Synthesis and biological activities of vitamin D-like inhibitors of CYP24 hydroxylase

• Published in: Steroids Vol. 77; no. 3; pp. 212 - 223
• Main Authors: Chiellini, Grazia, Rapposelli, Simona, Zhu, Jinge, Massarelli, Ilaria, Saraceno, Marilena, Bianucci, Anna Maria, Plum, Lori A., Clagett-Dame, Margaret, DeLuca, Hector F.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Inc 01-02-2012; Elsevier
• Subjects: 1,25-Dihydroxyvitamin D 3; 25-Hydroxyvitamin D3 1-alpha-Hydroxylase - antagonists & inhibitors; Amino Acid Sequence; Animals; Biological and medical sciences; Calcifediol - analogs & derivatives; Calcifediol - chemical synthesis; Calcifediol - chemistry; Calcium - chemistry; Cancer therapy; Cell Differentiation; Cyclopropanes - chemical synthesis; Cyclopropanes - chemistry; Cyclopropylamines; CYP24A1; Cytochrome P450 inhibitors; Enzyme Activation; Enzyme Inhibitors - chemical synthesis; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; Half-Life; HL-60 Cells; Humans; Hydroxycholecalciferols - chemistry; Magnetic Resonance Spectroscopy; Mice; Molecular docking; Molecular Sequence Data; Osteoblasts - drug effects; Rats; Sequence Homology, Amino Acid; Steroid Hydroxylases - antagonists & inhibitors; Transcriptional Activation; Vertebrates: endocrinology; Vitamin D - analogs & derivatives; Vitamin D - chemistry; Vitamin D3 24-Hydroxylase; 1,25-Dihydroxyvitamin D 3; CYP24A1; Cyclopropylamines; Cancer therapy; Molecular docking; Cytochrome P450 inhibitors; Enzyme; Steroid hormone; Cholecalciferol(1,25-dihydroxy); Cytochrome P450; Biosynthesis; Malignant tumor; Biological activity; Micronutrient; Vitamin D; 1,25-Dihydroxyvitamin D; Cancer
• ISSN: 0039-128X; 1878-5867
• DOI: 10.1016/j.steroids.2011.11.007

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► Potent vitamin D-like CYP24 inhibitors are efficiently prepared in convergent syntheses. ► The 25-
N-cyclopropylamine side chain modified vitamin D analog
3 selectively inhibits CYP24A1. ►
3 Causes differentiation of leukemia cells nearly as well as the natural hormone. ► The calcemic activity of
3 is considerably lower than that of the native hormone. ► Docking studies provide insights to the selectivity of
3 for CYP24A1 over CYP27B1.
Selective inhibitors of CYP24A1 represent an important synthetic target in a search for novel vitamin D compounds of therapeutic value. In the present work, we show the synthesis and biological properties of two novel side chain modified 2-methylene-19-nor-1,25(OH)
2D
3 analogs, the 22-imidazole-1-yl derivative
2 (VIMI) and the 25-
N-cyclopropylamine compound
3 (CPA1), which were efficiently prepared in convergent syntheses utilizing the Lythgoe type Horner–Wittig olefination reaction. When tested in a cell-free assay, both compounds were found to be potent competitive inhibitors of CYP24A1, with the cyclopropylamine analog
3 exhibiting an 80–1 selective inhibition of CYP24A1 over CYP27B1. Addition of
3 to a mouse osteoblast culture sustained the level of 1,25(OH)
2D
3, further demonstrating its effectiveness in CYP24A1 inhibition. Importantly, the
in vitro effects on human promyeloid leukemia (HL-60) cell differentiation by
3 were nearly identical to those of 1,25(OH)
2D
3 and
in vivo the compound showed low calcemic activity. Finally, the results of preliminary theoretical studies provide useful insights to rationalize the ability of analog
3 to selectively inhibit the cytochrome P450 isoform CYP24A1.