Benzinga | Apr 9, 2021 09:02AM EDT

Aptevo Therapeutics To Present At American Association For Cancer Research Virtual Annual Meeting; Co Will Provide Preclinical Updates On APVO603 And APVO442

Aptevo Therapeutics Inc. (NASDAQ:APVO), a clinical-stage biotechnology company focused on developing novel immuno-oncology therapeutics based on its proprietary ADAPTIRTM and ADAPTIR-FLEXTM platform technologies, today announced that it will present two new posters at the American Association for Cancer Research Virtual Annual Meeting, to be held in two virtual sessions - Saturday, April 10th to Thursday, April 15th, 2021 and Monday, May 17th to Friday, May 21st, 2021.

The posters will provide preclinical updates on APVO603 and Aptevo's newest pipeline candidate, APVO442.

Title: APVO603:A Dual 4-1BB and OX40 bispecific approach utilizing ADAPTIR technology designed to deliver a conditional T cell/NK response against solid tumors(LB173)

Summary: The data to be presented will highlight the potential benefits of dual targeting of 4-1BB and OX40 by APVO603. In vitro data includes demonstration of APVO603's ability to reduce or reverse the negative effects of T-cell exhaustion and suppressive immune responses by augmenting cytokine production and reducing markers of T-cell exhaustion following repeat stimulation. In preclinical in vivo studies, APVO603 therapy induced a dose-dependent anti-tumor response and significantly increased the survival of mice in a murine bladder cancer model. A non-GLP NHP PK/Tox study was completed and it was found that APVO603 had a favorable safety profile without liver toxicity and a PK profile that supports clinical dosing. CMC activities are in progress and IND-enabling studies are underway to progress the program towards clinical development.

Title: APVO442: A bispecific T cell-engaging candidate utilizing the ADAPTIR-FLEX platform technology with unique properties designed to optimize drug tumor distribution and cytotoxic response against PSMA-expressing solid tumors

Summary: The data to be presented will highlight the unique properties of APVO442, Aptevo's first molecule utilizing our ADAPTIR-FLEX technology, designed with low affinity, monovalent targeting of CD3 and high affinity, bivalent targeting of PSMA to potentially reduce safety signals and improve efficacy for treatment of a solid tumor. In vitro, APVO442 retains strong binding to tumor cell lines with a range of (high to low) surface PSMA expression, and demonstrates reduced binding to CD3+ T cell lines when compared to higher affinity CD3 binding molecules. In vitro efficacy studies show that, despite lower CD3 binding affinity, APVO442 elicits equivalent T-cell activation, proliferation, and cytotoxicity against PSMA+ tumor cells, while limiting cytokine release, when compared to higher affinity CD3 engaging molecules. In vivo, APVO442 demonstrated a dose-dependent ability to limit tumor burden at responses comparable to a high affinity T-cell engager response in a murine xenograft PSMA+ prostate cancer model. APV0442 retains key manufacturability characteristics of the ADAPTIR platform and preclinical data to support the potential for a beneficial safety and efficacy profile. Continued pre-clinical evaluation and CMC efforts are ongoing to progress APVO442 toward clinical development.

Details of the e-Poster Presentations: The abstracts and the accompanying e-posters will be available in the Virtual Poster Hall to registered attendees from 8:30 am EST on Saturday, April 10th, 2021, until the Virtual Poster Hall closes on Monday June 21st, 2021. Chat and live meeting requests will be available for questions and discussion with the presenters. Details can be found on the AACR abstract website and will also be posted on the Aptevo Therapeutics website.