The potential for enhanced tumour localisation by poly(ethylene glycol) modification of anti-CEA antibody

Abstract

Attachment of poly(ethylene glycol) (PEG) to proteins can greatly alter their pharmacological properties, including extending the plasma half-life and reducing immunogenicity, both of which are potentially beneficial to tumour targeting. IgG, F(ab')2 and Fab' fragments of the anti-CEA antibody A5B7 were chemically modified with PEG (M(r) 5,000), labelled with 125I and their pharmacokinetics compared with the unmodified forms in the LS174T colonic xenograft in nude mice. PEG modification of the intact antibody had little effect on biodistribution, although tumour localisation was slightly reduced. In contrast, similar modification of F(ab')2 and Fab'A5B7 significantly prolonged plasma half-life and increased radioantibody accumulation in the tumour and to a lesser extent in normal tissues, but reduced tissue to blood ratios. Prior to modification, Fab' A5B7 (M(r) 50,000) cleared more rapidly from the circulation than F(ab')2 (M(r) 100,000), but after PEG attachment their biodistributions converged, while the tumour to blood ratios were reduced and resembled that of the intact antibody. The enhanced tumour accumulation, reduced normal tissue to blood ratios and potentially reduced immunogenicity of fragments after PEG attachment may therefore prove superior to either unmodified fragments or intact antibody for antibody-targeted therapy, although the increased plasma half-life may necessitate the use of a clearance mechanism.

Improving the pharmacokinetic properties of biologics by fusion to an anti-HSA shark VNAR domain

“…[15][16][17][18] Other re-formatting strategies such as alterations to site-specific glycosylation have shown moderate increased plasma half-life 19 while exploitation of the FcRn re-cycling system by molecular Fc fusions have significantly extended circulating antibody fragment concentrations. 20 Another strategy that hijacks this natural recycling system involves use of serum albumin binding to extend the circulating half-life of smaller proteins or peptides.…”

Improving Protein Pharmacokinetics by Genetic Fusion to Simple Amino Acid Sequences

“…Although polymer conjugation to hormones and enzymes may lead to a reduction in their biological/ enzymatic activities (45)(46)(47). Furthermore, chemical coupling methods usually result in a mixture of heterogeneous molecules displaying different in vivo performances (2,(45)(46)(47). Genetic techniques constitute an interesting alternative, since this method allows the allocation of the desired sequences far from the active site of the target molecule.…”

“…To overcome this problem, covalent coupling of drugs or proteins to polyethylene glycol has been extensively applied (13). Although polymer conjugation to hormones and enzymes may lead to a reduction in their biological/ enzymatic activities (45)(46)(47). Furthermore, chemical coupling methods usually result in a mixture of heterogeneous molecules displaying different in vivo performances (2,(45)(46)(47).…”

Antibody Therapy in the Management of Shiga Toxin-Induced Hemolytic Uremic Syndrome

“…Smaller antibody molecules, including variable fragments, single-chain variable fragments, Fabs, and (FabЈ) 2 s which are less than 60 to 70 kDa in size, below the threshold for renal uptake, and are therefore rapidly cleared in the kidneys. If Fabs are efficacious but require a longer serum half-life to be effective, this can be achieved by coupling them with polyethylene glycol (11,97).…”