Active metabolite of vitamin D3 that activates the vitamin D receptor (VDR). Displays calcemic actions; stimulates intestinal and renal Ca2+ absorption and regulates bone Ca2+ turnover. Exhibits antitumor activity; inhibits in vivo and in vitro cell proliferation in a wide range of cells including breast, prostate, colon, skin and brain carcinomas and myeloid leukemia cells. Purity 99%. MW (observed): 416.64