Samples of CMC-544 or G5/44 were diluted in the HBS buffer (10 mM HEPES, pH 7.4 containing 150 mM NaCl, 3 mM EDTA and 0.005% polysorbate 20 (v/v)) and injected in the concentration range of 1 to 100 nM over the CD22mFc-coated biosensor chip surface at a flow rate of 30 ul/min for 3 min to allow binding. After the binding phase, dissociation of the bound antibody was monitored by washing the chip with the HBS buffer over a 15 min period. The antigenic surface was regenerated by washing the Biosensor chip with 15 ul of the regeneration buffer (10 mM NaOH and 200 mM NaCI) for 30 seconds, followed by a stabilization time of 2 min before the next cycle. Kinetic constants were calculated by nonlinear least square regression analysis using a 1:1 Langmuir binding curve fitting model and BIAevaluation program (version 3.0, BIAcore). The antigen binding of CMC-544 was evaluated by surface plasmon resonance analysis using CD22mFc covalently immobilized on a biosensor chip. The results of kinetic analyses of the binding of CMC-544 and G5/44 to CD22mFc show that, after the data were fitted globally to a 1:1 Langmuir binding model with compensation for mass transfer, both CMC-544 and unconjugated G544 bound CD22 with a similar affinity (CMC-544:CD22 KD= 200 pM; G5/44:CD22 KD = 235 pM). Conjugation to calicheamicin did not impact the ability of G5/44 to effectively bind CD22mFc.