I-BET151 (GSK1210151A)

Biological activity

I-BET151 (GSK1210151A) is a novel selective BET inhibitor for BRD2, BRD3 and BRD4 with IC50 of 0.5 μM, 0.25 μM, and 0.79 μM in cell-free assays, respectively.

In vitro

I-BET151 exhibits potent selectivity over an extensive range of diverse protein types such as COX-2, P450, Aurora B, GSK3β, PI3K-γ, GPCR, ion channels, and transporters. Similar to I-BET762 (GSK525762A), I-BET151 displays potent binding affinity to BRD2, BRD3 and BRD4 with KD of 0.02-0.1 μM, and significantly inhibits lipopolysaccharide-stimulated IL-6 cytokine production in human peripheral blood mononuclear cells (PBMC) and whole blood (WB) as well as rat WB with IC50 of 0.16 μM, 1.26 μM, and 1.26 μM, respectively. I-BET151 (0.5 or 5 μM) inhibits the binding of BETs (BRD2, BRD3, BRD4, and BRD9) but not the binding of 23 other bromodomain proteins in HL60 nuclear extract to acetylated histone peptides. I-BET151 has potent efficacy against cell lines harboring different MLL-fusions such as MV4;11, RS4;11, MOLM13, and NOMO1 cells with IC50 of 15-192 nM. Consistently, I-BET151 completely ablates the colony-forming potential of MLL-fusion-driven leukaemias (MOLM13) but not leukaemias driven by tyrosine kinase activation (K562). I-BET151 also displays potent efficacy in both liquid culture and clonogenic assays using primary murine progenitors transformed with either MLL-ENL or MLL-AF9. I-BET151 treatment significantly induces apoptosis and prominent G0/G1 arrest in MLL-fusion cell lines driven by distinct MLL fusions (MOLM13 and MV4;11 containing MLL-AF9 and MLL-AF4, respectively) but not the K562 cells, probably due to the inhibition of transcription of BCL2, C-MYC and CDK6 by blocking the recruitment of BRD3/4, PAFc and SEC components into transcriptional start site (TSS).

In vivo

Administration of I-BET151 at 30 mg/kg/day significantly inhibits tumor growth of murine MLL-AF9 and human MLL-AF4 leukaemia in mice, and provides marked survival benefit.

Description

The bromodomain and extra terminal domain (BET) family of proteins including BRD2, BRD3, and BRD4 play a key role in many cellular processes, including inflammatory gene expression, mitosis, and viral/host interaction by controlling the assembly of histone acetylation-dependent chromatin complexes. I-BET151 is an isoxazole class pan-BET family inhibitor, blocking BRD2, BRD3, and BRD4 with IC₅₀ values of 0.5, 0.25, and 0.79 μM, respectively. Through this action, it blocks the growth of leukemic cell lines driven by mixed lineage leukemia (MLL) fusions at nanomolar concentrations, whereas tyrosine kinase activated cells were much less sensitive. Specifically, I-BET151 induces apoptosis via reduced expression of BCL2 or triggers G₀/G₁ cell cycle arrest in MLL-fusion cell lines. I-BET151 is effective in vivo, suppressing MLL leukemia progression in two different mouse models.

Chemical Properties

Off-White Solid

Uses

GSK1210151A or I-BET151 has been used to study its inhibitory effect on BET (bromodomain and extra terminal) recruitment to chromatin in treating MLL (mixed-lineage leukemia)-fusion leukemia.

Uses

I-BET 151 is part of a novel series of quinoline isoxazole BET family bromodomain inhibitors, a family of four proteins that selectively bind to aceylated lysine residues in histone. I-BET 151 play ke y roles in many cellular processes, including anti-inflammatory gene expression, mitosis, and viral/host interaction by controlling the conformation of histone acetylation -dependent chromatin complex es. Studies have shown that I-BET 151 increased ApoA1 expression within the nanomolar range in human hepatic cell line HepG2. The upregulation by I-BET 151 suggested potential anti-inflammatory activi ties upon administration.

Definition

ChEBI: I-BET151 is a member of the class of imidazoquinolines that is 1,3-dihydro-2H-imidazo[4,5-c]quinolin-2-one substituted by (1R)-1-(pyridin-2-yl)ethyl, 3,5-dimethyl-1,2-oxazol-4-yl, and methoxy groups at positions 1, 7, and 8, respectively. It is a pan-BET bromodomain inhibitor. It has a role as an apoptosis inducer, an antineoplastic agent and a BET bromodomain inhibitor. It is an imidazoquinoline, a member of pyridines, an aromatic ether and a member of isoxazoles.

Biochem/physiol Actions

GSK1210151A (I-BET151) is an inhibitor of the BET (bromodomain and extra terminal domain protein) family of acetyl-lysine recognizing, chromatin ′adaptor′ proteins. GSK1210151A displaces BRD3 and BRD4, PAFc and SEC components from chromatin resulting in inhibition of transcription at key genes (BCL2, C-MYC and CDK6) involved in the initiation of mixed lineage leukemia (MLL). GSK1210151A (I-BET151) showed good efficacy in 2 MLL animal models.

Synthesis

7-(3,5-dimethylisoxazol-4-yl)-6-methoxy-4-(((R)-1-(pyridin-2-yl)ethyl)amino-3-quinolinecarboxamide (45 g, 102 mmol) was used as a starting material, which was dissolved in methanol (500 mL), followed by the addition of potassium hydroxide (7.47 g, 133 mmol). The reaction mixture was placed in an ice bath and stirred, then iodobenzene diacetate (39.6 g, 123 mmol) was added in batches over 20 minutes and stirring was continued for 1 hour. Upon completion of the reaction, the solvent was removed by vacuum evaporation, the residue was diluted with water (1 L), and the gelatinous suspension formed was extracted with dichloromethane (2 × 300 mL). The organic phases were combined, dried with sodium sulfate, and directly upsampled onto a silica column (750 g), which was eluted using a methanol/dichloromethane gradient (0-10%) of 2 M ammonia. The eluate was concentrated in vacuum to afford the target product 7-(3,5-dimethylisoxazol-4-yl)-8-methoxy-1-((R)-1-(pyridin-2-yl)ethyl)-1H-imidazo[4,5-c]quinolin-2(3H)-one (32.7 g, 77% yield) as a beige solid. The product was structurally confirmed by 1H-NMR (600 MHz, DMSO-d6), 13C NMR (151 MHz, DMSO-d6), mass spectrometry (MS) and high resolution mass spectrometry (HRMS).

target

BRD2

References

[1] Bioorganic and Medicinal Chemistry Letters,  2012,  vol. 22,  # 8,  p. 2963 - 2967
[2] Patent: US2012/232074,  2012,  A1. Location in patent: Page/Page column 33
[3] Patent: WO2011/54846,  2011,  A1. Location in patent: Page/Page column 84
[4] http://www.selleckchem.com/products/i-bet151-gsk1210151a.html