Because of the critical roles of aberrant signaling in cancer, both c-MET and ALK receptor tyrosine kinases are attractive oncology targets for therapeutic intervention. The cocrystal structure of 3 (PHA-665752), bound to c-MET kinase domain, revealed a novel ATP site environment, which served as the target to guide parallel, multiattribute drug design. A novel 2-amino-5-aryl-3-benzyloxypyridine series was created to more effectively make the key interactions achieved with 3. In the novel series, the 2-aminopyridine core allowed a 3-benzyloxy group to reach into the same pocket as the 2,6-dichlorophenyl group of 3 via a more direct vector and thus with a better ligand efficiency (LE). Further optimization of the lead series generated the clinical candidate crizotinib (PF-02341066), which demonstrated potent in vitro and in vivo c-MET kinase and ALK inhibition, effective tumor growth inhibition, and good pharmaceutical properties.

The c-Met receptor tyrosine kinase and its ligand, hepatocyte growth factor (HGF), have been implicated in the progression of several human cancers and are attractive therapeutic targets.

A t(2;5) chromosomal translocation resulting in expression of an oncogenic kinase fusion protein known as nucleophosmin-anaplastic lymphoma kinase

Purpose: Axitinib (AG-013736) is a potent and selective inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases 1to 3 that is in clinical development for the treatment of solid tumors. We provide a comprehensive description of its in vitro characteristics and activities, in vivo antiangiogenesis, and antitumor efficacy and translational pharmacology data. Experimental Design: The potency, kinase selectivity, pharmacologic activity, and antitumor efficacy of axitinib were assessed in various nonclinical models. Results: Axitinib inhibits cellular autophosphorylation of VEGF receptors (VEGFR) with picomolar IC 50 values. Counterscreening across multiple kinase and protein panels shows it is selective for VEGFRs. Axitinib blocks VEGF-mediated endothelial cell survival, tube formation, and downstream signaling through endothelial nitric oxide synthase, Akt and extracellular signal-regulated kinase. Following twice daily oral administration, axitinib produces consistent and dose-dependent antitumor efficacy that is associated with blocking VEGFR-2 phosphorylation, vascular permeability, angiogenesis, and concomitant induction of tumor cell apoptosis. Axitinib in combination with chemotherapeutic or targeted agents enhances antitumor efficacy in many tumor models compared with single agent alone. Dose scheduling studies in a human pancreatic tumor xenograft model show that simultaneous administration of axitinib and gemcitabine without prolonged dose interruption or truncation of axitinib produces the greatest antitumor efficacy. The efficacious drug concentrations predicted in nonclinical studies are consistent with the range achieved in the clinic. Although axitinib inhibits platelet-derived growth factor receptors and KIT with nanomolar in vitro potencies, based on pharmacokinetic/pharmacodynamic analysis, axitinib acts primarily as a VEGFR tyrosine kinase inhibitor at the current clinical exposure. Conclusions: The selectivity, potency for VEGFRs, and robust nonclinical activity may afford broad opportunities for axitinib to improve cancer therapy.

SUMMARY We report the preclinical evaluation of PF-06463922, a potent and brain penetrant ALK/ROS1 inhibitor. Compared to other clinically available ALK inhibitors, PF-06463922 displayed superior potency against all known clinically acquired ALK mutations, including the highly resistant G1202R mutant. Furthermore, PF-06463922 treatment led to regression of EML4-ALK driven brain metastases, leading to prolonged mouse survival, in a superior manner. Finally, PF-06463922 demonstrated high selectivity and safety margins in a variety of preclinical studies. These results suggest that PF-06463922 will be highly effective for the treatment of patients with ALK-driven lung cancers, including those who relapsed on clinically available ALK inhibitors due to secondary ALK kinase domain mutations and/or due to the failed control of brain metastases.

This work provides a perspective on the qualification and verification of physiologically based pharmacokinetic (PBPK) platforms/models intended for regulatory submission based on the collective experience of the Simcyp Consortium members. Examples of regulatory submission of PBPK analyses across various intended applications are presented and discussed. European Medicines Agency (EMA) and US Food and Drug Administration (FDA) recent draft guidelines regarding PBPK analyses and reporting are encouraging, and to advance the use and acceptability of PBPK analyses, more clarity and flexibility are warranted.

Acute, s.c. administration of a ␥-secretase inhibitor, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), to young PDAPP mice dose dependently decreases cortical amyloid-␤ (A␤). The present studies replicated these findings in Tg2576 mice and examined further whether DAPT would reduce cerebrospinal fluid (CSF) A␤ comparably in young (plaque-free) and aged (plaque-bearing) mice. In the first study, vehicle or DAPT (10, 30, or 100 mg/kg s.c.) administered to young Tg2576 mice (6 months old) dose dependently reduced A␤ peptide levels in the cortex as seen previously in the PDAPP mice. Additionally, a dose-dependent decrease in plasma A␤ levels was evident. The same dosing regime was applied next to aged mice (17 months old) to assess A␤ changes in the CSF in addition to plasma and brains. DAPT dose dependently reduced A␤ levels in the CSF and plasma, but not in the brain wherein A␤ levels were 400 to 500 times higher than those in young mice, consistent with a large pool of A␤ extracted from amyloid deposits. In subsequent studies, effects of oral DAPT (100 or 200 mg/kg) were examined concurrently in young and aged mice. DAPT reduced A␤ levels in CSF and plasma to a similar extent at both ages. In contrast, DAPT reduced brain A␤ levels primarily in young mice, with minimal effects in aged mice. These results demonstrate that A␤ levels in CSF and plasma decrease dose dependently after ␥-secretase inhibition, and this response is not affected by amyloid plaque burden. We conclude that CSF and plasma A␤ may offer a clinically applicable, mechanism-based biomarker for inhibitors of A␤ production.

ABSTRACT:(R)-3-[1-(2,6-Dichloro-3-fluoro-phenyl)-ethoxy]-5-(1-piperidin-4-yl-1H-pyrazol-4-yl)-pyridin-2-ylamine (PF02341066) was identified as an orally available, ATP-competitive small molecule inhibitor of cMet receptor tyrosine kinase. The objectives of the present studies were to characterize 1) the pharmacokinetic-pharmacodynamic relationship of the plasma concentrations of PF02341066 to cMet phosphorylation in tumor (biomarker) and 2) the relationship of cMet phosphorylation to antitumor efficacy (pharmacological response). Athymic mice implanted with GTL16 gastric carcinoma or U87MG glioblastoma xenografts were treated with PF02341066 once daily at doses selected to encompass ED 50 values. Plasma concentrations of PF02341066 were best described by a one-compartment pharmacokinetic model. A time-delay (hysteresis) was observed between the plasma concentrations of PF02341066 and the cMet phosphorylation response. A link model was therefore used to account for this hysteresis. The model fitted the time courses of cMet phosphorylation well, suggesting that the main reason for the hysteresis is a rate-limiting distribution from plasma into tumor. The EC 50 and EC 90 values were estimated to be 19 and 167 ng/ml, respectively. For tumor growth inhibition, the exponential tumor growth model fitted the time courses of individual tumor growth inhibition well. The EC 50 for the GTL16 tumor growth inhibition was estimated to be 213 ng/ml. Thus, the EC 90 for the inhibition of cMet phosphorylation corresponded to the EC 50 for the tumor growth inhibition, suggesting that near-complete inhibition of cMet phosphorylation (>90%) is required to significantly inhibit tumor growth (>50%). The present results will be helpful in determining the appropriate dosing regimen and in guiding dose escalation to rapidly achieve efficacious systemic exposure in the clinic.Pharmacokinetic-pharmacodynamic (PKPD) modeling is increasingly being applied in drug discovery and development. Specific applications include 1) the selection of drug candidates with most favorable PKPD properties and 2) the prediction of exposure response in patients with the aim of optimizing the design of early clinical trials. The increased understanding of drug action derived from PKPD-based drug development leads to more information, especially with regard to the identification of drug dosage regimen that results in optimal therapeutic outcome (Derendorf et al., 2000;Lesko et al., 2000;Chien et al., 2005). The use of PKPD modeling in this context relies on prediction of the time course of drug effects in patients, using information from preclinical investigation. Preclinical studies are useful alternatives to investigate PKPD relationships to get insight into the in vivo mechanism of drug action. The integration of PKPD modeling and simulation in drug development has provided opportunities to accelerate the evaluation of new chemical entities in the clinic. Thus, the PKPD investigation could contribute to shortening the overall period of drug development.