Safety and tolerability of CFI-400945, a first-in-class, selective PLK4 inhibitor in advanced solid tumours: a phase 1 dose-escalation trial

Background

CFI-400945 is a first-in-class oral inhibitor of polo-like kinase 4 (PLK4) that regulates centriole duplication. Primary objectives of this first-in-human phase 1 trial were to establish the safety and tolerability of CFI-400945 in patients with advanced solid tumours. Secondary objectives included pharmacokinetics, pharmacodynamics, efficacy, and recommended phase 2 dose (RP2D).

Methods

Continuous daily oral dosing of CFI-400945 was evaluated using a 3+3 design guided by incidence of dose-limiting toxicities (DLTs) in the first 28-day cycle. Safety was assessed by CTCAE v4.0. ORR and CBR were evaluated using RECIST v1.1.

Results

Forty-three patients were treated in dose escalation from 3 to 96 mg/day, and 9 were treated in 64 mg dose expansion. After DLT occurred at 96 and 72 mg, 64 mg was established as the RP2D. Neutropenia was a common high-grade (19%) treatment-related adverse event at ≥ 64 mg. Half-life of CFI-400945 was 9 h, with C_max achieved 2–4 h following dosing. One PR (45 cycles, ongoing) and two SD ≥ 6 months were observed (ORR = 2%; CBR = 6%).

Conclusions

CFI-400945 is well tolerated at 64 mg with dose-dependent neutropenia. Favourable pharmacokinetic profiles were achieved with daily dosing. Response rates were low without biomarker pre-selection. Disease-specific and combination studies are ongoing.

Trial Registration

Clinical Trials Registration Number – NCT01954316 (Oct 1st, 2013)

Abstract CT066: First-in-human phase I trial of the oral PLK4 inhibitor CFI-400945 in patients with advanced solid tumors

Background: CFI-400945 is a first-in-class, potent, selective, orally active inhibitor of Polo-like kinase 4 (PLK4) (Ki = 0.26 nM), a conserved master regulator of centriole duplication that is important for maintenance of genomic integrity. In preclinical studies, CFI-400945 demonstrated robust anti-tumor activity, including durable complete tumor regression, in a large number of patient-derived xenograft models from multiple tumor types (breast, ovarian, pancreas, prostate carcinomas; some derived from heavily pre-treated patients). The objectives of this first-in-human phase I trial are to establish safety, tolerability, pharmacokinetics, and recommended phase II dose (RP2D) of CFI-400945.

Methods: Patients with advanced solid tumors age >18 years, with ECOG performance status of 0-1, adequate organ function and RECIST-measurable disease progressing on standard treatments are eligible. Dose escalation follows a standard 3+3 design, with a starting dose of 3mg once daily continuous oral dosing based upon preclinical data and a severely toxic dose to 10 percent (STD10) in rats of 3 mg/kg. The primary endpoint is the incidence of dose limiting toxicities (DLTs) during the first cycle. Safety assessments using CTCAE version 4.03 criteria are performed weekly during the first three cycles and then every two weeks. Response assessments are performed every two cycles.

Results: From April/14 to December/15, 31 patients were enrolled across eight pre-defined dose levels (3, 6, 11, 16, 24, 32, 48 and 72 mg). No DLT events have been observed. Dose escalation at 96mg is currently ongoing. The most frequent treatment-related adverse events (trAEs) include fatigue (24%), diarrhea (17.2%), nausea (17.2%), decreased appetite (13.8%) and vomiting (6.9%). All trAEs were grade 1 or grade 2. Fifteen serious adverse events (SAEs) have occurred in 9 patients, all considered unrelated to CFI-400945 treatment. Preliminary PK results estimate a half-life of about 10 hours, with Cmax and AUC showing dose proportionality. Two patients enrolled at the 48 mg dose level have completed >6 cycles, including a patient with KRAS mutant colorectal cancer who achieved 24% reduction in target lesions and >50% reduction in serum CEA levels.

Conclusions: CFI-400945 is well tolerated at doses up to 72mg with a favorable PK profile. Preliminary evidence of anti-tumor activity has been observed. Exploration of 96mg daily dosing is ongoing and once the RP2D has been established exploration of anti-tumor activity in biomarker-driven expansion arms of CFI-400945 in indications including advanced breast cancer is planned. Updated results of this ongoing trial will be presented at the meeting.

Citation Format: Philippe L. Bedard, David W. Cescon, Graham Fletcher, Trish Denny, Richard Brokx, Peter Sampson, Mark R. Bray, Dennis J. Slamon, Tak W. Mak, Zev A. Wainberg. First-in-human phase I trial of the oral PLK4 inhibitor CFI-400945 in patients with advanced solid tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT066.

Discovery of Pyrazolo[1,5-a]pyrimidine TTK Inhibitors: CFI-402257 is a Potent, Selective, Bioavailable Anticancer Agent

This work describes a scaffold hopping exercise that begins with known imidazo[1,2-a]pyrazines, briefly explores pyrazolo[1,5-a][1,3,5]triazines, and ultimately yields pyrazolo[1,5-a]pyrimidines as a novel class of potent TTK inhibitors. An X-ray structure of a representative compound is consistent with 1(1)/2 type inhibition and provides structural insight to aid subsequent optimization of in vitro activity and physicochemical and pharmacokinetic properties. Incorporation of polar moieties in the hydrophobic and solvent accessible regions modulates physicochemical properties while maintaining potency. Compounds with enhanced oral exposure were identified for xenograft studies. The work culminates in the identification of a potent (TTK K i = 0.1 nM), highly selective, orally bioavailable anticancer agent (CFI-402257) for IND enabling studies.