We have recently described a new (R-Ahx-R) 4 -CPP (in which Arg residues are interspersed with nonnatural 6-aminohexanoic acid amino-acid spacers) which leads to efficient splicing correction at low concentration in the absence of endosomolytic agents. (R-Ahx-R) 4 is less cytotoxic and much more active to deliver splice correcting PMO and PNA in vitro than the parent oligoarginine (R n ) peptide and than the prototypic Tat 48-60 peptide (4) . Importantly, (R-Ahx-R) 4 -PMO conjugates also lead to efficient exon skipping in murine and dog Duchenne muscular dystrophy (DMD) models (5) and inhibit the replication of viruses in several murine models (6) (7) (8) (9) .