Preclinical optimization of MDM2 antagonist scheduling for cancer treatment by using a model-based approach.

Purpose: Antitumor clinical activity has been demonstrated for the MDM2 antagonist RG7112, but patient tolerability for the necessary daily dosing was poor. Here, utilizing RG7388, a second-generation nutlin with superior selectivity and potency, we determine the feasibility of intermittent dosing to guide the selection of initial phase I scheduling regimens.

Experimental Design: A pharmacokinetic-pharmacodynamic (PKPD) model was developed on the basis of preclinical data to determine alternative dosing schedule requirements for optimal RG7388-induced antitumor activity.

Discovery of a highly potent, orally active mitosis/angiogenesis inhibitor r1530 for the treatment of solid tumors.

A new series of 7,8-disubstituted pyrazolobenzodiazepines based on the lead compound 1 have been synthesized and evaluated for their effects on mitosis and angiogenesis. Described herein is the design, synthesis, SAR, and antitumor activity of these compounds leading to the identification of R1530, which was selected for clinical evaluation.

MDM2 small-molecule antagonist RG7112 activates p53 signaling and regresses human tumors in preclinical cancer models.

MDM2 negatively regulates p53 stability and many human tumors overproduce MDM2 as a mechanism to restrict p53 function. Thus, inhibitors of p53-MDM2 binding that can reactivate p53 in cancer cells may offer an effective approach for cancer therapy. RG7112 is a potent and selective member of the nutlin family of MDM2 antagonists currently in phase I clinical studies.

Resistance to selective BRAF inhibition can be mediated by modest upstream pathway activation.

A high percentage of patients with BRAF(V600E) mutant melanomas respond to the selective RAF inhibitor vemurafenib (RG7204, PLX4032) but resistance eventually emerges. To better understand the mechanisms of resistance, we used chronic selection to establish BRAF(V600E) melanoma clones with acquired resistance to vemurafenib. These clones retained the V600E mutation and no second-site mutations were identified in the BRAF coding sequence.

Antitumor activity of BRAF inhibitor vemurafenib in preclinical models of BRAF-mutant colorectal cancer.

The protein kinase BRAF is a key component of the RAS-RAF signaling pathway which plays an important role in regulating cell proliferation, differentiation, and survival. Mutations in BRAF at codon 600 promote catalytic activity and are associated with 8% of all human (solid) tumors, including 8% to 10% of colorectal cancers (CRC). Here, we report the preclinical characterization of vemurafenib (RG7204; PLX4032; RO5185426), a first-in-class, specific small molecule inhibitor of BRAF(V600E) in BRAF-mutated CRC cell lines and tumor xenograft models.

Preclinical evaluation of the novel multi-targeted agent R1530.

Purpose: This study describes the antiproliferative activity of the multikinase inhibitor R1530 in vitro and its antitumor and anti-angiogenic activity, pharmacokinetics, and tolerability in vivo.

Methods: The antiproliferative activity of R1530 was investigated in a range of human tumor, endothelial and fibroblast cell lines. Tolerability and antitumor activity were assessed in mice bearing a range of human tumor xenografts, and anti-angiogenic properties were established in the murine corneal pocket assay.

MDM2 antagonists boost antitumor effect of androgen withdrawal: implications for therapy of prostate cancer.

Background: Hormone therapy is the standard of care for newly diagnosed or recurrent prostate cancers. It uses anti-androgen agents, castration, or both to eliminate cancer promoting effect of testicular androgen. The p53 tumor suppressor controls a major pathway that can block cell proliferation or induce apoptosis in response to diverse forms of oncogenic stress.

High tumor levels of IL6 and IL8 abrogate preclinical efficacy of the γ-secretase inhibitor, RO4929097.

Interest continues to build around the early application of patient selection markers to prospectively identify patients likely to show clinical benefit from cancer therapies. Hypothesis generation and clinical strategies often begin at the preclinical stage where responder and nonresponder tumor cell lines are first identified and characterized. In the present study, we investigate the drivers of in vivo resistance to the γ-secretase inhibitor RO4929097.

Pyrazolobenzodiazepines: part I. Synthesis and SAR of a potent class of kinase inhibitors.

A novel series of pyrazolobenzodiazepines 3 has been identified as potent inhibitors of cyclin-dependent kinase 2 (CDK2). Their synthesis and structure-activity relationships (SAR) are described. Representative compounds from this class reversibly inhibit CDK2 activity in vitro, and block cell cycle progression in human tumor cell lines.

Small-molecule inducer of cancer cell polyploidy promotes apoptosis or senescence: Implications for therapy.

Polyploidy results from deregulated cell division and has been considered an undesirable event leading to increased mutation rate and cancer development. However, polyploidy may also render cancer cells more vulnerable to chemotherapy. Here, we identify a small-molecule inducer of polyploidy, R1530, which interferes with tubulin polymerization and mitotic checkpoint function in cancer cells, leading to abortive mitosis, endoreduplication and polyploidy.

RG7204 (PLX4032), a selective BRAFV600E inhibitor, displays potent antitumor activity in preclinical melanoma models.

The BRAF(V600E) mutation is common in several human cancers, especially melanoma. RG7204 (PLX4032) is a small-molecule inhibitor of BRAF(V600E) kinase activity that is in phase II and phase III clinical testing. Here, we report a preclinical characterization of the antitumor activity of RG7204 using established in vitro and in vivo models of malignant melanoma.

Optimizing chemotherapy dose and schedule by Norton-Simon mathematical modeling.

Background: to hasten and improve anticancer drug development, we created a novel approach to generating and analyzing preclinical dose-scheduling data so as to optimize benefit-to-toxicity ratios.

Methods: we applied mathematical methods based upon Norton-Simon growth kinetic modeling to tumor-volume data from breast cancer xenografts treated with capecitabine (Xeloda®, Roche) at the conventional schedule of 14 days of treatment followed by a 7-day rest (14-7).

Results: the model predicted that 7 days of treatment followed by a 7-day rest (7-7) would be superior.

Preclinical in vivo evaluation of efficacy, pharmacokinetics, and pharmacodynamics of a novel MEK1/2 kinase inhibitor RO5068760 in multiple tumor models.

Targeting the Ras/Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway represents a promising anticancer strategy. Recently, we have reported a novel class of potent and selective non-ATP-competitive MEK1/2 inhibitors with a unique structure and mechanism of action. RO5068760 is a representative of this class showing significant efficacy in a broad spectrum of tumors with aberrant mitogen-activated protein kinase pathway activation.

Novel regimens of capecitabine alone and combined with irinotecan and bevacizumab in colorectal cancer xenografts.

Background: Xenograft and mathematical models have shown that the antitumor activity of capecitabine can be increased by modifying the schedule from 14 days on, 7 off (14/7) to 7/7.

Materials And Methods: Capecitabine at two-thirds maximum tolerated dose (MTD) administered using 14/7 (267 mg/kg) and 7/7 (467 mg/kg) schedules, alone and in doublet and triplet combinations with irinotecan (40 mg/kg intraperitoneally) and bevacizumab (5 mg/kg intraperitoneally) were studied in mice bearing HT29 colorectal xenografts.

Results: Tumor growth inhibition was >100% in doublet and triplet regimens with capecitabine 7/7 compared with 70% and 98%, respectively, with 14/7.

Characterization of a novel mitogen-activated protein kinase kinase 1/2 inhibitor with a unique mechanism of action for cancer therapy.

The mitogen-activated protein kinase (MAPK) signal transduction pathway plays a central role in regulating tumor cell growth, survival, differentiation, and angiogenesis. The key components of the Ras/Raf/MEK/ERK signal module are frequently altered in human cancers. Targeting this pathway represents a promising anticancer strategy.

In vivo activity of novel capecitabine regimens alone and with bevacizumab and oxaliplatin in colorectal cancer xenograft models.

Modifying the capecitabine dosing schedule from 14 days on, 7 days off (14/7) to 7 days on, 7 days off (7/7) may enable higher doses and improved antitumor efficacy in colorectal cancer xenografts. Capecitabine 14/7 (267 or 400 mg/kg) and 7/7 (467 or 700 mg/kg) schedules in doublet and triplet combinations with optimally dosed bevacizumab (5 mg/kg) and oxaliplatin (6.7 mg/kg) were studied in female athymic nude mice bearing HT29 colorectal xenografts.

Antitumor activity of capecitabine and bevacizumab combination in a human estrogen receptor-negative breast adenocarcinoma xenograft model.

Background: Capecitabine and bevacizumab have each been shown to inhibit tumor growth. Their combination failed to improve survival in a phase III trial of metastatic breast cancer (MBC), although it should be noted patients had been heavily pretreated with anthracyclines and taxanes. Our aim was to evaluate whether combination treatment would increase tumor growth inhibition and survival in a breast cancer model.

In vitro and in vivo activity of R547: a potent and selective cyclin-dependent kinase inhibitor currently in phase I clinical trials.

The cyclin-dependent protein kinases are key regulators of cell cycle progression. Aberrant expression or altered activity of distinct cyclin-dependent kinase (CDK) complexes results in escape of cells from cell cycle control, leading to unrestricted cell proliferation. CDK inhibitors have the potential to induce cell cycle arrest and apoptosis in cancer cells, and identifying small-molecule CDK inhibitors has been a major focus in cancer research.

Antitumor activity of HER1/EGFR tyrosine kinase inhibitor erlotinib, alone and in combination with CPT-11 (irinotecan) in human colorectal cancer xenograft models.

Erlotinib (Tarceva, OSI-774) is a potent, orally available, small-molecule inhibitor of HER1/EGFR tyrosine-kinase activity. In this study, the antitumor activity of erlotinib was evaluated in two human colorectal tumor xenograft models (LoVo and HCT116) in athymic mice. When erlotinib was administered as monotherapy, significant tumor growth inhibition (TGI) was seen in the LoVo model at both 100 mg/kg [TGI > 100%, P < 0.

Preclinical evaluation of tumor microvascular response to a novel antiangiogenic/antitumor agent RO0281501 by dynamic contrast-enhanced MRI at 1.5 T.

Inhibition of tumor angiogenesis is a promising approach in cancer treatment. The purpose of this study was to evaluate the vascular response of human lung tumor xenografts in vivo to RO0281501, an inhibitor of tyrosine kinase receptors, including vascular endothelial growth factor receptor 2, fibroblast growth factor receptor, and platelet-derived growth factor receptor, using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Human non-small cell lung carcinoma (H460a) xenografts grown s.

Biological evaluation of a multi-targeted small molecule inhibitor of tumor-induced angiogenesis.

RO4396686 is a small molecule KDR, FGFR, and PDGFR inhibitor with good pharmacokinetic properties in rodents. In a mouse corneal neovascularization assay, this compound inhibited VEGF-induced angiogenesis. Tested in a H460a xenograft tumor model this agent effected significant tumor growth inhibition at doses as low as 50mg/kg.

Small-molecule MDM2 antagonists reveal aberrant p53 signaling in cancer: implications for therapy.

The p53 tumor suppressor retains its wild-type conformation and transcriptional activity in half of all human tumors, and its activation may offer a therapeutic benefit. However, p53 function could be compromised by defective signaling in the p53 pathway. Using a small-molecule MDM2 antagonist, nutlin-3, to probe downstream p53 signaling we find that the cell-cycle arrest function of the p53 pathway is preserved in multiple tumor-derived cell lines expressing wild-type p53, but many have a reduced ability to undergo p53-dependent apoptosis.

RO4383596, an orally active KDR, FGFR, and PDGFR inhibitor: synthesis and biological evaluation.

(+/-)-1-(anti-3-Hydroxy-cyclopentyl)-3-(4-methoxy-phenyl)-7-phenylamino-3,4-dihydro-1H-pyrimido[4,5-d]pyrimidin-2-one (RO4383596) is a potent and selective inhibitor of the pro-angiogenic receptor tyrosine kinases KDR, FGFR, and PDGFR. This agent has an excellent pharmacokinetic profile and is highly efficacious in rodent models of angiogenesis upon oral administration.

Antitumor activity of erlotinib (OSI-774, Tarceva) alone or in combination in human non-small cell lung cancer tumor xenograft models.

Our objective was the preclinical assessment of the pharmacokinetics, monotherapy and combined antitumor activity of the epidermal growth factor receptor (HER1/EGFR) tyrosine kinase inhibitor erlotinib in athymic nude mice bearing non-small cell lung cancer (NSCLC) xenograft models. Immunohistochemistry determined the HER1/EGFR status of the NSCLC tumor models. Pharmacokinetic studies assessed plasma drug concentrations of erlotinib in tumor- and non-tumor-bearing athymic nude mice.

Interleukin-12 antagonist activity of mouse interleukin-12 p40 homodimer in vitro and in vivo.

Mo(p40)2 is a potent IL-12 antagonist that interacts strongly with the beta 1 subunit of the IL-12R to block binding of moIL-12 to the high-affinity mouse IL-12R. Mo(p40)2, alone or in synergy with the 2B5 mAb specific for the moIL-12 heterodimer, blocked IL-12-induced responses in vitro, Mo(p40)2 was thus used alone or with 2B5 mAb to examine the role of IL-12 in vivo, Mo(p40)2 caused a dose-dependent inhibition of both the rise in serum IFN-gamma levels in mice injected with endotoxin and the Th1-like response to immunization with KLH. Treatment with mo(p40)2 plus 2B5 anti-moIL-12 mAb also suppressed DTH responses to methylated bovine serum albumin but not specific allogeneic CTL responses in vivo.