The activity of AFPep (Panel A) or of cyclo[EKTOVNOGN]FI (Panel B, indicated as N-FI) is decreased in the presence of an analog with an intact pharmacophore and a hydrophilic tail (cyclo[EKTOVNOGN]FS, indicated as N-FS) which may bind preferentially to, and activate, a putative low affinity receptor. The activity of AFPep is enhanced (Panel C), while the activity of cyclo[EKTOVNOGN]FI (indicated as N-FI) is unaffected (Panel D) in the presence of an analog with a disrupted pharmacophore and a hydrophilic tail, (namely cyclo[EKTOVGOGN]FS, indicated as G-FS) which may bind preferentially to, but not activate, the low affinity receptor.