Abstract
Many synthetic peptides have been developed for diagnosis and therapy of human cancers based on their ability to target specific receptors on cancer cell surface or to penetrate the cell membrane. Chemical modifications of amino acid chains have significantly improved the biological activity, the stability and efficacy of peptide analogues currently employed as anticancer drugs or as molecular imaging tracers. The stability of somatostatin, integrins and bombesin analogues in the human body have been significantly increased by cyclization and/or insertion of non-natural amino acids in the peptide sequences. Moreover, the overall pharmacokinetic properties of such analogues and others (including cholecystokinin, vasoactive intestinal peptide and neurotensin analogues) have been improved by PEGylation and glycosylation. Furthermore, conjugation of those peptide analogues to new linkers and bifunctional chelators (such as AAZTA, TETA, TRAP, NOPO etc.), produced radiolabeled moieties with increased half life and higher binding affinity to the cognate receptors. This review describes the most important and recent chemical modifications introduced in the amino acid sequences as well as linkers and new bifunctional chelators which have significantly improved the specificity and sensitivity of peptides used in oncologic diagnosis and therapy.
Highlights
Natural or synthetic peptides are short chains of amino acids useful to analyze functions of the full length proteins and in particular the specific binding to cognate cell-membrane associated receptors and their subsequent internalization
Main chemical modifications include the synthesis of pseudo-peptides containing D-amino acids or more stable non-natural amino acids, modifications at the C- or N-terminus, multimerization, cyclization, PEGylation, glycosylation, etc. [5,6]
Different chelators have been designed, synthesized and conjugated to synthetic peptides to improve the stability of radiolabeled molecules and their biodistribution in the human body [7]
Summary
Natural or synthetic peptides are short chains of amino acids useful to analyze functions of the full length proteins and in particular the specific binding to cognate cell-membrane associated receptors and their subsequent internalization. The increased expression of peptide receptors in many human tumors allowed to develop a wide range of moieties useful for diagnostic imaging, cancer radiotherapy and immunotherapy [1,2,3]. In this this review, review, we we summarize summarize recent recent advances advances in in chemical chemical modifications modifications of of amino amino acid acid sequences, sequences,linkers linkersand andchelators chelatorsto toproduce produceoptimal optimalmoieties moietiesfor fordiagnosis diagnosisand andtherapy therapyof ofhuman human neoplastic neoplasticdiseases.
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