TEI-9648, an analogue of Vitamin D3 Lactone, acts as a potent and specific antagonist to the vitamin D receptor (VDR). This compound effectively blocks the genomic actions mediated by VDR and the Vitamin D responsive element (VDRE) of 1α,25(OH)2D3. Furthermore, TEI-9648 prevents the differentiation of HL-60 cells induced by 1α,25(OH)2D3, indicating its utility in bone metabolism studies[1][2].

TEI-9648 (10-1000 nM) dose-dependently blocks the reciprocal changes of CD11b and CD71 expression associated with HL-60 cell differentiation induced by 1α,25(OH)2D3[1]. TEI-9648 has consistently weaker suppressive effect than TEI-9647[1]. TEI-9648 can not induce cell differentiation even after treatment at 1 μM in HL-60 cell[1]. TEI-9648 alone can not induce activation of NBT-reducing activity or α-NB esterase activity. In contrast, TEI-9648 markedly suppresses the up-regulation induced by 1α,25(OH)2D3 (0.1 nM) in HL-60 cells[1].