Evaluation of the pinocytic uptake and cellular processing of antibody-N-(2-hydroxypropyl)methacrylamide copolymer conjugates and estimation of their potential use in "targeted" drug delivery

Abstract

125 I-labelled protein (entibody or trensferrin)-N-(2-hydroxypropy1)methacrylamide (HPMA)copolymer conjugates were characterised using gel permeation chromatography and their average molecular weight (Kw) determined (Chapter 3). It was estimated that within a protein-HPMA copolymer conjugate each protein residue was probably bound to 10-20 molecules of HPHA copolymer.
The human transferrin receptor was used as a model target antigen/receptor. Pinocytic uptake of HPHA copolymer conjugated to monoclonal antibody B3/25 (specific for the transferrin receptor) or transferrin (as potential targeting residues) was up to 9 -fold higher than the uptake of parent copolymer (Chapter 4). The ability of these conjugates to bind specifically was confirmed by Scatchard analysis of their cell-surface binding (Chapter 6). Also, using a Percoll density gradient (Chapter 5), it was shown that internalisation of protein-HPMA copolymer conjugates is dependent upon their Nw and that internalised conjugates reach the lysosomal compartment.
The transferrin receptor was found to nave limited potential as an in vivo model antigen/receptor. HPMA copolymer conjugates containing either monoclonal antibody B3/25 or transferrin were detected in all rapidly dividing organs/tissues studied (Chapter 7). Conjugates containing anti-Thy-1.2 polyclonal antibody (as a targeting residue) were shown to localise preferentially in the thymus, spleen, liver, skin and bone marrow. The ability of only <1% (administered dose) of conjugate to reach a major target organ, the thymus, was consistent with published values (Chapter 8).
Conjugation of HPMA to antibody (IgG) was shown to produce a 2B0-fo1d reduction in inmunogenicity of the antibody (Chapter 9, preliminary results).
Although the stoichiometry and stereochemistry of the conjugates used in this study were not ideal (Chapters 3, 10) use of similar conjugates 1n targeted drug-delivery has potential.