A polypeptide specifically binding to interleukin-23 (IL-23) comprising an amino acid sequence having the general formula HRS1-L1-HRS2-L2-HRS3, - wherein each of HRS1, HRS2 and HRS3 is independently a heptad repeat sequence comprising 2 to 7 consecutive but not necessarily identical heptad repeat units, - wherein said heptad repeat units are 7-residue (poly)peptide fragments represented as 'abcdefg' or 'defgabc', wherein the symbols 'a' to 'g' denote conventional heptad positions and wherein said heptad repeat sequence is represented by (abcdefg) n or (defgabc) n wherein n is equal or greater than 2, - wherein at least 50% of all heptad a- and d-positions are occupied by isoleucine residues, - wherein each HRS starts with an aliphatic or aromatic amino acid residue located at a heptad a-position or 'd" position, - wherein each of L1 and L2 are independently a linker fragment, which covalently connect HRS1 to HRS2 and HRS2 to HRS3, respectively, characterized in that - in HRS1: (i) the heptad f-position of the second heptad repeat unit is occupied by glutamic acid or alanine, (ii) the heptad g-position of the second heptad repeat unit is occupied by valine, (iii) the heptad c-position of the third heptad repeat unit is occupied by alanine or glycine, and (iv) the heptad g-position of the third heptad repeat unit is occupied by tyrosine or tryptophan, and - in HRS3: (i) the heptad e-position of the second heptad repeat unit is occupied by glutamine or lysine, (ii) the heptad b-position of the third heptad repeat unit is occupied by leucine or isoleucine or valine, (iii) the heptad e-position of the third heptad repeat unit is occupied by tyrosine, and (iv) HRS3 comprises a partial (a-f) heptad repeat unit following the third heptad repeat and the heptad b-position therein is occupied by methionine. - wherein each of HRS1, HRS2 and HRS3 is independently a heptad repeat sequence comprising 2 to 7 consecutive but not necessarily identical heptad repeat units, - wherein said heptad repeat units are 7-residue (poly)peptide fragments represented as 'abcdefg' or 'defgabc', wherein the symbols 'a' to 'g' denote conventional heptad positions and wherein said heptad repeat sequence is represented by (abcdefg) n or (defgabc) n wherein n is equal or greater than 2, - wherein at least 50% of all heptad a- and d-positions are occupied by isoleucine residues, - wherein each HRS starts with an aliphatic or aromatic amino acid residue located at a heptad a-position or 'd" position, - wherein each of L1 and L2 are independently a linker fragment, which covalently connect HRS1 to HRS2 and HRS2 to HRS3, respectively, - in HRS1: (i) the heptad f-position of the second heptad repeat unit is occupied by glutamic acid or alanine, (ii) the heptad g-position of the second heptad repeat unit is occupied by valine, (iii) the heptad c-position of the third heptad repeat unit is occupied by alanine or glycine, and (iv) the heptad g-position of the third heptad repeat unit is occupied by tyrosine or tryptophan, and (i) the heptad f-position of the second heptad repeat unit is occupied by glutamic acid or alanine, (ii) the heptad g-position of the second heptad repeat unit is occupied by valine, (iii) the heptad c-position of the third heptad repeat unit is occupied by alanine or glycine, and (iv) the heptad g-position of the third heptad repeat unit is occupied by tyrosine or tryptophan, and - in HRS3: (i) the heptad e-position of the second heptad repeat unit is occupied by glutamine or lysine, (ii) the heptad b-position of the third heptad repeat unit is occupied by leucine or isoleucine or valine, (iii) the heptad e-position of the third heptad repeat unit is occupied by tyrosine, and (iv) HRS3 comprises a partial (a-f) heptad repeat unit following the third heptad repeat and the heptad b-position therein is occupied by methionine. (i) the heptad e-position of the second heptad repeat unit is occupied by glutamine or lysine, (ii) the heptad b-position of the third heptad repeat unit is occupied by leucine or isoleucine or valine, (iii) the heptad e-position of the third heptad repeat unit is occupied by tyrosine, and (iv) HRS3 comprises a partial (a-f) heptad repeat unit following the third heptad repeat and the heptad b-position therein is occupied by methionine.