Abstract 4834: CT7001: An orally bioavailable CDK7 inhibitor is a potential therapy for breast, small-cell lung and haematological cancers
Authors: Edward K. Ainscow, Andrew Leishman, Elaine Sullivan, Bo Li, William Gallagher, Adam Peall, Kristopher Clark, Stuart Thomson, Simak Ali, Raoul C. Coombes, Ash Bahl
Journal: Cancer Research (2018)

Abstract CDK7 inhibition has emerged as a promising strategy in a range of cancer indications. CDK7 acts as a regulator of transcription through its role in phosphorylating and activating RNA Polymerase II (polII) as well as a master regulator of the cell cycle through phosphorylation of members of the CDK family. Inhibition of CDK7 in cancer cells has been shown to be effective in blocking transcriptional addiction to a defined cluster of genes (Wang et al 2015) and leads to decreased cell cycling, a decrease in the levels of proto-oncogenes such as c-Myc and induction of apoptosis. Here we describe the properties of a potent, selective and orally bioavailable CDK7 inhibitor CT7001 (formerly known as ICEC0942). Profiling across a pan-cancer cell line panel showed that CT7001 has anti-proliferative activity in a range of cancer types including acute myeloid leukaemia (AML), small cell lung (SCL) and hormone sensitive and triple negative breast cancers (TNBC).Mechanistic investigations revealed that CT7001s activity was associated with both a decrease in cell proliferation and an induction of apoptosis. Inhibition of cell proliferation was commensurate with a decrease in the levels of c-Myc, Mcl-1 and phospho-Pol II as determined by Western Blot analysis.CT7001 was then evaluated in a range of pre-clinical cancer models. CT7001 was shown to lead to cell death in a panel of patient derived models of small-cell lung cancer (SCLC) in 3D spheroid assays. In an in vivo orthotopic-patient derived xenograft model of TNBC in nu/nu mice, orally administered CT7001 monotherapy produced strong and sustained regression of the tumour that persisted during the dosing schedule, and strong suppression was still maintained upon cessation of treatment. At doses that produced regression CT7001 was well tolerated with little effect on body weight (&amp;lt;10%). Similarly, CT7001 produced a near complete regression in an MV-4-11 xenograft model of AML. Pre-clinical toxicity studies in rat and dog demonstrated that CT7001 was well tolerated at biologically active doses, with no evidence for neutropenia that is associated with inhibitors of other members of the CDK family.Taken together these studies indicate CT7001 is a potent, selective and orally bioavailable inhibitor of CDK7 that shows excellent promise as a potential new treatment in a number of oncology indications. A Phase I study to explore the safety and tolerability of CT7001 was initiated in November 2017. Reference: Wang et al Cell. 2015 163(1):174-86 Citation Format: Edward K. Ainscow, Andrew Leishman, Elaine Sullivan, Bo Li, William Gallagher, Adam Peall, Kristopher Clark, Stuart Thomson, Simak Ali, Raoul C. Coombes, Ash Bahl. CT7001: An orally bioavailable CDK7 inhibitor is a potential therapy for breast, small-cell lung and haematological cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4834.