Management Change/Compensation (Form 8-K)

Aptevo Announces Executive Leadership Transitions to Support Next Phase of Growth

Clinical progress, pipeline expansion, and operational momentum underpin leadership continuity as the Company advances into 2026 and beyond

SEATTLE, WA - February 3, 2026 - Aptevo Therapeutics Inc. (Nasdaq: APVO), a clinical-stage biotechnology company developing novel immune-oncology therapeutics based on its proprietary ADAPTIR™ and ADAPTIR-FLEX™ platform technologies, today announced executive leadership transitions to support the Company's continued execution, drive achievement of long-term strategic objectives, and next phase of growth.

Effective April 1, 2026, Marvin White, who has served as President and Chief Executive Officer since 2016, has chosen to retire from this position and assume the role of Executive Chair, where he will focus on cultivating strategic opportunities to help shape long-term success. Jeff Lamothe, currently Chief Operating Officer, will assume the role of President and Chief Executive Officer and will join Aptevo's Board of Directors. John E. Niederhuber, M.D., will transition from Chairman of the Board to Lead Independent Director. All three leaders have been part of Aptevo since the Company's inception in 2016, and the leadership changes reinforce continuity while supporting the Company's continued execution and future success.

"Aptevo has reached an important inflection point," said Mr. White. "We have a clinically proven platform, a growing body of patient data, a strong balance sheet, access to liquidity sources, and a leadership team that has been executing together for many years. I am not stepping away from the Company; rather, this transition reflects a purposeful shift in how we are aligned as a leadership team. With Jeff serving as President and CEO, I will be able to devote more time serving the Company by identifying and advancing strategic growth opportunities."

Under the leadership of Mr. White and Mr. Lamothe, Aptevo has evolved into a company with a clinically validated platform, an expanded and diversified pipeline, and a strong financial foundation. During their tenure, the Company established proof-of-concept for its proprietary technology, introduced ADAPTIR-FLEX™ as a second platform that complements ADAPTIR™, and built a pipeline of eight molecules. Aptevo also broadened its therapeutic scope beyond bispecific antibodies to include two trispecific programs, while creating and executing a strategy to leverage its proprietary and differentiated CD3 binding domain. We believe these advances have translated into meaningful clinical outcomes, enabling many patients enrolled in Aptevo's clinical trials to achieve complete remission. More than 100 patients have now been treated with the Company's CD123 x CD3 program, mipletamig, which has demonstrated consistent signals of strong efficacy alongside a differentiated safety profile in acute myeloid leukemia. In

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parallel, Aptevo has expanded its pipeline through both internal development and external collaboration, including its partnership with Alligator Bioscience for the development of ALG.APV-527 in solid tumors.

At the same time, Aptevo has strengthened its financial position, establishing a cash runway into 2029, including capital available under the recently announced $60 million equity line of credit. Collectively, these accomplishments reflect disciplined execution across technology development, clinical advancement, pipeline expansion, and financial stewardship.

"I want to thank John for his leadership as Chairman and for the thoughtful, steady guidance he has provided to Aptevo over the years. I am grateful that he will continue to serve the Company as Lead Independent Director, and I value his continued partnership," said Mr. White.

He continued, "Jeff has been a driving force behind many of the Company's most important advances, and both the Board and I have complete confidence in his leadership. He is the right leader to guide Aptevo forward at this stage, and I am excited to continue working closely with him as Executive Chair as we focus on advancing our strategy, expanding partnerships, and building on the momentum we have created."

Mr. White's move to Executive Chair will deepen Aptevo's focus on harnessing strategic opportunities that align with corporate growth goals and maintaining continuity at the leadership level. As Executive Chair, he will also serve as a strategic advisor, leveraging his experience to help guide Aptevo's next stage of growth.

Mr. Lamothe's appointment reflects his central role in Aptevo's accomplishments and his leadership across day-to-day operations and vision for growth. Many of the Company's key advances-including clinical progress, pipeline development, operational discipline, and financial execution-have occurred under his direct leadership as Chief Operating Officer, in close partnership with Mr. White.

"Jeff has been instrumental in building the operational foundation we have today," Mr. White added. "He understands this organization deeply, has earned the confidence of the Board, and is the right leader to carry Aptevo forward as we execute against our goals."

"I am honored to step into the role of President and CEO at this stage of Aptevo's journey," said Mr. Lamothe. "We have a strong team, a clear plan, and a pipeline we believe has the meaningful potential to positively impact the lives of patients fighting cancer. Our focus remains on disciplined execution-completing the mipletamig Phase 1b program, advancing our pipeline, and pursuing business development opportunities that align with our strategy and capabilities."

In his most recent role as Chief Operating Officer, Mr. Lamothe oversaw Clinical, Research and Development, Quality, Manufacturing, and Operations, strengthening execution across the organization while advancing Aptevo's programs. Previously, as Chief Financial Officer, he led

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Finance, Business Development, Investor Relations, and Information Technology, providing broad strategic and operational perspective.

"It has been a privilege to serve as Chairman of Aptevo's Board," said Dr. Niederhuber. "As Lead Independent Director, I look forward to continuing to support the Company and working closely with Marvin and Jeff as Aptevo builds on its progress and pursues its next chapter."

With a proven platform, advancing clinical programs, and a leadership structure aligned to support both execution and long-term strategy, we believe Aptevo is well positioned to continue progressing toward its objectives and delivering meaningful impact for patients fighting many different types of cancer.

About Aptevo Therapeutics

Aptevo Therapeutics Inc. (Nasdaq: APVO) is a clinical-stage biotechnology company focused on developing novel multispecifics immunotherapies for the treatment of cancer. The Company has two clinical candidates. Mipletamig is currently being evaluated in RAINIER, a two-part Phase 1b/2 trial for the treatment of frontline acute myeloid leukemia in combination with standard-of-care venetoclax + azacitidine. Mipletamig has received orphan drug designation ("orphan status") for AML according to the Orphan Drug Act. ALG.APV-527, a bispecific conditional 4-1BB agonist, designed to only be active upon simultaneous binding to 4-1BB and 5T4, is being co-developed with Alligator Bioscience and was most recently evaluated in a Phase 1 clinical trial for the treatment of multiple solid tumor types likely to express 5T4. The Company has six preclinical candidates with different mechanisms of action designed to target a range of solid tumors. All pipeline candidates were created from two proprietary platforms, ADAPTIR™ and ADAPTIR-FLEX™. The Aptevo mission is to improve treatment outcomes and transform the lives of cancer patients. For more information, please visit www.aptevotherapeutics.com.