Michael B. Bass

Safety, Pharmacokinetics, and Efficacy of AMG 706, an Oral Multikinase Inhibitor, in Patients With Advanced Solid Tumors

PURPOSE AMG 706 is an investigational, orally bioavailable inhibitor of vascular endothelial growth factor receptors 1, 2, and 3, platelet-derived growth factor receptor, and stem-cell factor receptor. This phase I, dose-finding study evaluated the safety, pharmacokinetics, and pharmacodynamics of AMG 706 in patients with refractory advanced solid tumors. PATIENTS AND METHODS AMG 706 was administered at escalating doses of 50 to 175 mg once daily or 25 mg bid for the first 21 days of a 28-day cycle. The 125-mg once-daily dose was also administered continuously. The maximum-tolerated dose (MTD), safety, pharmacokinetics, tumor response, and serum levels of proangiogenic markers were determined. RESULTS Seventy-one patients received AMG 706. The MTD was 125 mg once daily administered continuously. The most frequent adverse events were fatigue (55%), diarrhea (51%), nausea (44%), and hypertension (42%). Plasma AMG 706 concentrations increased in a dose-proportional manner with no accumulation after multiple doses. Five patients (7%) had a partial response, 35 patients (49%) had stable disease (at least through day 50), and 31 patients (44%) had progressive disease. Changes in tumor size correlated significantly with an increase in placental growth factor (P = .003) and a decrease in soluble kinase domain receptor (P = .001). CONCLUSION In this study of patients with advanced refractory solid tumors, AMG 706 was well tolerated and displayed favorable pharmacokinetics and evidence of antitumor activity. Additional studies of AMG 706 as monotherapy and in combination with various agents are ongoing.

Cyclin E2, a novel G1 cyclin that binds Cdk2 and is aberrantly expressed in human cancers.

ABSTRACT A novel cyclin gene was discovered by searching an expressed sequence tag database with a cyclin box profile. The human cyclin E2 gene encodes a 404-amino-acid protein that is most closely related to cyclin E. Cyclin E2 associates with Cdk2 in a functional kinase complex that is inhibited by both p27Kip1 and p21Cip1. The catalytic activity associated with cyclin E2 complexes is cell cycle regulated and peaks at the G1/S transition. Overexpression of cyclin E2 in mammalian cells accelerates G1, demonstrating that cyclin E2 may be rate limiting for G1 progression. Unlike cyclin E1, which is expressed in most proliferating normal and tumor cells, cyclin E2 levels were low to undetectable in nontransformed cells and increased significantly in tumor-derived cells. The discovery of a novel second cyclin E family member suggests that multiple unique cyclin E-CDK complexes regulate cell cycle progression.

Prediction of Nephrotoxicant Action and Identification of Candidate Toxicity-Related Biomarkers

A vast majority of pharmacological compounds and their metabolites are excreted via the urine, and within the complex structure of the kidney, the proximal tubules are a main target site of nephrotoxic compounds. We used the model nephrotoxicants mercuric chloride, 2-bromoethylamine hydrobromide, hexachlorobutadiene, mitomycin, amphotericin, and puromycin to elucidate time- and dose-dependent global gene expression changes associated with proximal tubular toxicity. Male Sprague–Dawley rats were dosed via intraperitoneal injection once daily for mercuric chloride and amphotericin (up to 7 doses), while a single dose was given for all other compounds. Animals were exposed to 2 different doses of these compounds and kidney tissues were collected on day 1, 3, and 7 postdosing. Gene expression profiles were generated from kidney RNA using 17K rat cDNA dual dye microarray and analyzed in conjunction with histopathology. Analysis of gene expression profiles showed that the profiles clustered based on similarities in the severity and type of pathology of individual animals. Further, the expression changes were indicative of tubular toxicity showing hallmarks of tubular degeneration/regeneration and necrosis. Use of gene expression data in predicting the type of nephrotoxicity was then tested with a support vector machine (SVM)-based approach. A SVM prediction module was trained using 120 profiles of total profiles divided into four classes based on the severity of pathology and clustering. Although mitomycin C and amphotericin B treatments did not cause toxicity, their expression profiles were included in the SVM prediction module to increase the sample size. Using this classifier, the SVM predicted the type of pathology of 28 test profiles with 100% selectivity and 82% sensitivity. These data indicate that valid predictions could be made based on gene expression changes from a small set of expression profiles. A set of potential biomarkers showing a time- and dose-response with respect to the progression of proximal tubular toxicity were identified. These include several transporters (Slc21a2, Slc15, Slc34a2), Kim 1, IGFbp-1, osteopontin, α-fibrinogen, and Gstα.

Biomarkers as Predictors of Response to Treatment with Motesanib in Patients with Progressive Advanced Thyroid Cancer

CONTEXT Antiangiogenic therapies have shown potential in the treatment of advanced thyroid cancer, but it is uncertain which patients are most likely to benefit from therapy. OBJECTIVE This prespecified exploratory analysis investigated whether baseline levels and/or changes in circulating biomarkers could predict tumor response and/or progression-free survival (PFS) among patients enrolled in a phase 2 study of motesanib in advanced thyroid cancer. DESIGN/SETTING/PATIENTS Patients with progressive locally advanced or metastatic medullary or differentiated thyroid cancer received motesanib 125 mg once daily for up to 48 wk in a phase 2 interventional study. Samples for assessment of circulating biomarkers of angiogenesis or apoptosis were collected at study wk 1 (baseline), 2, 4, 8, 16, 24, 32, 40, 48, and 4 wk after cessation of motesanib treatment. Tumor response was assessed per Response Evaluation Criteria in Solid Tumors by independent review. RESULTS Change from baseline in serum placental growth factor (PlGF) after 1 wk of treatment correlated with best tumor response (Kendall rank correlation, 0.28; P < 0.0001). Using a Fisher exact test, the most significant separation between patients who had an objective response and those who did not was at a 4.7-fold increase in PlGF. The response rate among patients with a greater than 4.7-fold increase in PlGF was 30% compared with 3% below this threshold. There was also a significant separation between responders and nonresponders at a 1.6-fold decrease in soluble vascular endothelial growth factor (VEGF) receptor 2 after 3 wk of treatment. Patients with baseline serum VEGF less than 671 pg/ml had significantly longer PFS times than the remainder of patients. CONCLUSIONS Changes in PlGF and soluble VEGF receptor 2 levels after initiation of therapy predicted response to motesanib in patients with advanced differentiated thyroid cancer or metastatic medullary thyroid cancer. Lower baseline VEGF levels were associated with longer PFS.

Phase 1 Study of AMG 386, a Selective Angiopoietin 1/2–Neutralizing Peptibody, in Combination with Chemotherapy in Adults with Advanced Solid Tumors

Purpose: To evaluate the safety, pharmacokinetics, and antitumor activity of AMG 386, an investigational selective angiopoietin 1/2-neutralizing peptibody, in combination with FOLFOX-4 (F), carboplatin/paclitaxel (C/P), or docetaxel (D), in adult patients with advanced solid tumors. Experimental Design: Three cohorts of patients (F, n = 6; C/P, n = 8; D, n = 12) received one full cycle of chemotherapy alone during the pretreatment phase, followed by administration of AMG 386 10 mg/kg i.v. weekly in combination with chemotherapy until disease progression or intolerance. Safety and tolerability, tumor response, pharmacokinetic profiles, and biomarkers were assessed. Results: Twenty-six patients were enrolled; 22 received treatment with AMG 386. No dose-limiting toxicities or grade 3 or 4 adverse events related to AMG 386 were reported. The most common adverse events were diarrhea and hypomagnesemia (n = 3 each). One patient developed grade 2 hypertension and one had grade 1 subconjunctival eye hemorrhage. No neutralizing antibodies to AMG 386 were detected. There were no pharmacokinetic interactions between AMG 386 and F, C/P, or D. One patient receiving AMG 386 plus C/P for bladder cancer refractory to gemcitabine/cisplatin had a complete response at week 8. The remaining best tumor responses were partial response (n = 3, one from each cohort), stable disease ≥8 weeks (n = 13), and progressive disease (n = 1). Conclusions: Weekly administration of AMG 386 in combination with three common chemotherapy regimens was well tolerated in patients with advanced solid tumors. No pharmacokinetic interactions between AMG 386 and any of the tested chemotherapy regimens were noted. Promising antitumor activity was observed with all three treatment combinations. Clin Cancer Res; 16(11); 3044–56. ©2010 AACR.

AMG 386 in Combination With Sorafenib in Patients With Metastatic Clear Cell Carcinoma of the Kidney: A Randomized, Double-Blind, Placebo-Controlled, Phase 2 Study

This study evaluated the tolerability and antitumor activity of AMG 386, a peptibody (a peptide Fc fusion) that neutralizes the interaction of angiopoietin‐1 and angiopoietin‐2 with Tie2 (tyrosine kinase with immunoglobulin‐like and EGF‐like domains 2), plus sorafenib in patients with clear cell metastatic renal cell carcinoma (mRCC) in a randomized controlled study.

Sources of variation in baseline gene expression levels from toxicogenomics study control animals across multiple laboratories

BackgroundThe use of gene expression profiling in both clinical and laboratory settings would be enhanced by better characterization of variance due to individual, environmental, and technical factors. Meta-analysis of microarray data from untreated or vehicle-treated animals within the control arm of toxicogenomics studies could yield useful information on baseline fluctuations in gene expression, although control animal data has not been available on a scale and in a form best served for data-mining.ResultsA dataset of control animal microarray expression data was assembled by a working group of the Health and Environmental Sciences Institutes Technical Committee on the Application of Genomics in Mechanism Based Risk Assessment in order to provide a public resource for assessments of variability in baseline gene expression. Data from over 500 Affymetrix microarrays from control rat liver and kidney were collected from 16 different institutions. Thirty-five biological and technical factors were obtained for each animal, describing a wide range of study characteristics, and a subset were evaluated in detail for their contribution to total variability using multivariate statistical and graphical techniques.ConclusionThe study factors that emerged as key sources of variability included gender, organ section, strain, and fasting state. These and other study factors were identified as key descriptors that should be included in the minimal information about a toxicogenomics study needed for interpretation of results by an independent source. Genes that are the most and least variable, gender-selective, or altered by fasting were also identified and functionally categorized. Better characterization of gene expression variability in control animals will aid in the design of toxicogenomics studies and in the interpretation of their results.

Sclerostin expression is induced by BMPs in human Saos-2 osteosarcoma cells but not via direct effects on the sclerostin gene promoter or ECR5 element

Sclerostin is a secreted inhibitor of Wnt signaling and plays an essential role in the regulation of bone mass. The expression of sclerostin is largely restricted to osteocytes although its mode of transcriptional regulation is not well understood. We observed regulated expression of sclerostin mRNA and protein that was directly correlated with the mineralization response in cultured human Saos-2 osteosarcoma cells and rat primary calvarial cells. Sclerostin mRNA and protein levels were increased following treatment of cells with BMP2, BMP4 and BMP7. Analysis of deletion mutants from the -7.4 kb upstream region of the human sclerostin promoter did not reveal any specific regions that were responsive to BMPs, Wnt3a, PTH, TGFβ1 or Activin A in Saos-2 cells. The downstream ECR5 element did not show enhancer activity in Saos-2 cells and also was not affected when Saos-2 cells were treated with BMPs or PTH. Genome-wide microarray analysis of Saos-2 cells treated with BMP2 showed significant changes in expression of several transcription factors with putative consensus DNA binding sites in the region of the sclerostin promoter. However, whereas most factors tested showed either a range of inhibitory activity (DLX family, MSX2, HEY1, SMAD6/7) or lack of activity on the sclerostin promoter including SMAD9, only MEF2B showed a positive effect on both the promoter and ECR5 element. These results suggest that the dramatic induction of sclerostin gene expression by BMPs in Saos-2 cells occurs indirectly and is associated with late stage differentiation of osteoblasts and the mineralization process.

New variants in the Enpp1 and Ptpn6 genes cause low BMD, crystal-related arthropathy, and vascular calcification.

A large genome‐wide, recessive, N‐ethyl‐N‐nitrosourea (ENU)‐induced mutagenesis screen was performed on a mixed C57BL/6J and C3H.SW‐H2/SnJ mouse background to identify genes regulating bone mass. Approximately 6500 male and female G3 hybrid mice were phenotyped at 8 and 10 wk of age by DXA analysis for evidence of changes in unadjusted or body weight–adjusted BMD or BMC. Phenodeviant lines were identified based on statistical criteria that included a false discovery rate (FDR) <20% and Z‐score >2.8. Genome‐wide mapping scans were initiated on 22 lines, with evidence of high or low BMD or BMC that deviated by approximately −30% to +50% from the means. Several lines were discontinued as showing lack of heritability, but two heritable lines were identified with narrow chromosomal regions that allowed sequencing of potential mutant candidate genes. Novel mutations were identified in the Enpp1 (C397S) gene on chromosome 10 (line 4482) and the Ptpn6 (I482F) gene on chromosome 6 (line 4489) that were both associated with low bone mass. In addition, the phenotype of the Enpp1 mice showed a striking joint disease and calcification of blood vessels including the aorta, myocardium, and renal arteries and capillaries. These results support a role for the Enpp1 gene in the pathogenesis associated with mineralization of articular cartilage and vascular calcification. This work confirms the utility of the chemical mutagenesis approach for identification of potential disease genes and confirms the role of Enpp1 and Ptpn6 in regulating mineralization and skeletal bone mass.

A phase I, open-label study of trebananib combined with sorafenib or sunitinib in patients with advanced renal cell carcinoma.

BACKGROUND Trebananib, an investigational peptibody, binds to angiopoietin 1 and 2, thereby blocking their interaction with Tie2. PATIENTS AND METHODS This open-label phase I study examined trebananib 3 mg/kg or 10 mg/kg intravenous (I.V.) once weekly plus sorafenib 400 mg twice per day or sunitinib 50 mg once per day in advanced RCC. Primary end points were adverse event incidence and pharmacokinetics. RESULTS Thirty-seven patients were enrolled. During trebananib plus sorafenib administration (n = 17), the most common treatment-related adverse events (TRAEs) included rash (n = 12; 71%), diarrhea (n = 12; 71%), hypertension (n = 11; 65%), and fatigue (n = 11; 65%); grade ≥ 3 TRAEs (n = 7; 41%); and 2 patients (12%) had peripheral edema. During trebananib plus sunitinib administration (n = 19), the most common TRAEs included diarrhea (n = 14; 74%), fatigue (n = 13; 68%), hypertension (n = 11; 58%), and decreased appetite (n = 11; 58%); grade ≥ 3 TRAEs (n = 13; 68%); and 8 (42%) patients had peripheral edema. Trebananib did not appear to alter the pharmacokinetics of sorafenib or sunitinib. No patient developed anti-trebananib antibodies. Objective response rates were 29% (trebananib plus sorafenib) and 53% (trebananib plus sunitinib). CONCLUSION The toxicities of trebananib 3 mg/kg or 10 mg/kg I.V. plus sorafenib or sunitinib in RCC were similar to those of sorafenib or sunitinib monotherapy, with peripheral edema being likely specific to the combinations. Antitumor activity was observed.