Efficacy and safety of motesanib, an oral inhibitor of VEGF, PDGF, and Kit receptors, in patients with imatinib-resistant gastrointestinal stromal tumors

Advances in Drug Therapy for Gastrointestinal Stromal Tumour

INTRODUCTION

Gastrointestinal stromal tumour (GIST) is a common gastrointestinal sarcoma located in the stromal cells of the digestive tract, and molecular studies have revealed the pathogenesis of mutations in KIT and PDGFRA genes. Since imatinib opened the era of targeted therapy for GIST, tyrosine kinase inhibitors (TKIs) that can treat GIST have been developed successively. However, the lack of new drugs with satisfactory therapeutic standards has made addressing resistance a significant challenge for TKIs in the face of the resistance to first-line and second-line drugs. Therefore, we need to find as many drugs and new treatments that block mutated genes as possible.

METHODS

We conducted a comprehensive collection of literature using databases, integrated and analysed the selected literature based on keywords and the comprehensive nature of the articles, and finally wrote articles based on the content of the studies.

RESULTS

In this article, we first briefly explained the relationship between GIST and KIT/ PDGFRα and then introduced the related drug treatment. The research progress of TKIs was analyzed according to the resistance of the drugs.

CONCLUSION

This article describes the research progress of some TKIs and briefly introduces the currently approved TKIs and some drugs under investigation that may have better therapeutic effects, hoping to provide clues to the research of new drugs.

Tumor Microenvironment as a Therapeutic Target in Melanoma Treatment

The role of the tumor microenvironment in tumor growth and therapy has recently attracted more attention in research and drug development. The ability of the microenvironment to trigger tumor maintenance, progression, and resistance is the main cause for treatment failure and tumor relapse. Accumulated evidence indicates that the maintenance and progression of tumor cells is determined by components of the microenvironment, which include stromal cells (endothelial cells, fibroblasts, mesenchymal stem cells, and immune cells), extracellular matrix (ECM), and soluble molecules (chemokines, cytokines, growth factors, and extracellular vesicles). As a solid tumor, melanoma is not only a tumor mass of monolithic tumor cells, but it also contains supporting stroma, ECM, and soluble molecules. Melanoma cells are continuously in interaction with the components of the microenvironment. In the present review, we focus on the role of the tumor microenvironment components in the modulation of tumor progression and treatment resistance as well as the impact of the tumor microenvironment as a therapeutic target in melanoma.

The role of VEGF in cancer-induced angiogenesis and research progress of drugs targeting VEGF

Angiogenesis is a double-edged sword; it is a mechanism that defines the boundary between health and disease. In spite of its central role in physiological homeostasis, it provides the oxygen and nutrition needed by tumor cells to proceed from dormancy if pro-angiogenic factors tip the balance in favor of tumor angiogenesis. Among pro-angiogenic factors, vascular endothelial growth factor (VEGF) is a prominent target in therapeutic methods due to its strategic involvement in the formation of anomalous tumor vasculature. In addition, VEGF exhibits immune-regulatory properties which suppress immune cell antitumor activity. VEGF signaling through its receptors is an integral part of tumoral angiogenic approaches. A wide variety of medicines have been designed to target the ligands and receptors of this pro-angiogenic superfamily. Herein, we summarize the direct and indirect molecular mechanisms of VEGF to demonstrate its versatile role in the context of cancer angiogenesis and current transformative VEGF-targeted strategies interfering with tumor growth.

Medical Oncological Treatment for Patients with Gastrointestinal Stromal Tumour (GIST) - a Systematic Review

BACKGROUND

Chemotherapy is ineffective in treating patients with Gastrointestinal Stromal Tumour (GIST). However, several types of tyrosine kinase inhibitors have been investigated since the approval of imatinib in 2001. The purpose of this report was to systematically review studies on the efficacy of neoadjuvant, adjuvant, and lifelong medical oncological treatment of GIST.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed throughout the review process. The protocol was submitted to the International prospective register of systematic reviews database (ID 251724). A systematic literature search was performed, including phase II- and III studies of biological treatment, reporting on treatment effect in patients with GIST.

RESULTS

Of 308 identified publications, 42 studies were included in this review.

CONCLUSION

This review gives an overview of the existing evidence for approved lines of oncological treatments and potential alternatives for patients with GIST in the neoadjuvant-, adjuvant- and life-long setting.

Anti-Angiogenic Tyrosine Kinase Inhibitors and Reversible Posterior Leukoencephalopathy Syndrome: Could Hypomagnesaemia Be the Trigger?

Reversible posterior leukoencephalopathy syndrome (RPLS), also known frequently as posterior reversible encephalopathy syndrome (PRES), is a characteristic acute neuro-radiology syndrome with clinical presentation that typically includes acute hypertension, seizures and other neurological symptoms and signs. Many patients with RPLS have (a history of) pre-existing hypertension and in receipt of diuretics. It is being diagnosed more frequently and in association with an increasing number of morbidities and medications. Drugs most frequently implicated are immunosuppressant drugs and anticancer agents, including a number of anti-angiogenic tyrosine kinase inhibitors (TKIs). Hypomagnesaemia is a frequent finding at presentation in RPLS patients, which is known to lead to or aggravate hypertension. Pre-eclampsia, a variant of RPLS, responds effectively to intravenous magnesium. Cyclosporin, tacrolimus and some TKIs that induce RPLS are also known to give rise to both hypertension and hypomagnesaemia. This raises an interesting hypothesis that hypomagnesaemia may play a contributory role in triggering RPLS in some patients by acutely raising the blood pressure further. Additional systematic studies are required to test this hypothesis. If the hypothesis is confirmed, hypomagnesaemia offers an effective target for risk mitigation and prevention of RPLS in patients identified at risk.

Dovitinib in patients with gastrointestinal stromal tumour refractory and/or intolerant to imatinib

Background:

This multicentre phase II trial (DOVIGIST) evaluated the antitumour activity of dovitinib as second-line treatment of patients with gastrointestinal stromal tumour (GIST) refractory to imatinib or who do not tolerate imatinib.

Methods:

Patients received oral dovitinib 500 mg day⁻¹, 5 days on/2 days off, until GIST progression or unacceptable toxicity, with an objective to evaluate efficacy, assessed as the disease control rate (DCR) at 12 weeks. Tumour assessment and response to dovitinib therapy were evaluated by Response Evaluation Criteria In Solid Tumours (RECIST v1.1) and the Choi criteria. Secondary objectives included assessment of progression-free survival (PFS), safety and tolerability, and DCR at the end of treatment.

Results:

Thirty-eight of the 39 patients enrolled had histologically confirmed GIST. The DCR at 12 weeks was 52.6% (90% confidence interval (CI), 38.2–66.7%) meeting the preset efficacy criterion for the primary end point. The objective response rate (complete response+partial response) was 2.6% (1 of 38; 90% CI, 0.1–11.9%), and 5.3% (n=2; 90% CI, 0.9–15.7%) at the end of the study. The median PFS was 4.6 months (90% CI, 2.8–7.4 months). Dose interruption was required in 26 patients (66.7%), of which 18 (69.2%) were due to adverse events. The most frequently observed grade 3 adverse events included hypertension (n=7), fatigue (n=5), vomiting (n=4), hypertriglyceridaemia (n=4), and γ-glutamyltransferase increase (n=4).

Conclusions:

Dovitinib is an active treatment for patients with GIST who are intolerant to imatinib or whose GIST progresses on imatinib.

Imaging therapy response of gastrointestinal stromal tumors (GIST) with FDG PET, CT and MRI: a systematic review

Purpose

Improvement of the therapeutic approaches in gastrointestinal stromal tumors (GIST) by the introduction of targeted therapies requires appropriate diagnostic tools, which allow sufficient assessment of therapeutic response, including differentiation of true progression from pseudoprogression due to myxoid degeneration or intratumoral hemorrhage. In this literature review the impact and limitations of different imaging modalities used in GIST therapy monitoring are discussed.

Methods

PubMed and Cochrane library search were performed using appropriate keywords. Overall, 39 original papers fulfilled the defined criteria and were included in this systematic review.

Results

Morphological imaging modalities like computed tomography (CT) are primarily used for both diagnosis and therapy monitoring. However, therapy with tyrosine kinase inhibitors and other targeted therapies in GIST may lead only to a minor tumor volume reduction even in cases of response. Therefore, the use of Response Evaluation Criteria in Solid Tumors (RECIST) has limitations. To overcome those limitations, modified response criteria have been introduced for the CT-based therapy assessment, like the Choi criteria as well as criteria based on dual energy CT studies. Functional imaging techniques, mostly based on FDG PET-CT are in use, in particular for the assessment of early treatment response.

Conclusions

The impact and the limitations of PET-based therapy monitoring, as well as its comparison with CT, MRI and survival data are discussed in this review. CT is still the standard method for the evaluation of therapy response despite its several limitations. FDG PET-CT is helpful for the assessment of early therapy response; however, more prospective data are needed to define its role as well as the appropriate time intervals for therapy monitoring. A multiparametric evaluation based on changes in both morphological and functional data has to be assessed in further prospective studies.

Novel anti-angiogenic therapeutic strategies in colorectal cancer

INTRODUCTION

Anti-angiogenetic agents are currently the standard of care in metastatic CRC patients. Bevacizumab, aflibercept, regorafenib and recently ramucirumab have significantly improved both progression-free and overall survival in different lines of treatment. Since bevacizumab's approval, a number of novel anti-VEGF agents have been tested in preclinical and clinical models.

AREAS COVERED

This review is focused on the most recent clinical results of novel agents targeting VEGF and its receptors with a major focus on those investigated recently in clinical trials.

EXPERT OPINION

In the last 15 years, a number of new anti-angiogenetic agents have been tested. Unfortunately, most of them have demonstrated unacceptable toxicities or failed to show activity. When tested as single agents, encouraging preliminary results were reported with fruquintinib, famitinib, and nintedanib. Interesting novel mechanisms of action are also being explored: VGX-100 is a monoclonal antibody (mAb) which binds to VEGF-C, inhibiting activation of VEGFR-2 and VEGFR-3 when combined with bevacizumab; tanibirumab is a mAb which binds to VEGFR-2 and vanucizumab is a bispecific mAb binding both to VEGF-A and Angiopoietin-2. Data about the combination of these agents with chemotherapy are very encouraging, even though preliminary. However, the definition of specific predictive biomarkers remains a priority.

Beyond standard therapy: drugs under investigation for the treatment of gastrointestinal stromal tumor

INTRODUCTION

Gastrointestinal stromal tumor (GIST) is the most common nonepithelial malignancy of the GI tract. With the discovery of KIT and later platelet-derived growth factor α (PDGFRA) gain-of-function mutations as factors in the pathogenesis of the disease, GIST was the quintessential model for targeted therapy. Despite the successful clinical use of imatinib mesylate, a selective receptor tyrosine kinase (RTK) inhibitor that targets KIT, PDGFRA and BCR-ABL, we still do not have treatment for the long-term control of advanced GIST.

AREAS COVERED

This review summarizes the drugs that are under investigation or have been assessed in trials for GIST treatment. The article focuses on their mechanisms of actions, the preclinical evidence of efficacy, and the clinical trials concerning safety and efficacy in humans.

EXPERT OPINION

It is known that KIT and PDGFRA mutations in GIST patients influence the response to treatment. This observation should be taken into consideration when investigating new drugs. RECIST was developed to help uniformly report efficacy trials in oncology. Despite the usefulness of this system, many questions are being addressed about its validity in evaluating the true efficacy of drugs knowing that new targeted therapies do not affect the tumor size as much as they halt progression and prolong survival.

Systemic therapy options for advanced gastrointestinal stromal tumors beyond first-line imatinib: a systematic review

ABSTRACT 

This systematic review aims at assessment of the available evidence for systemic therapy options for patients with advanced gastrointestinal stromal tumors beyond first-line imatinib. Eligible trials were identified using databases search. In total, 26 studies were eligible and included in the final analysis. Among second-line studies, median progression-free survival ranged from 1.9 to 10 months while median overall survival ranged from 15 to 62 months. Among third-line agents, median progression-free survival ranged from 1.8 to 4.6 months while median overall survival ranged from 8.2 to 19 months. The available data for the second-line suggest that sunitinib is the best option while in the third line, regorafenib is the best option.

Therapeutic targets in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common type of mesenchymal tumor of the gastrointestinal tract. The tumorigenesis of GISTs is driven by gain-of-function mutations in KIT or platelet-derived growth factor receptor α (PDGFRA), resulting in constitutive activation of the tyrosine kinase and its downstream signaling pathways. Oncogenic KIT or PDGFRA mutations are compelling therapeutic targets for the treatment of GISTs, and the KIT/PDGFRA inhibitor imatinib is the standard of care for patients with metastatic GISTs. However, most GIST patients develop clinical resistance to imatinib and other tyrosine kinase inhibitors. Five mechanisms of resistance have been characterized: (1) acquisition of a secondary point mutation in KIT or PDGFRA; (2) genomic amplification of KIT; (3) activation of an alternative receptor tyrosine kinase; (4) loss of KIT oncoprotein expression; and (5) wild-type GIST. Currently, sunitinib is used as a second-line treatment for patients after imatinib failure, and regorafenib has been approved for patients whose disease is progressing on both imatinib and sunitinib. Phase II/III trials are currently in progress to evaluate novel inhibitors and immunotherapies targeting KIT, its downstream effectors such as phosphatidylinositol 3-kinase, protein kinase B and mammalian target of rapamycin, heat shock protein 90, and histone deacetylase inhibitor. Other candidate targets have been identified, including ETV1, AXL, insulin-like growth factor 1 receptor, KRAS, FAS receptor, protein kinase c theta, ANO1 (DOG1), CDC37, and aurora kinase A. These candidates warrant clinical evaluation as novel therapeutic targets in GIST.

Growth Factors and COX2 Expression in Canine Perivascular Wall Tumors

Canine perivascular wall tumors (PWTs) are a group of subcutaneous soft tissue sarcomas developing from vascular mural cells. Mural cells are involved in angiogenesis through a complex crosstalk with endothelial cells mediated by several growth factors and their receptors. The evaluation of their expression may have relevance since they may represent a therapeutic target in the control of canine PWTs. The expression of vascular endothelial growth factor (VEGF) and receptors VEGFR-I/II, basic fibroblast growth factor (bFGF) and receptor Flg, platelet-derived growth factor B (PDGFB) and receptor PDGFRβ, transforming growth factor β1 (TGFβ1) and receptors TGFβR-I/II, and cyclooxygenase 2 (COX2) was evaluated on frozen sections of 40 PWTs by immunohistochemistry and semiquantitatively scored to identify their potential role in PWT development. Statistical analysis was performed to analyze possible correlations between Ki67 labeling index and the expression of each molecule. Proteins of the VEGF-, PDGFB-, and bFGF-mediated pathways were highly expressed in 27 (67.5%), 30 (75%), and 19 (47.5%) of 40 PWTs, respectively. Proteins of the TGFβ1- and COX2-mediated pathways were highly expressed in 4 (10%) and 14 (35%) of 40 cases. Statistical analysis identified an association between VEGF and VEGFR-I/II (P = .015 and .003, respectively), bFGF and Flg (P = .038), bFGF and PDGFRβ (P = .003), and between TGFβ1 and COX2 (P = .006). These findings were consistent with the mechanisms that have been reported to play a role in angiogenesis and in tumor development. No association with Ki67 labeling index was found. VEGF-, PDGFB-, and bFGF-mediated pathways seem to have a key role in PWT development and growth. Blockade of tyrosine kinase receptors after surgery could represent a promising therapy with the aim to reduce the PWT relapse rate and prolong the time to relapse.

Motesanib with or without panitumumab plus FOLFIRI or FOLFOX for the treatment of metastatic colorectal cancer

PURPOSE

This study assessed the safety, efficacy, and pharmacokinetics of motesanib, a multitargeted small molecule angiogenesis inhibitor, with and without panitumumab, in combination with FOLFIRI or FOLFOX in patients with metastatic colorectal cancer (mCRC).

METHODS

This open-label, phase 1b, two-part, multicenter study in patients with mCRC and ≤1 prior treatment evaluated escalating doses (50, 75, 100, or 125 mg QD, 75 mg BID) of motesanib with panitumumab and chemotherapy (Part 1) and the target dose of motesanib with chemotherapy (Part 2).

RESULTS

At 17 sites in the USA and Australia, 119 patients were enrolled between December 2004 and February 2010. In Part 1 [motesanib plus panitumumab/FOLFIRI (n = 36) or plus panitumumab/FOLFOX (n = 17)], all motesanib doses tested were tolerated and 125 mg QD was deemed the target dose. Following toxicity results for combination therapy in other trials, panitumumab was withdrawn from the study. Part 2 evaluated motesanib 125 mg with chemotherapy [FOLFIRI (n = 37); FOLFOX (n = 29)]. The primary endpoint, objective response rate in patients with measurable disease by RECIST, was 20 % overall and was higher among patients receiving first-line (27 % overall; FOLFOX, 24 %; FOLFIRI, 27 %) compared with second-line therapy (14 % overall; FOLFOX, 0 %; FOLFIRI, 20 %). The most common adverse events were diarrhea, nausea, fatigue, and hypertension. We observed a low rate of cholecystitis [3 of 119 (2.5 %)], a known adverse event of motesanib and other small molecule VEGF inhibitors.

CONCLUSIONS

Motesanib 125 mg QD in combination with FOLFIRI or FOLFOX chemotherapy was tolerated and demonstrated modest efficacy in first-/second-line mCRC.

Investigational therapies up to Phase II which target PDGF receptors: potential anti-cancer therapeutics

INTRODUCTION

The platelet-derived growth factor receptor (PDGFR) pathway has important functions in cell growth and, by overexpression or mutation, could also be a driver for tumor development. Moreover, PDGFR is expressed in a tumoral microenvironment and could promote tumorigenesis. With these biological considerations, the PDGFR pathway could be an interesting target for therapeutics. Currently, there are many molecules under development that target the PDGFR pathway in different types of cancer.

AREAS COVERED

In this review, the authors report the different molecules under development, as well as those approved albeit briefly, which inhibit the PDGFR pathway. Furthermore, the authors summarize their specificities, their toxicities, and their development.

EXPERT OPINION

Currently, most PDGFR kinase inhibitors are multikinase inhibitors and therefore do not simply target the PDGFR pathway. The development of more specific PDGFR inhibitors could improve drug efficacy. Moreover, selecting tumors harboring mutations or amplifications of PDGFR could improve outcomes associated with the use of these molecules. The authors believe that new technologies, such as kinome arrays or pharmacologic assays, could be of benefit to understanding resistance mechanisms and develop more selective PDGFR inhibitors.

Meta-analysis for the association between overall survival and progression-free survival in gastrointestinal stromal tumor

PURPOSE

Gastrointestinal stromal tumor (GIST) is a relatively rare tumor that is treated with targeted therapies in advanced stages. Randomized clinical trials (RCT) often require long follow-up and large sample sizes to evaluate overall survival (OS), the gold-standard measure of treatment efficacy. However, changes in therapy following disease progression may complicate survival assessments. Establishing surrogate endpoints may facilitate the drug approval and availability of new efficacious treatments; however, no published studies have investigated this topic in unresectable and/or metastatic GIST.

EXPERIMENTAL DESIGN

A systematic literature review identified 14 RCTs and five observational studies of sufficient methodologic quality published between January 1995 and December 2013 (29 treatment arms; 2,189 patients). Weighted linear regression was used to evaluate the relation between median OS and median progression-free survival (PFS) for all arms combined and stratified by treatment line, treatment type, and quality score.

RESULTS

Median OS and PFS were positively related with a correlation of 0.91. The association was still moderate (correlation 0.72) after eliminating four influential data points. In stratified analyses, correlation of OS and PFS was greater in later lines of therapy (first line = 0.52; second line = 0.80; third- and later-line = 0.70) and imatinib showed a stronger association (0.91) than other evaluated treatments (-0.26 to 0.69).

CONCLUSION

This analysis identified a strong relationship between median OS and PFS, especially in later lines of therapy. Findings suggest that PFS could serve as a surrogate marker for OS; however, analyses of patient-level data are needed to establish its validity in GIST.

Efficacy of motesanib diphosphate in non-small-cell lung cancer

INTRODUCTION

Angiogenesis plays a crucial role in the proliferation and in the metastatic spread of tumour cells. Several agents with anti-angiogenic activity have been tested in advanced non-small-cell lung cancer (NSCLC) patients. Motesanib (AMG 706) is a promising anti-angiogenic multi-targeted tyrosine kinase inhibitor (TKI), which has been investigated as a monotherapy or in combination with chemotherapy, in several types of cancer.

AREAS COVERED

We have reviewed the literature, and we have presented the results of clinical trials that have investigated the administration of motesanib in advanced NSCLC patients.

EXPERT OPINION

Encouraging results have been described with the administration of motesanib as first-line treatment in combination with carboplatin and paclitaxel in Asian patients with non-squamous advanced NSCLC. Further studies are needed in order to identify the predictive biomarkers of response and to select patients who may benefit from this anti-angiogenic treatment.

Clinical efficacy of second-generation tyrosine kinase inhibitors in imatinib-resistant gastrointestinal stromal tumors: a meta-analysis of recent clinical trials

BACKGROUND

Primary and secondary resistance to imatinib, a selective receptor tyrosine kinase inhibitor (TKI), is a serious clinical problem in the control of advanced gastrointestinal stromal tumors (GIST). Here we report on a meta-analysis we performed to evaluate the efficacy of second-generation TKIs in the treatment of patients with imatinib-resistant GIST.

METHODS

Randomized controlled trials evaluating the clinical efficacy of second-generation TKIs were identified by searching PubMed and EMBASE from 2000 to February 2014. Outcomes subjected to analysis were progression-free survival and overall survival. Statistical analyses were performed using Review Manager version 5.1.0 (Cochrane Collaboration, Oxford, UK). Weighted hazard ratios (HR) with 95% confidence intervals (CIs) were calculated for the outcomes. Fixed-effects or random-effects models were used, depending on the degree of heterogeneity across the selected studies.

RESULTS

Three randomized controlled trials were selected for meta-analysis. Among imatinib-resistant or imatinib-intolerant patients, 541 received second-generation TKIs (sunitinib, nilotinib, or regorafenib) and 267 controls received placebo or best supportive care. Progression-free survival was significantly improved in the TKI-treated group (HR 0.38; 95% CI 0.24-0.59; P<0.0001). No statistically significant difference was detected in overall survival between the treatment group and the control group (HR 0.85; 95% CI 0.71-1.03; P=0.09). In the subgroup of patients who were resistant or intolerant to both imatinib and sunitinib, TKI therapy (nilotinib or regorafenib) improved progression-free survival (HR 0.40; 95% CI 0.19-0.84; P=0.02) but not overall survival (HR 0.83; 95% CI 0.63-1.08; P=0.17). Regorafenib was shown to be effective in terms of progression-free survival across different subpopulations of patients who were resistant to both imatinib and sunitinib.

CONCLUSION

Second-generation TKIs (sunitinib, nilotinib, and regorafenib) are effective in improving progression-free survival but not overall survival in patients with GIST who are resistant or intolerant to imatinib or to imatinib and sunitinib. Regorafenib is promising as a third-line treatment option for patients with advanced GIST.

[18F]Fluorodeoxyglucose PET/Computed Tomography in Gastrointestinal Malignancies

This article discusses the current state-of-the-art application of 2-deoxy-2-[(18)F]fluoro-d-glucose (FDG)-PET and FDG-PET/computed tomography (CT) in the management of patients with gastrointestinal malignancies. Gastrointestinal malignancies include many different cell types, several common malignancies of which may be imaged by FDG-PET/CT. This review focuses on gastric carcinoma, pancreatic carcinoma, hepatocellular carcinoma, cholangiocarcinoma, colorectal carcinoma, and stroma cell tumors. The role of FDG-PET/CT in staging these malignancies is discussed, in addition to (re)staging, detection of recurrent disease, patient selection/prognostication, and response assessment, using the currently available literature.

Roles of mTOR and p-mTOR in gastrointestinal stromal tumors

OBJECTIVE

This study aimed to examine the relationship between expression of mammal target of rapamycin (mTOR) and phosphorylation of mTOR (p-mTOR) protein in the PI3K/Akt/mTOR signaling pathways in gastrointestinal stromal tumors and relatiuonships with clinical factors.

METHODS

Immunohistochemistry was used to detect the expression of the associated proteins mTOR, p-mTOR, and phosphorylation of the tumor suppressor genes PTEN, P27, VEGF, and EGFR in 40 cases of gastrointestinal stromal tumors, with division into a very low and low risk group as well as a moderate and high risk group.

RESULTS

The positive rate of mTOR and p-mTOR was significantly increased in the moderate and high risk group compared with the very low and low risk group. The difference was statistically significant (P<0.05). When grouped according to size, the positive mTOR expression rate exhibited a statistical difference (P<0.05), which was significantly increased in the group of tumors larger than 5 cm. The difference in the positive mTOR and p-mTOR expression rate exhibit no statistical significance among the PTEN, P27, VEGF, and EGFR expression subgroups (P>0.05).

CONCLUSION

The different expressions of mTOR and p-mTOR in the signal transduction pathway of gastrointestinal stromal tumor in the different degree-of-risk groups suggested that the mTOR and p-mTOR of the signal transduction pathway serve an important function in the occurrence and development of gastrointestinal stromal tumors.

Motesanib (AMG706), a potent multikinase inhibitor, antagonizes multidrug resistance by inhibiting the efflux activity of the ABCB1

Cancer cells often become resistant to chemotherapy through a phenomenon known as multidrug resistance (MDR). Several factors are responsible for the development of MDR, preeminent among them being the accelerated drug efflux mediated by overexpression of ATP binding cassette (ABC) transporters. Some small molecule tyrosine kinase inhibitors (TKIs) were recently reported to modulate the activity of ABC transporters. Therefore, the purpose of this study was to determine if motesanib, a multikinase inhibitor, could reverse ABCB1-mediated MDR. The results showed that motesanib significantly sensitized both ABCB1-transfected and drug-selected cell lines overexpressing this transporter to its substrate anticancer drugs. Motesanib significantly increased the accumulation of [(3)H]-paclitaxel in ABCB1 overexpressing cells by blocking the efflux function of ABCB1 transporter. In contrast, no significant change in the expression levels and localization pattern of ABCB1 was observed when ABCB1 overexpressing cells were exposed to 3μM motesanib for 72h. Moreover, motesanib stimulated the ATPase activity of ABCB1 in a concentration-dependent manner, indicating a direct interaction with the transporter. Consistent with these findings, the docking studies indicated favorable binding of motesanib within the transmembrane region of homology modeled human ABCB1. Here, we report for the first time, motesanib, at clinically achievable plasma concentrations, antagonizes MDR by inhibiting the efflux activity of the ABCB1 transporter. These findings may be useful for cancer combination therapy with TKIs in the clinic.

Anti-angiogenic therapy, a new player in the field of sarcoma treatment

Sarcomas encompass a heterogeneous family of mesenchymal malignancies. In metastatic disease improvement in outcome has been limited and there is a clear need for the development of new therapies. One potential target is angiogenesis, already an accepted target for treatment of more prevalent cancers. Multiple (pre)clinical studies focused on the role of angiogenesis and anti-angiogenic treatment in sarcomas. However, getting significant results is complicated due to the relatively small number of patients and the broad range of sarcoma subtypes. Recently, pazopanib has been approved for the treatment of advanced soft tissue sarcoma patients, which is an important step forward and paves the way for the introduction of anti-angiogenic treatment in sarcomas. However, more studies are needed to understand the biological mechanisms by which patients respond to angiogenic inhibitors and to detect markers of response. This review covers the knowledge that has been gained on the role of angiogenesis and anti-angiogenic therapy in sarcomas.

Regorafenib for treatment of advanced gastrointestinal stromal tumors

INTRODUCTION

Gastrointestinal stromal tumors (GISTs) are abdominal sarcomas which are extremely refractory to chemotherapy treatment. The treatment of GISTs has been revolutionized by use of KIT/platelet-derived growth factor receptor-α (PDGFRA) kinase inhibitors. Unfortunately, most tumors develop resistance to front-line (imatinib) or second-line (sunitinib) therapy. Regorafenib, a KIT/PDGFRA/vascular endothelial growth factor receptor (VEGFR) oral kinase inhibitor, has been shown to improve progression-free survival in the third- or fourth-line setting.

AREAS COVERED

This review covers the preclinical and clinical studies of regorafenib for treatment of GIST. A literature search on regorafenib was carried out using the PubMed database up to October 2013.

EXPERT OPINION

Currently, imatinib and sunitinib represent the only proven first- and second-line therapies, respectively, for advanced GISTs. Based on the results of a Phase III study, regorafenib is now established as the only proven third-line therapy. Regorafenib activity in this setting is believed to be due to its activity against oncogenic forms of KIT/PDGFRA. Although side effects are common with this agent, they can be effectively managed with a combination of supportive care, dose interruptions/reductions. The toxicity profile is similar to other oral kinase inhibitors with anti-VEGFR activity. Regorafenib is mainly metabolized by CYP3A4, and concomitant use of strong inducers/inhibitors of this enzyme should be avoided.

Management of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) comprise <1% of all gastrointestinal tumors, but are the most common mesenchymal tumors of the GI tract. This review highlights the dramatic changes in clinical practice with regards to GIST in the last decade, with a focus on overall management and recent developments. For localized primary GISTs, surgical resection is the mainstay of therapy with the 5-year survival rate after complete resection averaging approximately 50-65%. Factors such as tumor size, mitotic rate, tumor location, kinase mutational status and occurrence of tumor rupture have been extensively studied and proposed to be predictors of outcome. Adjuvant imatinib is proposed as an option for those patients with a substantial risk of relapse. Unresectable metastatic or recurrent GIST can be treated with imatinib, with a remarkable response rate (50-70%) and prolonged survival (median progression-free survival: 18-20 months; median overall survival: 51-57 months). Sunitinib is licensed as a second-line therapy following progression on imatinib. Other promising systemic therapies include regorafenib and agents targeting the PI3K/mTOR pathway.

Targeted therapy for cancer: the gastrointestinal stromal tumor model

Gastrointestinal stromal tumors (GISTs) are unique tumors, arising largely due to oncogenic mutations in KIT or PDGFRA tyrosine kinases. Although surgery remains the most effective treatment, the remarkable clinical success achieved with kinase inhibition has made GIST one of the most successful examples of targeted therapy for the treatment of cancer. The insight gained from this approach has allowed a deeper understanding of the molecular biology driving kinase dependent cancers, and the adaptations to kinase inhibition, linking genotype to phenotype. Mutation tailored kinase inhibition with second generation TKI's, and combination immunotherapy to harness the effects of TKIs remain exciting areas of investigation.

The effect of different dosing regimens of motesanib on the gallbladder: a randomized phase 1b study in patients with advanced solid tumors

BACKGROUND

Gallbladder toxicity, including cholecystitis, has been reported with motesanib, an orally administered small-molecule antagonist of VEGFRs 1, 2 and 3; PDGFR; and Kit. We assessed effects of motesanib on gallbladder size and function.

METHODS

Patients with advanced metastatic solid tumors ineligible for or progressing on standard-of-care therapies with no history of cholecystitis or biliary disease were randomized 2:1:1 to receive motesanib 125 mg once daily (Arm A); 75 mg twice daily (BID), 14-days-on/7-days-off (Arm B); or 75 mg BID, 5-days-on/2-days-off (Arm C). Primary endpoints were mean change from baseline in gallbladder size (volume by ultrasound; independent review) and function (ejection fraction by CCK-HIDA; investigator assessment).

RESULTS

Forty-nine patients received ≥1 dose of motesanib (Arms A/B/C, n = 25/12/12). Across all patients, gallbladder volume increased by a mean 22.2 cc (from 38.6 cc at baseline) and ejection fraction decreased by a mean 19.2% (from 61.3% at baseline) during treatment. Changes were similar across arms and appeared reversible after treatment discontinuation. Three patients had cholecystitis (grades 1, 2, 3, n = 1 each) that resolved after treatment discontinuation, one patient developed grade 3 acute cholecystitis requiring cholecystectomy, and two patients had other notable grade 1 gallbladder disorders (gallbladder wall thickening, gallbladder dysfunction) (all in Arm A). Two patients developed de novo gallstones during treatment. Twelve patients had right upper quadrant pain (Arms A/B/C, n = 8/1/3). The incidence of biliary "sludge" in Arms A/B/C was 39%/36%/27%.

CONCLUSIONS

Motesanib treatment was associated with increased gallbladder volume, decreased ejection fraction, biliary sludge, gallstone formation, and infrequent cholecystitis.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00448786.

Clinical significance of vascular endothelial growth factor and vascular endothelial growth factor receptor-2 gene polymorphisms in patients with gastrointestinal stromal tumors

AIM

The vascular endothelial growth factor (VEGF) or its family might play role in tumor-related angiogenesis in gastrointestinal stromal tumors (GIST), thereby affecting the prognosis. Accordingly, the present study analyzed the impact of VEGF and VEGF receptor-2 (VEGFR-2) gene polymorphisms on the prognosis for GIST patients.

METHODS

In all, 213 consecutive patients with GIST from five medical centers were enrolled in the present study. The genomic DNA was extracted from paraffin-embedded tumor tissue, and four VEGF (-2578C/A, -1498C/T, -634G/C, and +936C/T) and one VEGFR-2 (+1416A/T) gene polymorphisms were determined using a Sequenom MassARRAY system.

RESULTS

With a median follow up of 18.4 months, the estimated 5-year relapse-free survival and overall survival rates were 70 and 87%, respectively. In a multivariate analysis including age, sex, primary site of disease, pathology and risk stratification, no significant association was observed between the polymorphism of the VEGF and VEGFR-2 genes and survival.

CONCLUSION

None of the five VEGF and VEGFR-2 gene polymorphisms investigated in this study was found to be an independent prognostic marker for Korean patients with surgically resected GIST. However, further studies on a larger scale are warranted to clarify the role of VEGF and VEGFR gene polymorphisms as a prognostic biomarker for GIST patients.

A phase II evaluation of motesanib (AMG 706) in the treatment of persistent or recurrent ovarian, fallopian tube and primary peritoneal carcinomas: a Gynecologic Oncology Group study

OBJECTIVES

Vascular endothelial growth factors (VEGF) and their receptors have a critical role in stimulating the growth of ovarian cancer cells. Motesanib is a small molecule inhibitor of multiple receptor tyrosine kinases including VEGF receptors 1-3, as well as c-KIT and platelet-derived growth factor which are related to the VEGF family.

PATIENTS AND METHODS

Twenty-two eligible patients with recurrent ovarian, fallopian tube or primary peritoneal carcinoma were treated with an oral daily dose of 125 mg of motesanib. Peripheral blood was analyzed for circulating tumor cells (CTC) and circulating endothelial cells/circulating endothelial progenitors (CEC/CEP), VEGF levels and cell-free circulating DNA (cfDNA).

RESULTS

The study was abruptly halted after four patients developed posterior reversible encephalopathy syndrome. One patient had a partial response and seven patients had stable disease at the time they were removed from study treatment. Twelve of the 22 patients (50%) had indeterminate responses at trial closure. Early closure without clinical efficacy data precludes meaningful correlative studies.

CONCLUSIONS

The serious central nervous system toxicity observed in patients with recurrent ovarian cancer precluded full examination of this agent in this population. There were no clear cut explanations for the high incidence of this known class effect in the study population compared with patients with other cancers.

Vascular endothelial growth factor (VEGF) receptors: drugs and new inhibitors

The recent launch onto the market of five VEGFR inhibitors indicates the therapeutic value of these agents and the importance of the research in the field of angiogenesis inhibitors for future oncologic therapy. In this Perspective we briefly report the inhibitors that are in clinical use, while we dedicate two wider sections to the compounds that are in clinical trials and to the new derivatives appearing in the literature. We especially consider the medicinal chemistry aspect of the topic and report the structure-activity relationship studies and the binding mode of some inhibitors as well as the biological data of the compounds discovered in the past 5 years.

Current and emerging strategies for the management of imatinib-refractory advanced gastrointestinal stromal tumors

Since its approval by the US Food and Drug Administration in February 2002, the tyrosine kinase inhibitor, imatinib, has become the standard of care for patients with metastatic or unresectable KIT-positive gastrointestinal stromal tumors (GISTs). Imatinib functions by blocking the adenosine triphosphate binding site of the constitutively activated mutant KIT or platelet-derived growth factor receptor α, effectively shutting down the oncogenic signal that drives up to 90% of these tumors. In doing so, it has transformed the management of a condition previously refractory to systemic treatments and established GIST as a model for the use of targeted therapies and oncogene addiction in solid tumors. However, while more than 80% of patients will receive clinical benefit from imatinib monotherapy, more than half will develop progressive disease by 2 years. In this article we review the mechanism and patterns of imatinib resistance in GIST; attempt to offer a practical schema for managing imatinib-refractory patients; and lastly, offer some insight as to future directions and emerging therapeutics for the management of this highly interesting and challenging disease.

Current management and prognostic features for gastrointestinal stromal tumor (GIST)

Stromal or mesenchymal neoplasms affecting the gastrointestinal (GI) tract have undergone a remarkable evolution in how they are perceived, classified, approached, diagnosed and managed over the last 30 years. Gastrointestinal stromal tumors (GIST) account for approximately 1% to 3% of all malignant GI tumors. The clinical features can vary depending on the anatomic location, size and aggressiveness of the tumor. Metastatic GIST represents a successful example of molecular targeted therapy. In this comprehensive review, we discuss the epidemiology, clinical features and diagnostic modalities for GIST. We also describe treatment options for early stage, locally advanced and metastatic GIST. Indications for neoadjuvant and adjuvant therapy along with duration of therapy are also explained. A brief discussion of latest biomarkers and updates from recent meetings is also provided.

Personalized tumor response assessment in the era of molecular medicine: cancer-specific and therapy-specific response criteria to complement pitfalls of RECIST

OBJECTIVE

The purpose of this article is to review cancer- and therapy-specific tumor response assessment criteria used in clinical trials and in practice, with illustrative case examples, and to discuss future directions toward "personalized" tumor response assessment.

CONCLUSION

Although Response Evaluation Criteria in Solid Tumors will remain as the primary generalized criteria for response assessment, newer cancer- and therapy-specific criteria will play an important role in providing state-of-the-art response assessment of tumor following molecular targeted therapy and will contribute to personalized cancer care in the era of molecular medicine.

Recent advances and novel agents for gastrointestinal stromal tumor (GIST)

The discovery of CD117 mutation in almost all gastrointestinal stromal tumors (GISTs) marked a milestone. Other spindle cell neoplasms arising from the GI tract including lipoma, schwannoma, hemangioma, leiomyoma, and leiomyosarcoma are typically CD117-negative. GIST research and clinical care now represent a paradigm of translating discoveries in the molecular pathogenesis of cancer into highly effective targeted therapies that selectively inhibit etiologic “driver” pathways, leading to dramatically improved clinical outcomes. A series of investigations and trials are underway to develop novel and effective ways to treat patients with GIST. In this review, we discuss the highlights of recent advances and novel agents for GIST therapy.

F-FDG PET Imaging in the Evaluation of Treatment Response to New Chemotherapies beyond Imatinib for Patients with Gastrointestinal Stromal Tumors

Aim. (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) is a powerful tool for staging and defining "good responders" to chemotherapy in tumor setting. Gastrointestinal stromal tumors (GISTs) are sarcoma involving gastrointestinal tract and may require a chemotherapy including imatinib, a tyrosine kinase inhibitor agent. Some GIST patients become refractory to imatinib; therefore, other tyrosine kinase inhibitors or concomitant chemotherapy may be considered for treatment. The aim of this paper is to assess if (18)F-FDG PET imaging is a useful tool to evaluate treatment response to new chemotherapies beyond imatinib for GIST patients. Methods. We performed a review of the literature about the role of (18)F-FDG PET in the evaluation of treatment response to new chemotherapies beyond imatinib for GIST patients. Results and Conclusions. (18)F-FDG PET seems to be able to assess therapy response earlier than computed tomography (CT) imaging in imatinib refractory GIST patients treated with other agents. However, a dual modality PET-CT imaging is recommendable to achieve a better detection of all lesions.