Preliminary Results from a Phase 2 Open-Label, Multicenter, Dose Optimization Clinical Study of the Safety, Tolerability, and Pharmacokinetic (PK) and Pharmacodynamic (PD) Profiles of Cfi-400945 As a Single Agent or in Combination with Azacitidine or Decitabine in Patients with Acute Myeloid Leukemia, Myelodysplastic Syndrome or Chronic Myelomonocytic Leukemia (TWT-202)

Background: CFI-400945 is a potent, selective, orally administered, first-in-class inhibitor of the serine/threonine kinase, Polo-like kinase 4 (PLK4). PLK4 is a highly conserved master upstream regulator of centriole duplication and is critical for maintenance of genomic integrity. Aberrant expression of PLK4 results in a number of effects including the centrosome amplification often seen in aneuploid cancers, pointing to a potentially causative role for PLK4 in genome instability and cancer progression. A Phase 1 study has been completed evaluating CFI-400945 as a monotherapy in solid tumors, showing a tolerable safety profile and promising signs of activity. Given acute myeloid leukemia (AML) is characterized by genomic instability, CFI-400945 has been evaluated in pre-clinical and clinical studies in AML. In pre-clinical studies, CFI-400945 showed potent activity towards leukemia cell lines and primary human samples in vitro, as well as marked efficacy in two subcutaneous models of leukemia. A prior Phase 1 trial in AML was initiated at the Princess Margaret Cancer Center (PMCC), and of six patients evaluable for response, two (33%) achieved complete remission (CR) at 96 mg and 128 mg, and 3 patients (50%) had stable disease (with one patient having a 78% reduction in marrow blast count) at 64 mg (2 patients) and 96 mg [re: Murphy et al, ASH 2020]. Responses were seen in patients with adverse cytogenetics. The optimal dosing of CFI-400945 and its potential role as a combination agent are not yet clinically defined.