Pharmacokinetics and biodistribution of genetically-engineered antibodies

D. Colcher, G. Pavlinkova, G. Beresford, B. J.M. Booth, A. Choudhury, S. K. Batra

Research output: Contribution to journalReview articlepeer-review

160 Scopus citations


Monoclonal antibodies (MAbs), because of their inherent specificity, are ideal targeting agents. They can be used to deliver radionuclides, toxins or cytotoxic drugs to a specific tissue or malignant cell populations. Intact immunoglobulin (IgG) molecules have several practical limitations of their pharmacology; their relatively large size of approximately 150,000 daltons leads to a slow clearance from the blood pool and the body resulting in significant exposure to normal organs with limited quantities delivered to tumors. The IgG molecule shows a relatively poor diffusion from the vasculature into and through the tumor. Attempts to modify the pharmacology of the Ig molecule have classically involved the use of proteases to generate F(ab')2 and Fab' fragments with molec-binding affinity similar to that of a monovalent Fab' fragment; this however, represents a relative decrease in binding affinity when compared to intact antibodies. The scFv with its faster clearance and lower affinity results in a lower percent-injected dose localizing in tumors when compared to the divalent IgG molecule. This may be adequate for imaging but probably not for therapy. The valency of the MAb fragment is critical for the functional affinity of an antibody to a cell surface or a polymeric antigen. In attempts to generate multivalent forms of scFv molecules, noncovalently linked scFv dimeric and trimeric molecules, disulfide linked dimeric scFvs, as well as covalently linked chimetic scFvs have been studied. These multivalent scFvs generally have a higher functional affinity than the monovalent form resulting in better in vivo targeting. Another way to alter the pharmacology of the scFvs is to modify its net charge. Charge-modified scFvs with desired isoelectric points (pI), have been prepared by inserting negatively charged amino acids on the template of the variable region genes. This can help to overcome undesirable elevations in renal uptake seen with most antibody fragments. In conclusion, genetic manipulations of the immunoglobulin molecules are effective means of altering stability, functional affinity, pharmacokinetics, and biodistribution of the antibodies required for the generation of the 'magic bullet'.

Original languageEnglish (US)
Pages (from-to)225-241
Number of pages17
JournalQuarterly Journal of Nuclear Medicine
Issue number4
StatePublished - 1998


  • Antibodies
  • Antibody engineering
  • Monoclonal
  • Single chain antibody fragments

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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