Affinity maturation of antibody against membrane-bound GPCR molecules. Affinity maturation of antibody against membrane-bound GPCR molecules

G protein coupled receptors (GPCRs), also known as seven-transmembrane domain receptors, are among the most important targets against which many small molecule drugs have been developed. However, only two antibody drugs targeting GPCRs have been approved for clinical use although many antibody drugs against non-GPCR protein targets have been successfully developed for various disease indications. One of the challenges for developing anti-GPCR drugs is the high difficulty to perform affinity maturation due to their insolubility in aqueous solutions. To address this issue, CHO cell display libraries of single-chain variable fragments (scFvs) and full-length antibodies were maturated directly against vesicle probes prepared from CHO cells displaying GPCR molecules. ETaR is a model GPCR molecule used in this study. Four rounds of affinity maturation combining vesicles as probes with the CHO cell display platform improved affinity by 13.58 folds for scFvs and 5.05 folds for full-length antibodies. We expect that this method is not only for affinity maturation of antibodies against GPCRs, but will also be used to mature antibodies for the other types of proteins the conformation/activity of which depends on proper membrane environment.