Sunitinib in the treatment of advanced solid tumors

Sunitinib is an oral multikinase inhibitor that blocks the vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) alpha and beta, c-kit, and other receptors. These attributes have proven to be efficacious in the treatment of metastatic renal cell carcinoma (RCC), unresectable gastrointestinal stromal tumors (GIST), and well-differentiated advanced pancreatic neuroendocrine tumors (PNET). Though activity has been reported in other tumor types, phase III trials have not yet demonstrated improved survival outcomes in these cancers. Most side effects including hypertension, hand-foot syndrome, and diarrhea are generally well manageable. This review will detail the preclinical data leading up to the results of the pivotal phase III clinical trials that have led to the widespread use of sunitinib in advanced RCC, GIST, and PNET.

Challenges and opportunities for converting renal cell carcinoma into a chronic disease with targeted therapies

Optimum efficacy is the primary goal for any cancer therapy, and entails controlling tumour growth and prolonging survival as far as possible. The prognosis for patients with metastatic renal cell carcinoma (mRCC) has greatly improved with the introduction of targeted therapies. This review examines the development and efficacy of targeted agents for the management of mRCC, the challenges offered by their rapid emergence, and discusses how mRCC treatment may evolve in the future. Improvements in progression-free survival and overall survival rates, observed with targeted agents, indicate that it may now be possible to change mRCC from a rapidly fatal and largely untreatable condition into a chronic disease. The major challenges to further advances in targeted therapy for mRCC include overcoming drug resistance, identifying the most effective sequence or combination of targeted agents, optimising clinical trial design and managing the cost of treatment.

SABRE-B: an evaluation of paclitaxel and bevacizumab with or without sunitinib as first-line treatment of metastatic breast cancer

BACKGROUND

The vascular endothelial growth factor (VEGF) pathway can be targeted through VEGF neutralization or VEGF receptor (VEGFR) blockade using tyrosine kinase inhibition. Because laboratory models suggest that combining these approaches might be synergistic, we sought to evaluate the feasibility and efficacy of combining sunitinib with paclitaxel + bevacizumab (PB).

METHODS

Patients with human epidermal growth factor receptor 2 (HER2)-negative, metastatic breast cancer receiving first-line chemotherapy were randomized to PB or PB with sunitinib (PBS), with planned escalation of the sunitinib dose.

RESULTS

Forty-six patients were randomized to PB or PBS with sunitinib dosed at 25 mg p.o. daily. Patients receiving PBS encountered substantial toxicity that precluded adequate treatment. The percentage of patients with grade ≥3 adverse events was greater in the PBS arm than the PB arm (83% versus 57%), and sunitinib dosing was modified in 78% of patients, most often due to neutropenia, febrile neutropenia, and fatigue. In addition, 44% of patients had sunitinib dose reduction to 12.5 mg, and 39% required discontinuation. Patients receiving PBS had more bevacizumab treatment interruptions and discontinuations because of toxicity. Median treatment duration was longer in the PB arm compared with the PBS arm (14.1 versus 11.1 weeks), reflecting early treatment discontinuation of PBS. Because of poor tolerability of the addition of sunitinib to PB, the planned sunitinib dose escalation was halted and the study accrual was terminated.

CONCLUSION

Adding sunitinib to standard doses of bevacizumab plus paclitaxel for metastatic breast cancer is not feasible. Different strategies will be required to evaluate whether there is additional clinical benefit to combining VEGF/VEGFR-targeted agents.

Targeted therapy for metastatic renal cell carcinoma: current treatment and future directions

An understanding of vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) pathways has greatly changed the way metastatic renal cell carcinoma (RCC) is treated. Based on available phase III randomized trials, anti-VEGF agents such as sunitinib, sorafenib, bevacizumab-based therapy, and mTOR-targeted agents such as temsirolimus and everolimus have been used in the treatment armamentarium for this disease. Now that agents directed against these pathways have largely replaced immunotherapy as the standard of care, new questions have emerged and are the subject of ongoing clinical trials. The development of new targeted therapies including axitinib, pazopanib, cediranib, volociximab, tivozanib (AV-951), BAY 73-4506, and c-met inhibitors such as GSK1363089 and ARQ197 may potentially expand the list of treatment options. Sequential and combination targeted therapies are currently under investigation in advanced disease as are adjuvant and neo-adjuvant approaches around nephrectomy.

Sunitinib

Sunitinib is an oral multikinase inhibitor that blocks the vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) alpha and beta, c-kit, and other receptors. These attributes have proven to be efficacious in the treatment of metastatic renal cell carcinoma (RCC) and unresectable gastrointestinal stromal tumors (GIST). Most side effects, including hypertension, hand-foot syndrome, and diarrhea are generally well manageable. Clinical trials are underway to determine the efficacy of sunitinib in other tumor types including metastatic breast, colorectal, and lung cancers. This chapter will detail the preclinical data leading to the results of the pivotal phase III clinical trials that have led to the widespread use of sunitinib in metastatic RCC and advanced GIST.

Sunitinib treatment for patients with clear-cell metastatic renal cell carcinoma: clinical outcomes and plasma angiogenesis markers

BACKGROUND

Sunitinib is a protein tyrosine kinase-inhibitor targeting VEGFR, c-kit and PDGFR. It has been approved for the treatment of metastatic renal-cell carcinoma and gastrointestinal stromal tumors. Although it has been shown to prolong disease-free and overall survival in renal-cell carcinoma patients, only 70% of the treated population receive a clinical benefit (CB) from the treatment. Markers that could predict clinical benefit to sunitinib would be an important aid in monitoring and following their treatment. We assessed the outcome and plasma proangiogenic factors in patients with metastatic renal cell carcinoma (mRCC) treated with sunitinib in our institution.

METHODS

We have treated 42 patients with metastatic clear-cell renal carcinoma with sunitinib. Plasma concentrations of VEGF-A, sVEGFR2 and PDGF were determined by ELISA.

RESULTS

At the time of analysis 39 patients were evaluable for response and 30 patients had obtained a clinical benefit (CB). Median progression-free survival was 268 days (8.93 months) and median overall survival was 487 days (16.23 months). Interestingly, disease stabilization or objective response resulted in comparable overall survival. Most treatment-related adverse events were of mild-to-moderate intensity with one treatment-related death. Plasma sVEGFR2 and PDGF levels had no predictive value. Fold-increase in plasma VEGF was significantly lower in patients that obtained a CB as compared to patients that progressed after two cycles of treatment. Plasma VEGF did not increase in patients with initial CB at the time of progression.

CONCLUSION

Sunitinib showed substantial activity in mRCC. Disease stabilization or objective response resulted in comparable overall survival and both outcomes should be considered positive. Fold-increase in plasma VEGF predicts for CB and could be a candidate marker. Progression after initial CB is not associated with elevated plasma VEGF, implying a different mechanism of resistance.

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.

Vertical VEGF targeting: A combination of ligand blockade with receptor tyrosine kinase inhibition

The aim of this study was to examine the anti-tumour effects of dual vertical VEGF targeting consisting in the association between bevacizumab, a VEGF-depleting drug, and the VEGF receptor antityrosine kinase AZD2171. Mice bearing human head and neck CAL33 xenografted tumours were treated once daily for 11 d with either vehicle (controls), AZD2171 (2.5mg/kg/day, p.o.), bevacizumab (5mg/kg/day, i.p.) or the bevacizumab-AZD2171 combination. The AZD2171-bevacizumab combination produced additive effects on tumour growth and reduced the number of proliferating cells relative to control. Bevacizumab did not influence tumour vascular necrosis whilst AZD2171 (p=0.01) and the combination (p=0.01) increased it. The number of mature tumour cells decreased significantly with the combination treatment only (p=0.001), which induced the largest increase in the Bax/Bcl2 ratio (up to 25-fold) and a progressive 3-fold decrease in HIF1-alpha expression between 24h and 192h. The present data indicate that there is no redundancy in targeting the same angiogenic pathway with the presently tested clinically applicable drugs. The study provides a strong rationale for future clinical trials.

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.

A Review of the Cardiovascular Effects of Oncology Agents

Cardiovascular toxicity is an important adverse effect of several classes of oncology drugs. Because cancer survivors are living longer, the late effects of cancer therapy must be addressed. Many patients diagnosed with cancer are already at an increased risk for cardiovascular disease before drug treatment. Select chemotherapy agents further complicate the issue because of their own ability to induce cardiovascular toxicities or exacerbate preexisting conditions. Hypertension, dyslipidemia, heart failure, and arrhythmia are known consequences of some cancer therapies. This review provides an overview of the epidemiology, mechanism of action, monitoring, and management of these cardiovascular effects.

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.