CHIR-124

CHIR-124, a selective inhibitor, inhibits Chk1 with IC50 value of 0.3nM 2,000-fold more potently than Chk2 with IC50 value of 0.7μM. CHIR-124 also potently targets other kinases such as PDGFR with IC50 value of 6.6nM and FLT3 with IC50 value of 5.8nM [1].

CHIR-124 abrogates the S and G2-M checkpoints induced by topoisomerase I poisons and selectively sensitizes tumors lacking p53 function to undergo mitotic death. In addition, CHIR-124 enhances the antitumor effect of irinotecan in tumor xenografts by inhibiting the G2-M checkpoint and inducing apoptosis.

In vitro, the effect of a matrix of camptothecin and CHIR-124 combinations in a number of human cancer cell lines, including breast carcinoma (MDA-MB-231and MDAMB-435) and colon carcinoma (SW-620 and Colo205), all of which are mutant for p53. When cells were simultaneously exposed to a matrix of different concentration combinations of CHIR-124 and SN-38 for 48 h, significant synergy or >10% deviation from additivity was observed in the concentration ranges of ≥4.2×108 mol/L for SN-38 and≥ 6.0×108 mol/L for CHIR-124. Compared to IR alone, the number of mitotic cells increased dramatically in p53-/- HCT116 cells after concomitant Chir-124 exposure, while no such effect was observed in p53-sufficient WT HCT116 cells. Chir-124 was able to radiosensitize HCT116 cells that lack checkpoint kinase-2 (CHK2) or that were deficient for the spindle checkpoint protein Mad2. Additionally, Chir-124 could radiosensitize tetraploid cell lines, which were resistant to DNA damaging agents. Radiosensitization mediated by Chir-124 is greatly influenced by the p53 and cell cycle checkpoint system [1, 2].

In vivo, severe combined immunodeficient mice harboring MDA-MD-435 tumor xenografts were randomized into the treatment of 10 mg/kg CHIR-124, 20 mg/kg CHIR-124, 10 mg/kg CHIR-124 with 5 mg/kg CPT-11, or 20 mg/kg CHIR-124 with 5 mg/kg CPT-11. CPT-11 was given i.p. four times daily ×5 on days 1 to 5, while CHIR-124 was given orally four times daily ×6 on days 2 to 7 in captisol. Tumors harvested from mice sacrificed on day 4 of treatment were examined for apoptosis by terminal deoxynucleotidyl transferase-mediated nick-end labeling staining and for mitotic index by immunofluorescence labeling with phospho-histone H3 antibody in a similar study [1].

References:
[1]. Tse AN, Rendahl KG, Sheikh T, et al. CHIR-124, a novel potent inhibitor of Chk1, potentiates the cytotoxicity of topoisomerase I poisons in vitro and in vivo. Clinical Cancer Research, 2007, 13(2): 591-602.
[2]. Tao YG, Leteur C, Yang CY, et al. Radiosensitization by Chir-124, a selective CHK1 inhibitor Effects of p53 and cell cycle checkpoints. Cell Cycle, 2007, 8(8): 1196-1205.

Radiosensitization by Chir-124, a selective CHK1 inhibitor: effects of p53 and cell cycle checkpoints.[Pubmed:19305158]

Cell Cycle. 2009 Apr 15;8(8):1196-205.

Checkpoint kinase-1 (CHK1) is a key regulator of the DNA damage-elicited G(2)-M checkpoints. The aim of the present study was to investigate the effects of a selective CHK1 inhibitor, Chir124, on cell survival and cell cycle progression following ionizing radiation (IR). Treatment with CHIR-124 resulted in reduced clonogenic survival and abrogated the IR-induced G(2)-M arrest in a panel of isogenic HCT116 cell lines after IR. This radiosensitizing effect was relatively similar between p53(-/-) and p53-sufficient wild type (WT) HCT116 cells. However, the number of mitotic cells (as measured by assessing the phosphorylation of mitotic proteins) increased dramatically in p53(-/-) HCT116 cells after concomitant CHIR-124 exposure, compared to IR alone, while no such effect was observed in p53-sufficient WT HCT116 cells. In p53(-/-) cells, CHIR-124 treatment induced a marked accumulation of polyploid cells that were characterized by micronucleation or multinucleation. p21(-/-) HCT116 cells displayed a similar pattern of response as p53(-/-) cells. CHIR-124 was able to radiosensitize HCT116 cells that lack checkpoint kinase-2 (CHK2) or that were deficient for the spindle checkpoint protein Mad2. Finally, CHIR-124 could radiosensitize tetraploid cell lines, which were relatively resistant against DNA damaging agents. Altogether these results suggest that CHIR-124-mediated radiosensitization is profoundly influenced by the p53 and cell cycle checkpoint system.

CHIR-124, a novel potent inhibitor of Chk1, potentiates the cytotoxicity of topoisomerase I poisons in vitro and in vivo.[Pubmed:17255282]

Clin Cancer Res. 2007 Jan 15;13(2 Pt 1):591-602.

PURPOSE: Chk1 kinase is a critical regulator of both S and G(2)-M phase cell cycle checkpoints in response to DNA damage. This study aimed to evaluate the biochemical, cellular, and antitumor effects of a novel Chk1 inhibitor, CHIR124. EXPERIMENTAL DESIGN: CHIR-124 was evaluated for its ability to abrogate cell cycle checkpoints, to potentiate cytotoxicity, and to inhibit Chk1-mediated signaling induced by topoisomerase I poisons in human tumor cell line and xenograft models. RESULTS: CHIR-124 is a quinolone-based small molecule that is structurally unrelated to other known inhibitors of Chk1. It potently and selectively inhibits Chk1 in vitro (IC(50) = 0.0003 micromol/L). CHIR-124 interacts synergistically with topoisomerase poisons (e.g., camptothecin or SN-38) in causing growth inhibition in several p53-mutant solid tumor cell lines as determined by isobologram or response surface analysis. CHIR-124 abrogates the SN-38-induced S and G(2)-M checkpoints and potentiates apoptosis in MDA-MD-435 breast cancer cells. The abrogation of the G(2)-M checkpoint and induction of apoptosis by CHIR-124 are enhanced by the loss of p53. We have also shown that CHIR-124 treatment can restore the level of cdc25A protein, which is normally targeted by Chk1 for degradation following DNA damage, indicating that Chk1 signaling is suppressed in the presence of CHIR-124. Finally, in an orthotopic breast cancer xenograft model, CHIR-124 potentiates the growth inhibitory effects of irinotecan by abrogating the G(2)-M checkpoint and increasing tumor apoptosis. CONCLUSIONS: CHIR-124 is a novel and potent Chk1 inhibitor with promising antitumor activities when used in combination with topoisomerase I poisons.

CHIR-124 is a potent and selective Chk1 inhibitor with IC50 of 0.3 nM, and also potently targets PDGFR and FLT3 with IC50s of 6.6 nM and 5.8 nM.

CHIR-124,405168-58-3,Natural Products,Chk, buy CHIR-124 , CHIR-124 supplier , purchase CHIR-124 , CHIR-124 cost , CHIR-124 manufacturer , order CHIR-124 , high purity CHIR-124