A synthetic analog of vitamin D with potential antineoplastic activity. In the liver, doxercalciferol is converted to its biologically active vitamin D metabolites, which control the intestinal absorption of dietary calcium, the tubular reabsorption of calcium by the kidney and, in conjunction with parathyroid hormone (PTH), the mobilization of calcium from the skeleton. Through interaction with specific receptor proteins in target tissues, these vitamin D metabolites act directly on osteoblasts to stimulate skeletal growth, and on the parathyroid glands to suppress PTH synthesis and secretion. This agent has also been shown to inhibit the growth of retinoblastomas, and may exhibit some antiproliferative activity against prostate cancer cells.