Preclinical data demonstrates inhibited tumor cell growth in vitro when paired with a T-cell engager bispecific

SEATTLE, WA / ACCESSWIRE / 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, today announced 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) 2021 Annual Meeting.

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 13^th 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 ADAPTIR^TM 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.

About Aptevo Therapeutics

Aptevo Therapeutics Inc. is a clinical-stage biotechnology company focused on developing novel bispecific immunotherapies for the treatment of cancer. Aptevo is seeking to improve treatment outcomes and transform the lives of cancer patients. For more information, please visit www.aptevotherapeutics.com.

Safe Harbor Statement

This press release includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements, other than statements of historical fact, including, without limitation, Aptevo's expectations about the activity, efficacy and safety of its therapeutic candidates and potential use of any such candidates as therapeutics for treatment of disease, advancement of its clinical trials and its expectations regarding the effectiveness of its ADAPTIR and ADAPTIR-FLEX platforms, and any other statements containing the words "may," "believes," "expects," "anticipates," "hopes," "intends," "optimism," "potential," "designed," "engineered," "breakthrough," "innovative," "innovation," "promising," "plans," "forecasts," "estimates," "will" and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based on Aptevo's current intentions, beliefs, and expectations regarding future events. Aptevo cannot guarantee that any forward-looking statement will be accurate. Investors should realize that if underlying assumptions prove inaccurate or unknown risks or uncertainties materialize, actual results could differ materially from Aptevo's expectations. Investors are, therefore, cautioned not to place undue reliance on any forward-looking statement.

There are several important factors that could cause Aptevo's actual results to differ materially from those indicated by such forward-looking statements, including a deterioration in Aptevo's business or prospects; adverse developments in clinical development, including unexpected safety issues observed during a clinical trial; adverse developments in the U.S. or global capital markets, credit markets or economies generally; and changes in regulatory, social, and political conditions. For instance, actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including the uncertainties inherent in the initiation, enrollment and maintenance of patients, and completion of clinical trials, availability and timing of data from ongoing clinical trials, expectations for the timing and steps required in the regulatory review process, including our ability to obtain regulatory clearance to commence clinical trials, expectations for regulatory approvals, the impact of competitive products, actions of activist stockholders, our ability to enter into agreements with strategic partners and other matters that could affect the availability or commercial potential of the Company's product candidates, business or economic disruptions due to catastrophes or other events, including natural disasters or public health crises such as the novel coronavirus (referred to as COVID-19). These risks are not exhaustive, Aptevo faces known and unknown risks. Additional risks and factors that may affect results are set forth in Aptevo's filings with the Securities and Exchange Commission, including its Annual Report on Form 10-K for the fiscal year ended December 31, 2020, and its subsequent reports on Form 10-Q and current reports on Form 8-K. The foregoing sets forth many, but not all, of the factors that could cause actual results to differ from Aptevo's expectations in any forward-looking statement. Any forward-looking statement speaks only as of the date of this press release, and, except as required by law, Aptevo does not assume any obligation to update any forward-looking statement to reflect new information, events, or circumstances.

CONTACTS:

Investors
Miriam Weber Miller
Aptevo Therapeutics
Email: IR@apvo.com or Millerm@apvo.com
Phone: 206-859-6629

Media
Jules Abraham
JQA Partners
Email: jabraham@jqapartners.com
Phone: 917-884-7378

SOURCE: Aptevo Therapeutics