Anti-microbial peptides

1. A non-naturally occurring anti-microbial peptide comprising between 7 and 17 natural, synthetic, or chemically modified residues, the peptide comprising the sequence according to Formula I: X 1 —X 2 -X 3 -R 1 -R 2 -[R 3 -R 4 -R 5 -R 6 -R 7 -R 8 -R 9 -R 10 -R 11 -R 12 -R 13 -R 14 -R 15 -R 16 -R 17 ]-Y 1 -Y 2 -Y 3 , wherein:

X 1 , X 2 , and X 3 represent optional N-terminal stabilizing residues;

R 1 to R 17 represent residues of the anti-microbial peptide;

Y 1 , Y 2 , and Y 3 represent degradation-resistant C-terminal stabilizing residues;

wherein:

R 1 is absent or is arginine;

R 2 is absent or is arginine;

R 3 is aspartic acid;

R 4 is Arg or Trp;

R 5 is Arg, Trp, Gln, D -Nal2′, Pro, or His;

R 6 is Arg, Gln, Trp, Tyr, Leu, Nal, D -Nal2′, or Pro;

R 7 is Lys, Trp, Tyr, Leu, Arg, Phe, Nal, or D -Nal2′;

R 8 is absent or is Lys, Trp, Tyr, Leu, Arg, Nal, or D -Nal2′;

R 9 is absent or is Lys, Arg, Tyr, Trp, Leu, or Phe;

R 10 is absent or is Lys, Phe, Trp, Leu, or Arg;

R 11 is absent or is Lys, Leu, Trp, or Arg;

R 12 is absent or is Lys or Trp;

R 13 is absent or is Lys or Trp;

R 14 is absent or is Lys;

R 15 -R 17 are absent;

wherein at least one of R 7 to R 14 is lysine, wherein the peptide is cyclized through a side chain lactam between R 3 and said lysine;

wherein Y 1 -Y 2 is D -Ala- D -Pro; D -Ala- D -Val; β-Ala-β-Pro; β-Ala-β-Val; D -Leu- D -Pro; D -Leu- D -Val; β-Leu-β-Pro; β-Leu-β-Val; D -Phe- D -Val; D -Pro- D -Ala; D -Pro- D -Leu; β-Pro-β-Ala; β-Pro-β-Leu; β-Pro-β-Val; D -Val- D -Ala; D -Val- D -Pro; D -Val- D -Phe; D -Val- D -Leu; β-Val-β-Ala; β-Val-β-Leu; β-Val-β-Pro; 3-methyl-β-Val-β-Pro; 3-methyl-β-Val-β-Ala; or 3-methyl-β-Val-β-Leu; and

wherein Y 3 is absent.

2. The non-naturally occurring anti-microbial peptide of claim 1 , wherein:

each of X 1 , X 2 and X 3 are independently selected for each occasion and may be absent or are selected from the group consisting of D -threonine, L -threonine, D -proline, L -proline, β-homo proline, D -alanine, L -alanine, β-alanine, D -valine, L -valine, β-valine, 3-methyl-β-valine, D -leucine, L -leucine, β-leucine, D -norleucine, L -norleucine, D -isoleucine, L -isoleucine, β-isoleucine, and a piperazin-2-one ring.

3. The non-naturally occurring anti-microbial peptide of claim 1 , wherein:

X 1 and X 2 are absent; and

X 3 is N-acetylated norleucine.

4. The non-naturally occurring anti-microbial peptide of claim 1 , wherein the C-terminus is amidated.

5. The non-naturally occurring anti-microbial peptide of claim 1 , wherein

R 4 is Arg;

R 5 is Pro;

R 6 is D -Nal2′;

R 7 is Arg;

R 8 is Trp or D -Nal2′;

R 9 is absent or Arg;

R 10 is Lys; and

Y 1 -Y 2 is D -Val- D -Pro.