Abstract B172: Potent anti-tumor activity of a selective and orally bioavailable reversible covalent CDK12 inhibitor

Abstract

Abstract Cyclin-dependent kinase 12 (CDK12), in association with Cyclin K (CycK), regulates the elongation of transcription by modifying RNA polymerase II (RNAP II) through phosphorylation at Serine 2 (pS2) in the C-terminal domain, CDK12 plays an important role in maintaining genomic stability by modulating crucial cellular processes such as DNA damage response, splicing, and pre-mRNA processing. Overexpression of CDK12 has been observed in various tumor types, suggesting its potential oncogenic properties like other kinases involved in transcription. Given its significance in transcription and RNA processing, CDK12 has emerged as a promising therapeutic target for cancer treatment. We have identified a highly potent and selective reversible covalent inhibitor of CDK12, AU-22880, which exhibits significant anti-proliferative activity across various cancer cell lines. The covalent mode of action and on-target activity of AU-22880 were confirmed in a CDK12 target engagement assay and selective pS2 RNAPII inhibition respectively in a cellular context. Additionally, it has shown synergistic activity in combination with several standard-of-care agents in breast cancer, ovarian cancer, pancreatic cancer, and prostate cancer cell lines. AU-22880 shows desirable ADME-PK properties and demonstrates excellent anti-tumor activity in xenograft models. In the HCC-70 TNBC xenograft model, AU-22880 demonstrated anti-tumor efficacy at well-tolerated doses. A pharmacokinetic-pharmacodynamic (PK-PD) study revealed dose-dependent target engagement, as evidenced by the inhibition of pS2 RNAPII and DNA damage repair (DDR) genes. Furthermore, AU-22880 exhibited good tolerability in rodents, dog, and monkeys at exposure levels that demonstrated efficacy. Efficacy of AU-22880 in combination with approved SOCs targeting DDR pathway are currently being investigated. The findings reported here highlight the promising therapeutic potential of AU-22880, both as a monotherapy and in combination with existing treatments for the treatment of cancers characterized by DDR dysregulation. Citation Format: Leena Khare, Ramulu Poddutoori, Subhendu Mukherjee, Samiulla DS, Devaraja TS, Sivapriya Marappan, Shilpa Nayak, Sasirekha Sivakumar, Lakshmi Kaza, Suraj Tgore, Amit Dhudashiya, Raghavendra NR, Bhargav Gunnepalli, Aravind A B, Amith A, Charamanna KB, Thomas Antony, Kavitha Nellore, Girish Daginakatte, Shekar Chelur, Sanjeev Giri, Murali Ramachandra, Susanta Samajdar. Potent anti-tumor activity of a selective and orally bioavailable reversible covalent CDK12 inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B172.