UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO Commission File Number 001-37746 APTEVO THERAPEUTICS INC. (Exact name of Registrant as specified in its Charter) (State or other jurisdiction of incorporation o ...

Exhibit 99.1 Aptevo Provides State of the Business Report and 2025 Financial Results Highlights Aptevo entered 2026 with momentum: Latest mipletamig data delivers 86% clinical benefit rate with no cytokine release syndrome in 28 frontline AML patients, supporting its potential to enhance standard-of-care combination therapy Company expands CD3 pipeline and introduces first trispecific drug candidates SEATTLE, WA – March 26, 2026 – Aptevo Therapeutics Inc. (Nasdaq: APVO), a clinical-stage biotechnology compa ...

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SEATTLE, WA / ACCESS Newswire / March 19, 2026 / Aptevo Therapeutics Inc. (NASDAQ:APVO), a clinical-stage biotechnology company developing novel immune-oncology therapeutics based on its proprietary ADAPTIRâ"¢ and ADAPTIR-FLEXâ"¢ platform technologies, today announced its participation in the following March conferences: The 38th Annual Roth Conference March 22-24, 2026, in Dana Point, CA. Aptevo incoming President and Chief Executive Officer Jeff Lamothe will participate in a Company-focused fireside chat ...

Core Insights - Mipletamig demonstrates an 86% clinical benefit rate in combination with venetoclax and azacitidine for newly diagnosed acute myeloid leukemia (AML) patients, with no cases of cytokine release syndrome (CRS) reported [1][2] - The data indicates a strong efficacy profile and favorable safety, suggesting mipletamig could enhance current AML treatment standards, particularly for older or unfit patients [1][2] Clinical Data Highlights - Among 28 evaluable frontline patients, 100% remained free of CRS, with an 86% clinical benefit rate observed [1] - 79% of patients achieved complete remission (CR) or complete remission with incomplete blood marker recovery (CRi), with 61% achieving CR [1] - 55% of patients who achieved CR/CRi reached measurable residual disease-negative levels, indicating stronger responses [1] - 35% of patients with remissions had the TP53 genetic mutation, a high-risk biomarker associated with poor prognosis in AML [1] Company Overview - Aptevo Therapeutics is a clinical-stage biotechnology company focused on developing novel immunotherapies for cancer, utilizing proprietary ADAPTIR and ADAPTIR-FLEX platforms [2] - The company aims to improve treatment outcomes for cancer patients, with mipletamig being a key candidate for AML treatment [2]

Core Insights - Aptevo Therapeutics is undergoing executive leadership transitions to support its strategic objectives and growth as it advances into 2026 and beyond [1][2] Leadership Transition - Effective April 1, 2026, Marvin White will retire as President and CEO, transitioning to Executive Chair to focus on strategic opportunities [2] - Jeff Lamothe, currently Chief Operating Officer, will become the new President and CEO and join the Board of Directors [2] - John E. Niederhuber, M.D., will move from Chairman of the Board to Lead Independent Director, ensuring continuity in leadership [2] Company Progress - Aptevo has reached a significant inflection point with a clinically proven platform, a growing body of patient data, and a strong financial position [3] - The company has established proof-of-concept for its proprietary technology and expanded its pipeline to include eight molecules, including two trispecific programs [3] - More than 100 patients have been treated with the CD123 x CD3 program, mipletamig, showing strong efficacy and a differentiated safety profile in acute myeloid leukemia [3] Financial Position - Aptevo has strengthened its financial position, establishing a cash runway into 2029, including a $60 million equity line of credit [4] - The company's accomplishments reflect disciplined execution across technology development, clinical advancement, pipeline expansion, and financial stewardship [4] Leadership Confidence - Marvin White expressed confidence in Jeff Lamothe's leadership, highlighting his instrumental role in the company's key advances [6][7] - Lamothe emphasized the importance of disciplined execution and advancing the pipeline to positively impact cancer patients [8] Future Outlook - The leadership structure is aligned to support both execution and long-term strategy, positioning Aptevo to continue progressing toward its objectives [9]

As filed with the Securities and Exchange Commission on January 28, 2026 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 APTEVO THERAPEUTICS INC. (Exact Name of Registrant as Specified in Its Charter) (State or Other Jurisdiction of Incorporation or Organization) (Primary Standard Industrial Classification Code Number) Delaware 2834 81-1567056 (I.R.S. Employer Identification Number) 2401 4th Avenue ...

Core Insights - Aptevo Therapeutics has entered into a $60 million equity line of credit (ELOC) agreement with Yorkville Advisors Global, LP, enhancing its financial flexibility and extending its funding runway into 2029 [1][2][3] Financial Flexibility - The ELOC allows Aptevo to raise funds incrementally at its discretion under market-based conditions, providing affordable capital financing with minimal fees and no warrants [2][3] - The combination of the ELOC and cash on hand is projected to fund the company for three years, allowing for the achievement of key clinical and preclinical milestones [1][3] Clinical Development - Aptevo's portfolio includes five CD3-engaging assets, with mipletamig being a first-in-class CD123 x CD3 bispecific currently evaluated in a Phase 1b/2 trial for frontline acute myeloid leukemia (AML) [5][7] - Mipletamig has shown high remission rates and a favorable safety profile in over 100 patients across three trials, with no observed cytokine release syndrome events [5][6] Pipeline and Innovation - The company is advancing a portfolio of tumor-directed CD3 programs, including bispecific candidates for prostate cancer and solid tumors, utilizing proprietary CRIS-7-derived CD3 binding domains [6][7] - Aptevo has two clinical candidates and six preclinical candidates targeting various solid tumors, all developed from its ADAPTIR and ADAPTIR-FLEX platforms [7]

Core Viewpoint - Aptevo Therapeutics Inc. will conduct a reverse stock split at a ratio of 1-for-18, effective December 29, 2025, at 5:01 p.m. [1] Company Summary - Aptevo Therapeutics Inc. is a clinical-stage biotechnology company focused on developing novel immune-oncology therapeutics [1] - The company utilizes its proprietary ADAPTIR™ and ADAPTIR-FLEX™ platform technologies for its therapeutic developments [1]

Core Insights - 100% of patients in Cohorts 1-3 remain free of cytokine release syndrome, indicating a strong safety profile for the CD3 design used in the study [1] - The study evaluates mipletamig, a CD123 x CD3 bispecific molecule, in combination with azacitidine and venetoclax for newly diagnosed acute myeloid leukemia patients unfit for intensive chemotherapy [1] - Preliminary results were presented at the American Society of Hematology Annual Meeting, highlighting the potential of the ADAPTIR™ and ADAPTIR-FLEX™ platform technologies developed by the company [1] Company Summary - Aptevo Therapeutics Inc. is a clinical-stage biotechnology company focused on developing novel immune-oncology therapeutics [1] - The company utilizes proprietary ADAPTIR™ and ADAPTIR-FLEX™ platform technologies in its research and development efforts [1] Industry Context - The ongoing Phase 1b/2 RAINIER study is significant for the treatment of acute myeloid leukemia, particularly for patients who cannot undergo intensive chemotherapy [1] - The combination of mipletamig with standard treatments like azacitidine and venetoclax represents a potential advancement in the therapeutic options available for AML [1]