The synthesis and pharmacological properties of a novel type of vasorelaxant hybrid compounds are... more The synthesis and pharmacological properties of a novel type of vasorelaxant hybrid compounds are described. The investigated compounds originate from fluorinated 4-aryl-1,4-dihydropyridines, which are known calcium channel blockers, and/or from fluorinated analogues of pinacidil, which is an opener of ATP-sensitive potassium channels. In particular, we studied the most potent hybrid, 2,6-dimethyl-3,5-dicarbomethoxy-4-(2-difluoromethoxy-5-N-(N' '-cyano-N'-1,2,2-trimethyl-propylguanidyl)-phenyl)-1, 4-dihydropyridine (4a), together with its parent compounds, the dihydropyridine 1b and the pinacidil analogue 3. In isolated rat mesenteric arteries, micromolar concentrations of 4a relaxed contractions exerted by K(+)-depolarization or by norepinephrine. The latter effect was sensitive to the potassium channel blocker glibenclamide. Micromolar 4a also inhibited [(3)H](+)-isradipine and [(3)H]P1075 binding to rat cardiac membranes, and it blocked L-type calcium channels expressed in a mammalian cell line. The respective parent compounds 1b and 3 were always more potent and more selective regarding calcium channel or potassium channel interaction, respectively. In contrast, 4a combined both effects within the same concentration range, indicating that it may represent a lead structure for a novel class of pharmacological hybrid compounds.
Rearrangements of the mixed-lineage leukemia (MLL) gene occur predominately in pediatric leukemia... more Rearrangements of the mixed-lineage leukemia (MLL) gene occur predominately in pediatric leukemia cases and are generally predictors of a poor prognosis. These chromosomal rearrangements result in fusion of the protein MLL to one of more than 60 protein partners. MLL fusions are potent inducers of leukemia through activation of oncogene expression; therefore, targeting this transcriptional activation function may arrest MLL-rearranged (MLL-R) leukemia. Leukemic cell lines harboring the most common fusion protein, MLL-AF4, require the direct interaction of AF4 with the transcription factor AF9 to survive and self-renew; disrupting this interaction with a cell-penetrating AF4-derived peptide results in cell death, suggesting that the AF4-AF9 interaction could be a viable target for a novel MLL-R leukemia therapy. Here we describe the use of AlphaScreen technology to develop a high-throughput screening (HTS) assay to detect nonpeptidic inhibitors of AF4-AF9 binding. The assay is economical, requiring only low nanomolar concentrations of biotinylated AF4-derived peptide and FLAG-tagged AF9 in low-volume 384-well plates. A Z'-factor of 0.71 and a signal-to-background ratio of 21.3 showed the assay to be robust, and sensitivity to inhibition was demonstrated with competing AF4-derived peptides. Two pilot screens comprising 5,680 compounds served as validation for HTS at Nemours and the Broad Institute. Assay artifacts were excluded using a counterscreen comprising a biotinylated FLAG peptide. This is the first reported HTS-compatible assay to identify compounds that inhibit a key binding interaction of an MLL fusion partner, and the results presented here demonstrate suitability for screening large chemical libraries in high-density, low-volume plate formats.
The synthesis and pharmacological properties of a novel type of vasorelaxant hybrid compounds are... more The synthesis and pharmacological properties of a novel type of vasorelaxant hybrid compounds are described. The investigated compounds originate from fluorinated 4-aryl-1,4-dihydropyridines, which are known calcium channel blockers, and/or from fluorinated analogues of pinacidil, which is an opener of ATP-sensitive potassium channels. In particular, we studied the most potent hybrid, 2,6-dimethyl-3,5-dicarbomethoxy-4-(2-difluoromethoxy-5-N-(N' '-cyano-N'-1,2,2-trimethyl-propylguanidyl)-phenyl)-1, 4-dihydropyridine (4a), together with its parent compounds, the dihydropyridine 1b and the pinacidil analogue 3. In isolated rat mesenteric arteries, micromolar concentrations of 4a relaxed contractions exerted by K(+)-depolarization or by norepinephrine. The latter effect was sensitive to the potassium channel blocker glibenclamide. Micromolar 4a also inhibited [(3)H](+)-isradipine and [(3)H]P1075 binding to rat cardiac membranes, and it blocked L-type calcium channels expressed in a mammalian cell line. The respective parent compounds 1b and 3 were always more potent and more selective regarding calcium channel or potassium channel interaction, respectively. In contrast, 4a combined both effects within the same concentration range, indicating that it may represent a lead structure for a novel class of pharmacological hybrid compounds.
Rearrangements of the mixed-lineage leukemia (MLL) gene occur predominately in pediatric leukemia... more Rearrangements of the mixed-lineage leukemia (MLL) gene occur predominately in pediatric leukemia cases and are generally predictors of a poor prognosis. These chromosomal rearrangements result in fusion of the protein MLL to one of more than 60 protein partners. MLL fusions are potent inducers of leukemia through activation of oncogene expression; therefore, targeting this transcriptional activation function may arrest MLL-rearranged (MLL-R) leukemia. Leukemic cell lines harboring the most common fusion protein, MLL-AF4, require the direct interaction of AF4 with the transcription factor AF9 to survive and self-renew; disrupting this interaction with a cell-penetrating AF4-derived peptide results in cell death, suggesting that the AF4-AF9 interaction could be a viable target for a novel MLL-R leukemia therapy. Here we describe the use of AlphaScreen technology to develop a high-throughput screening (HTS) assay to detect nonpeptidic inhibitors of AF4-AF9 binding. The assay is economical, requiring only low nanomolar concentrations of biotinylated AF4-derived peptide and FLAG-tagged AF9 in low-volume 384-well plates. A Z'-factor of 0.71 and a signal-to-background ratio of 21.3 showed the assay to be robust, and sensitivity to inhibition was demonstrated with competing AF4-derived peptides. Two pilot screens comprising 5,680 compounds served as validation for HTS at Nemours and the Broad Institute. Assay artifacts were excluded using a counterscreen comprising a biotinylated FLAG peptide. This is the first reported HTS-compatible assay to identify compounds that inhibit a key binding interaction of an MLL fusion partner, and the results presented here demonstrate suitability for screening large chemical libraries in high-density, low-volume plate formats.
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Papers by Stefan Herzig