title: Evaluation of ¹¹¹in-labelled exendin-4 derivatives containing different meprin β-specific cleavable linkers.
abstract: BACKGROUND
  Cleavable linkers, which are specifically cleaved by defined conditions or enzymes, are powerful tools that can be used for various purposes. Amongst other things, they have been successfully used to deliver toxic payloads as prodrugs into target tissues. In this work novel linker sequences targeting meprin β, a metalloprotease expressed in the kidney brush-border membrane, were designed and included in the sequence of three radiolabelled exendin-4 derivatives. As radiolabelled exendin-4 derivatives strongly accumulate in the kidneys, we hypothesised that specific cleavage of the radiolabelled moiety at the kidney brush-border membrane would allow easier excretion of the activity into the urine and therefore improve the pharmacological properties of the peptide.
  
  
  RESULTS
  The insertion of a cleavable linker did not negatively influence the in vitro properties of the peptides. They showed a good affinity to the GLP-1 receptor expressed in CHL cells, a high internalisation and sufficiently high stability in fresh human blood plasma. In vitro digestion with recombinant meprin β rapidly metabolised the corresponding linker sequences. After 60 min the majority of the corresponding peptides were digested and at the same time the anticipated fragments were formed. The peptides were also quickly metabolised in CD1 nu/nu mouse kidney homogenates. Immunofluorescence staining of meprin β in kidney sections confirmed the expression of the protease in the kidney brush-border membrane. Biodistribution in GLP-1 receptor positive tumour-xenograft bearing mice revealed high specific uptake of the 111In-labelled tracers in receptor positive tissue. Accumulation in the kidneys, however, was still high and comparable to the lead compound 111In-Ex4NOD40.
  
  
  CONCLUSIONS
  In conclusion, we show that the concept of cleavable linkers specific for meprin β is feasible, as the peptides are rapidly cleaved by the enzyme while retaining their biological properties.
authors: Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland.
authors: Andreas
authors: A
authors: Jodal
authors: Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland; Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland.
authors: Fabienne
authors: F
authors: Pape
authors: Institute of Biochemistry, University of Kiel, Kiel, Germany.
authors: Christoph
authors: C
authors: Becker-Pauly
authors: Department of Radiology and Nuclear Medicine, Division of Nuclear Medicine, University Hospital Basel, Basel, Switzerland.
authors: Ole
authors: O
authors: Maas
authors: Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland; Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland.
authors: Roger
authors: R
authors: Schibli
authors: Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland.
authors: Martin
authors: M
authors: Béhé
mesh_terms: D000818:Animals; D002460:Cell Line; D016503:Drug Delivery Systems; D000077270:Exenatide; D000067757:Glucagon-Like Peptide-1 Receptor / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007205:Indium Radioisotopes / Q000008:administration & dosage; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors / Q000235:genetics*; D051379:Mice; D058990:Molecular Targeted Therapy; D010455:Peptides / Q000008:administration & dosage / Q000097:blood / Q000235:genetics*; D011355:Prodrugs / Q000008:administration & dosage* / Q000378:metabolism; D014688:Venoms / Q000008:administration & dosage / Q000097:blood / Q000235:genetics*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000067757:Glucagon-Like Peptide-1 Receptor; D007205:Indium Radioisotopes; D010455:Peptides; D011355:Prodrugs; D014688:Venoms; D000077270:Exenatide; D008666:Metalloendopeptidases; C053833:meprin A