SRA737

SRA737 monotherapy in vivo prolonged survival in CCNE1 amp models, suggesting a potential biomarker for CHK1i therapy. Combination SRA737 and PARPi therapy increased tumor regression in both PARPi-resistant and CCNE1 amp patient-derived xenograft models, warranting further study in these HGSOC subgroups.

Mechanistically, SRA737 synergized with AZD1775 by blocking AZD1775-induced feedback activation of CHK1 in prostate cancer cells, resulting in increased mitotic entry and accumulation of DNA damage. In summary, this preclinical study shows that CHK1 inhibitor SRA737 alone and its combination with AZD1775 offer potential effective treatments for CRPC and NEPC.

Also, greater anti-proliferative and cell killing effects were noted in the TP53 MUT cells than in the TP53 WT cells. This study's data suggests that P53 status/functioning is a key factor in determining the sensitivity of NSCLC and CRC cancer cells towards CHK1 inhibition, even in circumstances conducive to high replicative stress.

An e-pharmacophore model was developed based on the three-dimensional crystal structure of the CHK1 protein in complex with CCT245737. Thus, we propose the combined application of cisplatin and procaterol as a novel potential therapeutic strategy against human gastric cancer. The findings also highlight the relevance of CHK1 kinase as a drug target for enhancing the sensitivity of cytotoxic agents in cancer.

SRA737 was well tolerated at doses that achieved preclinically relevant drug concentrations but single agent activity did not warrant further development as monotherapy. Given its mechanism of action resulting in abrogating DNA damage repair, further clinical development of SRA737 should be as combination therapy.

Using an autochthonous adenocarcinoma mouse prostate (TRAMP) model that gives rise to NEPC tumors, we assessed the efficacy of AZD1775 and a highly selective Chk1 inhibitor SRA737 as single agents and in combination on the progression, survival, and metastatic spread of NEPC tumors in vivo. Mechanistically, the combination of Chk1 and Wee1 inhibitors synergized to reduce the inhibitory phosphorylation of CDK1 at Y15 and Cdc25c at S216, resulting in enhanced activation of CDK1/cyclin B complex, abrogation of G2/M checkpoint, and consequent premature mitotic entry, which ultimately led to mitotic catastrophe and apoptosis. Our findings provide promising preclinical evidence supporting the therapeutic values of Wee1 and Chk1 inhibitors as single agents and in combination for the treatment of NEPC.

Conclusion AML cell lines have different sensibilities to DDR inhibitors, particularly CCT245737 and niraparib, with the NB-4 cell line appearing to be the most sensitive to DDR inhibition (namely CHK1 and PARP1/2 inhibition), whereas LAMA-84 appears to be the most resistant to this inhibition. In conclusion, this work may help to identify new therapeutic approaches that could eventually improve AML patients’ outcomes.

P1/2, N=153, Completed, Sierra Oncology, Inc. | Active, not recruiting --> Completed | Trial primary completion date: Jan 2020 --> Apr 2020

Leukemia, a malignant hematological disease, has poor therapeutic outcomes due to chemotherapeutic resistance. Interestingly, CCT245737 inhibited both BRCA1 and Rad51, the most important component of the HR repair pathway. In conclusion, these results revealed that CHK1 is potentially an ideal therapeutic target for the treatment of CML and that CCT245737 should be considered a candidate drug.

This regimen also led to a significant decrease in immunosuppressive M2 macrophage and MDSC populations, as well as an increase in the expression of the Type I interferon gene, IFNβ, and chemokines, CCL5 and CXCL10. Given that anti-PD-(L)1 drugs have recently been approved as monotherapy and in combination with chemotherapy for the treatment of SCLC, and that SRA737+low dose gemcitabine (LDG) regimen is currently in clinical trials for SCLC and other malignancies, our preclinical data provide a strong rational for combining this regimen with inhibitors of PD-(L)1 pathway.

OS lines (G292, MG63, U2OS, and TT2-77) were highly sensitive to single agent BETi/OTX-015, CHK1i/ SRA737 or CHK1i/LY2606368 at clinically relevant concentrations. It is possible that MYC, BETs, RAD21 and CHK1 protein levels could dictate sensitivity to combination BETi+CHK1i independent of MYC-RAD2 CNV+ status. Studies are in progress to identify responder versus non-responder signatures in OS.

To identify synthetic lethal therapeutic targets to overcome chemoresistance in SLFN11 deficient cells, we performed a genome-wide RNAi screen with the human druggable genome siRNA library by using camptothecin (CPT), a TOP1 inhibitor, in SLFN11 wild-type (WT) and knock-out (KO) prostate cancer DU145 cells...Treatment with non-toxic-doses of M4344 and SRA737 reversed drug resistance of the SLFN11 KO cells to TOP1 inhibitors [CPT, and clinically used topotecan and LMP400 (indotecan)]...We also confirmed synergy with ATR/CHK1 inhibitors in combination of other clinical DNA-damaging agents (TOP2 inhibitor: etoposide, alkylating agent: cisplatin, and PARP inhibitor: talazoparib)...Co-treatment with ATR inhibitor and CPT resulted in G2/M arrest and apoptotic cell death, and formation of micronuclei and fragmented nuclei in SLFN11 KO cells, compared with SLFN11 WT cells. Collectively, our results provide a new therapeutic rationale for the clinical development of combination treatments of chemotherapeutic DNA-targeted agents with ATR/CHK1 inhibitors based on SLFN11 status.