Phase I study of CFI-402257, an oral TTK inhibitor, in patients with advanced solid tumors.

Abstract

TPS2619 Background: TTK (MPS1), a dual-specificity serine-threonine kinase, is critical for the spindle assembly checkpoint (SAC), chromosome alignment and error correction in mitosis. Inhibition of TTK causes premature mitotic exit with unattached chromosomes, resulting in chromosomal missegregation, aneuploidy and cell death. TTK is overexpressed in several tumor types, which may contribute to survival and proliferation of aneuploid cells, and higher expression correlates with adverse outcomes. The Campbell Family Therapeutics Group at the University Health Network (UHN) has developed CFI-402257, a potent (Ki = 0.09 nM, IC50 = 1.2 nM), highly selective and orally active inhibitor of TTK, with negligible activity towards 265 other kinases. Robust suppression of tumor growth was achieved upon oral dosing of single agent CFI-402257 at tolerated doses in several cell line (breast, colorectal) and patient-derived (ovarian) xenograft models. Pharmacodynamic effects including reduction in phospho-histone H3 were observed. In syngeneic mouse colorectal cancer models, CFI-402257 + PD-1 immune checkpoint blockade demonstrated greater activity than either agent alone, and resulted in tumor regressions and immunity to rechallenge. Methods: This multi-center Phase I dose escalation study (3+3 design) will determine the safety, tolerability and maximum tolerated dose (MTD) of CFI-402257 administered as daily continuous oral treatment. Secondary and correlative endpoints include plasma PK, antitumor activity, and molecular features associated with response or clinical benefit. An expansion cohort (n = 12) will be enrolled at the MTD. Key inclusion criteria: adult patients with advanced solid tumors, measurable disease (RECIST 1.1), adequate organ function and performance status (ECOG 0-1). Exclusion criteria: uncontrolled medical illness, CNS metastases (unless stable x 3 months). CFI-402257 will be dosed once daily on a continuous schedule in 28-day cycles, beginning at 5 mg/day with planned escalation to 56 mg/day. DL1 completed enrolment 01/2017 and accrual is ongoing. Phase II studies are planned (Stand Up to Cancer Canada Breast Cancer Dream Team). Funding: UHN, CIRM. Clinical trial information: NCT02792465.