The present invention concerns molecules and a process in which one or more biologically active peptides are incorporated into an Fc domain. In this invention, pharmacologically active compounds may be prepared by a process comprising (a) selecting at least one peptide that modulates the activity of a protein of interest; and (b) preparing a pharmacologic agent comprising an amino acid sequence of the selected peptide in a loop region of an Fc domain. This process may be employed to modify an Fc domain that is already linked through an N- or C-terminus or sidechain to a peptide or to a polypeptide (e.g., etanercept). This process may also be employed to modify an Fc domain that is part of an antibody (e.g., adalimumab, epratuzumab, infliximab, Herceptin.RTM., and the like). In this way, different molecules can be produced that have additional functionalities, such as a binding domain to a different epitope or an additional binding domain to the precursor molecule's existing epitope. The peptide can be selected, for example, by phage display, E. coli display, ribosome display, RNA-peptide screening, yeast-based screening, chemical-peptide screening, rational design, or protein structural analysis.