Plasma stability and PK analysis of bispecific Db3-43xhu225-Ig molecules. (a) The Db-Ig molecules were diluted in 50% human plasma and incubated at 37°C for, 1, 3, or 7 days. Protein content was determined by ELISA using both antigens, EGFR-His or HER3-His. (b) Pharmacokinetic profile of Db-Ig molecules were analyzed in female CD-1 mice (n = 3). Mice received a single i.v. injection of 25 µg of the protein. Serum protein concentrations were determined by ELISA using both antigens, EGFR-His or HER3-His.