[Show abstract][Hide abstract] ABSTRACT: ABT-348 is a novel ATP-competitive Aurora inhibitor with nanomolar potency (IC50) for inhibiting binding and cellular auto-phosphorylation of Aurora B (7 and 13 nM), C (1 and 13 nM) and A (120 and 189 nM). Cellular activity against Aurora B is reflected by inhibition of phosphor-H3, induction of polyploidy, and inhibition of proliferation of a variety of leukemia, lymphoma, and solid tumor cell lines (IC50 values 0.3 - 21 nM). In vivo inhibition of Aurora B was confirmed in an engrafted leukemia model by observing a decrease in phosphorylation of histone H3 that persisted in a dose-dependent manner for 8 hours and correlated with plasma concentration of ABT 348. Evaluation of ABT 348 across a panel of 128 kinases revealed additional potent binding activity (Ki values <30 nM) against VEGFR/PDGFR families and the SRC family of cytoplasmic tyrosine kinases. VEGFR/PDGFR binding activity correlated with inhibition of auto-phosphorylation in cells and inhibition of VEGF-stimulated endothelial cell proliferation (IC50 ≤0.3 nM). Evidence of on-target activity in vivo was provided by the potency for blocking VEGF-mediated vascular permeability and for inducing plasma PlGF. Activity against the Src kinase family was evident in anti-proliferative activity against BCR-ABL CML cells and cells expressing the gleevec-resistant BCR-ABL T315I mutation. Based upon its unique spectrum of activity, ABT 348 was evaluated and found effective in representative solid tumor (HT1080 and MiaPaCa, tumor stasis) and hematological malignancy (RS4;11, regression) xenografts. These results provide the rationale for clinical assessment of ABT-348 as a therapeutic agent in the treatment of cancer.
Journal of Pharmacology and Experimental Therapeutics 08/2012; 343(3). DOI:10.1124/jpet.112.197087 · 3.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In an effort to identify kinase inhibitors with dual KDR/Aurora B activity and improved aqueous solubility compared to the Abbott dual inhibitor ABT-348, a series of novel pyrazole pyrimidines structurally related to kinase inhibitor AS703569 were prepared. SAR work provided analogs with significant cellular activity, measureable aqueous solubility and moderate antitumor activity in a mouse tumor model after weekly ip dosing. Unfortunately these compounds were pan-kinase inhibitors that suffered from narrow therapeutic indices which prohibited their use as antitumor agents.
[Show abstract][Hide abstract] ABSTRACT: Linifanib (ABT-869) is a multitargeted receptor tyrosine kinase inhibitor. This work aims to evaluate F-fluorodeoxyglucose-positron emission tomography (FDG-PET) as a pharmacodynamic (PD) biomarker for linifanib treatment utilizing the Calu-6 model of human non-small cell lung (NSCLC) cancer in SCID-beige mice. Animals received either vehicle or 12.5 mg/kg linifanib orally twice a day for the duration of the study. Imaging was performed at -1, 1, 3, and 7 days after beginning treatment (n = 12-14 per group). Linifanib inhibited tumor growth and suppressed tumor metabolic activity. Changes in tumor FDG uptake were observed as early as 1 day after beginning linifanib treatment and were sustained for the duration of the study. This study confirms that linifanib is efficacious in this xenograft model of human NSCLC and confirms FDG-PET is a potential PD biomarker strategy for linifanib therapy.
Cancer Chemotherapy and Pharmacology 02/2012; 69(6):1669-72. DOI:10.1007/s00280-012-1840-z · 2.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Longitudinal changes of 3'-[(18) F]fluoro-3'-deoxythymidine (FLT) and 2-deoxy-2-[(18) F]fluoro-D-glucose (FDG) in response to irinotecan therapy in an animal model of colorectal cancer were compared.
SCID/CB-17 mice with HCT116 tumors were treated with 50 mg/kg irinotecan by intraperitoneal injection weekly for 3 weeks. FLT and FDG-positron emission tomography (PET) were performed at baseline, the day after each treatment, and 5 days after the first treatment. Proliferation and apoptosis were evaluated by immunohistochemistry (IHC) after day 15 of imaging.
Irinotecan treatment resulted in a suppression of tumor growth. Tumor FLT uptake was decreased the day after each treatment but to a lesser extent 5 days after the first treatment. FDG uptake increased the day after each treatment with a continuous increase throughout the experiment. IHC analysis of phospho-H3 and Ki67 confirmed FLT-PET results, indicating a decrease in proliferation the day after the final irinotecan treatment. Increased apoptosis monitored by caspase-3 was observed after day 15 with irinotecan treatment.
FLT-PET may be a better method than FDG-PET for assessing treatment response to irinotecan. Changes in imaging occur before changes in tumor volume.
Molecular imaging and biology: MIB: the official publication of the Academy of Molecular Imaging 12/2011; 14(5):617-24. DOI:10.1007/s11307-011-0529-8 · 2.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tyrosine kinase inhibitors represent a class of targeted therapy that has proven to be successful for cancer treatment. Linifanib is a novel, orally active multi-targeted receptor tyrosine kinase (RTK) inhibitor that exhibits potent antitumor and antiangiogenic activities against a broad spectrum of experimental tumors and malignancies in patients. The compound is currently being evaluated in phase 2 and 3 clinical trials. To investigate the effectiveness of linifinib against gliomas and the mechanism of drug action, we characterized treatment-induced antitumor and antiangiogenic responses to linifanib in an orthotopic rat glioma model. The effect of linifanib treatment on tumor growth was determined by tumor volume assessment using anatomical magnetic resonance imaging (MRI). Changes in tumor microvessel function were evaluated with dynamic contrast-enhanced MRI (DCE-MRI). Immunohistochemistry (IHC) was applied to excised tumor samples to examine underlying changes in vascular structures and target receptor expression. Linifanib (10 mg/kg) given twice daily inhibited tumor growth following treatment for 7 days with tumor volumes being 149 ± 30 and 66 ± 7 mm(3) for vehicle-and linifanib-treated groups, respectively. A significant reduction of 37 ± 13% in tumor perfusion and microvessel permeability (measured by K (trans)) was observed as early as 2 h after administration compared with vehicle treatment. Continuous linifanib administration further reduced K (trans) at later time points until the end of the study (7 days post-treatment). At day 7, K (trans) was reduced by 75 ± 32% for linifanib treatment compared with vehicle treatment. Significant reduction in total blood vessel density and improved vessel wall integrity were observed, and staining for target receptor expression confirmed inhibition of phospho VEGFR-2 and PDGFR-β by linifanib treatment. These results demonstrate significant antitumor and antiangiogenic activity against gliomas by linifanib, a property that may result from the inhibition of VEGFR-2 and PDGFR-β-mediated vascular changes. DCE-MRI measured K (trans) changes at early treatment stages may be a useful pharmacodynamic marker for linifanib activity in clinical trials, and basal K (trans) may provide predictive value for tumor progression.
Cancer Chemotherapy and Pharmacology 11/2011; 69(4):911-21. DOI:10.1007/s00280-011-1740-7 · 2.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 7-Aminopyrazolo[1,5- a]pyrimidine urea receptor tyrosine kinase inhibitors have been discovered. Investigation of structure-activity relationships of the pyrazolo[1,5- a]pyrimidine nucleus led to a series of 6-(4- N, N'-diphenyl)ureas that potently inhibited a panel of vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR) kinases. Several of these compounds, such as 34a, are potent inhibitors of kinase insert domain-containing receptor tyrosine kinase (KDR) both enzymatically (<10 nM) and cellularly (<10 nM). In addition, compound 34a possesses a favorable pharmacokinetic profile and demonstrates efficacy in the estradiol-induced murine uterine edema (UE) model (ED 50 = 1.4 mg/kg).
[Show abstract][Hide abstract] ABSTRACT: Tumor angiogenesis is mediated by KDR and other VEGFR and PDGFR kinases. Their inhibition presents an attractive approach for developing anticancer therapeutics. Here, we report a series of aminopyrazolopyridine ureas as potent VEGFR/PDGFR multitargeted kinase inhibitors. A number of compounds have been identified to be orally bioavailable and efficacious in the mouse edema model.
[Show abstract][Hide abstract] ABSTRACT: In our continued efforts to search for potent and novel receptor tyrosine kinase (RTK) inhibitors as potential anticancer agents, we discovered, through a structure-based design, that 3-aminoindazole could serve as an efficient hinge-binding template for kinase inhibitors. By incorporating an N,N'-diaryl urea moiety at the C4-position of 3-aminodazole, a series of RTK inhibitors were generated, which potently inhibited the tyrosine kinase activity of the vascular endothelial growth factor receptor and the platelet-derived growth factor receptor families. A number of compounds with potent oral activity were identified by utilizing an estradiol-induced mouse uterine edema model and an HT1080 human fibrosarcoma xenograft tumor model. In particular, compound 17p (ABT-869) was found to possess favorable pharmacokinetic profiles across different species and display significant tumor growth inhibition in multiple preclinical animal models.
[Show abstract][Hide abstract] ABSTRACT: ABT-869 is a structurally novel, receptor tyrosine kinase (RTK) inhibitor that is a potent inhibitor of members of the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) receptor families (e.g., KDR IC50 = 4 nmol/L) but has much less activity (IC50s > 1 micromol/L) against unrelated RTKs, soluble tyrosine kinases, or serine/threonine kinases. The inhibition profile of ABT-869 is evident in cellular assays of RTK phosphorylation (IC50 = 2, 4, and 7 nmol/L for PDGFR-beta, KDR, and CSF-1R, respectively) and VEGF-stimulated proliferation (IC50 = 0.2 nmol/L for human endothelial cells). ABT-869 is not a general antiproliferative agent because, in most cancer cells, >1,000-fold higher concentrations of ABT-869 are required for inhibition of proliferation. However, ABT-869 exhibits potent antiproliferative and apoptotic effects on cancer cells whose proliferation is dependent on mutant kinases, such as FLT3. In vivo ABT-869 is effective orally in the mechanism-based murine models of VEGF-induced uterine edema (ED50 = 0.5 mg/kg) and corneal angiogenesis (>50% inhibition, 15 mg/kg). In tumor growth studies, ABT-869 exhibits efficacy in human fibrosarcoma and breast, colon, and small cell lung carcinoma xenograft models (ED50 = 1.5-5 mg/kg, twice daily) and is also effective (>50% inhibition) in orthotopic breast and glioma models. Reduction in tumor size and tumor regression was observed in epidermoid carcinoma and leukemia xenograft models, respectively. In combination, ABT-869 produced at least additive effects when given with cytotoxic therapies. Based on pharmacokinetic analysis from tumor growth studies, efficacy correlated more strongly with time over a threshold value (cellular KDR IC50 corrected for plasma protein binding = 0.08 microg/mL, >or=7 hours) than with plasma area under the curve or Cmax. These results support clinical assessment of ABT-869 as a therapeutic agent for cancer.
Molecular Cancer Therapeutics 05/2006; 5(4):995-1006. DOI:10.1158/1535-7163.MCT-05-0410 · 5.68 Impact Factor