The characterization of anti–IGSF9-DXd. (A) The basic structure of anti–IGSF9-DXd. (B) The purity of anti–IGSF9-DXd is assessed by size exclusion chromatography, and (C) the DAR values are determined by hydrophobic interaction chromatography. (D,E) The binding activities and serum half-life of anti-IGSF9 and anti–IGSF9-DXd are determined.