Chromatofocusing studies involving a monoclonal Fab'

Area of Science:

• Biochemistry
• Immunology
• Radiopharmaceutical Science

Background:

• Monoclonal antibodies (mAbs) are crucial in targeted therapies and diagnostics.
• The Fab' fragment is a common derivative used in imaging and therapy.
• Heterogeneity in antibody fragments can impact their in vivo behavior.

Purpose of the Study:

• To investigate the heterogeneity of the Fab' derivative of murine monoclonal antibody ZCE-025.
• To analyze the impact of isoelectric point (pI) variants on biodistribution and stability.
• To assess the implications for radioimmunoimaging applications.

Main Methods:

• Isoelectric focusing (IEF) and chromatofocusing to separate Fab' variants.
• Electrophoresis to confirm fragment integrity.
• Biodistribution studies in Balb/c and nude mice following injection of radiolabeled variants.
• Analysis of serum and urine samples post-injection.

Main Results:

• IEF detected at least six Fab' bands with pI ranging from 5.4 to 7.8.
• Low pI 125I-Fab' variants exhibited biodistribution similar to intact Fab', with good organ and tumor uptake.
• High pI 125I-Fab' variants were rapidly excreted and did not concentrate in tumors.
• Serum analysis revealed high and low molecular weight complexes, suggesting in vivo interactions.

Conclusions:

• The Fab' of ZCE-025 is heterogeneous, with variants exhibiting differential stability and biodistribution.
• High pI variants may be counterproductive for radioimmunoimaging due to rapid excretion.
• In vivo association with endogenous proteins could influence radiopharmaceutical biodistribution.