Mark Miglarese

Bypassing cellular EGF receptor dependence through epithelial-to-mesenchymal-like transitions

Over 90% of all cancers are carcinomas, malignancies derived from cells of epithelial origin. As carcinomas progress, these tumors may lose epithelial morphology and acquire mesenchymal characteristics which contribute to metastatic potential. An epithelial-to-mesenchymal transition (EMT) similar to the process critical for embryonic development is thought to be an important mechanism for promoting cancer invasion and metastasis. Epithelial-to-mesenchymal transitions have been induced in vitro by transient or unregulated activation of receptor tyrosine kinase signaling pathways, oncogene signaling and disruption of homotypic cell adhesion. These cellular models attempt to mimic the complexity of human carcinomas which respond to autocrine and paracrine signals from both the tumor and its microenvironment. Activation of the epidermal growth factor receptor (EGFR) has been implicated in the neoplastic transformation of solid tumors and overexpression of EGFR has been shown to correlate with poor survival. Notably, epithelial tumor cells have been shown to be significantly more sensitive to EGFR inhibitors than tumor cells which have undergone an EMT-like transition and acquired mesenchymal characteristics, including non-small cell lung (NSCLC), head and neck (HN), bladder, colorectal, pancreas and breast carcinomas. EGFR blockade has also been shown to inhibit cellular migration, suggesting a role for EGFR inhibitors in the control of metastasis. The interaction between EGFR and the multiple signaling nodes which regulate EMT suggest that the combination of an EGFR inhibitor and other molecular targeted agents may offer a novel approach to controlling metastasis.

Abstract B56: Insights into the role of Epithelial to Mesenchymal transition (EMT) as an important mechanism of drug-resistance to molecular targeted therapies

Resistance to targeted therapies is emerging as a major theme in cancer research. As more therapies become used routinely in the clinic it is apparent that although significant responses are observed the majority of patients progress while on therapy. Drug resistance can occur through a number of distinct mechanisms and no single mechanism can account for all the resistance that occurs in response to a particular therapy. These mechanisms include acquisition of secondary drug-resistant mutations within the target and activation of alternate prosurvival signaling pathways through compensatory signaling or epithelial to mesenchymal transitions (EMT). The ability of cancer cells to undergo an EMT has been implicated as a major factor driving metastasis, through the acquisition of enhanced migratory and invasive properties. However it is also clear that by undergoing this process the cancer cells become resistant to a number of targeted therapies. Recent retrospective analysis of phase 3 clinical trial samples has revealed that a poorer response to Erlotinib in the 2/3rd line setting in NSCLC was associated with a loss of E-cadherin (an epithelial tumor marker), suggesting that tumors that had undergone EMT were less responsive to EGFR-directed therapy. In addition an EMT phenotype has been reported in a number of EGFR-mutant NSCLC patients who have progressed while on erlotinib therapy. These clinical observations suggest that EMT plays an important role in mediating response to targeted therapy. In order to understand the full impact of these clinical observations and identify mechanisms of resistance in mesenchymal tumor cells we have modeled EMT in a number of different ways in vitro. We have used panels of NSCLC cell lines that are in a fixed epithelial or mesenchymal state, induced an EMT with TGFβ, or driven an EMT through prolonged exposure to EGFR-TKi targeted therapy (erlotinib). Using large-scale phosphoproteomic and transcriptomic datasets we used a systems biology approach to uncover important observations relating to the role of EMT as a drug-resistance mechanism. Firstly, these models confirm the clinical observations and show that tumor cells that have undergone EMT are less responsive to a number of targeted agents including EGFR and IGF1R-IR directed agents. Secondly, they reveal the plasticity of the EMT process where three distinct stages of EMT: epithelial, ‘metastable’ mesenchymal and ‘epigenetically-fixed’ mesenchymal are observed. Thirdly, upon undergoing EMT tumor cells acquire novel mechanisms of cellular signaling not apparent in their epithelial counterparts. These include receptor tyrosine kinase (RTK) autocrine and paracrine loops, such as PDGFR, FGFR, AXL and integrin α5β1 and up regulation of IL-6 and IL-11 mediated JAK-STAT signaling. Reciprocal activation of PDGFR signaling through EGFR inhibition was observed in the mesenchymal state. Lastly, these models indicate that as part of the EMT process the tumor cells display a CD44high/CD24low cancer stem cell phenotype and show enhanced colony formation. These observations reinforce the important role that EMT can have in driving drug resistance in tumor cells and highlight the wide diversity of mechanisms that can be used by tumor cells to evade targeted drug therapy. An understanding of these mechanisms and the contexts in which they are most likely to arise will have important implications in driving combinatorial drug therapy in cancer patients in the future.

Abstract 58: Understanding target biology using protein interactomes

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FLnnThe use of systematic genome-wide physical protein-protein interaction detection methods has led to the generation of large networks of putatively interconnected human proteins including a number of therapeutically relevant disease-associated proteins. These networks have intrinsic value for understanding the pathophysiology of proteins, identification of tractable drug targets within a network, and hypothesis generation with regard to potential pharmacodynamic and patient selection biomarkers for a drug target of interest.nnHere, we present a novel approach to utilize a high-confidence human focal adhesion kinase (FAK) protein interaction network to better understand FAK target biology. FAK is a well-studied signaling protein known to directly control cellular motility via mechanosensing. As a large 125 kDa protein with both protein tyrosine kinase and scaffolding functions, FAK is particularly rich in its potential to interact with numerous proteins through SH2 and other interaction domains. By forming a diverse array of target interactions that regulate cytoskeletal structural changes, cellular adhesion, cell migration and cellular proliferation, FAK is believed to be a key regulator of several critical processes in tumorigenesis. It has also been established that human tumors often exhibit FAK gene amplification with resulting increased FAK expression which correlates with cancer progression and poor prognosis. Although the plausible roles of FAK have been well-elaborated, there are limited data available on the precise interplay of biological entities controlling the FAK signaling pathway. In this study, we built a prototypical model representing cross-talk between multiple proteins believed to be involved in the FAK signaling pathway. In doing so, we describe a step by step procedure to assemble a FAK interactome using integrative data mining procedures with publicly available interaction databases such as MINT, BioGRID, DIP and HPRD. Next, we filter this data set by incorporating confidence scores and lines of evidence available corresponding to each interaction to finally derive a high-confidence FAK interactome.nnWe propose that this approach to generate high-confidence protein interactomes could also be applied to other proteins of interest to facilitate a systems biology approach to elucidate additional biological pathways influencing tumorigenesis, metastasis and other disease states amenable to rational drug discovery.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 58. doi:10.1158/1538-7445.AM2011-58

Abstract 1631: Tumorigenicity of IGF-1R and IR: Rationale for co-targeting IGF-1R and IR in cancer

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FLnnThe Type 1 insulin-like growth factor receptor (IGF-1R) is a well established mediator of tumor cell proliferation and survival. IGF-1R is required for cellular transformation by a number of oncogenes including Ras, and expression of IGF-1R can promote tumor formation in vivo. Blockade of IGF-1R signaling by either genetic or pharmacological methods results in inhibition of tumor cell proliferation. This understanding has spurred the evaluation of a number of IGF-1R inhibitors in the clinic, including both neutralizing antibodies and small molecule kinase inhibitors.nnIGF-1R is structurally and functionally related to the insulin receptor (IR). Although IR is appreciated for its classical role in glucose metabolism, IR can also regulate cellular proliferation. Furthermore, there is evidence for compensatory crosstalk between IGF-1R and IR. In embryonic development IR signaling can compensate for loss of IGF-1R to maintain normal embryonic weight. A growing body of data indicates that tumor cells may also exploit IR signaling for proliferation and survival. Tumor cells frequently co-express both IGF-1R and IR, and increased expression of both IGF ligands and insulin are associated with increased risk of cancer. Elevated expression of the IR(A) fetal variant, which is potently activated by both insulin and IGF-2, is observed in select human tumors. Although the tumorigenicity for IGF-1R is well described, the potential for IR as a tumor maintenance gene in vivo has thus far not been established. Herein, we sought to address the tumorigenic potential for IGF-1R compared with IR(A). We used a mouse mammary tumor model driven by an inducible human HER2 oncogene under doxycyclin-directed expression, where repression of HER2 expression upon doxycyclin withdrawal was followed by introduction of genes encoding either IGF-1R or IR(A) in combination with IGF2. We find that either IGF-1R or IR(A), in combination with the ligand IGF2, can complement tumor growth. The growth of both IGF-1R and IR(A) direct complementation (DC) tumor models could be inhibited by the dual IGF-1R/IR small molecule inhibitor OSI-906. Cell lines derived from the IGF-1R and IR(A) DC tumors show that expression of either receptor individually can maintain signaling through the IRS-AKT signaling pathway. Collectively, these observations show that either IGF-1R or IR(A) have tumorigenic potential, and indicate that dual targeting of IGF-1R and IR may be required for optimal activity in tumors where both receptors are present and activated.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1631. doi:10.1158/1538-7445.AM2011-1631

Abstract 3370: The role of epithelial to mesenchymal transition (EMT) in resistance to Erlotinib in EGFR mutant NSCLC cell line models

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FLnnThe EGFR kinase inhibitor erlotinib is approved as a maintenance therapy in 1st line NSCLC as well as for treatment of 2nd/3rd line NSCLC and in combination with Gemcitabine for pancreatic cancer. It has been observed that the most pronounced responses to EGFR tyrosine kinase inhibitors (TKIs) were observed in patients whose tumors expressed a mutated form of the EGFR kinase. These mutations mapped to the kinase domain of the receptor and functionally have been shown to render tumors and cells lines onco-addicted to EGFR signaling. Although patients expressing a mutated EGFR show a dramatic initial response to EGFR TKIs, ∼50% of these patients will progress while on therapy after 1-2 years. The mechanisms that underlie this acquired resistance to EGFR TKI therapy have been intensively studied and include but are not limited to the presence of a second mutation, T790M, or increased HGF-MET signaling.nnPreviously, the role of epithelial to mesenchymal transition (EMT) in resistance to EGFR kinase inhibitors has been described in the context of wild type EGFR. EMT. We were therefore interested in understanding whether EMT could play a role in resistance to EGFR TKIs in the context of an EGFR mutation. Here we show that a panel of NSCLC cell lines, expressing mutant EGFR, can undergo an EMT in response to TGFβ treatment. The cell lines take on a scattered and spindle-like morphology and also down regulate the expression of E-cadherin and up regulate expression of vimentin, classic protein markers of an EMT. Importantly we show that after undergoing EMT, the EGFR mutant line HCC827 has reduced sensitivity to erlotnib treatment which is regained after reversal of the EMT. To further explore whether EMT could play a role in acquired resistance to erlotinib, we generated in vitro cell line models that were resistant to EGFR inhibition through continued culturing in the presence of erlotinib over a 6 month period. Resistant clones generated from parental HCC4006 cells acquired a more scattered and spindle-like morphology consistent with an EMT. These clones had down-regulated E-cadherin and ErbB3 expression and upregulated vimentin, fibronectin and Zeb1 expression and also showed a gene expression pattern consistent with having undergone an EMT. In addition, the resistant H4006 clones were more migratory and invasive than their parental counterpart. Finally we show that the resistant clones are enriched for stem cell markers and have enhanced signaling through the Src family kinases and the JAK-STAT pathway suggesting a mechanistic rationale for their reduced sensitivity to EGFR inhibitors.nnTaken together. these data indicate that NSCLC cell lines that express a mutant version of EGFR are able to undergo an EMT which can influence the efficacy of EGFR TKIs, suggesting that this may be an additional mechanism underlying the acquired resistance of NSCLC patients to EGFR therapy in the clinic.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3370. doi:10.1158/1538-7445.AM2011-3370

Abstract 4463: OSI-027, a dual mTORC1/mTORC2 inhibitor, induces autophagy in cancer cells

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FLnnInhibitors of mTORC1 have proven clinical activity in renal cell carcinoma (RCC), indicating that mTOR is an important signaling hub in this tumor type. mTOR exists in two functionally distinct protein complexes: mTORC1 and mTORC2. mTORC1 regulates multiple cellular functions including protein translation and tumor metabolism While this complex binds rapamycin some aspects of mTORC1 function are rapamycin insensitive. mTORC2 controls distinct cellular functions including survival and is not directly inhibited by rapalogs. In order to evaluate the relative contribution of mTORC1 and mTORC2 to the survival of RCC cells, we compared the effects of rapamycin, an allosteric inhibitor of mTORC1, to OSI-027, a selective catalytic-site inhibitor of mTORC1/mTORC2.nnIn RCC cell lines, OSI-027 provided greater maximal inhibition of proliferation than rapamycin, with reduction of cell viability to less than baseline in 5 of 12 cell lines, however caspase 3/7-dependent apoptosis was observed only in one cell line. We identified a subset of RCC cell lines which were sensitive to OSI-027 but not rapamycin, and another set which was relatively sensitive to both. Comparison of gene expression profiles of these groups identified MAP1LC3, encoding LC3, a critical effector of autophagy, as significantly upregulated in cell lines which were preferentially sensitive to OSI-027. We therefore sought to further define the role of autophagy in response to OSI-027 treatment.nnAutophagy is a catabolic process by which cells consume proteins and organelles to promote survival under adverse conditions, and which can result in cell death. Both mTORC1 and mTORC2 have been shown to negatively regulate autophagy, and inhibition of mTOR has been shown to induce formation of autophagic vesicles. Treatment in vitro with OSI-027 resulted in the conversion of LC3 to the lipidated form LC3-II as well as accumulation of LC3 in autophagosomes, robust indicators of autophagy. Increased autophagosome content occurred in a dose-dependent manner and is inversely proportional to viable cell number although induction of apoptosis was not observed, implying that in these cells OSI-027-induced autophagy leads to complete growth arrest or apoptosis-independent cell death. OSI-027-mediated induction of autophagy occurred in the majority of RCC cell lines tested, whereas little or no autophagy resulted from rapamycin treatment. In xenograft tumors sensitive to OSI-027 but not rapamycin, we analyzed induction of LC3-II and apoptosis in tumor lysates. Consistent with our observations in vitro, we observed that treatment with OSI-027 but not rapamycin resulted in induction of autophagy in vivo, while neither compound induced apoptosis. Together these data indicate that autophagy may play a key role in mediating OSI-027 but not rapamycin efficacy and supports further exploration of the utility of dual mTORC1/mTORC2 inhibitors for the treatment of renal cell carcinoma.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4463. doi:10.1158/1538-7445.AM2011-4463

Abstract LB-388: Combination treatment of a dual IGF-1R/IR kinase inhibitor, OSI-906, with EGFR inhibitor erlotinib in models of non-small cell lung cancer with an EGFR activating mutation

Erlotinib is a tyrosine kinase inhibitor of EGFR approved for use in non-small cell lung cancer (NSCLC) and pancreatic cancer in combination with Gemcitabine. Within the context of NSCLC it has been observed that patients harboring an activating mutation within the kinase domain of EGFR demonstrate a high response to treatment. However, their disease often progresses within 1 year. OSI-906 targets IGF-1R and IR receptor tyrosine kinases and has shown combination efficacy with erlotinib in preclinical models of NSCLC with wild type EGFR. Here we report preclinical data suggesting that the combination of erlotinib and OSI-906 is more efficacious in NSCLC models expressing an EGFR mutation than either single agent. A panel of NSCLC cells lines with confirmed mutations in the EGFR kinase domain was screened for erlotinib and OSI-906 single agent drug sensitivities. All mutant EGFR models exhibited sensitivity to EGFR inhibition by erlotinib (IC50 7–33 nM) while none showed sensitivity to OSI-906 (IC50 7gt;10 uM). In vitro, the combination of erlotinib and OSI-906 resulted in synergistic inhibition of cell proliferation and induction of apoptosis in PC3 (JCP-1) cells. Mechanistically we found the combination had enhanced inhibition of signaling through the PI3K/AKT pathway compared to treatment with either single agent. We also observed that while OSI-906 showed no induction of cell death, erlotinib treatment caused almost complete cell death. However after 9 days of erlotinib treatment small colonies of viable cells still remained. Removal of drug allowed the cells to grow and expand. When cells were treated with both erlotinib and OSI-906, complete cell death occurred without any evidence of cell regrowth following removal of both drugs. In order to evaluate this combination effect in vivo the EGFR mutant human tumor xenograft models NCI-H1650 and PC-14 were employed. Both lines are highly sensitive to erlotinib single agent treatment but show no anti-tumor activity with OSI-906 single agent treatment. The combination of 100 mg/kg erlotinib and 10 mg/kg OSI-906 demonstrated enhanced tumor growth delay when compared to either single agent dosed at MTD. However, as a first step towards understanding preclinical mechanism of this interaction we investigated the combination of 25 mg/kg of erlotinib with 30 mg/kg of OSI-906 and identified potential in vivo synergy. These studies with 25 mg/kg of erlotinib and 30 mg/kg of OSI-906 showed initial tumor regressions, enhanced tumor inhibition and substantially prolonged tumor growth delay when compared to either single agent. Drug-drug interaction PK studies suggest that OSI-906 is not acting to enhance erlotinib exposure. This data provides preclinical proof-of-concept for the use of OSI-906 in combination with erlotinib to obtain greater anti-tumor activity in the mutant EGFR setting. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-388. doi:10.1158/1538-7445.AM2011-LB-388

Abstract 1654: Compensatory insulin receptor (IR) activation upon inhibition of insulin-like growth factor receptor (IGF-1R): Rationale for co-targeting IGF-1R and IR in cancer

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DCnnThe insulin-like growth factor receptor (IGF-1R) is a receptor tyrosine kinase (RTK) and a critical mediator of signaling through the PI3K-AKT pathway. IGF-1R is required for oncogenic transformation and tumorigenesis, and inhibiton of IGF-1R results in reduced proliferation and survival of tumor cells. These observations have spurred intense drug discovery and development efforts for both biologic and small molecule IGF-1R inhibitors for the treatment of cancer.nnThe ability for one RTK to compensate for another to maintain growth and survival signaling in tumor cells is emerging as a common mechanism of resistance to anti-tumor agents that selectively target individual RTKs. As IGF-1R is structurally and functionally related to the insulin receptor (IR), and IR can also activate tumor cell AKT signaling and cellular transformation, we asked whether IR signaling can contribute to resistance to IGF-1R inhibition in tumor cells.nnIn a panel of human tumor cell lines, IGF-1R/IR crosstalk was observed after treatment with a selective anti-IGF-1R monoclonal antibody, MAB391. Tumor cells treated with MAB391 responded with a compensatory increase in phospho-IR, which was also associated with an inability to fully inhibit phospho-IRS1 and phospho-AKT. In contrast, treatment with OSI-906, a small molecule dual kinase inhibitor of IGF-1R and IR, resulted in enhanced inhibition of the IRS1-AKT signaling pathway. OSI-906 showed superior efficacy compared to MAB391 in human tumor xenograft models where both phospho-IR and phospho-IGF-1R were detectable, and presumably both receptors were required by tumor cells for growth and/or survival. Both insulin and IGF-2 can activate the IR-AKT pathway and we show that treatment with either growth factor resulted in decreased sensitivity of tumor cells to MAB391, but not OSI-906. In tumor cells with an autocrine IGF-2 signaling loop, both OSI-906 and an anti-IGF-2 neutralizing antibody reduced phospho-IR and phospho-AKT levels, whereas MAB391 was ineffective. Collectively, these data indicate that OSI-906, which co-targets IGF-1R and IR, may provide superior efficacy as compared to agents that selectively target only IGF-1R.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1654.

Abstract 1632: Co-targeting mTOR and IGF-1R/IR results in synergistic activity against a broad array of tumor cell lines, independent of KRAS mutation status

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DCnnThe IGF-1 receptor (IGF-1R) and insulin receptor (IR) are known to couple via IRS-1 to the PI3K signaling axis. Upon activation, these receptor tyrosine kinases stimulate PI3K, initiating a cascade of ser/thr kinases, including mTOR. mTOR is associated with two complexes: mTORC1, rapamycin sensitive, and mTORC2, which does not bind rapamycin. Since mTOR functions downstream of IGF-1R and IR, it is thought that tumor cells sensitive to IGF-1R inhibition would also respond to mTORC1/mTORC2 inhibition. To test this hypothesis we evaluated the effects of OSI-906, a selective small molecule dual kinase inhibitor of IGF-1R and IR and OSI-027, a selective catalytic-site inhibitor of mTORC1/mTORC2, alone and in combination in cell proliferation assays using a broad array of tumor cell lines. Across multiple tumor types, cells with activating KRAS mutations were typically less sensitive to OSI-027 than those expressing wild-type KRAS. In contrast, mutant KRAS did not reduce sensitivity to OSI-906. Cell lines with activating mutations in PIK3CA or loss of PTEN were sensitive to OSI-027 but the presence of a concurrent mutation in KRAS decreased their sensitivity to OSI-027. In KRAS mutant cells, OSI-906 was more effective than OSI-027 at reducing phospho-AKT levels. Conversely, in tumor cell lines with wild-type KRAS cells, OSI-027 more effectively reduced phospho-AKT levels compared to OSI-906. Similar effects were observed in a pair of isogenic cell lines engineered to express either wild-type or mutant KRAS. The observation that tumor cell lines exhibit differential sensitivity to inhibitors of IGF-1R/IR or mTORC1/mTORC2 supports the concept that IGF-1R and IR can activate multiple pathways and are not limited to signaling through the mTOR axis. Also, mTOR is a central signaling hub which integrates signaling from multiple inputs, not only the IGF-1R/IR cascade. The combination of OSI-906 and OSI-027 synergistically inhibited the proliferation of cancer cell lines, including those expressing mutant KRAS. In some cases, the combination also resulted in synergistic induction of apoptosis. These data provide support for further exploration of the potential utility of combining OSI-906 (dual IGF-1R/IR inhibitor) with OSI-027 (dual mTORC1/mTORC2 inhibitor) for the treatment of human cancers, including those with activating mutations in KRAS.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1632.

Abstract A46: Pharmacodynamic biomarkers for OSI‐906, an insulin‐like growth factor‐1 receptor (IGF‐1R) tyrosine kinase inhibitor, in cancer patients with advanced solid tumors

Background: OSI‐906 is a potent small molecule inhibitor of the insulin-like growth factor 1 receptor (IGF‐1R), a receptor tyrosine kinase that is overexpressed in several human cancer types and implicated in resistance to chemotherapy. Disruption of the growth hormone‐IGF1 signaling axis can affect levels of biomarkers such as IGF1, growth hormone (GH) and insulin and can affect glucose homeostasis, making these potentially useful markers for demonstrating the activity of IGF‐1R inhibitors in solid tissues. Methods: Two phase I dose escalation trials were initiated in cancer patients with advanced solid tumors who received OSI‐906 on either continuous or intermittent dosing schedules. Pharmacodynamic (PD) and pharmacokinetic (PK) assessments were included as secondary objectives of these studies. Circulating biomarkers, including total IGF1, IGFBP3 and non‐fasting GH and insulin levels, were measured at various times during the dosing cycle (21 days for continuous dosing; 14 days for intermittent dosing) and changes were correlated with plasma concentrations of OSI‐906. Results: To date, patients have been treated with up to 450 mg QD and 200 mg BID on the continuous dosing schedule and up to 750 mg QD on the intermittent dosing schedule. Maximum tolerated dose (MTD) was determined to be 400 mg QD and 150 mg BID for continuous dosing and 600 mg QD for intermittent dosing. Preliminary analysis of the PK data suggests that the exposure of OSI‐906 increased with dose. Median plasma concentrations of OSI‐906 at MTD exceeded the predicted concentration required for efficacy based on the preclinical models (1 µM). Total IGF1 concentrations in plasma were increased relative to predose levels at doses ≥ 450 mg QD on the intermittent dosing schedule and ≥ 150 mg QD or 40 mg BID on the continuous dosing schedule. Elevations in non‐fasting plasma insulin levels were also observed in patients with plasma concentrations of OSI‐906 exceeding 5000 ng/mL. PK/PD relationships were observed for IGF1 and insulin. OSI‐906 did not affect plasma IGFBP3 levels in most patients. Analysis of additional biomarkers, including GH, is ongoing. Conclusions: At or below MTD, plasma concentrations of OSI‐906 could be achieved that exceed concentrations required for anti‐tumor efficacy based on the preclinical models. The pharmacodynamic data indicate that pharmacologically‐relevant concentrations of OSI‐906 were achieved in tissues involved in regulating the GH‐IGF1 signaling axis. Together, these PK and PD data indicate that the current recommended dosing regimens may provide sufficient exposure for activity against solid tumors. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A46.