Table 1.

Selected sequences of peptides, especially cell-penetrating peptides, that are studied for enhanced oligonucleotides delivery. The two main cellular mechanism of delivery used are direct penetration or energy-dependent endocytosis, described in the main text. Once internalized, some peptide sequences facilitate the endosomal escape.

Name	Sequence	Type	Application	Ref.
Hydrophobic
P4	LGAQSNF	ASO (PS)	SSO(2OMe) for DMD	[140]
Polycationic
TAT	RKKRRQRRR	siRNA	Neurodegenerative pathologies Lung and Malignant glioma	[141,142,143]
		ASO (PNA/PMO)	bacteria & nematodecell lines	[144,145]
pAnt	RQIKIWFQNRRMKWKKGGC	ASO (PNA/PS)	bacteria & nematodecell lines	[129,144]
PolyArg	Rn (n = 6–18) optimal 8 to 10	siRNA	Neurons and different cancers	[146,147]
(KFF)3K	KFFKFFKFFK	ASO (PNA/LNA)	Anti-bacterial	[144,148]
(RXR)4	RXRRXRRXRRXRXR	ASO (PMO)	Anti-viral anti-bacterial	[144,149,150,151,152]
B peptide	(RXRRBR)2XB	ASO (PMO)	SSO of DMD DM1	[153,154,155,156,157,158]
Pip5e	RXRRBRRXR-ILFQY-RXRBRXRB	ASO (PMO)	SSO of DMD, SMA	[159]
Pip6a	RXRRBRRXR-YQFLI-RXRBRXRB	ASO (PMO)	SSO of DMD, SMA	[160,161,162,163]
Pip6b	RXRRBRRXR-IQFLI-RXRBRXRB	ASO (PMO)	SSO of DMD, SMA	[164,165]
Amphipathic
MPG-8	GALFLGFLGAAGSTMGAWSQPKKKRK	siRNA	Xenograft tumor model	[166]
		ASO	Mammalian cells	[167]
Pep-1	KETWWETWWTEWSQPKKRK	siRNA	Cells	[168]
CADY	GLWRALWRLLRSLWRLLWRA	siRNA	Several cancer cells	[169]
		ASO	Anti-bacterial	[170]
RICK	KWLLRWLSRLLRWLARWLG	siRNA	H glioblastoma cells	[171]
599	GLFEAIEGFIENGWEGMIDGWY(G)4(R)9K	siRNA	Oral cancer	[172,173]
Pepfect6	AGYLLGK(ε-Mtt)INLKALAALAKKIL	siRNA	Cell lines (various)	[174]

ASO, antisense oligonucleotide; SSO, splice-switching oligonucleotides; DMD, Myotonic dystrophy; DM1, Myotonic dystrophy type J; SMA, spinal muscular atrophy; PS, phosphorothioate; PNA, peptide nucleic acids; PMO, phosphorodiamidate morpholinos; LNA, locked nucleic acid, 2OMe, 2′-O-methyl; X, 6-aminohexanoic acid; B, beta-alanine.