Tuesday, October 27, 2015

Drugs in Clinical Pipeline: PF-03814735

PF-03814735 [N-{2-[6-(4-Cyclobutylamino-5-trifluoromethyl-pyrimidine-2-ylamino)-(1S,4R)-1,2,3,4-tetrahydro-1,4-epiazano-naphthalen-9-yl]-2-oxo-ethyl}-acetamide] is a novel, potent, orally bioavailable, reversible inhibitor of both AURKA and AURKB kinases. Although PF-03814735 produces significant inhibition of several other protein kinases, the predominant biochemical effects in cellular assays are consistent with inhibition of Aurora kinases.

In in vitro enzymatic assays, the trifluoromethylpyrimidine derivative PF-03814735 was identified as a potent inhibitor of the AURKB and AURKA kinases, with IC50 values of 0.8 nM and 5 nM, respectively. The kinetics of inhibition of recombinant AURKB kinase by PF-03814735 indicated that inhibition was ATP competitive. PF-03814735 produced significant inhibition of several other protein kinases in recombinant kinase enzymatic assays. Of 220 kinases evaluated, 19 others showed greater than 90% inhibition at 100 nM of PF-03814735. The IC50 values of PF-03814735 for a subset of these kinases revealed the greatest potency for AURKA and AURKB, followed by Flt1, FAK, TrkA, Met, and FGFR1 (IC50 = 10, 22, 30, 100 and 100 nM, respectively). Thus, PF-03814735 was shown to be a potent inhibitor of AURKA and AURKB kinases as well as several other protein kinases in enzymatic assays [1].

A product from Pfizer, PF-03814735 is under Phase I trials for patients with advanced solid tumors.

The activity of PF-03814735 is as follows:

IC50 (AURKB enzyme assay) = 0.8 ± 0.6 nM
IC50 (AURKA enzyme assay) = 5 ± 3 nM
IC50 (FLT1 enzyme assay) = 10 nM
IC50 (FAK enzyme assay) = 22 nM
IC50 (TRKA enzyme assay) = 30 nM
IC50 (MET enzyme assay) = 100 nM
IC50 (FGFR1 enzyme assay) = 100 nM

Kinases that showed more than 90% inhibition at 100 nM of PF-03814735 include CDK5/p35; Flt3(D835Y); ARK5; NEK2; Flt4; Ret; MLK1; TrkB; Fer; JAK2; Flt3; MST3; CDK5/p25; MST2; Rsk3. Abl(T315I) showed 69%, and Abl showed 50% inhibition at same concentration.

Common Name: PF-03814735
Synonyms: PF-03814735; PF03814735; PF 0381473
IUPAC Name: N-{2-[6-(4-Cyclobutylamino-5-trifluoromethyl-pyrimidine-2-ylamino)-(1S,4R)-1,2,3,4-tetrahydro-1,4-epiazano-naphthalen-9-yl]-2-oxo-ethyl}-acetamide
CAS Number: 942487-16-3
Mechanism of Action: Kinase Inhibitor; AURKA Inhibitor; AURKB Inhibitor
Indication: Various Cancers
Development Stage: Phase I
Company: Pfizer

The Aurora family of highly related serine/threonine kinases plays a key role in the regulation of mitosis. In mammals, three related Aurora kinases known as Aurora-A (Aurora2, AURKA), Aurora-B (Aurora1, AURKB), and Aurora-C (Aurora3, AURKC) have been identified. Although these kinases have significant sequence homology, their subcellular localization, timing of activation, and biological functions during mitosis are largely distinct from one another. Aurora1 and Aurora2 play important but distinct roles in the G2 and M phases of the cell cycle and are essential for proper chromosome segregation and cell division. Overexpression and amplification of Aurora2 have been reported in different tumor types, including breast, colon, pancreatic, ovarian, and gastric cancer. Overall, these kinases play an important role in centrosome duplication, mitotic spindle formation, chromosome alignment, mitotic checkpoint activation, and cytokinesis.

MDA-MB-231 cells were exposed to PF-03814735 for 4 hours followed by fixation, staining for antibodies specific for various protein kinase substrates and quantitative image analysis. PF-03814735 treatment markedly reduced levels of AURKB phosphorylated on Thr 232 in cells, a sensitive marker of AURKB activity, with an IC50 ~20 nM. PF-03814735 also inhibited the phosphorylation of histone H3 on Ser10, another marker of AURKB kinase activity, with an IC50 ~50 nM. Researchers measured the inhibitory activity of PF-03814735 on the AURKA kinase in this cell line by the loss of cells staining positively for Aurora2 autophosphorylated on Thr288 and observed an IC50 of ~150 nM. These results suggest PF-03814735 was a potent inhibitor of the AURKB and AURKA kinases in cells [1].

Inhibition of cell proliferation by PF-03814735 was evaluated against several human cell lines from various tumor types (HCT-116, HL-60, A549, and H125) as well as tumor cell lines of rat (C6), mouse (L1210), and dog (MDCK) origin. Cell lines were exposed to PF-03814735 in culture for 48 hours followed by determination of cell counts. PF-03814735 treatment resulted in a reduction in cell number relative to untreated control cultures. For this panel of cell lines, the calculated IC50 for PF-03814735 was 42 to 150 nM. PF-03814735 treatment at 300 nM produced near-complete inhibition of proliferation of these cell lines tested. 

Moreover, the antiproliferative effects of PF-03814735 in vivo in mouse tumor models were also consistent with inhibition of Aurora kinases. Researchers observed reductions in levels of phosphorylated histone H3 in xenograft HCT-116 tumors at plasma concentrations associated with tumor growth inhibition in vivo and antiproliferative activity in cell culture. Although the biochemical effects on AURKA and AURKB seem to be the primary basis of the antiproliferative activity seen both in cell culture and in tumors in vivo, but that inhibition of one or more of the off-target kinases contributes to the effects of PF-03814735 cannot be ruled out either [1].

Phase I Study

In an accelerated dose-escalation study to identify the Maximum Tolerated Dose (MTD) and Recommended Phase II Dose, and to obtain proof-of-mechanism (by assessment of pH3 inhibition in tumor biopsies and FDG-PET) with PF-03814735 administered daily for 5 or 10 consecutive days in 3-week cycles,twenty patients (20) received a median of 2 cycles (1-4) across 7 dose levels from 5 to 100 mg/day for 5 days. Tumor types included colorectal (5), breast (3), NSCLC (4), SCLC (2), bladder, melanoma, ovarian, renal, head and neck and cancer of unknown primary (1 each). The dose was doubled in single patient cohorts until treatment-related grade 2 diarrhea occurred in one patient at 40 mg/day. Afterwards, cohorts included 3-7 patients with 20-50% dose increments per cohort. After a single dose, the total clearance of PF-03814735 is 1195±393 mL/hr and median terminal half-life is 19.1 hr. PK of PF-3814735 is linear [2].

In the first 16 patients, the most common treatment-related adverse events were mild to moderate diarrhea (50%), vomiting (25%), anorexia, fatigue, and nausea (19% each). Dose-limiting febrile neutropenia was observed in 2/7 patients treated at 100 mg/day [2].

1. Jakubczak, J. L.; et. al. PF-03814735, an Orally Bioavailable Small Molecule Aurora Kinase Inhibitor for Cancer Therapy. Mol Cancer Ther 2010, 9(4), 883-894.
2. Jones, S. F.; et. al. Phase I accelerated dose-escalation, pharmacokinetic (PK) and pharmacodynamic study of PF-03814735, an oral aurora kinase inhibitor, in patients with advanced solid tumors: Preliminary results. J Clin Oncol 2008, 26(15 suppl), 2517.
3. ClinicalTrials.gov Phase 1 Study Of Aurora Kinase Inhibitor PF-03814735 In Patients With Advanced Solid Tumors. NCT00424632 (retrieved 25-10-2015)