Cryo-EM for Structurally Enabled Therapeutic Antibody Development Against GPCRs

GPCR-targeting antibodies are increasingly important. Structurally aided maturation of GPCR-antibody interactions can enhance target engagement and reveal receptor conformational changes associated with antibody binding [1]. Cryo-electron microscopy (cryo-EM) is the preferred method for elucidating GPCR structures, including both agonist-bound active states and, increasingly, antagonist-bound inactive states [2]. Furthermore, cryo-EM provides an excellent tool for epitope mapping of GPCR-targeted antibodies. However, obtaining high-quality GPCR samples for antibody discovery and cryo-EM structure determination is challenging due to the inherent size, flexibility, and instability of GPCRs post-extraction from the membrane [3]. Effective strategies and critical decisions in construct design, expression, and purification are essential for producing high-quality samples to be used as immunogens and for successful imaging. We present a new cryo-EM structure of the 5-HT2A receptor, demonstrating scFv16 binding at its epitope and revealing a novel serotonin binding conformation.

1. Peterson, S. M.; Hutchings, C. J.; Hu, C. F.; et al. Discovery and Design of G Protein-Coupled Receptor Targeting Antibodies. Expert Opin. Drug Discov. 2023, 18, 417–428.
2. Danev, R.; Belousoff, M.; Liang, Y.-L.; et al. Routine Sub-2.5 Å Cryo-EM Structure Determination of GPCRs. Nat. Commun. 2021, 12, 4333.
3. Addis, P.; Bali, U.; Baron, F.; et al. Key Aspects of Modern GPCR Drug Discovery. SLAS Discov. 2023.