Aptevo Secures $1.5 Million Non-Dilutive Research Grant from the Andy Hill Care Fund to Advance APVO451, a Nectin-4-Targeted Trispecific Immunotherapy for Solid Tumors (Form 8-K)

Aptevo Secures $1.5 Million Non-Dilutive Research Grant from the Andy Hill Care Fund to Advance APVO451, a Nectin-4-Targeted Trispecific Immunotherapy for Solid Tumors

SEATTLE, WA - June 30, 2026 - Aptevo Therapeutics Inc. (Nasdaq: APVO), a clinical-stage biotechnology company developing novel immuno-oncology therapeutics based on its proprietary ADAPTIR™ and ADAPTIR-FLEX™ platform technologies, today announced it has been awarded a $1.5 million non-dilutive research grant from the Andy Hill Cancer Research Endowment (CARE) Fund under its Implementation and Outcomes Research program to support investigational new drug (IND)-enabling work for APVO451, Aptevo's novel trispecific antibody-like immunotherapy candidate for solid tumors.

Aptevo believes that obtaining this competitive award, reviewed by subject matter experts and awarded based on merit, provides external validation of APVO451's tumor-directed trispecific design and supports Aptevo's ongoing work around nectin-4-targeted therapies. Trispecific immunotherapies represent what Aptevo believes is the next generation of immuno-oncology therapies and are a strategic pipeline priority for Aptevo, with APVO451 advancing toward development candidate selection by year-end 2026 and initiation of IND-enabling studies in the first quarter of 2027. APVO451 is a strategic pipeline priority which reflects Aptevo's broader effort to extend its controlled immune-activation platform into solid tumors.

"Solid tumors continue to present significant challenges for immunotherapy, particularly because the tumor microenvironment can limit effective immune activation," said Michelle Nelson, Ph.D., Senior Director at Aptevo and Principal Investigator of the study. "This award supports the generation of additional APVO451 preclinical data to further evaluate how its tumor-directed trispecific design may leverage CD40-mediated immune activation while bringing together T-cell engagement in a coordinated anti-tumor response and subsequently advancing it toward IND-enabling development."

CARE Fund grants promote cancer research led by public and private entities conducting cancer research in Washington State. Through research grants and strategic partnerships, CARE Fund improves health outcomes by advancing transformational research across the cancer research continuum. The grant will support IND-enabling activities for APVO451, including preclinical studies and development work intended to advance the program toward development candidate selection and future regulatory-enabling studies. The study will be led by Michelle Nelson, who brings deep scientific leadership and execution experience to the project with her background in immunobiology, solid tumor immunotherapy, and IND-enabling development.

"APVO451 reflects what we believe trispecific immunotherapies can uniquely do: bring complementary immune mechanisms together in a coordinated, tumor-directed way," said Mary Janatpour, Ph.D., Senior Vice President and Chief Scientific Officer of Aptevo Therapeutics. "By combining nectin-4-targeting with CD40 and CD3 engagement, APVO451 is designed to activate both antigen-presenting cells and T cells within the tumor microenvironment. We are grateful to the Andy Hill CARE Fund for supporting this program and for recognizing the promise of this approach as we work to advance new treatment options for patients with difficult-to-treat cancers."

About the APVO451 Program

APVO451 is designed to address a central challenge in solid tumor immunotherapy: the tumor microenvironment can suppress immune activity and limit the body's ability to recognize and attack cancer cells. APVO451 brings together three functions in a single molecule: targeting nectin-4, a

tumor-associated marker expressed in multiple solid tumors; activating CD40 on antigen-presenting cells to engage innate immunity in the tumor milieu; and engaging CD3 on T-cells to direct tumor-cell killing.

Together, these mechanisms are intended to concentrate immune activation within the tumor microenvironment, stimulate T-cell activity and broader immune engagement, and support an amplified attack against solid tumors. Unlike approaches that broadly activate the immune system, APVO451 is designed so that its CD3 and CD40 activity depend on binding to nectin-4, helping focus immune activation where it is needed and reduce the risk of systemic immune activation. APVO451 also incorporates Aptevo's CRIS-7-derived CD3 binding domain, the same CD3 platform approach used in mipletamig, Aptevo's lead clinical program. Aptevo's CD3 strategy is designed to engage T cells while reducing the risk of excessive cytokine release, a key limitation that has historically challenged the development of T-cell-engaging therapies, particularly in solid tumors.

APVO451 is part of Aptevo's broader pipeline of multispecific immunotherapies designed to control immune activation with precision. The program builds on Aptevo's experience developing antibody-based candidates that seek to balance anti-tumor activity with tolerability while expanding the Company's platform opportunity into next-generation trispecific approaches for solid tumors.

About Aptevo Therapeutics
Aptevo Therapeutics Inc. (Nasdaq: APVO) is a clinical-stage biotechnology company developing novel bispecific and trispecific immunotherapies for the treatment of cancer. Aptevo's pipeline includes two clinical candidates and multiple preclinical programs spanning a range of mechanisms and tumor types, all built on its proprietary ADAPTIR™ and ADAPTIR-FLEX™ platforms. The Company's approach focuses on precise immune activation designed to deliver meaningful clinical benefit while maintaining a favorable safety profile. For more information, please visit www.aptevotherapeutics.com.