{Reference Type}: Journal Article
{Title}: CryoEM structure of a therapeutic antibody (favezelimab) bound to human LAG3 determined using a bivalent Fab as fiducial marker.
{Author}: Mishra AK;Shahid S;Karade SS;Agnihotri P;Kolesnikov A;Hasan SS;Mariuzza RA;
{Journal}: Structure
{Volume}: 31
{Issue}: 10
{Year}: 2023 10 5
{Factor}: 5.871
{DOI}: 10.1016/j.str.2023.07.013
{Abstract}: Lymphocyte activation gene 3 protein (LAG3) is an inhibitory receptor that is upregulated on exhausted T cells in tumors. LAG3 is a major target for cancer immunotherapy with many anti-LAG3 antibodies in clinical trials. However, there is no structural information on the epitopes recognized by these antibodies. We determined the single-particle cryoEM structure of a therapeutic antibody (favezelimab) bound to LAG3 to 3.5 Å resolution, revealing that favezelimab targets the LAG3-binding site for MHC class II, its canonical ligand. The small size of the complex between the conventional (monovalent) Fab of favezelimab and LAG3 (∼100 kDa) presented a challenge for cryoEM. Accordingly, we engineered a bivalent version of Fab favezelimab that doubled the size of the Fab-LAG3 complex and conferred a highly identifiable shape to the complex that facilitated particle selection and orientation for image processing. This study establishes bivalent Fabs as new fiducial markers for cryoEM analysis of small proteins.