INBRX-105 is a recombinant humanized bispecific antibody that targets programmed death-ligand 1 (PD-L1) and 4-1BB (CD137), exhibiting potential checkpoint inhibition, immune stimulation, and anti-tumor activity. By binding to 4-1BB on activated T-lymphocytes and PD-L1 on tumor cells, INBRX-105 enhances T-cell co-stimulation and inhibits PD-L1-mediated T-cell suppression, potentially reducing tumor growth. It demonstrates anti-tumor efficacy and increased T-cell frequency in patients with solid tumors and in vivo. Molecular weight: 101.9 kD.