PAB-005

PAB-005 is an investigational pro-antibody (conditionally activated antibody) agonist targeting OX40 (Tumor necrosis factor receptor superfamily member 4), developed by AJK Biopharmaceutical. Utilizing the company's proprietary Pro-Antibody (PAB) platform, the molecule is engineered as a masked agonist; the antigen-binding domain is shielded by a masking peptide that is selectively cleaved by proteases overexpressed within the tumor microenvironment. This localized activation is intended to trigger OX40-mediated T-cell co-stimulation specifically within tumors, thereby enhancing anti-tumor immune responses while minimizing the systemic immune-related adverse events (irAEs) often associated with conventional OX40 agonists. PAB-005 is currently in early-stage development for the treatment of various solid tumors.