• ALG.APV-527 Demonstrates Favorable Preclinical Efficacy and Safety Compared to a First Generation 4-1BB Antibody
• ALG.APV-527 Rapidly Progressing to Clinical Development for Evaluation in the Treatment of Solid Tumors after Receipt of IND Clearance from the US Food and Drug Administration in September

Lund, Sweden, and Seattle, Washington, November 9, 2022 - Alligator Bioscience AB ("Alligator") (Nasdaq Stockholm: ATORX) and Aptevo Therapeutics ("Aptevo") (Nasdaq: APVO) today announced the publication of a peer-reviewed article highlighting preclinical data that demonstrates a positive safety and anti-tumor activity profile in both in vitro and in vivo studies for ALG.APV-527, a novel second generation 4-1BB agonistic bispecific antibody that is designed to stimulate 4-1BB function only when co-engaged with the tumor-associated antigen 5T4.

The publication in Molecular Cancer Therapeutics, a journal of the American Association for Cancer Research (AACR), includes data provided in the companies’ investigational new drug (IND) application to the US Food and Drug Administration (FDA) supporting the advancement of ALG.APV-527 into the clinic for evaluation in the treatment of multiple solid tumor types. 

The article, entitled “The bispecific tumor antigen-conditional 4-1BB × 5T4 agonist, ALG.APV-527, mediates strong T cell activation and potent anti-tumor activity in preclinical studies”, demonstrates how the design, epitope, and molecular properties of ALG.APV-527 translate into a potentially safe and potent anti-cancer therapeutic both in vitro and in vivo for the treatment of multiple solid tumor types. The preclinical functional data presented demonstrate that ALG.APV-527 has the potential to activate key immune cell populations such as T cells and NK cells within the tumor microenvironment. Of particular importance is the favorable safety profile, where the preclinical data demonstrates a potentially wider therapeutic window for ALG.APV-527 compared to first generation 4-1BB agonists.

The full article is available in print and online via this link.

"We are pleased to see this peer-reviewed validation of our preclinical studies for ALG.APV-527 as we work together with our partners at Alligator to advance the compound into Phase 1 evaluation here in the US,” said Marvin White, President, and CEO of Aptevo. "We strongly believe ALG.APV-527 has the potential to positively impact the treatment paradigm for cancer patients with solid tumors and look forward to initiating our clinical program and advancing that promise.”

"The publication of this scientific paper in the prestigious Molecular Cancer Therapeutics journal is an exciting achievement and deserved recognition for the hard work of the scientific teams at Alligator and Aptevo," said Søren Bregenholt, PhD, CEO of Alligator Bioscience. "The preclinical safety studies suggest that ALG.APV-527 displays a wide therapeutic window which, given the unmet need for therapies in several cancer indications that express 5T4, means it has the potential to meaningfully improve response rates seen with the current standard of care in these indications."

In September 2022, the FDA issued a "may proceed" notification for the ALG.APV-527 IND. Alligator and Aptevo are working rapidly to initiate a multi-center Phase 1 trial in the US to evaluate ALG.APV-527 in the treatment of multiple solid tumor types expressing the tumor antigen 5T4.

About ALG.APV-527
ALG.APV-527 is an antibody with dual function: tumor-binding and 4-1BB immunomodulatory agonist effects. This has the potential to be clinically important because 4-1BB has the ability to stimulate the immune cells (antitumor-specific T cells) involved in tumor control, making 4-1BB a particularly compelling target for cancer immunotherapy.  Preclinical results, presented at the Society of Immunotherapy Cancer’s 2021 Annual Meeting, highlighted the differentiated design of the molecule that minimizes systemic immune activation, allowing for highly efficacious tumor-specific responses as demonstrated by potent activity in in vitro models. Alligator and Aptevo are working rapidly to advance ALG.APV-527 into Phase 1 clinical development in the US.

The information was submitted for publication, through the agency of the contact persons set out below at 5:15 p.m. CET on November 9, 2022.