Bicyclic peptides conjugated to an albumin-binding tag diffuse efficiently into solid tumors.
Monoclonal antibodies have long in vivo half-lives and reach high concentrations in tumors but cannot access all regions in the tissue, whereas smaller ligands such as peptides distribute better but are limited by low concentrations due to fast renal clearance. A potential solution to this problem might be offered by peptide-based ligands that are conjugated to an albumin-binding tag, and thus have a long plasma half-life. Herein, we tested if a small ligand based on a bicyclic peptide (1.9 kDa) conjugated to an albumin-binding peptide (2.3 kDa) can diffuse into tissues. Although the peptide conjugate (4.6 kDa) was most of the time bound to the large protein serum albumin (66.5 kDa), it diffused deeply into tissues and reached high nanomolar concentrations in wide areas of solid tumors. Most of the peptide conjugate isolated from tumor tissue was found to be fully intact 24 hours after administration. Because of its noncovalent interaction with albumin, the bicyclic peptide might dissociate to diffuse to tumor regions that are not accessible to larger ligands. Bicyclic peptides having high binding affinity for targets of interest and being proteolytically stable can be evolved by phage display; in conjunction with albumin-binding tags, they offer a promising format to access targets in solid tumors.
Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Lisa
L
Pollaro
Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Sandeep
S
Raghunathan
Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Julia
J
Morales-Sanfrutos
Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Alessandro
A
Angelini
Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Stephan
S
Kontos
Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland. christian.heinis@epfl.ch.
Christian
C
Heinis
D000418:Albumins / Q000378:metabolism*; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism*; D001643:Bridged Bicyclo Compounds / Q000008:administration & dosage* / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D045744:Cell Line, Tumor; D005260:Female; D006207:Half-Life; D006801:Humans; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D010456:Peptides, Cyclic / Q000008:administration & dosage* / Q000138:chemical synthesis / Q000493:pharmacokinetics*
D000418:Albumins; D001643:Bridged Bicyclo Compounds; D010456:Peptides, Cyclic