Abstract 51P
Background
Cyclin-dependent kinase 12 (CDK12) and CDK13, members of the CDK family, contribute to cancer progression, including breast and gastric cancer. CDK12/13 partners with cyclin K to regulate transcription by phosphorylating the C-terminal domain (CTD) of RNA polymerase Ⅱ (Pol Ⅱ). However, targeting the CDK12/13-cyclin K complexes in cancer is still underexplored. Here, we report the anti-cancer effects of novel CDK12/13 inhibitors as cyclin K molecular glues on triple-negative breast cancer (TNBC) and gastric cancer.
Methods
In vitro kinase assays using radioactive phosphorylated substrates were performed. Cell viability assay at 72 h was conducted using CellTiter-Glo reagents. Protein expression levels in cancer cells were measured using western blotting. The pharmacokinetic/pharmacodynamic (PK/PD) study was conducted in HCC70 mouse xenografts, and the PK profile was also determined in mice. The anti-tumor and anti-metastatic efficacy were evaluated in zebrafish xenograft models using HCC70 and AGS cells.
Results
IL6-54 and IL6-110 are novel and potent CDK12/13 inhibitors with high selectivity against CDK1, 2, and 7. In MDA-MB-231 cells, the phosphorylated levels of RNA Pol Ⅱ CTD at Ser2 were rapidly reduced after 6 hrs, and cyclin K degradation was detected at 1 nM within 8 hrs, thereby showing strong anti-proliferative activity. Strong growth inhibition was also observed in TNBC cells (HCC70, BT-20, MDA-MB-436) and gastric cancer cells (AGS, MKN45). In HCC70 cells, IL6-110 drastically lowered cyclin K levels, while the protein neddylation inhibitor MLN4924 prevented the cytotoxicity of IL6-110 by 7-fold. In mice, IL6-110 showed a favorable PK profile at a single oral dose. In HCC70 mouse xenografts, IL6-110 at 5 mg/kg markedly reduced tumor cyclin K levels on day 4, with IL6-110 concentrations in tumors remaining stable at 8 h post-dose. In a zebrafish xenograft model with HCC70 cells, IL6-110 significantly induced tumor regression, while in a zebrafish xenograft model with AGS cells, IL6-54 demonstrated both anti-tumor and anti-metastatic properties.
Conclusions
Our findings provide promising evidence of a novel CDK12/13 inhibitor as a cyclin K molecular glue for a new therapeutic modality in cancer treatment.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
iLeadBMS Co., Ltd.
Funding
iLeadBMS Co., Ltd.
Disclosure
A. Moon, K. Kim, D. Song: Financial Interests, Personal and Institutional, Stocks/Shares, Full time employee: iLeadBMS Co., Ltd. Y. Lee: Financial Interests, Personal and Institutional, Stocks/Shares, Member of Board of Directors: iLeadBMS Co., Ltd.