A cell-penetrating peptide characterized in that it comprises an amino acid sequence X3X4X1X2X5X4X1X2X6X7X1X8X9X10X11X12X13 (SEQ ID No: 11), wherein X1 is F or W, X2 is F, W or Y, X3 is beta-A or S, X4 is K, R or L, X5 is E, R or S, X6 is R. T or S, X7 is E, R or S, X8 is none, F or W, X9 is P or R, X10 is R or L, X11 is K, W or R, X12 is R or F and X13 is R or K.