The present invention relates generally to chemical agents useful in the prophylaxis and/or treatment of disease conditions and in particular chronic disease conditions such as inflammatory including allergic diseases, metastatic cancers and infection by pathogenic agents including bacteria, viruses or parasites. More particularly, the chemical agents contemplated by the present invention are selected from glycosaminoglycan (GAG) molecules derived from a larger GAG, GAG-like molecules which resemble GAGs in some of their characteristics but may be derived from a larger non-GAG polysaccharide and molecules having a GAG-like composite structure as well as agents which bind to the same sites as GAGs, GAG-like molecules or GAG-like composite molecules. The present invention also provides assays to identify GAG and GAG-like therapeutic agents including GAG-like composite structures as well as analogs, homologs and orthologs thereof.