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

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 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. As acute myeloid leukemia (AML) is a disease characterized by genomic instability, it is of significant interest as a potential indication for the clinical evaluation of CFI-400945. 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, specifically the MV4-11 FLT3-ITD AML. A Phase 1 trial in AML was initiated at the Princess Margaret Cancer Center in 2018, and of six patients evaluable for response, two (33%) achieved complete remission (CR), and 3 patients (50%) had stable disease (with one patient having a 78% reduction in marrow blast count) [re: Murphy et al, ASH 2020]. These promising results have led to a plan for an expanded trial examining CFI-400945 in AML, particularly focused on complex karyotype (CK).

Study Design and Methods: The study will have 4 parts, Part 1A (1A): a single agent dose escalation portion, Part 1B (1B): a food effect portion once the MTD of 1A is determined, and combinations with azacitidine (2A), and decitabine (2B). For parts 1A and 1B, patients with relapsed and/or refractory AML, MDS, or CMML after >1 prior therapy will be included. Patients with MDS or CMML must have progressed or had a lack of response after at least 4 cycles of hypomethylating agents. For parts 2A and 2B, patients should have relapsed and/or refractory AML or untreated MDS or CMML. Untreated patients who decline or are ineligible for intensive therapy may be included. The study will use a standard 3 + 3 design. The maximum tolerated dose (MTD) will be defined as the dose level where the number of dose limiting toxicities (DLTs) is <1 out of 6 at highest dose level below the maximally administered dose.

Biomarker Selection and companion Diagnostics: No biomarker based pre-selection of patients. PD evaluations will include blast reduction and markers of mitosis.

Study Treatment and Endpoints: Part 1: Each cycle will be 28 days (21 days on/7 days off). Starting does of CFI-400945 will be 32mg po. Once the MTD of 1A is determined, 1B will explore the food effect of a high fat meal on the PK of CFI-400945 at the MTD. 2A and 2B will explore the combination of CFI-400945 with standard dose of either azacitidine (2A) or decitabine (2B). The starting dose of CFI-400945 will be 32mg po for 21 days on/7 off. The DLTs will be defined as NCI CTCAE V5.0 Grade >3 related non-hematologic event(s) occurring during cycle 1 or prolonged pancytopenia in the presence of a hypocellular bone marrow > day 42 without evidence of disease. The efficacy endpoints for AML, MDS, and CMML include the overall response rate, and the CR rate per standard criteria. The aim of the food effect part of the study is the asses the effect of high fat food on the PK of CFI-400945. The safety endpoint is the incidence of treatment emergent adverse events. PK endpoints include evaluations of parameters such as half-life, AUC, etc. Exploratory endpoints include eval of minimal residual disease, genomic alterations and other molecular features associated with response and biological effects of PLK4 inhibition.