Biologically active noncalcemic analogs of 1α,25-dihydroxyvitamin D with an abbreviated side chain containing no hydroxyl

Abstract

Since the discovery of the active metabolite of vitamin D, i.e., 1α,25-dihydroxyvitamin D₃, there has been a continuous effort to synthesize analogs able to carry out many of the functions of the native hormone without raising serum calcium concentration. The present report provides a series of previously undescribed analogs wherein this goal is realized. We have prepared 2-methylene-19-nor-1α-hydroxyvitamin D analogs of 1,25-(OH)₂D₃ that possess only two to four carbons of the side chain without a hydroxyl thereon. Compared to 1,25-(OH)₂D₃, these analogs are slightly less active in binding to the vitamin D receptor, in causing HL-60 differentiation, and are slightly less active in in vitro transcription assays using the 24-hydroxylase promoter attached to a luciferase reporter gene. Of considerable importance is that these analogs, given to rats at daily doses of up to 70 μg/kg of body weight per day, are either unable or only slightly able to raise serum calcium concentration but are nevertheless able to suppress parathyroid hormone levels in plasma up to 100% and induce 24-hydroxylase mRNA in skin. Because of their ability to act in vivo without raising serum calcium levels, they may be of considerable interest for the systemic treatment of diseases such as psoriasis, cancer, and secondary hyperparathyroidism of renal failure, where a rise in serum calcium is undesirable.