NaPi2b-IN-1 is a potent and orally active inhibitor of sodium-dependent phosphate transport protein 2b ( NaPi2b ) with an IC 50 of 64 nM. NaPi2b is primarily expressed in the small intestine, lungs, and testes and plays an important role in phosphate homeostasis. NaPi2b-IN-1 has the potential for the research of hyperphosphatemia.