Immune checkpoint blockade with monoclonal antibodies (mAbs) that target 
programmed cell death protein-1 (PD-1) has remarkably revolutionized cancer 
therapy. Their binding kinetics measured by surface plasmon resonance does not 
always correlate well with their immunotherapeutic efficacies, mainly due to the 
lack of two-dimensional cell plasma membrane and the capability of force sensing 
and manipulation. In this regard, based on a more suitable and ultra-sensitive 
biomechanical nanotool, biomembrane force probe (BFP), we developed a 
Double-edge Smart Feedback control system as an ultra-stable platform to 
characterize ultra-long bond lifetimes of receptor-ligand binding on living 
cells. We further benchmarked the dissociation kinetics for three clinically 
approved PD-1 blockade mAbs (Nivolumab, Pembrolizumab, and Camrelizumab), 
intriguingly correlating well with the objective response rates in the 
hepatocellular carcinoma second-line treatment. This ultra-stable BFP 
potentially provides a compelling kinetic platform to direct the screening, 
optimization, and clinical selection of therapeutic antibodies in the future.