Phosphoproteomics Analysis Reveals a Potential Role of CHK1 in Regulation of Innate Immunity through IRF3.

Inhibitors of checkpoint kinase 1 (CHK1), a central component of DNA damage and cell cycle checkpoint response, represent a promising new cancer therapy, but the global cellular functions they regulate through phosphorylation are poorly understood. To elucidate the CHK1-regulated phosphorylation network, we performed a global quantitative phosphoproteomics analysis, which revealed 142 phosphosites whose phosphorylation levels were significantly different following treatment with the CHK1 inhibitor SCH 900776. Bioinformatics analysis identified phosphoproteins that function in ATR-CHK1 signaling, DNA replication, and DNA repair. Furthermore, IRF3 phosphorylation at S173 and S175 was significantly reduced following treatment with SCH 900776. Our findings indicate that the CHK1-dependent regulation of IRF3 phosphorylation at S173 and S175 may play a role in the induction of innate immune response after replication stress or DNA damage, which suggests a potential function of CHK1 in the innate immune response. Data are available via ProteomeXchange with identifier PXD015125.

Discovery of (R)-5-((5-(1-methyl-1H-pyrazol-4-yl)-4-(methylamino)pyrimidin-2-yl)amino)-3-(piperidin-3-yloxy)picolinonitrile, a novel CHK1 inhibitor for hematologic malignancies.

Through virtual screening, we identified the lead compound MCL1020, which exhibited modest CHK1 inhibitory activity. Then a series of 5-(pyrimidin-2-ylamino)picolinonitrile derivatives as CHK1 inhibitors were discovered by further rational optimization. One promising molecule, (R)-17, whose potency was one of the best, had an IC50 of 0.4 nM with remarkable selectivity (>4300-fold CHK1 vs. CHK2). Compound (R)-17 effectively inhibited the growth of malignant hematopathy cell lines especially Z-138 (IC50: 0.013 µM) and displayed low affinity for hERG (IC50 > 40 µM). Moreover, (R)-17 significantly suppressed the tumor growth in Z-138 cell inoculated xenograft model (20 mg/kg I.V., TGI = 90.29%) as a single agent with body weight unaffected. Taken together, our data demonstrated compound (R)-17 could be a promising drug candidate for the treatment of hematologic malignancies.