On November 11, 2021 Aptevo Therapeutics Inc. ("Aptevo" or the "Company") (Nasdaq:APVO), a clinical-stage biotechnology company focused on developing novel immuno-oncology therapeutics based on its proprietary ADAPTIR and ADAPTIR-FLEX platform technologies, reported the presentation of preclinical data for APVO603, the Company’s bispecific antibody targeting 4-1BB (CD137) and OX40 (CD134), at the Society for Immunology in Cancers (SITC) (Free SITC Whitepaper) 2021 Annual Meeting (Press release, Aptevo Therapeutics, NOV 11, 2021, View Source [SID1234595288]).

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Poster #795 entitled, "APVO603: A dual 4-1BB and OX40 bispecific approach utilizing ADAPTIR technology designed to deliver a conditional T cell/NK response against solid tumors," will be presented and displayed on-site on Saturday, November 13th in Washington, D.C. Data in the poster showed that APVO603 enhanced dose-dependent control of in vitro tumor cell lysis when paired with a bispecific T-cell engager when compared either alone. Of note, investigators show that APVO603 has minimal impact on regulatory T cell suppression of CD8+ T cells’ proliferation in vitro.

"APVO603 is a differentiated bispecific antibody with the potential to leverage the benefits of 4-1BB and OX40 in a single agent. Further, the tethering of molecules has the potential to reduce safety risks and improve potency profiles by targeting responses specifically to sites of active inflammation and limiting on-target toxicity," said Hilario Ramos, Senior Director of Immunobiology at Aptevo. "In addition, the data presented here demonstrate that this combination has the potential to promote anti-tumor responses two-fold. First, by improving the fitness of exhausted effector CD8+ T cells. Second, by reducing the potential for activation of suppressive responses by T regulatory subsets. This dual biological mechanism of action offers the potential for development of a compound that acts against both solid and hematologic tumors and in the presence of addition immunomodulatory treatments or modalities such as CAR T or adoptive immune cell therapies."

Aptevo CEO Marvin White commented, "We are very encouraged by the results reported in this poster, and we are excited to continue to develop APVO603 and provide this update on our progress as we work to advance the compound."

Title: APVO603: A dual 4-1BB and OX40 bispecific approach utilizing ADAPTIRTM technology designed to deliver a conditional T cell/NK response against solid tumors
Presenter: Hilario Ramos, Senior Director of Immunobiology at Aptevo
Date/Time: Saturday, November 13, 2021

About APVO603

APVO603 is a dual agonist bispecific antibody employing a novel mechanism of action to simultaneously target 4-1BB (CD137) and OX40 (CD134), both members of the TNF Receptor Superfamily. Dual targeting of 4-1BB and OX40 provides synergistic co-stimulation of T cells with the potential to amplify the cytotoxic function of activated T cells and NK cells, potentially leading to more robust anti-tumor responses.