PHARMACOKINETICS AND BIODISTRIBUTION OF RADIOLABELED AVIDIN, STREPTAVIDIN AND BIOTIN

The extraordinary high affinity of avidin and streptavidin for biotin may be exploited in a two-step approach for delivering radiolabeled bi otin derivatives suitable for imaging and therapy to target-bound stre ptavidin or avidin conjugated monoclonal antibodies (MAbs). The in viv o pharmacokinetics and biodistribution of radiolabeled avidin, strepta vidin (SA) and DTPA-biocytinamide (DTPA biotin) were studied in the ra bbit and dog. SA circulated in the blood similar to other 60 kDa prote ins, avidin cleared immediately and DTPA biotin exhibited plasma clear ance by glomerular filtration.