Compounds and peptides that bind to the erythropoietin receptor

Peptides of 10 to 40 amino acid residues in length that binds to and activates erythropoietin receptor or otherwise behaves as an erythropoietin agonist, and comprises a sequence of amino acids X3X4X5GPX6TWX7X8, optionally cyclized or dimerized, where each amino acid is indicated by standard one letter abbreviation; X6 is independently selected from any one of the 20 genetically coded L-amino acids; X3 is C, A, α-amino-γ-bromobutyric acid, or Hoc, where Hoc is homocysteine; X4 is R, H, L, or W; X5 is M, F, or I; X7 is D, E, I, L, or V; and X8 is C, A, α-amino-γ-bromobutyric acid, or Hoc, where hoc is homocysteine, provided that either X3 or X8 is C or Hoc.