[Update on recent progress in vitamin D research. Development of novel Vitamin D Derivatives.]

Vitamin D ₃ plays important roles in many physiological processes, including calcium and phosphate homeostasis, bone metabolism, and immune regulation. An active form of vitamin D ₃ , 1α,25(OH) ₂ D ₃ , binds to vitamin D nuclear receptor(VDR, vitamin D receptor), and regulates expression of specific target genes. Thousands of vitamin D ₃ analogs have been synthesized, and the structure-activity relationships of secosteroidal compounds have been examined in detail. On the other hand, development of non-secosteroidal VDR ligands remains limited, and only a few non-secosteroidal VDR ligands with potent activity have been reported so far. Development of novel structures with unique biological profiles would enable the new clinical application of vitamin D function.