Session Speaker
Cell Penetrating Peptides : Design, Cellular Trafficking and Applications to the Delivery of Oligonucleotides
Bernard Lebleu

Improved delivery strategies for biomolecules as peptides or nucleic acids have long been searched for since poor translocation across membrane barriers is a major limitation for many of their clinical applications. While efficient for the delivery of conjugated peptides or of fused proteins, cell penetrating peptides (CPP) as Tat48-60, Penetratin or oligoArg have turned out to be poorly efficient for the transfection of steric-block oligonucleotides (ON).

We have designed Arg-rich CPPs such as (RAhxR)n (in which Arg residues are interspersed with 4-aminohexanoic acid) or Pip (a series of Arg-extended Penetratin derivatives engineered for improved metabolic stability) which are able to deliver neutral steric-block ON analogs (PNA, PMO) at micromolar concentrations as attested by redirection of the splicing machinery in both in vitro and in vivo assays. However, mechanistic studies indicate that most of the transfected ONs remain entrapped in endocytic vesicles thus leaving room for much improvement. Ongoing efforts are geared towards identifying CPPs with improved endosomal escape and at setting up assays to monitor this limiting step in ON-CPP intracellular trafficking. The potential of CPP oligomerization and of CPP derivatization with fatty acids chains will be reported. We also propose liposome leakage to monitor the membrane destabilization potential of CPPs and as a potential convenient assay to model endosome escape.