Medicaments in the form of therapeutic molecules including inflammatory modulators are designed and selected. A target site is on Interleukin 13 (IL-13) in which a glycosaminoglycan (GAG) molecule or polyanionic glycoconjugate or anionic polysaccharide modulates IL-13 activity or function. The target site can include amino acids located in the AB loops and/or helix D of human IL-13 or its homolog or derivative. The IL-13 target site is used to design a medicament for modulating physiological processes. Therapeutic and prophylactic compositions can include the designed medicaments.