity for continued listing on Nasdaq. During the quarterly period ended June 30, 2025, the Company…

Changes in Registrant’s Certifying Accountant. On June 23, 2025, Aptevo Therapeutics Inc., (the "Company") was notified that Moss Adams LLP ("Moss Adams"), the Company's independent registered public accounting firm, merged with Baker Tilly US, LLP effective on June 3, 2025. The combined audit practices operate as Baker Tilly US, LLP (“Baker Tilly”). In connection with the notification of the merger, Moss Adams has resigned as the auditors of the Company, and the Audit Committee of the Compan…

Entry into a Material Definitive Agreement. On June 18, 2025, Aptevo Therapeutics Inc. (the "Company") entered into a securities purchase agreement (the “Purchase Agreement”) with certain institutional investors for the sale of (i) 2,105,000 shares of the Company’s common stock, par value $0.001 per share ("Common Stock") and (ii) pre-funded warrants ("Pre-funded Warrants") to purchase up to 360,000 shares of Common Stock. In addition, the Company sold to Investors common warrants to purchase…

In the Purchase Agreement, Yorkville represented to the Company, among other things, that it is an “accredited investor” (as such term is defined in Rule 501(a)(3) of Regulation D under the Securities Act). The securities referred to in this current report on Form 8-K are being issued and sold by the Company to Yorkville in reliance upon the exemptions from the registration requirements of the Securities Act afforded by Section 4(a)(2) of the Securities Act.

Entry into a Material Definitive Agreement. On June 16, 2025, Aptevo Therapeutics Inc. (the “Company”) entered into a Standby Equity Purchase Agreement (the “Purchase Agreement”) with YA II PN, LTD., a Cayman Islands exempt limited company (“Yorkville”). Pursuant to the Purchase Agreement, the Company has the right, but not the obligation, to issue and sell to Yorkville from time to time (each such occurrence, an “Advance”) up to $25.0 million (the “Commitment Amount”) of the Company’s common…

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing. On May 22, 2025, Aptevo Therapeutics Inc. (the “Company”) received a letter from The Nasdaq Stock Market LLC (“Nasdaq”) indicating that it is not in compliance with Nasdaq Listing Rule 5550(b)(1), which requires companies listed on The Nasdaq Capital Market to maintain a minimum of $2,500,000 in stockholders’ equity for continued listing. On its Quarterly Report for the quarterly period ended…