Abstract LB-317: Identification of a novel preclinical candidate for CDK7 inhibition

Cyclin-dependent kinase 7 (CDK7) is an important constituent of the cellular transcriptional machinery, where it phosphorylates the C-terminal domain (CTD) of RNAP polymerase II (RNAPII). Because many tumor types are critically dependent on transcription for maintenance of their oncogenic state, pharmacological modulation of CDK7 kinase activity is considered as an approach to treat cancer. Multiple series of covalent CDK7 inhibitors were identified by iterative medicinal chemistry efforts and SAR based approach. These compounds were optimized towards attaining good physicochemical properties, high potency, good selectivity and desirable pharmacokinetic profile to achieve anti-tumor activity. We have now identified a pre-clinical candidate AU-BGB-002 which is highly potent in inhibiting CDK7 in biochemical as well as cellular assays while fully efficiently engaging the target. In a panel of kinases, AU-BGB-002 shows selectivity for CDK7. A panel of cell lines derived from a diverse set of indications are sensitive to AU-BGB-002. AU-BGB-002 exhibits excellent drug-like characteristics including solubility, permeability, metabolic stability and good oral bioavailability. When tested in a xenograft model, AU-BGB-002 treatment resulted in dose dependent tumor growth inhibition in AML xenograft model with tumor stasis at a dose of 10 mg/kg. Potent inhibiton of tumor growth was accompanied by complete target engagement and suppression of pS5RNAPII RNAPolII Ser5 phosphorylation in a parallel PK-PD study. Efficacy studies in additional xenograft models, advanced DMPK and toxicity studies are ongoing for this compound. In summary, we have identified a novel and selective CDK7 covalent inhibitor candidate with desirable drug-like properties that shows excellent efficacy in an AML xenograft model. Findings presented here support further development of AU-BGB-002 for the treatment of cancer. Citation Format: Leena K. Satyam, Ramulu Poddutoori, Subhendu Mukherjee, Sivapriya Marappan, Sreevalsam Gopinath, Aravind Basavaraju, Lakshmi Narayana Kaza, Manoj Kumar Pothuganti, Shilpa Nayak, Nandish C, Amith A, Ravindra MV, Dabbeeru Madhu Babu, Nagaraju A, Suraj Tgore, Thomas Antony, Chetan Pandit, Murali Ramachandra, Shekar Chelur, Girish Daginakatte, Susanta Samajdar. Identification of a novel preclinical candidate for CDK7 inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-317. doi:10.1158/1538-7445.AM2017-LB-317