Multicenter Phase II Trial of Temsirolimus and Bevacizumab in Pancreatic Neuroendocrine Tumors

PURPOSE

There are few effective therapies for pancreatic neuroendocrine tumors (PNETs). Recent placebo-controlled phase III trials of the mammalian target of rapamycin (mTOR) inhibitor everolimus and the vascular endothelial growth factor (VEGF)/platelet-derived growth factor receptor inhibitor sunitinib have noted improved progression-free survival (PFS). Preclinical studies have suggested enhanced antitumor effects with combined mTOR and VEGF pathway-targeted therapy. We conducted a clinical trial to evaluate combination therapy against these targets in PNETs.

PATIENTS AND METHODS

We conducted a two-stage single-arm phase II trial of the mTOR inhibitor temsirolimus 25 mg intravenously (IV) once per week and the VEGF-A monoclonal antibody bevacizumab 10 mg/kg IV once every 2 weeks in patients with well or moderately differentiated PNETs and progressive disease by RECIST within 7 months of study entry. Coprimary end points were tumor response rate and 6-month PFS.

RESULTS

A total of 58 patients were enrolled, and 56 patients were eligible for response assessment. Confirmed response rate (RR) was 41% (23 of 56 patients). PFS at 6 months was 79% (44 of 56). Median PFS was 13.2 months (95% CI, 11.2 to 16.6). Median overall survival was 34 months (95% CI, 27.1 to not reached). For evaluable patients, the most common grade 3 to 4 adverse events attributed to therapy were hypertension (21%), fatigue (16%), lymphopenia (14%), and hyperglycemia (14%).

CONCLUSION

The combination of temsirolimus and bevacizumab had substantial activity and reasonable tolerability in a multicenter phase II trial, with RR of 41%, well in excess of single targeted agents in patients with progressive PNETs. Six-month PFS was a notable 79% in a population of patients with disease progression by RECIST criteria within 7 months of study entry. On the basis of this trial, continued evaluation of combination mTOR and VEGF pathway inhibitors is warranted.

Randomized Phase III Trial of Temsirolimus and Bevacizumab Versus Interferon Alfa and Bevacizumab in Metastatic Renal Cell Carcinoma: INTORACT Trial

Purpose

To prospectively determine the efficacy of combination therapy with temsirolimus plus bevacizumab versus interferon alfa (IFN) plus bevacizumab in metastatic renal cell carcinoma (mRCC).

Patients and Methods

In a randomized, open-label, multicenter, phase III study, patients with previously untreated predominantly clear-cell mRCC were randomly assigned, stratified by prior nephrectomy and Memorial Sloan-Kettering Cancer Center prognostic group, to receive the combination of either temsirolimus (25 mg intravenously, weekly) or IFN (9 MIU subcutaneously thrice weekly) with bevacizumab (10 mg/kg intravenously, every 2 weeks). The primary end point was independently assessed progression-free survival (PFS).

Results

Median PFS in patients treated with temsirolimus/bevacizumab (n = 400) versus IFN/bevacizumab (n = 391) was 9.1 and 9.3 months, respectively (hazard ratio [HR], 1.1; 95% CI, 0.9 to 1.3; P = .8). There were no significant differences in overall survival (25.8 ν 25.5 months; HR, 1.0; P = .6) or objective response rate (27.0% ν 27.4%) with temsirolimus/bevacizumab versus IFN/bevacizumab, respectively. Patients receiving temsirolimus/bevacizumab reported significantly higher overall mean scores in the Functional Assessment of Cancer Therapy–Kidney Symptom Index (FKSI) –15 and FKSI-Disease Related Symptoms subscale compared with IFN/bevacizumab (indicating improvement); however, no differences in global health outcome measures were observed. Treatment-emergent all-causality grade ≥ 3 adverse events more common (P < .001) with temsirolimus/bevacizumab were mucosal inflammation, stomatitis, hypophosphatemia, hyperglycemia, and hypercholesterolemia, whereas neutropenia was more common with IFN/bevacizumab. Incidence of pneumonitis with temsirolimus/bevacizumab was 4.8%, mostly grade 1 or 2.

Conclusion

Temsirolimus/bevacizumab combination therapy was not superior to IFN/bevacizumab for first-line treatment in clear-cell mRCC.

Temsirolimus for advanced renal cell carcinoma

Renal cell carcinomas (RCCs) represent one of the ten leading cancer entities with an increasing incidence especially in the western world. Unfortunately, about 25% of the patients develop metastatic RCC (mRCC) associated with a most unfavorable prognosis. In the recent years, various new agents targeting VEGF or VEGF receptor (VEGFR) or the mTOR pathway have been approved for the treatment of mRCC with significant prolongation of progression-free survival and, in part, of overall survival (OS). Targeting the mTOR kinase is an interesting option for mRCC. Temsirolimus, one of the available mTOR inhibitors, has been approved as a single agent in poor-risk mRCC patients based on the pivotal Phase III trial showing a significant superiority in OS versus IFN-α or temsirolimus + IFN-α, which has been verified by a pivotal Phase III trial. The benefit has been shown for clear cell carcinoma and papillary RCC as well. For poor prognosis patients, temsirolimus improves median survival by 3.6 months. In second-line treatment compared with sorafenib following first-line treatment with sunitinib temsirolimus showed a relative progression-free survival benefit for patients with nonclear cell RCC with temsirolimus. The median OS for the temsirolimus group was 12.27 and 16.64 months for the sorafenib group. In 2007, the US FDA granted approval for temsirolimus for the treatment of advanced RCC.

Recent developments in the treatment of renal cell carcinoma

Renal cell carcinoma (RCC) management has been imbued with new interest, in large part due to the recent success of new treatment options for advanced and metastatic disease. This has also been accompanied by less generally well known advances in the understanding of the molecular characterizations of subtypes of RCC with potential to lead to new therapeutic options. Additionally, the urologic oncology community is focusing on nephron-sparing surgical approaches with limited surgery if possible, and in conjunction with interventional radiologists, on ablative procedures for incidentally determined small renal masses. This report reviews some of the new biologic findings of adenocarcinoma of the kidney, and reviews the new therapeutics which continue to change the landscape for treatment of RCC.

Temsirolimus: a safety and efficacy review

INTRODUCTION

The vascular endothelial growth factor (VEGF) pathway and the mammalian Target of Rapamycin (mTOR) represent the most frequently exploited targets in renal cell carcinoma (RCC). Temsirolimus is an inhibitor of mTOR, and is a unique ester derivative of sirolimus, a macrocyclic lactone, with improved pharmaceutical properties, including stability and solubility. Temsirolimus binds to the cytoplasmic protein FKBP-12, and the complex binds and inhibits mTOR.

AREAS COVERED

This review summarizes the clinical findings and safety of temsirolimus in RCC patients.

EXPERT OPINION

A Phase III clinical trial has demonstrated that temsirolimus has statistically significant advantages over treatment with IFN-α in RCC patients with poor prognosis, in terms of OS (overall survival), PFS (progression-free survival), and tumor response. Median OS was improved 49% compared to IFN-α, and median PFS was approximately doubled. It is now considered the standard for RCC patients with poor prognostic features. The possibility that this agent is useful in metastatic non-clear cell carcinoma patients has also been suggested by a subset analysis of the pivotal Phase III trial. Studies in untreated favorable and intermediate risk clear cell and refractory mRCC patients are required.

Combination Agents Versus Multi-Targeted Agents – Pros and Cons

Cancer, in all its various forms, is perhaps the archetypical multi-factorial disease and it is therefore not surprising that single-target drugs are rarely useful as anti-cancer agents when used on their own. Traditional cancer therapy has relied on effective drug combinations and the more recent emergence of compounds that simultaneously modulate multiple targets has added to the oncology armoury and raised the question as to which approach, drug combinations or single compound multi-targeted drug, is to be preferred. This chapter reviews the basis for combining existing drugs and how these combinations are selected, and compares these with multi-targeted drugs (MTDs) such as sunitinib, a broad-spectrum kinase inhibitor that inhibits a range of growth factors. Whether using physical combinations or MTDs, or indeed combinations of MTDs, the choice of which targets and which pathways to attack is crucial and the rationale for selecting these is discussed in detail. The NCI Cancer Therapy Evaluation Program, designed to facilitate trials of novel combinations, will aid in the rational selection of targets and pathways to combine in future MTDs. The pros and cons of combinations and MTDs in terms of the relative challenges in clinical development are examined, and the systematic use of biomarkers, better approaches to patient selection, and improved design of trials to take account of the heightened potential for acute and delayed on- and off-target toxicities are highlighted.

Emerging roles for mammalian target of rapamycin inhibitors in the treatment of solid tumors and hematological malignancies

PURPOSE OF REVIEW

The mammalian target of rapamycin (mTOR) is a key regulator of cell growth and survival in mammalian cells. mTOR pathways are frequently dysregulated in various malignancies, providing targets for new anticancer drugs and therapeutic strategies. Here, we summarize the clinical experience of trials using the first generation of mTOR inhibitors, the rapalogs, and highlight the development of the next generation of catalytic inhibitors of the pathway.

RECENT FINDINGS

mTOR inhibitors have shown major clinical activity in the treatment of renal cell carcinoma and two rapalogs have been approved for treatment of this malignancy. Recently, clinically significant trials with these agents were conducted in mantle cell lymphoma, pancreatic neuroendocrine tumors and astrocytomas. There are also promising results emerging in sarcomas, breast cancer and lung carcinoma. Multiple agents targeting mTOR, belonging to the new class of catalytic inhibitors with activity against both mTORC1 and mTORC2, are currently in various stages of preclinical and clinical development.

SUMMARY

The rapalogs are the first mTOR inhibitors to show promising, yet modest, antitumor effects. To fully exploit the potential of targeting this pathway, it will be important to better understand the mechanisms of action and precise targets of the various inhibitors. Moreover, definition of biomarkers of susceptibility and identification of predictors and/or correlates to drug resistance will substantially advance this area.

Anti-VEGF and beyond: shaping a new generation of anti-angiogenic therapies for cancer

The anti-angiogenic class of drugs is one of the few where representatives have gained international approval for clinical use in oncology during the past decade. Most of the biological and clinical activity of the currently available generation of anti-angiogenic drugs targets vascular endothelial growth factor (VEGF) and its related pathways. However, the clinical benefits associated with the use of these drugs have, so far, been limited. There is, therefore, an unmet need for biomarkers that can be used to identify patients who are most likely to benefit therapeutically and also to predict the best schedule and dosage for these drugs. Here, we discuss some of the emerging new combination strategies involving the approved anti-angiogenic drugs, some of the emerging targets associated with neoplastic angiogenesis and some novel agents used as a paradigm of the next generation of anti-angiogenic drugs.

Future directions in renal cell carcinoma: 2011 and beyond

Emerging from a largely cytokine-based era, the last several years have witnessed a dramatic change in the therapeutic landscape of renal cancer. Molecularly targeted and antiangiogenic agents now form the backbone of most therapeutic strategies for patients with advanced renal cell carcinoma (RCC). Although the next few years may not see such broad paradigm shifts, there remains significant room for improvement in the care of patients with RCC. This review discusses challenges that face physicians and researchers as well as innovations that may contribute to improving the therapeutic outcomes for patients with RCC.

Future directions of mammalian target of rapamycin (mTOR) inhibitor therapy in renal cell carcinoma

With an explosion of available treatments for metastatic renal cell carcinoma (mRCC) in recent years, it is important to recognize that approved targeted therapies fall broadly into only two mechanistic categories. The first category, vascular endothelial growth factor (VEGF)-directed therapies, includes sunitinib, pazopanib, sorafenib and bevacizumab. The second category includes inhibitors of the mammalian target of rapamycin (mTOR), namely everolimus and temsirolimus. A pivotal trial of everolimus supports use of the agent in patients with mRCC refractory to VEGF- tyrosine kinase inhibitors (TKI) therapy, while pivotal data for temsirolimus supports use in poor-prognosis patients as first-line therapy. Multiple reviews exist to delineate the laboratory and clinical development of mTOR inhibitors. This paper will outline the future applications of these therapies. It will explore ongoing trials evaluating combinations of mTOR inhibitors with other targeted therapies, along with sequencing strategies and biomarker discovery efforts. The application of mTOR inhibitors in unique populations is also described.

Interface of signal transduction inhibition and immunotherapy in melanoma

Food and Drug Administration-approved treatment for metastatic melanoma, including interferon alpha and interleukin-2, offer a modest benefit. Immunotherapy, although has not enjoyed high overall response rates, is capable of providing durable responses in a subset of patients. In recent years, new molecular-targeted therapies have become available and offer promise of clinical benefit, although low durability of response. It is not yet clear how best to integrate these 2 novel modalities that target the immune response to melanoma (immune therapy) or that target molecular signaling pathways in the melanoma cells (targeted therapy). Many signal transduction pathways are important in both tumor cell and T-cell proliferation and survival, which generate risk in combining targeted therapy and immunotherapy. This review focuses on the role of targeted therapy and immunotherapy in melanoma, and discusses how to combine the 2 modalities rationally for increased duration and response.

Utilizing targeted cancer therapeutic agents in combination: novel approaches and urgent requirements

The rapid development of new therapeutic agents that target specific molecular pathways involved in tumour cell proliferation provides an unprecedented opportunity to achieve a much higher degree of biochemical specificity than previously possible with traditional chemotherapeutic anticancer agents. However, the lack of specificity of these established chemotherapeutic drugs allowed a relatively straightforward approach to their use in combination therapies. Developing a paradigm for combining new, molecularly targeted agents, on the other hand, is substantially more complex. The abundance of molecular data makes it possible, at least in theory, to predict how such agents might interact across crucial growth control networks. Initial strategies to examine molecularly targeted agent combinations have produced a small number of successes in the clinic. However, for most of these combination strategies, both in preclinical models and in patients, it is not clear whether the agents being combined actually hit their targets to induce growth inhibition. Here, we consider the initial approach of the US National Cancer Institute (NCI) to the evaluation of combinations of molecularly targeted anticancer agents in patients and provide a description of several new approaches that the NCI has initiated to improve the effectiveness of combination-targeted therapy for cancer.

Patient-based strategy for systemic treatment of metastatic renal cell carcinoma

There were only a few options 3 years ago to treat metastatic renal cell carcinoma (mRCC), a disease with a very poor prognosis. With the approval of targeted therapies for mRCC since December 2005, this situation has changed dramatically. Currently, oncologists can choose between several promising options to improve the longevity and quality of their patients' lives. A widely accepted treatment scheme for targeted therapies in mRCC does not yet exist. Based on a selective literature search, drawing on studies with six targeted therapies for mRCC, and including data from the latest American Society of Clinical Oncology (ASCO) and European Society for Medical Oncology (ESMO) Annual Meetings, this review introduces the available therapies, evaluates patient-specific criteria for their application and suggests an algorithm for a patient-based treatment scheme. Clinical experiences with sequential therapies are summarized and potential combination therapies discussed. In conclusion, the crucial criteria of the treatment scheme we propose are the tumor burden and the disease pace, as well as the quality of life of a patient. These define whether tumor control or tumor remission should be the primary therapeutic goal. This scheme suggests which kind of therapeutic sequence to pursue to optimize patient care in mRCC.

Treatment Options in Metastatic Renal Cell Carcinoma: Focus on mTOR Inhibitors

THE AGENTS CURRENTLY APPROVED FOR USE IN METASTATIC RENAL CELL CARCINOMA (MRCC) CAN BE DIVIDED BROADLY INTO TWO CATEGORIES: (1) vascular endothelial growth factor receptor (VEGFR)-directed therapies or (2) inhibitors of the mammalian target of rapamycin (mTOR). The latter category includes everolimus and temsirolimus, both approved for distinct indications in mRCC. Everolimus gained its approval on the basis of phase III data showing a benefit in progression-free survival relative to placebo in patients previously treated with sunitinib and/or sorafenib. In contrast, temsirolimus was approved on the basis of a phase III trial in treatment-naïve patients with poor-risk mRCC, demonstrating an improvement in overall survival relative to interferon-alfa. While these pivotal trials have created unique positions for everolimus and temsirolimus in current clinical algorithms, the role of mTOR inhibitors in mRCC is being steadily revised and expanded through ongoing trials testing novel sequences and combinations. The clinical development of mTOR inhibitors is outlined herein.

[mTOR inhibitors: temsirolimus and everolimus in the treatment of renal cell carcinoma]

mTOR signaling pathway (mammalian target of rapamycin) is a major pathway in cell physiology and malignant behavior implicated in cell growth, cell proliferation, cell metabolism, protein synthesis and angiogenesis. Temsirolimus has shown in a randomized phase III trial for patients with poor risk feature of metastatic renal cell carcinoma, a significant gain in overall survival compared to this obtained with alpha interferon (7.3 à 10.9 months; HR: 0.73; P < 0.0069). Everolimus has shown in a randomized phase III trial for patients with metastatic renal cell carcinoma having failed under VEGFR tyrosine kinase inhibitor a significant gain in progression-free survival compared to this obtained with placebo VEGFR (1,8 à 4,6 months; HR: 0.33; P < 0.001). Temsirolimus and everolimus are now part of the reference treatments in renal cell carcinoma. This paper is a review of these two drugs in this setting.

Targeting multiple kinase pathways: a change in paradigm

Anticancer drugs that target protein kinases include small molecule inhibitors and monoclonal antibodies. Feedback loops and cross talk between signaling pathways impact significantly on the efficacy of cancer therapeutics, and resistance to targeted agents is a major barrier to effective treatments. Increasingly, therapies are being designed to target multiple kinase pathways. This can be achieved using a single agent that inhibits multiple signaling pathways or a combination of highly selective agents. In this review we discuss the principles of specifically targeting multiple kinase pathways with particular reference to angiogenic signaling pathways.

mTOR signaling and drug development in cancer

Mammalian target of rapamycin (mTOR) is a protein kinase of the PI3K/Akt signaling pathway. Activation of mTOR in response to growth, nutrient and energy signals leads to an increase in protein synthesis, which is required for tumor development. This feature makes mTOR an attractive target for cancer therapy. First-generation mTOR inhibitors are sirolimus derivatives (rapalogs), which have been evaluated extensively in cancer patients. Everolimus and temsirolimus are already approved for the treatment of renal-cell carcinoma. Temsirolimus is also approved for the treatment of mantle-cell lymphoma. These drugs, in addition to ridaforolimus (formerly deforolimus) and sirolimus, are currently being evaluated in clinical trials of various cancers. Second-generation mTOR inhibitors are small molecules that target the kinase domain, and have also entered clinical development. Clinical trials are underway to identify additional malignancies that respond to mTOR inhibitors, either alone or in combination with other therapies. Future research should evaluate the optimal drug regimens, schedules, patient populations, and combination strategies for this novel class of agents.

Vascular endothelial growth factor and mTOR pathways in renal cell carcinoma: differences and synergies of two targeted mechanisms

Renal cell carcinoma (RCC) is among the most resistant tumours to chemotherapy, radiotherapy and hormonal therapy. Cytokine therapy is effective in a small subset of patients, but it is associated with substantial toxicity and rarely benefits patients with extensive tumour burdens or adverse prognostic factors. Since 2005, clinical trials have shown significant clinical benefits for five molecularly targeted therapies in patients with advanced RCC. These agents constitute two mechanistic classes: (i) angiogenesis inhibitors targeting the vascular endothelial growth factor (VEGF) ligand (bevacizumab, in combination with interferon-a) or VEGF receptors (sunitinib, sorafenib); and (ii) inhibitors of the mammalian target of rapamycin (mTOR) signalling (temsirolimus, everolimus). This review assesses the mechanistic distinctions and functional overlaps of these classes of agents, and discusses key characteristics of their respective clinical efficacy and side-effect profiles in patients with RCC, some of which might affect patient selection and treatment strategies. Current research is designed to optimize the use of these agents, as well as the development of new investigational therapies within these mechanistic classes. The differences and synergies are particularly important for understanding the best ways to integrate VEGF/VEGF receptor inhibitors and mTOR inhibitors for combination or sequential treatment of patients with advanced RCC.

Combination systemic therapy for advanced renal cell carcinoma

Outcomes for patients with advanced renal cell carcinoma (RCC) have improved significantly in recent years with the development of novel noncytotoxic systemic therapies. The multitargeted kinase inhibitors sunitinib and sorafenib have been approved for the treatment of advanced RCC, and bevacizumab, a monoclonal anti-vascular endothelial growth factor antibody, has shown significant clinical activity, both as a single agent and in combination with interferon-alpha. The mammalian target of rapamycin inhibitors temsirolimus and everolimus have led to longer overall survival times in poor-risk patients in the first-line setting and longer progression-free survival times in kinase inhibitor refractory patients in the second-line setting, respectively. Despite these advances, almost all patients develop resistance to treatment and cure is rarely seen. There is therefore a need to overcome resistance, induce longer lasting remissions, and improve survival. A potential approach to this is to combine active agents, and the clinical data for combination therapy with novel targeted agents in advanced RCC are reviewed here.

Treatment of metastatic renal cell carcinoma

PURPOSE

To review the treatment of metastatic renal cell carcinoma (RCC), including the use of new targeted therapies.

METHODS

A search of MEDLINE (1966 to August 2008) and American Society of Clinical Oncology Meeting abstracts (2005 to May 2008) was preformed using the search terms bevacizumab, everolimus, interferon-alfa (IFN-alpha), interleukin-2 (IL-2), sorafenib, sunitinib, temsirolimus, and RCC. Articles most pertinent to the treatment of metastatic RCC are reviewed.

RESULTS

The treatment of metastatic RCC has undergone a paradigm shift over the past 5 years from biologic response modifiers to new targeted therapies. Historically, response rates for the biological response modifiers, aldesleukin (IL-2), and IFN-alpha were approximately 15%. Recently, three targeted agents, sorafenib, sunitinib, and temsirolimus have been approved for the treatment of RCC. Additionally, bevacizumab has been investigated and shown to increase progression free survival in RCC. IL-2 remains the only agent to induce complete, durable remissions; however, many patients are not eligible for this therapy. Newer agents (sorafenib, sunitinib, and temsirolimus) have shown to be superior to IFN-alpha or placebo and bevacizumab combined with IFN-alpha has shown activity when compared to IFN-alpha alone. Unlike IL-2, the greatest benefit obtained with targeted therapies is in achieving stable disease (SD). Despite their benefit, targeted therapies have never been compared with each other in clinical trials and choosing the most appropriate agent remains challenging. To date, the optimal sequence or combination of treatments has not been defined; however, everolimus has recently demonstrated activity in patients progressing on targeted therapy.

CONCLUSIONS

IL-2 remains the most active regimen in inducing complete responses; however, its use is accompanied by substantial morbidity and is limited to those with a good performance status. Targeted therapies are also efficacious in the treatment of RCC, with the major benefit being induction of SD. Future research will better define the sequencing of therapies, as well as, explore the activity of novel combination regimens.

Bevacizumab: direct anti-VEGF therapy in renal cell carcinoma

Bevacizumab, in combination with IFN, is approved in the EU as first-line therapy for advanced and/or metastatic renal cell carcinoma (mRCC). Data from Avastin and Roferon in Renal Cell Carcinoma [BO17705] (AVOREN), a Phase III trial, demonstrated that bevacizumab plus IFN significantly improves progression-free survival and response rate in patients with previously untreated mRCC compared with IFN plus placebo. Furthermore, bevacizumab plus IFN is well tolerated and has a predictable and well-established tolerability profile; reducing the dose of IFN, when necessary, can effectively manage IFN-related side effects without compromising efficacy. The rapid evolution of options for RCC therapy means that the optimal use of available agents to maximize patient benefit is not currently well defined. Combination regimens and sequencing of agents are both being investigated to maximize future outcomes, with bevacizumab playing a key role in first-line regimens. Trials over the next 5 years will guide clinical practice, but bevacizumab plus IFN is currently a standard first-line option for mRCC.

Systemic therapy for metastatic renal cell carcinoma

Renal cell cancer (RCC) is the most common form of cancer of the kidney and accounts for approximately 44,000 cases per year in the United States. Historically, only immunotherapy showed activity in metastatic RCC. The improved survival and quality of life for patients with metastatic RCC over the last several years are direct results of advances made in understanding the development of RCC. Three targeted therapies-sunitinib, sorafenib, and temsirolimus-have been approved for use in the United States recently. Current research is aimed at developing new drugs and combining available drugs to improve upon the responses and survival seen with approved single agents.

The role of mTOR in the management of solid tumors: an overview

Mammalian target of rapamycin (mTOR) is a key protein kinase controlling signal transduction from various growth factors and upstream proteins to the level of mRNA and ribosome with a regulatory effect on cell cycle progression, cellular proliferation and growth. TOR genes were discovered rather serendipitously while investigating the cause of resistance to immunosuppressant rapamycin in yeast. In normal cells, mTOR controls brilliantly the load of signals from its effectors resulting in a normal cell function. On the contrary, in various diseases and mainly in cancer this balance is lost due to mutations or overactivation of upstream pathways leading to a persistent proliferation and tumor growth. What makes mTOR attractive to researchers seems to be its key position which is on the crossroad of various signal pathways (Ras, PI3K/Akt, TSC, NF-kappaB) towards mRNA, ribosome, protein synthesis and translation of significant molecules, the uncontrolled production of which may lead to tumor proliferation and growth. Inhibition of mTOR by rapamycin (a natural product) or its analogs aims to prevent the deleterious effects of the abnormal signaling, regardless at which point of the signal pathway has the abnormality launched. Here, we will review the physiological functions of mTOR, its association to carcinogenesis and the latest evidence regarding the use of mTOR inhibitors in cancer treatment as well as future trends and aims of research.

Genetic basis for kidney cancer: opportunity for disease-specific approaches to therapy

BACKGROUND

Kidney cancer is not a homogenous entity; it is comprised of many different tumor types, with different biologies and molecular mechanisms leading to disease and therefore different treatment approaches.

OBJECTIVE

To describe the genetic basis and biochemical pathways underlying inherited forms of renal cancer, specifically in four described syndromes (von Hippel-Lindau [VHL], hereditary papillary renal cancer [HPRC], Birt-Hogg-Dubé [BHD] and hereditary leiomyomatosis renal cell carcinoma [HLRCC]), and to elucidate how the understanding of these diseases enables the possibility of disease-specific approaches to therapy.

METHODS

A systematic review of the published literature on inherited and sporadic forms of renal cancer was performed.

CONCLUSION

Understanding of the biology and mechanisms of different forms of kidney cancer provides an opportunity for development of new treatment options.

Improving outcomes in patients with advanced renal cell carcinoma

The emergence of targeted therapies for advanced renal cell carcinoma has been a dramatic turning point in improving outcomes for the majority of patients with this disease. In study populations comprising primarily good- and intermediate-risk patients with clear cell renal cell carcinoma and prior nephrectomy, prolonged progression-free survival was demonstrated for three angiogenesis-targeted agents: sunitinib (compared with interferon [IFN]), bevacizumab plus IFN (vs IFN alone) and sorafenib (vs placebo in cytokine-refractory patients). As a first-line treatment for patients with multiple poor-risk factors, temsirolimus, which inhibits mTOR, has improved not only progression-free survival compared with IFN but, more importantly, overall survival. Further studies are needed to determine whether combinations and/or sequencing of these targeted agents can further improve outcomes.

Update on the medical treatment of metastatic renal cell carcinoma

CONTEXT

Metastatic renal cell carcinoma (mRCC) has long been treated only by immunotherapy with good results only in a small population of patients. In recent years, major improvements in treatment possibilities have occurred with the advent of anti-angiogenic drugs. In the past 2 yr, pivotal phase III trials have confirmed this major breakthrough by increasing the progression-free survival rates and/or overall survival rates provided by sunitinib, sorafenib, and bevacizumab, and more recently by the mTOR (mammalian target of rapamycin) inhibitors temsirolimus and everolimus.

OBJECTIVE

To update the previous review on smart drugs published in the European Journal in 2006 (Patard JJ, et al. Understanding the importance of smart drugs in renal cell carcinoma. Eur Urol 2006; 49:633-43).

EVIDENCE ACQUISITION

Critical review of published literature 2006-2008 (Pubmed website search words: renal cell carcinoma and/or targeted therapy and prospective trials) and more recent meeting abstracts (American Society of Clinical Oncology 2007). Quality assessment included prospective phase I-III trials and critical evaluations with low numbers of patients, retrospective analyses, and slide presentations of meeting abstracts.

EVIDENCE SYNTHESIS

This review presents the current situation and provides more recent data on sequential treatment, the association of targeted drugs, and the treatment of non-clear-cell histologies.

CONCLUSIONS

Treatment of mRCC with targeted therapy centers on at least two major pathways: angiogenesis and mTOR involving inhibiting drugs that may be used alone, in combination, or sequentially.

Targeted therapy for advanced renal cell carcinoma

BACKGROUND

Advanced renal cell carcinoma has been resistant to drug therapy of different types and new types of drug therapy are needed. Targeted agents inhibit known molecular pathways involved in cellular proliferation and neoangiogenesis, the induction by the tumour of host microvascular networks. Angiogenesis is of special interest in the clear cell histologic subtype of renal cancer because of its vascularity and constitutively activated hypoxia-inducible path in the majority of tumours.

OBJECTIVES

1) To provide a systematic review of studies testing targeted agents.2) To identify the type and degree of clinical benefit, if any, of targeted agents over the prior standard of care, particularly any impact on overall survival.

SEARCH STRATEGY

1) Electronic search of CENTRAL, MEDLINE and EMBASE databases.2) Hand search of international cancer meeting abstract and other sources specified in the protocol.

SELECTION CRITERIA

Randomized controlled studies of targeted agents in patients with advanced renal cell cancer reporting major remission rate or overall survival by allocation. Progression-free survival (PFS) was adopted as an additional outcome because PFS was a commonly chosen primary outcome, and because several pivotal studies allowed crossover from the control to the investigational arm after closure to accrual thereby making overall survival a problematic endpoint.

DATA COLLECTION AND ANALYSIS

Nineteen fully eligible studies tested ten different targeted agents (Table 04). One additional study was excluded because no outcome data by allocation have been reported (Hutson 2007). For purposes of comparison, the studies were divided into three groups: Group 1 studies compared different doses of the same agents; Group 2 studies examined the impact of targeted agents in patients who had received prior cytokine or other systemic therapy; and Group 3 studies tested targeted agents in systemically naive patients, either against standard interferon-alfa or against another control therapy. Meta-analysis was not utilized because there were very few situations where the same agents had been tested in the same group in more than one study.

MAIN RESULTS

In systemically untreated patients in studies using subcutaneous interferon-alfa as control therapy, the major findings were: 1) An improvement in overall survival has been demonstrated only with the use of weekly intravenous temsirolimus in patients with unselected renal cancer histology and adverse prognostic features (median survival 10.9 months versus 7.3 months for temsirolimus or interferon-alfa respectively, HR 0.73, P = 0.008 log rank, Hudes 2007). However, the chance of major remission was low and not improved with temsirolimus. 2) In patients with mostly good or intermediate prognostic risk with clear cell renal cancer, oral sunitinib improves the chance of major remission, the probability of symptomatic improvement, and freedom from disease progression (Motzer 2007); in a similar setting, the addition of biweekly intravenous bevacizumab to interferon-alfa also improved the chance of major remission and prolonged progression-free survival (Escudier 2007b); overall survival had not changed at the time of interim reporting of either study. In patients with clear cell renal cancers who had failed prior cytokine therapy, oral sorafenib gives a better quality of life than placebo as well as improved chance of being free of disease progression; overall survival may have improved but is hard to evaluate because of crossover of placebo-assigned patients after the study closed to accrual (Escudier 2007a).

AUTHORS' CONCLUSIONS

Based on less than a decade of experience, some targeted agents with specified molecular targets have demonstrated clinically useful benefits over the previous standard of care for patients with advanced renal cancer. Much more research is required to fully establish the role of targeted agents in this condition.

Inhibition of mTOR pathway by everolimus cooperates with EGFR inhibitors in human tumours sensitive and resistant to anti-EGFR drugs

Inhibition of a single transduction pathway is often inefficient due to activation of alternative signalling. The mammalian target of rapamycin (mTOR) is a key intracellular kinase integrating proliferation, survival and angiogenic pathways and has been implicated in the resistance to EGFR inhibitors. Thus, mTOR blockade is pursued to interfere at multiple levels with tumour growth. We used everolimus (RAD001) to inhibit mTOR, alone or in combination with anti-EGFR drugs gefitinib or cetuximab, on human cancer cell lines sensitive and resistant to EGFR inhibitors, both in vitro and in vivo. We demonstrated that everolimus is active against EGFR-resistant cancer cell lines and partially restores the ability of EGFR inhibitors to inhibit growth and survival. Everolimus reduces the expression of EGFR-related signalling effectors and VEGF production, inhibiting proliferation and capillary tube formation of endothelial cells, both alone and in combination with gefitinib. Finally, combination of everolimus and gefitinib inhibits growth of GEO and GEO-GR (gefitinib resistant) colon cancer xenografts, activation of signalling proteins and VEGF secretion. Targeting mTOR pathway with everolimus overcomes resistance to EGFR inhibitors and produces a cooperative effect with EGFR inhibitors, providing a valid therapeutic strategy to be tested in a clinical setting.

Using Molecular Biology to Develop Drugs for Renal Cell Carcinoma

BACKGROUND: Renal cell carcinoma is a disease marked by a unique biology which has governed it's long history of poor response to conventional cancer treatments. The discovery of the signaling pathway activated as a result of inappropriate constitutive activation of the hypoxia inducible factors (HIF), transcription factors physiologically and transiently stabilized in response to low oxygen, has provided a primary opportunity to devise treatment strategies to target this oncogenic pathway. OBJECTIVE: A review of the molecular pathogenesis of renal cell cancer as well as molecularly targeted therapies, both those currently available and those in development, will be provided. In addition, trials involving combination or sequential targeted therapy are discussed. METHODS: A detailed review of the literature describing the molecular biology of renal cell cancer and novel therapies was performed and summarized. RESULTS/CONCLUSION: Therapeutics targeting angiogenesis have provided the first class of agents which provide clinical benefit in a large majority of patients and heralded renal cell carcinoma as a solid tumor paradigm for the development of novel therapeutics. Multiple strategies targeting this pathway and now other identified pathways in renal cell carcinoma provide numerous potential opportunities to make major improvements in treating this historically devastating cancer.

Antibody therapy in renal cell carcinoma

The treatment of metastasized renal cell carcinoma (RCC) still represents a formidable challenge, despite the development of small molecule, tyrosine kinase inhibitors (TKI) that have made a major impact on the disease. Although the percentage of patients achieving a partial response or stabilization of disease has been impressive, these effects are mostly non-durable. Additionally, drug-related side effects can be quite severe. Alternative treatment modalities might be monoclonal antibodies (mAbs). mAbs against RCC-associated antigens have been developed and have shown promise. Additionally, current efforts focus on Bevacizumab that recognizes vascular endothelial growth factor (VEGF). VEGF overexpression in RCC provides the opportunity to inhibit this proangiogenic pathway. Also with Bevacizumab, promising results have been obtained, particularly in combination with other treatment modalities. It is likely that mAbs, either as single agents or in combination with other agents, may become useful additions to the armamentarium to diagnose and treat RCC.