Emerging VEGF-receptor inhibitors for colorectal cancer

Introduction: Targeted agents have dramatically improved and enriched the therapeutical choices for patients with metastatic colorectal cancer (mCRC). By better understanding the role of the angiogenic pathway in colorectal cancer (CRC), new therapies have been developed. Bevacizumab, the first anti-angiogenetic agent approved for the treatment of mCRC provide a proof of concept since it has improved the progression-free survival and overall survival when combined with cytotoxic chemotherapy.

Areas covered: This review is focused on the most recent findings on the VEGF signaling pathway and new therapeutic drugs explored in clinical trials.

Expert opinion: Despite the advantage offered by bevacizumab, the median overall survival of mCRC patient exceeds 21 months; thus, investigational efforts are needed. Several antiangiogenic agents for the treatment of mCRC are being tested in preclinical and clinical Phase I/II trials. Unfortunately a discrete number of Phase III trials produced negative results. Recently aflibercept and regorafenib, two new antiangiogenic drugs, have been approved as the new-targeted agents for the treatment of mCRC, according to the positive findings from the VELOUR and the CORRECT studies. In order to maximize clinical impact it will be important to validate predictive biomarkers and best combination treatments to offer for mCRC patients; further research and intense investigation is still required.     

An overview of experimental and investigational multikinase inhibitors for the treatment of metastatic colorectal cancer

Introduction: The era of molecular-targeted agents, particularly bevacizumab and cetuximab, has revolutionized the treatment paradigm for metastatic colorectal cancer (mCRC). Amongst the multikinase inhibitors (MKIs) examined, regorafenib was the first to establish its role in mCRC. Despite its modest efficacy, this finding had reignited interest in exploring MKIs with the hope of maximizing their therapeutic potential in mCRC.

Areas covered: This review summarizes the previous studies of MKIs in mCRC, targeting two signaling pathways activated through vascular endothelial growth factor receptors and epidermal growth factor receptors. The article provides discussion with a focus on: the challenges encountered when combining MKI with chemotherapy, the lack of predictive markers, and strategies utilized to address escape pathways through combining MKIs with other targeted agents.

Expert opinion: Clinical progress using MKIs in mCRC has been disappointing due to their limited efficacy. The exact role of regorafenib, apart from in chemo-refractory disease setting, requires further delineation. The role of MKIs in combination with other targeted agents or chemotherapy and in the maintenance setting is still considered experimental and warrants further investigation. The broader role of the current generation of MKIs will depend upon the accurate identification of patients with specific molecular phenotypes and better pharmacodynamic understanding of these agents to minimize toxicity.     

Beyond bevacizumab: new anti-VEGF strategies in colorectal cancer

Introduction: Treatment of colorectal cancer (CRC) has changed dramatically over the past decade, mainly due to the advent of molecularly targeted agents. In particular, an improved understanding of the role of the angiogenesis pathway in CRC has led to advancements in treatment. Bevacizumab has been shown to improve the progression-free survival and overall survival when combined with cytotoxic chemotherapy in patients with metastatic CRC (mCRC) and at present is the only antiangiogenesis agent approved for the treatment of this cancer.

Areas covered: In this review, the authors outline the most recent data on the VEGF signaling pathway and on new therapeutic reagents that target it, provide insight into their mechanisms, and describe results from recent clinical trials.

Expert opinion: In the new decade of ‘modern therapy', an increasing number of antiangiogenic agents for the treatment of mCRC are being tested in preclinical models, and dozens of studies on these drugs are ongoing. Presently, eight novel antiangiogenic agents are in Phase III trials and a wide range of other candidates are being tested in Phase I/II trials. Given the preliminary positive results of two recent Phase III trials, aflibercept and regorafenib, probably, will be new-targeted agents approved for the treatment of mCRC. Furthermore, the list of potentially approved agents seems to increase in the next years and to maximize their potential clinical impact, is critically important to introduce efficient molecular diagnostic methodologies into the drug development process to indentify the subset of patients who would benefit most from their use.     

Safety and efficacy of nintedanib for the treatment of metastatic colorectal cancer

Introduction: Nintedanib (BIBF 1200) is an oral tyrosine kinase inhibitor that targets the vascular endothelial growth factor (VEGFR), platelet-derived growth factor (PDGFR) and fibroblast growth factor (FGFR) receptors. It is approved in Europe in combination with docetaxel for patients with advanced lung adenocarcinoma who have progressed to first-line chemotherapy. However, its role in the treatment of metastatic colorectal cancer (mCRC) is uncertain. Recent results from the LUME-Colon 1 pivotal phase III trial showed only a marginal increase in progression free survival over placebo in refractory mCRC patients, with a toxicity profile similar to other antiangiogenic agents, and no benefit in overall survival.

Areas covered: The aim of this review is to summarize the pharmacology, efficacy and safety profile of nintedanib in the context of mCRC, and to provide some perspective regarding the role of this drug in clinical practice.

Expert commentary: Nintedanib provides limited clinical benefit in refractory CRC and its use in this clinical setting is not warranted. Efforts shall continue to pursue the identification of predictive biomarkers that allow the selection of subpopulations with a greater likelihood to benefit from this therapeutic approach, in order to improve the benefit-risk and cost-benefit ratios of this and other antiangiogenic agents.     

Overview of different available chemotherapy regimens combined with radiotherapy for the neoadjuvant and definitive treatment of esophageal cancer

Introduction: Neoadjuvant chemoradiotherapy (CTRT) is the current standard of care for treatment of locally advanced cancer of the esophagus or gastroesophageal junction. Many efforts have been made over the last years to identify the best chemotherapy and radiotherapy combination regimen, but specific randomized trials addressing this issue are still lacking.

Areas covered: A systematic review of the literature was performed searching in PubMed all published studies of combinations CTRT regimens for operable or unresectable esophageal cancer to describe activity and toxicity. Studies considered were prospective series or clinical phase II-III trials including at least 40 patients and published in English language.

Expert commentary: Long-term results of CROSS trial have established RT combined with carboplatin plus paclitaxel chemotherapy as the preferred neoadjuvant treatment option for both squamous and adenocarcinoma of the esophagus. More effective multimodal treatment strategies integrating novel biological agents including immunotherapy and based on an extensive molecular tumor characterization are eagerly awaited.     

Regorafenib in the treatment of colorectal cancer

Introduction: Colorectal cancer (CRC) is among the most frequently diagnosed malignancies, and is commonly associated with metastatic disease at presentation. While chemotherapy represents a mainstay of management, options at the time of disease progression are limited. Regorafenib is a novel multikinase inhibitor which has been evaluated for patients with chemo-refractory metastatic CRC (mCRC) and is currently approved for use in a last-line-of-treatment setting.

Areas covered: Articles searchable on MEDLINE/PubMed were reviewed to provide context for use of regorafenib in the management of mCRC. Specific drug properties are discussed, including chemistry, pharmacodynamics, pharmacokinetics, and metabolism. Additionally, clinical efficacy is reported with consideration of Phases I–III data.

Expert opinion: Phase III evaluation has confirmed the efficacy of regorafenib for patients with chemo-refractory mCRC. Importantly, the rapid accrual of the CORRECT trial revealed the degree of unmet need for this patient population, and proved that it was feasible to compare novel agents to placebo when multiple lines of standard therapy have failed. In the coming years, the role of regorafenib in the management of mCRC should be further clarified, especially through identification of the patient population with greatest anticipated benefit and exploration of its use as an adjuvant or maintenance agent.     

Advances in chemotherapy in advanced non-small-cell lung cancer

Importance of the field: Lung cancer is the most common cancer in the world today, in terms of both incidence and mortality. Non-small-cell lung cancer (NSCLC) accounts for about 85% of all lung cancers diagnosis, and the majority of people diagnosed with NSCLC have advanced disease.

Areas covered in this review: In this review the main advances achieved in the medical treatment of advanced NSCLC are discussed, regarding both targeted therapies and chemotherapy. Among targeted therapies, recent data on the anti-vascular endothelial growth factor (VEGF) monoclonal antibody bevacizumab and the epidermal growth factor receptor tyrosyne kinase inhibitors (EGFR-TKIs) gefitinib and erlotinib are described. Among chemotherapeutic agents, the role of pemetrexed is discussed.

What the reader will gain: The reader will gain up-to-date information on the main advances, achieved in the last 3 years in the medical treatment of advanced NSCLC.

Take home message: Some recent advances have changed the face of the first-line chemotherapy of advanced NSCLC, giving physicians more options to tailor choice in this challenging setting.     

Management of advanced and/or metastatic carcinoid tumors: historical perspectives and emerging therapies

Introduction: Carcinoid tumors are uncommon neoplasms that offer unique therapeutic challenges to practicing physicians. Several chemotherapy combinations and IFN-α have been used for the treatment of unresectable carcinoid tumors over the last decades, but they have shown variable clinical results. Given the heterogeneity of these tumors, there is no clear therapeutic agent or combination that confers a significant advantage over others.

Areas covered: The authors provide a comprehensive evaluation of the existing therapies for advanced carcinoid tumors such as traditional agents, combination therapies and newer drugs.

Expert opinion: Somatostatin analogs are known to provide symptomatic relief in patients with carcinoid syndrome, but their antiproliferative effect has not been proven beyond the reasonable doubt. Traditional streptozocin-based regimens may offer a survival benefit in patients with advanced carcinoids, yet their toxicity is not negligible. Temozolomide has shown efficacy alone and in combination with other agents, and its further testing in advanced carcinoid tumors appears warranted. Efficacy of various tyrosine kinase inhibitors, VEGF inhibitors and mTOR inhibitors appears promising, and should be explored in patients with metastatic carcinoid tumors. In addition, use of these agents in combination with traditional chemotherapeutic agents should also be investigated.     

Outcomes and safety of rapid desensitization for chemotherapy hypersensitivity

Importance of the field: The incidence of hypersensitivity reactions (HSRs) to chemotherapy agents has increased because of increasing number of cancer survivors are exposed to repeated courses of sensitizing agents. Replacement with an alternative chemotherapy regimen is often limited by tumor sensitivity. Rapid desensitization offers an effective mean to allow continuation of the treatment to which patients have presented HSRs.

Areas covered in this review: We review the methods, outcome and safety of the rapid desensitization protocol developed at Brigham and Women's Hospital, Harvard Medical School Affiliate, based on our recent publication “‘Hypersensitivity reactions to chemotherapy: outcome and safety of rapid desensitization in 413 cases”. Literature search was conducted through Medline (from January 1976 to September 2009), using PubMed.

What the reader will gain: The article will give insight to clinical manifestations of immediate HSR to various chemotherapy agents and their presumably different immunopathomechanism. Risk assessment, including skin testing in those presented HSRs to platins and details on rapid desensitization process and its pitfalls will be discussed.

Take home message: Standa"rd protocol of rapid desensitization, administering under multidisciplinary team approach, is safe and effective in overcoming immediate HSRs to platins, taxanes, doxorubicin and rituximab via both intravenous and intraperitoneal routes.     

The safety of ramucirumab for the treatment of colorectal cancer

Introduction: Ramucirumab, a human monoclonal antibody against vascular endothelial growth factor receptor 2 (VEGFR-2), is an antiangiogenic therapy that has been approved in combination with FOLFIRI in second-line treatment of metastatic colorectal cancer (mCRC), after progression on or after therapy with bevacizumab, oxaliplatin, and a fluoropyrimidine. A thorough review of the safety of ramucirumab in this setting and in the context of other antiangiogenic agents is merited.

Areas covered: We provide an overview of activity and summarize in detail the overall safety and tolerability profile of ramucirumab in mCRC patients on the basis of a literature review of all published clinical trials in this setting, including both single-agent and combination studies. A focus on adverse events of interest and specific populations is included, as well as a critical comparison with other antiangiogenic therapies.

Expert opinion: As an effective agent in pretreated mCRC patients, the toxicity profile of ramucirumab is similar to those of other angiogenesis inhibitors used in the second-line mCRC setting. The next challenge will be to find biomarkers of response and toxicity to antiangiogenic therapies in order to more effectively implement personalized medicine in these patients.     

Present and future therapeutic options for locally advanced and metastatic renal cell carcinoma

Introduction: Locally advanced or metastatic renal cell carcinoma (RCC) is notoriously chemo- and radioresistant, leaving immunotherapy as the only treatment option. In recent years, targeted therapies have offered significant increases in progression-free survival (PFS). Despite this, the majority of patients soon develops resistant disease and finally succumbs. The need to implement treatment strategies that improve overall survival while having an acceptable safety profile is imperative.

Areas covered: This review provides information on the efficacy of recently studied treatment strategies for advanced RCC. These include sequential and combination therapy of established drugs as well as data on agents in early clinical development. The Medline and ASCO database were searched for clinical trials on medical therapy of advanced RCC from 2004 until May 2010. Data on targeted therapies, including tyrosine kinase inhibitors, vascular endothelial growth factor inhibitors, mammalian target of rapamycin inhibitors, and antiepidermal growth factor receptor agents are summarized.

Expert opinion: Improvements in response rates and PFS in patients with advanced RCC have been observed with new treatment strategies. The benefit in overall survival is less clear and needs further evaluation. Toxicity represents a concern especially in combination regiments.     

Current synthetic pharmacotherapy for treatment-resistant colorectal cancer: when urgent action is required

Introduction: Colorectal cancer (CRC) remains a global concern. Fourteen antineoplastics are approved for metastatic CRC (mCRC); however, the 5-year overall survival remains poor for the overwhelming majority of patients. Poor outcomes continue to highlight the critical need for therapeutic advancement.

Areas covered: mCRC represents a clinical and molecular complex malignancy with several treatment barriers. Prognostic and predictive factors have and continue to emerge anatomically, molecularly, and via patient-related factors. Herein, the authors review the current understanding and promising future directions amongst these different subtypes.

Expert opinion: CRC is largely considered a common cancer. Consequently, treatment approaches have been rather homogenous with systemic chemotherapy combinations. Of significance is the recent identification of targetable rare subsets of mCRC, notably for microsatellite instability-high (MSI-H) patients and for BRAF mutated patients. As a result, we are at the forefront of interpreting biological differences that provide targetable approaches and/or additional insight. To continue to do so, future clinical trial developments must focus on diverse subtypes of mCRC rather than all-encompassing mCRC proposals. Yet of greatest need is identifying options for RAS-mutated and microsatellite-stable mCRC patients. For the majority of these patients, we continue to seek novel innovative approaches to improve the overall survival of these patients.     

The potential role of nintedanib in treating colorectal cancer

Introduction: Angiogenesis leads to the growth, progression, and metastases of a variety of solid tumors, including metastatic colorectal cancer (mCRC), involving particularly the family of vascular endothelial growth factors (VEGF) and their receptors (VEGFR). Several anti-angiogenic inhibitors are already registered for mCRC therapy: bevacizumab, aflibercept, ramucirumab, regorafenib. Nintedanib is a new triple angiokinase oral inhibitor that potently blocks the proangiogenic pathways mediated by VEGFR, platelet-derived growth factor receptor (PDGFR), and fibroblast growth factor receptor (FGFR).

Areas covered: The current state-of-the-art of anti-angiogenic inhibitors employed in the treatment mCRC patients, and in particular the role of nintedanib in this setting, is reviewed and discussed here. A structured search of bibliographic databases for peer-reviewed research literature and of main meetings using a focused review question was undertaken.

Expert opinion: In first-line therapy, a phase II randomized trial showed that nintedanib plus chemotherapy was not inferior to the bevacizumab-based regimen. In heavily pretreated mCRC patients nintedanib improved some outcomes. During the natural history of mCRC resistances to anti-angiogenic therapies can set in and in this context, nintedanib, due to its triple inhibition, might play a role in compensatory angiogenesis overcoming the resistance developed due to VEGF directed therapy.     

Emerging drugs in endometrial cancers

Importance of the field: Endometrial cancer remains the most common gynecologic malignancy. The treatment of endometrial cancer is rapidly evolving.

Areas covered in this review: In this article, we aim to review current and future treatment options in the medical treatment of endometrial cancers.

What the reader will gain: The cornerstone of curative therapy for patients with endometrial cancer is surgical treatment. Cytotoxic chemotherapy is the mainstay of therapy for metastatic and advanced endometrial cancer. The most active chemotherapy agents are anthracyclines, platinum compounds and taxanes. Combination chemotherapy has produced higher response rates than single agent therapy. Cisplatin and doxorubicin combination chemotherapy has served as the control arm in many trials. Three-drug combination regimen has shown the highest response rate but with increased toxicity. Despite the lack of published data supporting the superiority of the paclitaxel plus carboplatin combination over doxorubicin and cisplatin, many centers prefer this regimen as a standard of care. Hormonal therapy should be considered in patients with low grade tumors and in those with a poor performance status. Recent advances in the understanding of the molecular biology of endometrial cancer have led to development of targeted therapies. Among these the more promising ones are mTOR inhibitors and antiangiogenic agents.

Take home message: Clinical trials are planned to further explore how to best incorporate novel agents into the current treatment algorithm with the aim to improve outcome for women with endometrial adenocarcinomas.     

Anti-angiogenic drug discovery: lessons from the past and thoughts for the future

Introduction: Since the pioneering work of Judah Folkman, the discovery of bevacizumab has introduced the use of anti-angiogenic agents as a new modality for the treatment of cancer. Currently, hundreds of clinical trials involving anti-angiogenic agents, targeting different elements of the tumour angiogenesis pathway, are underway. However, thus far, the benefits of anti-angiogenic therapy in unselected patient populations are often marginal with harmful side effects.

Areas covered: This article presents a detailed discussion of the lessons learnt from the use of bevacizumab and other VEGF pathway inhibitors in the clinical setting. Specifically, this article provides a review of the literature on anti-VEGF agents and other angiogenesis inhibitors used in pre-clinical and clinical trials for cancer treatment.

Expert opinion: Future anti-angiogenic drug design centres on multiple protein targets and combinations including: growth factors, hypoxia-inducible factor and tumour endothelial cell markers unique to the tumour vasculature. Furthermore, treatment dosing, scheduling and combination with radiation and chemotherapy require further investigation, as does the potential of treating early disease, and the development of biomarkers which accurately predict response to therapy. These are essential for the future development of these drugs with individualised therapy likely to be the ultimate goal.     

Molecular targeted therapy of advanced hepatocellular carcinoma beyond sorafenib

Importance of the field: With the recent advances in the knowledge of molecular biology of hepatocellular carcinoma (HCC), there have been encouraging developments in targeted therapy for advanced HCC.

Areas covered in this review: This review discusses the development of targeted therapy for advanced HCC patient since 2006. Among the newly identified targets, promising results have been shown in targeting the anti-angiogenic pathway. Pure anti-angiogenic agents such as bevacizumab and PTK 787 demonstrate modest activity in treating patients with advanced HCC. Sorafenib, a multi-targeted tyrosine kinase inhibitor with both anti-angiogenic and anti-proliferative effects, has been shown to prolong the overall survival of patients with advanced HCC in two Phase III randomized trials. Like sorafenib, other anti-angiogenic multi-targeted tyrosine kinase inhibitors, such as sunitinib, pazopanib, brivanib and linifanib, also show promising activity in various stages of clinical trials. Other on-going early-phase studies are exploring the activities of drugs targeting novel pathways, such as PI3K/AKT/m TOR, hepatocyte growth factor/mesenchymal epithelial transition factor and insulin-like growth factor.

What the reader will gain: After reading this review, the reader should have an in-depth understanding of the latest developments in the molecular targeted therapy of advanced HCC.

Take home message: The development of sorafenib in the treatment of advanced HCC proves the concept that molecular targeted therapies, especially anti-angiogenic agents, play a pivotal role in the treatment of this otherwise chemoresistant neoplasm. Future progress depends on further unraveling more molecular mechanisms of HCC for therapeutic intervention.     

Targeting epidermal growth factor receptor in the treatment of non-small-cell lung cancer

Importance of the field: The management of non-small-cell lung cancer (NSCLC) has undergone a paradigm shift in the last decade, with the survival advantage demonstrated by the incorporation of anti-epidermal growth factor receptor (EGFR) agents to the standard treatment of advanced/metastatic NSCLC.

Areas covered in this review: We review the existing data regarding the distinct anti-EGFR agents in the NSCLC treatment and the potential role of the investigated biomarkers in the clinical outcome.

What the reader will gain: Tyrosine kinase inhibitors have been used in first-line, second-line and more settings with extremely good results in a subgroup of patients. Cetuximab remains the only anti-EGFR monoclonal antibody to show survival benefit when combined with a cytotoxic agent in the front-line setting. Anti-EGFR treatment is associated with a dramatic clinical benefit in a subgroup of patients, emphasizing the importance of customizing treatment. Several biomarkers have been investigated for their predictive or prognostic value. Validation of identification of biomarkers remains a focus of intense research that may ultimately guide therapeutic decision making, as none of these is considered ideal to discriminate responding from non-responding patients. However, the current evidence of the EGFR mutation analysis from a recent randomised trial suggests that EGFR mutation analysis is quite a good predictive marker for responsiveness to anti-EGFR TKIs. Moreover, the identification of surrogate markers to indicate optimal activity of the anti-EGFR agent is also needed. This review article provides data from large clinical trials using anti-EGFR agents and correlates these results with the tested biomarkers.

Take home message: EGFR inhibition has shown very encouraging results and has improved the outcome of the NSCLC treatment. However, a plateau of significant clinical benefit seems to have been reached and we believe that the time to move away from the traditional treatment approach to more individualizing therapies has come.     

The development of the tumor vascular-disrupting agent ASA404 (vadimezan,DMXAA): current status and future opportunities

Importance of the field: Targeting tumor vasculature with antiangiogenic agents improves outcomes achieved with chemotherapy in some cancers, but toxicity limits their applicability. Tumor vascular-disrupting agents (tumor-VDAs) induce an acute collapse in tumor vascular supply; ASA404 (vadimezan, 5,6-dimethylxanthenone-4-acetic acid [DMXAA]) is the tumor-VDA most advanced in clinical development. Recent randomized trials of ASA404 in combination with chemotherapy suggested a survival advantage in NSCLC comparable to that achieved with bevacizumab, but with little additional toxicity. Phase III trials in advanced NSCLC have completed accrual, and a review of this exciting agent is timely.

Areas covered in this review: This review focuses on the development of ASA404 to date, its mechanisms of action, the current body of clinical research and potential avenues for therapeutic use. It includes all completed clinical trials since it entered clinical testing in 1995 through to 2009.

What the reader will gain: This review will help the reader to understand why ASA404 is unique among tumor-VDAs; the clinical trial methodology required to evaluate such agents; and its remarkable potential clinical utility.

Take home message: ASA404 is a tumor-VDA that offers considerable potential to improve outcomes in cancer patients in combination with existing treatments.     

Emerging tyrosine kinase inhibitors for the treatment of metastatic colorectal cancer

Introduction: Colorectal cancer (CRC) is a leading cause of cancer death worldwide. Over the last decade, the addition of antibodies that block the epidermal growth factor receptor (EGFR) or angiogenesis to the classic chemotherapy backbone has improved overall survival in metastatic colorectal cancer (mCRC). However, the role of the other major targeted therapy, the tyrosine kinase inhibitors (TKIs), is not yet fully clarified.

Areas covered: This review discusses key published and ongoing studies with TKIs in mCRC, the mechanisms of resistance to standard treatments that are potentially targetable with these small molecules, along with the role of biomarkers in therapeutic decision-making process.

Expert opinion: The current effectiveness of TKIs is limited by two principal reasons, firstly the use of combination chemotherapy necessitates lower dose-density to manage the toxicity profile and secondly, development of these drugs has mainly been performed in molecularly unselected populations. mCRC is a heterogeneous and dynamic disease, and clinical trials with TKIs must be designed on the basis of specific molecular alterations targeted by these drugs. Success with this approach relies on identifying mutations at the time of progression, raising the importance of minimally-invasive monitoring tools. Liquid biopsies are a promising option, although this technique remains to be validated. Overall, this approach contributes to the move towards personalized and precision therapeutic strategies.