A DIALOG ON ANALOGS - NEWER VITAMIN-D DRUGS FOR USE IN BONE-DISEASE, PSORIASIS, AND CANCER

Many new analogues of the vitamin-D hormone, 1 alpha,25-dihydroxy-vitamin D-3[1 alpha,25-(OH)(2)D-3; calcitriol], have emerged that can mimic its various actions in classic calcium transport systems and/or in the regulation of cell proliferation and cell differentiation. Though some of these analogues have accentuated activity in cell differentiation assays in vitro, they lack appreciable ''calcemic'' activity in vivo, leading to the name ''noncalcemic analogues''. Several of these analogues are promising candidates for use in treatment of psoriasis and in tumor suppression, one of them, calcipotriol, being already widely approved for the former indication. New generations of calcemic analogues with altered pharmacokinetics are appearing for use in secondary hyperparathyroidism and osteoporosis. We believe that the selective properties of both types of analogues stem from altered receptor binding, blood protein binding, and rate of catabolism.