The potent antitumoral cyanoguanidine CHS 828 and its prodrug EB 1627 have successfully been labelled with tritium. The pyridyl-3,5-dibromo derivative of CHS 828 was debrominated with tritium-gas using Pd/C catalyst to give [Pyridlyl-3,5-H-3(2)]CHS 828 with a radiochemical purity of 99.3% and a specific activity of 1960GBq/mmol. Similarly, the pyridyl-3-bromo derivative of the prodrug EB 1627 was debrominated with tritium-gas to give [pyridyl-3-H-3]-EB 1627 with a radiochemical purity of 98.1% and a specific activity of 894GBq/mmol. Copyright (c) 2005 John Wiley & Sons, Ltd.

The potent antitumoral cyanoguanidine CHS 828 and its prodrug EB 1627 have successfully been labelled with tritium. The pyridyl-3,5-dibromo derivative of CHS 828 was debrominated with tritium-gas using Pd/C catalyst to give [pyridyl-3,5-3H2]-CHS 828 with a radiochemical purity of 99.3% and a specific activity of 1960 GBq/mmol. Similarly, the pyridyl-3-bromo derivative of the prodrug EB 1627 was debrominated with tritium-gas to give [pyridyl-3-3H]-EB 1627 with a radiochemical purity of 98.1% and a specific activity of 894 GBq/mmol. Copyright © 2005 John Wiley & Sons, Ltd.

Hapten derivatives of 1alpha,25-dihydroxyvitamin D(3) and its 20-epimer were synthesized and conjugated to a carrier protein for raising polyclonal antibodies. The haptens were linked through spacers at C-16, thereby exposing both the A-ring and the side chain of the molecules, to maximize antibody specificity. The spacers were introduced via stereoselective hydroboration of 16-ene intermediates as the key step. In immunoassays, the antibodies raised toward the natural hormone were selective to this compound over derivatives with modifications in the A-ring or the side chain. The antibodies toward the 20-epimer, however, were unable to recognize modifications in the side chain.

1 1 alpha,25-dihydroxyvitamin(3) (VD) is a nuclear hormone that has important cell regulatory functions but also a strong calcemic effect. EB1089 is a potent antiproliferative VD analogue, which has a modified side chain resulting in increased metabolic stability and a selective functional profile. Since EB1089 is considered for potential systemic application, it will be investigated to what extent its recently identified metabolites (hydroxylated at positions C26 and C26a) contribute to biological profile of the VD analogue.2 Limited protease digestion analysis demonstrated that EB1089 is able to stabilize the high affinity ligand binding conformation of the VDR, starting at concentrations of 0.1 nM and affecting up to 80% of all receptor molecules. The metabolites EB1445 and EB1470 showed to be 100 fold less potent than EB1089, whereas the remaining three metabolites (EB1435, EB1436 and EB1446) showed a clearly reduced ability to stabilize the high affinity ligand binding conformation. Interestingly, at pharmacological concentrations all EB1089 metabolites stabilized a second, apparently lower affinity conformation to a much higher extent than EB1089.3 In reporter gene assays all metabolites showed lower potency than EB1089. Moreover, the preference of EB1089 for activation of VDR binding to sites formed by inverted palindromic arrangements spaced by nine nucleotide (OPE-type VD response elements) appeared to be reduced (with EB1445 and EB1470) or completely lost (with EB1435, EB1436 and EB1446). The ranking of EB1089 and its metabolites that was obtained by limited protease digestion and reporter gene assays was confirmed by an analysis of their antiproliferative effect in breast cancer cells.4 The potency and selectivity of the EB1089 metabolites in mediating gene regulatory effects was found to be drastically reduced in comparison to the parent compound suggesting that the contribution of the metabolites to the biological effect of EB1089 is minor. However, the compounds showed to be interesting tools for understanding the selective biological profile of EB1089.