A-196 A selective chemical probe for SUV420H1/H2

This probe is available from Sigma, Cayman Chemical and Tocris.

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Histone H4 lysine 20 methylation is emerging as a crucial modification to ensure genomic integrity both in the absence and presence of genotoxic stress [1]. The majority of histone H4 methylation is detected in the lysine 20 (H4K20) and is evolutionarily conserved from yeast to human [2,3]. Each methylation state results in distinct biology: dimethylated H4K20 (H4K20me2) is involved in DNA replication and DNA damage repair, and trimethylated H4K20 (H4K20me3) results in silenced heterochromatic regions [1]. Loss of histone H4 lysine 20 trimethylation (H4K20me3) is characteristic of human cancer and a potential prognostic marker in many types of cancers [4].

SUV420H1 and SUV420H2 are two highly homologous methyltransferases that di- and tri-methylate  'Lys-20' of histone H4. A collaboration between AbbVie and the SGC has resulted in the discovery of A-196 [5], the first potent and selective chemical probe for SUV420H1 and SUV420H2. The in vitro activity of A-196 includes inhibition of SUV420H1 with IC50 = 25 nM and SUV420H2 with IC50 = 144 nM for methylation of H4K20me and greater than 100-fold selectivity over other histone methyltransferases and non-epigenetic targets. In cell assays, A-196 inhibits the di- and tri-methylation of H4K20me in multiple cell lines with IC50 < 1 µM.

in vitro / biochemical potency

Mechanism of action


Physical and chemical properties for A-196
Molecular weight358.1
Molecular formulaC18H16Cl2N4
IUPAC name8,9-dichloro-N-cyclopentyl-5-(pyridin-4-yl)-3,4-diaza-bicyclo[4.4.0]deca-1(10),2,4,6,8-pentaen-2-amine
No. of chiral centres0
No. of rotatable bonds3
No. of hydrogen bond acceptors3
No. of hydrogen bond donors1
Physical and chemical properties for A-197
Molecular weight408.1            
Molecular formulaC19H22Cl2N4O2
IUPAC name(8,9-dichloro-5-cyclopentylamino-3,4-diaza-bicyclo[4.4.0]deca-1(10),2,4,6,8-pentaen-2-yl)-(4-hydroxy-piperidin-1-yl)-methanone
No. of chiral centres0
No. of rotatable bonds4
No. of hydrogen bond acceptors5
No. of hydrogen bond donors2
  • A-196: [H]N(C1CCCC1)c1c2cc(c(cc2c(c2ccncc2)nn1)[Cl])[Cl]
  • A-197: C1CCC(C1)Nc1c2cc(c(cc2c(C(N2CCC(CC2)O)=O)nn1)[Cl])[Cl]
  • InChI:
  • A-196:InChI=1S/C18H16Cl2N4/c19-15-9-13-14(10-16(15)20)18(22-12-3-1-2-4-12)24-23-17(13)11-5-7-21-8-6-11/h5-10,12H,1-4H2,(H,22,24)
  • A-197: InChI=1S/C19H22Cl2N4O2/c20-15-9-13-14(10-16(15)21)18(22-11-3-1-2-4-11)24-23-17(13)19(27)25-7-5-12(26)6-8-25/h9-12,26H,1-8H2,(H,22,24)
  • InChIKey:
selectivity profile

Selectivity of A-196 is selective against 29 methyltransferases

Selectivity of A-196 against epigenetic reader domains

in vitro potency
cell based assay data

Cell Assay


[1] Jorgensen S, Schotta G, Sorenson CS. (2013) Histone H4 Lysine 20 methylation: key player in epigenetic regulation of genomic integrity. Nucleic Acids Research 41: 2797-806.

[2] Schotta G, Lachner M, Sarma K, Ebert A, Sengupta R, et al. (2004) A silencing pathway to induce H3-K9 and H4-K20 trimethylation at constitutive heterochromatin. Genes Dev. 18:1251–1262.

[3] Sanders SL, Portoso M, Mata J, Bahler J, Allshire RC, et al. (2004) Methylation of histone H4 lysine 20 controls recruitment of Crb2 to sites of DNA damage. Cell; 119:603–614.

[4] Fraga MF, Ballestar E, Villar-Garea A, Boix-Chornet M, Espada J, et al. (2005) Loss of acetylation at Lys16 and trimethylation at Lys20 of histone H4 is a common hallmark of human cancer. Nat Genet 37:391-400.

[5] Bromberg KD, Mitchell TR, Upadhyay AK, Jakob CG, Jhala MA, et al. (2017 Jan 23) The SUV4-20 inhibitor A-196 verifies a role for epigenetics in genomic integrity. Nat Chem Biol. 

pk properties
co-crystal structures
synthetic schemes
materials and methods