Pharmacokinetics of Monoclonal Antibodies

Development of a spectroscopic assay for bifunctional ligand-protein conjugates based on copper

A simple, non-radioactive method for the determination of ligand-to-protein ratio (L/P) for novel ligand-antibody conjugates has been developed based on an exchange equilibrium with the purple Cu(II) complex of arsenazo III. The method requires a UV/Vis spectrometer and has been verified for monoclonal antibody Herceptin conjugates of a variety of ligand modalities, including common macrocyclic compounds NOTA and TETA, and with a new bifunctional tachpyridine (1H-Pyrrole-1-butanamide,N-[4-[[(1alpha,3alpha,5alpha)-3,5-bis[(2-pyridinylmethyl)amino]cyclohexyl](2-pyridinylmethyl)amino]butyl]-2,5-dihydro-2,5-dioxo-(9CI)). The spectroscopically derived values for L/P were verified by titration of the ligand-antibody conjugate with 64Cu. In each case, the value obtained by UV/Vis spectroscopy matches that found by radiolabeling. The method is rapid, taking less than 30 minutes with each ligand in this study.

Synergy between vascular targeting agents and antibody-directed therapy

PURPOSE

Tumor heterogeneity necessitates the use of combined therapies. We have shown that combining antibody-directed therapy with antivascular agents converts a subcurative to a curative treatment. The purpose of this study was to investigate, by radioluminographic and microscopic techniques, the regional effects of the two complementary therapies.

METHODS AND MATERIALS

Nude mice bearing colorectal tumors were injected with 125I-labeled anti-carcinoembryonic antigen antibody, and images were obtained for antibody distribution and modeling studies using radioluminography. For therapy studies, the mice were given radioimmunotherapy alone (131I-A5B7 anti-carcinoembryonic antigen antibody), the antivascular agent combretastatin A-4 3-0-phosphate (200 mg/kg), or both. Extra mice were used to study the regional tumor effects of these therapies over time: relevant histochemical procedures were performed on tissue sections to obtain composite digital microscopic images of apoptosis, blood vessels, perfusion, hypoxia, and morphology.

RESULTS

Antibody distribution, modeling, and immunohistochemistry showed how radioimmunotherapy (7.4 MBq/40 microg antibody) effectively treated the outer, well-oxygenated tumor region only. Combretastatin A-4 3-0-phosphate treated the more hypoxic center, and in doing so altered the relationship between tumor parameters.

CONCLUSION

The combined complementary therapies produced cures by destroying tumor regions with different pathophysiologies. Relating these regional therapeutic effects to the relevant tumor parameters microscopically allows optimization of therapy and improved translation to clinical trials.

PEGylated antibodies and antibody fragments for improved therapy: a review

The use of covalent attachment of poly(ethylene glycol) to various different proteins in order to modify their function has been reported over many years. One class of protein that this technology has more recently been applied to is antibodies and antibody fragments. PEG has been predominantly used to reduce the immunogenicity and increase the circulating half-lives of antibodies. It may also have a beneficial effect on the use of antibodies in certain clinical settings such as tumour targeting. This review describes previously reported experience with PEGylated antibodies and antibody fragments, and where these types of molecules may find clinical usefulness in the future.