Peptide optimization and conjugation strategies in the development of molecularly targeted magnetic resonance imaging contrast agents

Methods Mol Biol. 2014;1088:185-211. doi: 10.1007/978-1-62703-673-3_13.

Abstract

Peptides are highly selective, high-affinity ligands for a diverse array of disease targets, but suitably derivatizing them for application as diagnostic or therapeutic agents often presents a significant challenge. Covalent modification with metal chelates frequently results in decreased binding affinity, so a variety of strategies must be explored to find suitable locations for modification and facile peptide conjugation chemistries that maintain or enhance binding affinity. In this chapter, we present a paradigm for systematically optimizing peptide binding and determining the favorable sites and methods for peptide conjugation. This strategy is illustrated by two case studies of peptide-based targeted gadolinium contrast agents: EP-2104R for diagnosis of thrombosis and EP-3533 for diagnosis of cardiac perfusion and fibrosis. Two different architectures for the peptide-metal complex conjugation were designed: EP-2104R contains a total of four gadolinium (Gd) chelates linked at the N- and C-termini, whereas EP-3533 is derivatized with three Gd chelates, two on the N-terminus and one on a lysine side chain. Detailed protocols are provided for two Gd chelate conjugation methods.

MeSH terms

  • Amino Acid Sequence
  • Collagen / chemistry
  • Collagen / metabolism
  • Contrast Media* / chemistry
  • Fibrin / metabolism
  • Gadolinium / chemistry
  • Gadolinium DTPA / chemistry
  • Heterocyclic Compounds / chemistry
  • Humans
  • Magnetic Resonance Imaging*
  • Molecular Sequence Data
  • Organometallic Compounds / chemistry
  • Peptides* / chemical synthesis
  • Peptides* / chemistry
  • Staining and Labeling
  • Structure-Activity Relationship

Substances

  • Contrast Media
  • EP-2104R
  • Heterocyclic Compounds
  • Organometallic Compounds
  • Peptides
  • Fibrin
  • Collagen
  • gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate
  • Gadolinium
  • Gadolinium DTPA