profile, compound 77 displayed poor PK properties, not being suitable for further
evaluation in cell-based assays.
Via a high-throughput screen, NSC663284 (78, Fig. 9) has been identified and
validated as potent SETD8 inhibitor by suppressing the H4K20me1 mark of SETD8
mark at single doses of 1–5 μM in HEK293T cells leading to characteristic S/G2/Mphase cell-cycle defects as observed for RNAi-mediated SETD8 knockdown
[132]. More recently, a completely different approach based on the use of an H4
substrate peptide (amino acids 16–23 of histone H4) as a starting point for molecular
design led to the discovery of a potent peptide-based inhibitor of SETD8. In detail,
Judge et al. replaced the K20 with more hydrophobic nonnatural amino acids. The
replacement of K20 with nor-leucine led to the identification of the novel substratecompetitive inhibitor 79 (Fig. 9, IC 50 : 0.33 μM). The new inhibitor showed also a
good selectivity profile for SETD8 over a panel of 32 methyltransferases [133]. Due
to its peptide nature, this compound is not cell permeable, thus not suitable for in-cell
investigation.
SUV420H1 and SUV420H2 are two highly homologous methyltransferases that
di- and trimethylate H4K20 have recently emerged as important regulators of
genomic integrity, being important in the regulation of proliferation, cell cycle,
and chromatin remodeling [134]. Aberrant H4K20 methylation has been associated
with human cancer; thus modulation of the methylation status might be beneficial in
cancer [135]. Indeed, A-196 (80, Fig. 9) has been recently described as the first
potent, selective inhibitor of SUV420H1 and SUV420H2 [134], exhibiting IC 50
values of 25 and 144 nM, respectively. Reduced levels of H4K20me2 and
H4K20me3 and increased levels of H4K20me1 were found after treatment with
this inhibitor throughout the cell cycle in U2OS osteosarcoma cells and LnCaP
prostate adenocarcinoma cells. Compound 80 was not exhibiting significant toxic
effects in cells being a valuable lead compound that can serve as a starting point for
med-chem optimization but also as a chemical probe to further study the biological
functions of SUV4–20H1/2 [134].
2 Conclusions
In this book chapter, we highlighted the discovery, characterization, and application
of selective KMTs inhibitors, useful for dissecting their physiological functions as
well as their disease implications. A growing body of literature is indicating that
KMTs play a crucial role for transcriptional regulation and involved in cancer and
various other human diseases, thus being of high interest as potential therapeutic
targets.
Over the past decade, there has been an impressive progress regarding the PMT
inhibitors discovery, especially conjugating the research interest with the available
and novel techniques including new assay methods, high-throughput screening,
structural biology, and medicinal chemistry approaches. Our goal was to point out
146
G. Stazi et al.
evaluation in cell-based assays.
Via a high-throughput screen, NSC663284 (78, Fig. 9) has been identified and
validated as potent SETD8 inhibitor by suppressing the H4K20me1 mark of SETD8
mark at single doses of 1–5 μM in HEK293T cells leading to characteristic S/G2/Mphase cell-cycle defects as observed for RNAi-mediated SETD8 knockdown
[132]. More recently, a completely different approach based on the use of an H4
substrate peptide (amino acids 16–23 of histone H4) as a starting point for molecular
design led to the discovery of a potent peptide-based inhibitor of SETD8. In detail,
Judge et al. replaced the K20 with more hydrophobic nonnatural amino acids. The
replacement of K20 with nor-leucine led to the identification of the novel substratecompetitive inhibitor 79 (Fig. 9, IC 50 : 0.33 μM). The new inhibitor showed also a
good selectivity profile for SETD8 over a panel of 32 methyltransferases [133]. Due
to its peptide nature, this compound is not cell permeable, thus not suitable for in-cell
investigation.
SUV420H1 and SUV420H2 are two highly homologous methyltransferases that
di- and trimethylate H4K20 have recently emerged as important regulators of
genomic integrity, being important in the regulation of proliferation, cell cycle,
and chromatin remodeling [134]. Aberrant H4K20 methylation has been associated
with human cancer; thus modulation of the methylation status might be beneficial in
cancer [135]. Indeed, A-196 (80, Fig. 9) has been recently described as the first
potent, selective inhibitor of SUV420H1 and SUV420H2 [134], exhibiting IC 50
values of 25 and 144 nM, respectively. Reduced levels of H4K20me2 and
H4K20me3 and increased levels of H4K20me1 were found after treatment with
this inhibitor throughout the cell cycle in U2OS osteosarcoma cells and LnCaP
prostate adenocarcinoma cells. Compound 80 was not exhibiting significant toxic
effects in cells being a valuable lead compound that can serve as a starting point for
med-chem optimization but also as a chemical probe to further study the biological
functions of SUV4–20H1/2 [134].
2 Conclusions
In this book chapter, we highlighted the discovery, characterization, and application
of selective KMTs inhibitors, useful for dissecting their physiological functions as
well as their disease implications. A growing body of literature is indicating that
KMTs play a crucial role for transcriptional regulation and involved in cancer and
various other human diseases, thus being of high interest as potential therapeutic
targets.
Over the past decade, there has been an impressive progress regarding the PMT
inhibitors discovery, especially conjugating the research interest with the available
and novel techniques including new assay methods, high-throughput screening,
structural biology, and medicinal chemistry approaches. Our goal was to point out
146
G. Stazi et al.