Highly Potent Vitamin D Receptor Antagonists: Design, Synthesis, and Biological Evaluation

Abstract

Vitamin D receptor (VDR) antagonists have attracted significant levels of interest because of their potential utility in the treatment of Paget's disease, which is known as the most flagrant example of disordered bone remodeling and the second most common bone disease after osteoporosis in Anglo-Saxons. Recent studies on Paget's disease suggested a specific increase in osteoclasts' sensitivity to the differentiation activity of active vitamin D(3) as the principal mechanism for abnormal bone formation. We set out to conduct a structure-activity relationship study on the first VDR antagonists, TEI-9647 and TEI-9648 (25-dehydro-1alpha-hydroxyvitamin D(3)-26,23-lactone), with the goal of improved VDR antagonistic activity. Given that both potent agonists and antagonists must have high affinity for the VDR, we hoped that our accumulated knowledge in the field of VDR agonists would help us identify potent antagonists. First 2alpha-modified TEI-9647 analogues were synthesized, and then 24-substitution to stabilize the lactone structure under physiological conditions was investigated. Finally, 2alpha-modified 24-methyl-, 24,24-dimethyl-, and 24,24-ethano-25-dehydro-1alpha-hydroxyvitamin D(3)-26,23-lactone analogues were synthesized. The synthesis of the 24,24-ethano-TEI lactone was accomplished through Ru-catalyzed intermolecular enyne metathesis of the alkynone CD-ring side chain with ethylene to give a dienone, followed by regioselective cyclopropanation. It was found that 2alpha,24,24-trimethyl-TEI-9647 (39) possessed an antagonistic activity (IC(50)=0.093 nM) approximately 90 times that of the original TEI-9647 (IC(50)=8.3 nM).

The Centennial Collection of VDR Ligands: Metabolites, Analogs, Hybrids and Non-Secosteroidal Ligands

“…This binding allows the interaction of the 1,25(OH) 2 D 3 -VDR complex with target genes in the cell nucleus, modulating their expression and mediating a biological response. The following color scheme was used in the figures: dark blue corresponds to marketed compounds ( Figures 1,3,4,8 and 9), light violet to outstanding compounds with interesting properties ( Figures 2,[4][5][6][7][8][9][10][12][13][14][15][17][18][19][20][21], and dark green to non-secosteroidal VDR ligands (Figures 9,11,12,(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27).…”

Inhibitors for the Vitamin D Receptor–Coregulator Interaction

“…Further analogs of TEI-9647 include compounds with different substituents at the 2-position (Figure 10) (73–77). Compound 6a bearing a methyl substituent had 3 times greater affinity towards VDR than TEI-9647; however the ability to differentiate HL60 cells was only 32% of that of TEI-9647 (74). A 28-fold improvement of antagonist activity (HL60 differentiation) was observed for 5b in comparison to TEI-9647 exhibiting the same VDR affinity.…”

Vitamin D and Its Synthetic Analogs

“…25-Dehydro-1α-hydroxy-vitamin D 3 -26,23 lactones with double modifications of C-24 and C-2α were synthesized via a convergent approach by Pd-catalyzed ring closure of a enyne and subsequent coupling with a functionalized vinyl bromide. , Numerous analogs have been synthesized with variations in their C-23 configuration, C-24 mono- or disubstitution [H, Me, Et, c -Pr, n -Pr, n -Bu, i -Bu ( 40 , 41 , 48 , 50, 52 , 54 , 56 , 58 , 60 , 62 , 64 , 66 , 68 , 70 , 72 )] and C-2α substitution [H, Me, CH 2 CH 2 CH 2 OH, OCH 2 CH 2 CH 2 OH, ( 42 – 47 , 49 , 51 , 53 , 55 , 57 , 59 , 61 , 63 , 65 , 67 , 69 , 71 , 73 )] (Figure ). The principal characteristic of these analogs is their antagonist activity, probably due to locking the VDR-LBD in a conformation where it does not effectively interact with coactivator proteins.…”