Peptides as selective il-23 receptor inhibitors

A peptide compound of formula (I):

• wherein
• X1 is absent or is a Butyl moiety and
• when X1 is a Butyl moiety, then (§ 1) represent an alkyl bond between X1 and X9 and (#1) represents an alkyl bond between X1 and X2, or
• when X1 is absent, then (@2) represents an amide bond between X2 and X9,
• X2 is an amino acid residue selected among a residue of Add, Ade, Ahd, Aoa, Atd, Atea, Aud, Dad, Dae, Dec, Dod, Dpa, Kme, Kme(αAc), Lys(αAc), Nmapt, Nmha and Oca;
• X3 is an amino acid residue selected among a residue of Nak, Trp, Wdm, Wim, Wme, Wcl and Wfl;
• X4 is an amino acid residue selected among a residue of Aib, Gln, Glu, Ile, Iva, Leu, Lys, Lys(Ac), Mle, Mly, Mva, Phe, Thr, Trp and Val;
• X5 is an amino acid residue selected among a residue of Aib, Mkdm, Mle, and Thp;
• X6 is an amino acid residue selected among a residue of Trp, Tyr, Yae, Yde and Yme;
• X7 is an amino acid residue selected among a residue of Nak, Nal and Trp;
• X8 is an amino acid residue selected among a residue of Aib, Cba, Cit, Gln, Leu, Lys, Lys(Ac), Mle, Mly, D-Mkdm, Mkdm, Thp, D-Trp and D-Tza;
• X9 is an amino acid residue selected among a residue of Asp, Glu, Kme, Lys and Orn;
• X10 is an amino acid residue selected among a residue of Ala, Asn, Gly and Ser;
• X11 is an amino acid residue selected among a residue of Ala, Asn, Bal, Gly, Hol, Hph, His, Ile, Iva, Leu, Mhis, Pal, Pyal, PyEA, Val, and their corresponding D-forms;
• X12 is absent or is an amino acid residue selected among a residue of Bal, Dnmy, Ile, Lys, Mep, Mhis and Sar;
• X13 is absent or is a residue of Lys;
• and,
• R1 is absent or is selected among —NH2, —OH and —N(C2H5)2;
• or a salt or a solvate thereof.