Peptide libraries with non-canonical amino acids

A method for identifying a target binding compound, the method comprising:

• (A) providing a first peptide library comprising a plurality of first peptide library members, the first peptide library members optionally comprising an alkyne, azide, reporter moiety, or combinations thereof;
• (B) contacting the first peptide library with a target or a truncated analogue thereof, the target or truncated analogue thereof comprising a first binding site and optionally an alkyne, azide, reporter moiety, or combinations thereof;
• (C) identifying a first peptide library member with affinity for the first binding site and optionally modifying the first peptide library member to include an alkyne or azide moiety;
• and optionally;
• (D) providing a second peptide library comprising a plurality of second peptide library members, the second peptide library members comprising an azide or alkyne or both;
• (E) contacting the second peptide library with a composition comprising the target or truncated analogue thereof and the first peptide library member of step C;
• (F) forming a triazole-linked conjugate between the first peptide library member of step C and a second peptide library member, the second peptide library member having affinity for a second binding site on the target or truncated analogue thereof,
• wherein the first peptide library, the second peptide library, or both, comprise cyclic peptides comprising:
• (i) a sequence region comprising amino and carboxy termini and a variable peptide sequence of two to twenty amino acids selected from a set of amino acids, wherein the set of amino acids comprises a combination of canonical amino acids and non-canonical amino acids, wherein two or more of the amino acids in the set are non-canonical amino acid and four or more of the amino acids in the set are canonical amino acids;
• and
• (ii) a linker region comprising a α-amino carbonyl, α-amido carbonyl, a methionine amino acid, or combinations thereof, and optionally comprising an alkyne, an azide, a linkage to a solid support or a linkage to a reporter moiety or a combination thereof, the linker region covalently linking the amino and carboxy termini of the sequence region.

A method for inhibiting activity of a protein in a subject, the method comprising administering an effective amount of a cyclic peptide to a subject in need thereof, the cyclic peptide having the following structure (I′):

• or a salt, tautomer or stereoisomer thereof, wherein:
• L1 and L2 are each individually optionally substituted linker moieties, each linker moiety optionally comprising a linkage to a solid support, a linkage to a reporter moiety, a linkage to a peptide ligand, a linkage to an azide or alkyne moiety or combinations thereof;
• G is a triazole;
• M is absent or methionine;
• R is H, -L3-A or —C(═O)-L3-A, where L3 is a linker moiety and A is an alkyne, azide, or a bond to a peptide ligand;
• R1 is H or C1-C6 alkyl;
• y1 and y2 are each individually 0 or 1;
• and
• SEQ is a variable peptide sequence.