A series of iron-clearing efficiencies (ICEs), ferrokinetics, and toxicity studies for ( S)-2-(2,4-dihydroxyphenyl)-4,5-dihydro-4-methyl-4-thiazolecarboxylic acid (deferitrin, 1), ( S)-4,5-dihydro-2-[2-hydroxy-4-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid ( 2), and (S)-4,5-dihydro-2-[2-hydroxy-3-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid ( 3) are reported. The ICEs in rodents are shown to be dose-dependent and saturable for ligands 2 and 3 and superior to 1. Both polyether analogues in subcutaneous (sc) versus oral (po) administration in rodents and primates demonstrated excellent bioavailability. Finally, in a series of toxicity studies of ligands 1- 3, the dosing regimen was shown to have a profound effect in animals treated with ligand 1. When ligand 1 was given at doses of 237 micromol/kg/day twice a day (b.i.d.), there was serious proximal tubule damage versus 474 micromol/kg/day once daily (s.i.d.). With 2 and 3, in iron-overloaded and/or non-iron-loaded rodents, kidney histopathologies remained normal.