title: Pharmacodynamic enhancement of the anti-platelet antibody fab abciximab by site-specific pegylation.
abstract: Monoclonal antibodies have been firmly established as human therapeutics. Their high affinity and specificity for target antigens minimize adverse reactions and their molecular size results in extended circulation times relative to small molecule pharmaceuticals. The ability to customize the pharmacokinetics in a rational manner can enhance the potential for these and other classes of biologicals. We have systematically studied the effect of site-specific pegylation of the Fab' fragment of the anti-GPIIb/IIIa, alphavbeta3 antibody c7E3. Regardless of the molecular weight of the PEG molecules, the intrinsic affinity of the resulting constructs remained unchanged. However, in functional assays measuring inhibition of platelet aggregation, the calculated IC50 values of the conjugates decreased with increasing molecular weight of the conjugated PEG. It was determined that the molecular size of the conjugates affects antigen accessibility and whereas high levels of binding to antigen molecules on cells with high antigen density can be demonstrated with the Fab fragment, comparable levels are not achievable with large molecular weight conjugates. In spite of the inability of the larger PEG constructs to achieve saturation binding, functional inhibition of platelet aggregation consistent with saturation binding was demonstrated and the increased molecular size of the conjugates led to predictably prolonged inhibition of platelet aggregation.
authors.affiliation: Pharmaceutical Research, Centocor, Inc., 200 Great Valley Parkway, Malvern, PA 19355, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Knight
authors.forename: Robert E
authors.initials: RE
authors.lastname: Jordan
authors.forename: Marian
authors.initials: M
authors.lastname: Kruszynski
authors.forename: Susan H
authors.initials: SH
authors.lastname: Tam
authors.forename: Jill
authors.initials: J
authors.lastname: Giles-Komar
authors.forename: George
authors.initials: G
authors.lastname: Treacy
authors.forename: George A
authors.initials: GA
authors.lastname: Heavner
mesh_terms: D000077284:Abciximab; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000276:immunology / Q000494:pharmacology; D002460:Cell Line; D000882:Haplorhini; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry* / Q000276:immunology / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000737:chemistry* / Q000276:immunology / Q000493:pharmacokinetics; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors; D011092:Polyethylene Glycols / Q000737:chemistry*
chemical_list: D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011092:Polyethylene Glycols; D000077284:Abciximab