An isolated peptide comprising a Huntingtin (Htt) amino acid sequence being no longer than 15 amino acids, wherein said Htt amino acid sequence comprises the sequence X1X2X3X4 X5, wherein X1 is a hydrophobic amino acid or threonine, X2 is a hydrophobic amino acid, X3 is a hydrophobic amino acid, X4 is an acidic amino acid and X5 is selected from the group consisting of glycine, serine and alanine, the peptide capable of specifically inhibiting the activity of caspase 6.