Alligator Bioscience AB and Aptevo Therapeutics announced that the US Food and Drug Administration (FDA) has issued a "may proceed" notification for the ALG.APV-527 investigational new drug application (IND), allowing the companies to initiate clinical trials evaluating the compound for the treatment of 5T4-expressing tumor antigens in multiple solid tumor types. The companies are moving rapidly to initiate a multi-center Phase 1 trial in the US. 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 immune cell stimulation through 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 vitro models. The tumor-binding function of ALG.APV-527 targets the 5T4 tumor-associated antigen.

5T4 is a protein expression in multiple solid tumor types and limited expression in normal tissues, making 5T4 a compelling target molecule for cancer therapy.