Alligator Bioscience & Aptevo Therapeutics Announce Dosing of First Patient with ALG.APV-527 in Phase 1 Clinical Trial

Trial to Evaluate Safety, Tolerability and Clinical Activity in Solid Tumors Expressing 5T4

Lund, Sweden, and Seattle, Washington, February 13, 2023 – Alligator Bioscience AB ("Alligator") (Nasdaq Stockholm: ATORX) and Aptevo Therapeutics ("Aptevo") (Nasdaq: APVO) today announced the dosing of the first patient in the companies’ Phase 1 trial evaluating ALG.APV-527 for the treatment of solid tumors expressing the tumor-associated antigen 5T4. ALG.APV-527 is a bispecific antibody with a tumor-directed 4-1BB agonistic effect and the ability to specifically stimulate antitumor-specific T cells and NK cells involved in tumor control. 

“We are very pleased to announce the initiation of a clinical trial to evaluate ALG.APV-527 in patients with solid tumors with high prevalence of 5T4. For Aptevo, the initiation of a second clinical program means we are now developing therapeutics to treat both solid tumors and hematological malignancies – a strategic win for our company,” said Marvin White, President, and CEO of Aptevo. “ALG.APV-527 is a compelling candidate, as preclinical studies showed it has the potential to activate key immune cell populations within the tumor microenvironment while demonstrating a favorable safety profile. We look forward to sharing preliminary results, which we anticipate will be available in 2023.”

"The start of this Phase 1 first in human study is an important milestone in the development of ALG.APV-527 and demonstrates the growing strength and effectiveness of our partnership with Aptevo," said Søren Bregenholt, PhD, CEO of Alligator Bioscience. "It also marks Alligator's third asset currently in clinical development and we are particularly excited to evaluate its tumor-directed 4-1BB function with its promise of a broad therapeutic window and, alike ATOR-1017, highly differentiated safety and efficacy profile compared to the first generation 4-1BB agonists."

The ALG.APV-527 Phase 1 trial is a multi-center, multi-cohort, open-label trial that will include six cohorts in a 3+3 design. The trial will be conducted at up to 10 sites in the U.S. among adult patients with multiple solid tumor types/histologies likely to express the 5T4 antigen, including (but not limited to) non-small cell lung cancer (NSCLC), gastric/gastro-esophageal cancer and head and neck cancer. ALG.APV-527 will be given intravenously once every two weeks. The trial will assess the safety and tolerability, pharmacokinetic, pharmacodynamic and preliminary anti-tumor activity of ALG.APV-527.

About ALG.APV-527
ALG.APV-527 is a bispecific conditional 4-1BB agonist, only active upon simultaneous binding to 4-1BB and 5T4. This has the potential to be clinically important because 4-1BB has the ability to stimulate the immune cells (antitumor-specific T cells and NK cells) involved in tumor control, making 4-1BB a particularly compelling target for cancer immunotherapy. 5T4 is an oncofetal tumor associated antigen overexpressed on numerous solid tumors including non-small-cell lung carcinoma (NSCLC), breast, head and neck, cervical, renal, gastric, and colorectal cancer.
Preclinical studies, highlighting the differentiated design of the molecule that minimizes systemic immune activation, allowing for highly efficacious tumor-specific responses as demonstrated by potent activity in preclinical models, were recently published in the peer-reviewed publication, Molecular Cancer Therapeutics, a journal of the American Association for Cancer Research (AACR). The full article is available via this link.

The information was submitted for publication, through the agency of the contact persons set out below at 2:05 p.m. CET on February 13, 2023.

Updated 2023-02-13