A CRUK first-in-human phase I trial of a CDC7 Inhibitor, LY3143921 hydrate, in patients with advanced solid tumors

TPS3167 Background: CDC7 is a protein with key roles in DNA replication initiation, the intra-S-phase checkpoint and M-phase completion. CDC7 is over-expressed in malignant compared to non-malignant cells, particularly those with TP53 mutations, making it an attractive therapeutic target. LY3143921 hydrate is an orally administered ATP-competitive CDC7 inhibitor. Pre-clinical studies in colorectal cancer (CRC) and squamous non-small cell lung cancer (sqNSCLC) demonstrate favourable anti-cancer activity, particularly in squamous NSCLC and in CRC with TP53 null and missense mutations. We hypothesise that solid tumours mutated in TP53 will be sensitive to LY3143921 therapy. Methods: This is a first-in-human, phase I trial of LY3143921 hydrate (LY3143921) monotherapy given twice daily, continuously on a 21 day schedule until disease progression, patient (pt) withdrawal or unacceptable toxicity (NCT03096054). Eligible pts have histologically proven advanced/metastatic solid tumours for which no further standard therapy exists and WHO PS 0-1. Pts have regular clinical assessment and tumour imaging every 2 cycles. Phase Ia (dose escalation) is recruiting in a 3+3 design following 3 initial single patient cohorts (starting dose 30 mg OD), enriching for patients with malignancies associated with p53 mutations (CRC, sqNSCLC, high grade serous ovarian, squamous cell oesophageal, squamous cell head & neck, urothelial, pancreatic and triple negative breast cancer). Recruitment to cohort 6 (180 mg BD) is ongoing. On determination of the maximum tolerated dose (MTD) and recommended phase II dose and schedule (RP2D), 2 expansion cohorts (≤ 25 pts each) of patients with CRC and sqNSCLC will be evaluated. Primary objectives: assess safety and tolerability of LY3143921, determine MTD and RP2D. Secondary objectives: evaluate preliminary efficacy and PK profile of LY3143921. All pts will have archival tumour tissue retrospectively analysed, while patients in phase Ib will also have pre- and on-treatment tumour biopsies. Evaluation of potential predictive and pharmacodynamic biomarkers including p53 mutations, phosphorylated MCM2, cyclin B1 and molecular subgroups of target tumours will be included. Clinical trial information: NCT03096054.