Circulating proteins as potential biomarkers of sunitinib and interferon-α efficacy in treatment-naïve patients with metastatic renal cell carcinoma

Diagnostic, predictive and prognostic molecular biomarkers in clear cell renal cell carcinoma: A retrospective study

Clear cell renal cell carcinoma (ccRCC) is a common and aggressive subtype of kidney cancer. Many patients are diagnosed at advanced stages, making early detection crucial. Unfortunately, there are currently no noninvasive tests for ccRCC, emphasizing the need for new biomarkers. Additionally, ccRCC often develops resistance to treatments like radiotherapy and chemotherapy. Identifying biomarkers that predict treatment outcomes is vital for personalized care. The integration of artificial intelligence (AI), multi-omics analysis, and computational biology holds promise in bolstering detection precision and resilience, opening avenues for future investigations. The amalgamation of radiogenomics and biomaterial-basedimmunomodulation signifies a revolutionary breakthrough in diagnostic medicine. This review summarizes existing literature and highlights emerging biomarkers that enhance diagnostic, predictive, and prognostic capabilities for ccRCC, setting the stage for future clinical research.

Mechanisms of tyrosine kinase inhibitor resistance in renal cell carcinoma

Renal cell carcinoma (RCC), the most prevalent type of kidney cancer, is a significant cause of cancer morbidity and mortality worldwide. Antiangiogenic tyrosine kinase inhibitors (TKIs), in combination with immune checkpoint inhibitors (ICIs), are among the first-line treatment options for patients with advanced RCC. These therapies target the vascular endothelial growth factor receptor (VEGFR) tyrosine kinase pathway and other kinases crucial to cancer proliferation, survival, and metastasis. TKIs have yielded substantial improvements in progression-free survival (PFS) and overall survival (OS) for patients with advanced RCC. However, nearly all patients eventually progress on these drugs as resistance develops. This review provides an overview of TKI resistance in RCC and explores different mechanisms of resistance, including upregulation of alternative proangiogenic pathways, epithelial-mesenchymal transition (EMT), decreased intracellular drug concentrations due to efflux pumps and lysosomal sequestration, alterations in the tumor microenvironment including bone marrow-derived cells (BMDCs) and tumor-associated fibroblasts (TAFs), and genetic factors such as single nucleotide polymorphisms (SNPs). A comprehensive understanding of these mechanisms opens the door to the development of innovative therapeutic approaches that can effectively overcome TKI resistance, thereby improving outcomes for patients with advanced RCC.

Circulating Biomarkers in Patients With Locally Advanced or Metastatic Renal Cell Carcinoma Treated With Everolimus in the Pre-nephrectomy Setting

Many drugs are available in renal cell carcinoma (RCC), yet clinicians are still looking for predictive biomarkers of disease recurrence or progression supporting more personalised treatments. An assessment of circulating biomarkers over time was carried out in this French, open-label, single-arm, multicentre trial conducted in 25 patients with either locally advanced (n = 14) or metastatic RCC (n = 11) who received everolimus (10 mg daily) for 6 weeks prior to nephrectomy (NEORAD, NCT01715935). Circulating biomarkers, including circulating tumour cells, haematopoietic and endothelial cells, plasma angiogenesis and inflammatory markers were quantified at baseline, upon everolimus and post-nephrectomy. We assessed tumour burden, objective response rate upon RECIST1.1, disease-free survival (DFS) and progression-free survival (PFS). The correlation between circulating biomarkers was evaluated with multiple factor analysis and biomarker association with DFS/PFS by Cox regression. No objective response rate was obtained before nephrectomy. Upon everolimus, neutrophils, platelets and sVEGFR2 significantly decreased. We did not find any association between circulating biomarkers and DFS/PFS, but patients with the highest tumour burden at baseline had significantly higher plasma levels of interleukin-6, an inflammatory circulating biomarker, and lower levels of sVEGFR2, related to angiogenesis. Further understanding of the link between these circulating biomarkers could help to optimise drug combinations in RCC.

Sunitinib resistance in renal cell carcinoma: From molecular mechanisms to predictive biomarkers

Currently, renal cell carcinoma (RCC) is the most prevalent type of kidney cancer. Targeted therapy has replaced radiation therapy and chemotherapy as the main treatment option for RCC due to the lack of significant efficacy with these conventional therapeutic regimens. Sunitinib, a drug used to treat gastrointestinal tumors and renal cell carcinoma, inhibits the tyrosine kinase activity of a number of receptor tyrosine kinases, including vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), c-Kit, rearranged during transfection (RET) and fms-related receptor tyrosine kinase 3 (Flt3). Although sunitinib has been shown to be efficacious in the treatment of patients with advanced RCC, a significant number of patients have primary resistance to sunitinib or acquired drug resistance within the 6-15 months of therapy. Thus, in order to develop more efficacious and long-lasting treatment strategies for patients with advanced RCC, it will be crucial to ascertain how to overcome sunitinib resistance that is produced by various drug resistance mechanisms. In this review, we discuss: 1) molecular mechanisms of sunitinib resistance; 2) strategies to overcome sunitinib resistance and 3) potential predictive biomarkers of sunitinib resistance.

Development and validation of a novel immunotype for prediction of overall survival in patients with clear cell renal cell carcinoma

Background

Clear cell renal cell carcinoma (ccRCC) is a highly immunogenic tumor. The purpose of the present study was to establish a novel immunotype for different immune infiltration and overall survival (OS) of patients with ccRCC.

Methods

Based on the Cancer Genome Atlas Project (TCGA) database (discovery set), a novel immunotype was established using ssGSEA methods. The databases of Fudan University Shanghai Cancer Center (FUSCC) and Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine (XHH) served as an external validation set. GSEA was carried out to identify the immunotype associated signal transduction pathways.

Results

A total of 652 ccRCC patients were included in our study. We constructed a novel immunotype of ccRCC to classify patients into three groups: high-immunity, moderate-immunity, and low-immunity. The high-immunity and moderate-immunity groups had higher ImmuneScores, ESTIMATEScores, StromalScores, and lower tumor purity than that of the low-immunity group in both sets. Additionally, the patients from the high-immunity and moderate-immunity groups had longer survival than patients from low-immunity group in both discovery set and validation set (HR = 2.54, 95% CI: 1.56–4.13, p < 0.01; HR = 2.75, 95% CI: 1.24–6.11, p = 0.01).

Conclusion

In summary, we defined a novel immunotype of ccRCC. The immune types could be used as a clinical predictive tool to identify ccRCC patients with different survival. In addition, the immune-related biological signaling pathway also brought new insights on the mechanism of ccRCC.

The Role of Circulating Biomarkers in the Oncological Management of Metastatic Renal Cell Carcinoma: Where Do We Stand Now?

Renal cell carcinoma (RCC) is an increasingly common malignancy that can progress to metastatic renal cell carcinoma (mRCC) in approximately one-third of RCC patients. The 5-year survival rate for mRCC is abysmally low, and, at the present time, there are sparingly few if any effective treatments. Current surgical and pharmacological treatments can have a long-lasting impact on renal function, as well. Thus, there is a compelling unmet need to discover novel biomarkers and surveillance methods to improve patient outcomes with more targeted therapies earlier in the course of the disease. Circulating biomarkers, such as circulating tumor DNA, noncoding RNA, proteins, extracellular vesicles, or cancer cells themselves potentially represent a minimally invasive tool to fill this gap and accelerate both diagnosis and treatment. Here, we discuss the clinical relevance of different circulating biomarkers in metastatic renal cell carcinoma by clarifying their potential role as novel biomarkers of response or resistance to treatments but also by guiding clinicians in novel therapeutic approaches.

Outcomes based on plasma biomarkers in METEOR, a randomized phase 3 trial of cabozantinib vs everolimus in advanced renal cell carcinoma

BACKGROUND

In the phase 3 METEOR trial, cabozantinib improved progression-free survival (PFS) and overall survival (OS) versus everolimus in patients with advanced RCC after prior antiangiogenic therapy.

METHODS

In this exploratory analysis, plasma biomarkers from baseline and week 4 from 621 of 658 randomized patients were analyzed for CA9, HGF, MET, GAS6, AXL, VEGF, VEGFR2, and IL-8. PFS and OS were analyzed by baseline biomarker levels as both dichotomized and continuous variables using univariate and multivariable methods. For on-treatment changes, PFS and OS were analyzed using fold change in biomarker levels at week 4. Biomarkers were considered prognostic if p < 0.05 and predictive if p_interaction < 0.05 for the interaction between treatment and biomarker.

RESULTS

Hazard ratios for PFS and OS favored cabozantinib versus everolimus for both low and high baseline levels of all biomarkers (hazard ratios ≤0.78). In univariate analyses, low baseline HGF, AXL, and VEGF were prognostic for improvements in both PFS and OS with cabozantinib, and low HGF was prognostic for improvements in both PFS and OS with everolimus. Low AXL was predictive of relative improvement in PFS for cabozantinib versus everolimus. Results were generally consistent when baseline biomarkers were expressed as continuous variables, although none were predictive of benefit with treatment. In multivariable analysis, low baseline HGF was independently prognostic for improved PFS for both cabozantinib and everolimus; low HGF, GAS6, and VEGF were independently prognostic for improved OS with cabozantinib. No biomarkers were independently prognostic for OS with everolimus. On-treatment increases in some biomarkers appeared prognostic for PFS or OS with cabozantinib in univariate analyses; however, none were independently prognostic in multivariable analysis.

CONCLUSIONS

PFS and OS were improved with cabozantinib versus everolimus at high and low baseline levels of all biomarkers. Low baseline HGF was consistently identified as a prognostic biomarker for improved PFS or OS with cabozantinib or everolimus, supporting further prospective evaluation of the prognostic significance of HGF in advanced RCC.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01865747 (registered on 05/31/2013).

The Immunotherapy Landscape in Renal Cell Carcinoma

The past 30 years have borne witness to a gradual evolution in the treatment landscape of advanced renal cell carcinoma (aRCC). Early immunotherapy approaches such as interferon-α and high-dose interleukin-2 (IL-2) therapy in this immunogenic tumor provided durable responses in only a minority of patients and came with toxic side effects. A growing understanding of the tumor biology elucidated pathways of tumorigenesis, which in turn revealed novel targets amenable to targeted therapies. Inhibition of angiogenesis and cell signaling emerged as cornerstones of treatment with the approval of bevacizumab and several pan-kinase and tyrosine kinase inhibitors. Though effective, their use has been limited by low rates of durable response, resistance, and side effects. The immunotherapy revolution of the past decade has led to immunotherapy-based combination regimens such as ipilimumab plus nivolumab, pembrolizumab plus axitinib, and avelumab plus axitinib, displacing single agent anti-angiogenic therapy in the first-line setting by demonstrating durable responses and improved survival over sunitinib. These immunotherapy-based combinations define first-line standard of care for aRCC today. The pipeline of second-line agents for consideration in patients who have disease progression despite immunotherapy regimens is robust but still in early stages of development.

Correlative serum biomarker analyses in the phase 2 trial of lenvatinib-plus-everolimus in patients with metastatic renal cell carcinoma

Background

No biomarkers have been established to predict treatment efficacy in renal cell carcinoma (RCC). In an exploratory retrospective analysis of a Phase 2 study, we constructed composite biomarker scores (CBSs) to predict progression-free survival (PFS) and overall survival (OS) in patients with metastatic RCC randomised to receive lenvatinib-plus-everolimus.

Methods

Of 40 biomarkers tested, the 5 most strongly associated with PFS (HGF, MIG, IL-18BP, IL-18, ANG-2) or OS (TIMP-1, M-CSF, IL-18BP, ANG-2, VEGF) were used to make a 5-factor PFS-CBS or OS-CBS, respectively. A 2-factor CBS was generated with biomarkers common to PFS-CBS and OS-CBS. Patients were divided into groups accordingly (5-factor-CBS high: 3−5, CBS-low: 0–2; 2-factor-CBS high: 1–2, CBS-low: 0).

Results

PFS/OS with lenvatinib-plus-everolimus were significantly longer in the 5-factor CBS-high group versus the CBS-low group (P = 0.0022/P < 0.0001, respectively). In the CBS-high group, PFS/OS were significantly longer with lenvatinib-plus-everolimus versus everolimus (P < 0.001/P = 0.0079, respectively); PFS was also significantly longer with lenvatinib-plus-everolimus versus lenvatinib (P = 0.0046). The 5-factor-CBS had a predictive role in PFS and OS after multivariate analysis. Similar trends were observed with the 2-factor-CBS for PFS (i.e., lenvatinib-plus-everolimus versus everolimus).

Conclusions

The 5-factor CBS may identify patients with metastatic RCC who would benefit from lenvatinib-plus-everolimus versus everolimus; additional validation is required.

Clinical trial registration

The clinical trial registration number is NCT01136733.

Prospective Translational Study Investigating Molecular PrEdictors of Resistance to First-Line PazopanIb in Metastatic reNal CEll Carcinoma (PIPELINE Study)

OBJECTIVES

Despite the initial clinical benefit, resistance to antiangiogenic therapies develops through the activation of alternative pathways. We measured plasma levels of circulating angiogenic factors to explore their predictive role in metastatic renal cell carcinoma (mRCC) patients treated with pazopanib.

MATERIALS AND METHODS

mRCC patients receiving first-line pazopanib were prospectively enrolled. The levels of circulating interleuchine (IL)-6, IL-8, stromal derived factor-1, vascular endothelial growth factor-A, hepatocyte growth factor (HGF), osteopontin, and E-selectin were quantified at baseline and every 4 weeks until disease progression (PD). Patients were dichotomized into "low" and "high" subgroups by a cutoff point defined by the respective median circulating angiogenic factor (CAF) value at baseline. Then, association with the objective response was determined. Changes in CAF levels between baseline and PD were also compared.

RESULTS

Among 25 patients included in the final data set, 6 patients were still on treatment. As best response, 12 patients presented a partial response (48%), 9 showed stable disease, and 4 showed PD. The median follow-up was 31.9 months. The median progression-free survival was 14.8 months. Low baseline levels of IL-6, IL-8, HGF, and osteopontin were found to be significantly associated with objective response. In addition, patients with low baseline levels of HGF showed longer progression-free survival and overall survival, whereas patients with low baseline levels of IL-8 showed longer overall survival. Among patients experiencing PD, the median plasma levels of stromal derived factor-1 and vascular endothelial growth factor-A were significantly higher compared with the baseline (P=0.01; P=0.011). Conversely, the median levels of E-selectin were significantly lower compared with the baseline (P=0.017).

CONCLUSION

Changes in levels of selected CAFs were associated with response/resistance to pazopanib in mRCC patients.

Resistance to Systemic Therapies in Clear Cell Renal Cell Carcinoma: Mechanisms and Management Strategies

Renal cell carcinoma (RCC) is the most common form of kidney cancer. It is categorized into various subtypes, with clear cell RCC (ccRCC) representing about 85% of all RCC tumors. The lack of sensitivity to chemotherapy and radiation therapy prompted research efforts into novel treatment options. The development of targeted therapeutics, including multi-targeted tyrosine kinase inhibitors (TKI) and mTOR inhibitors, has been a major breakthrough in ccRCC therapy. More recently, other therapeutic strategies, including immune checkpoint inhibitors, have emerged as effective treatment options against advanced ccRCC. Furthermore, recent advances in disease biology, tumor microenvironment, and mechanisms of resistance formed the basis for attempts to combine targeted therapies with newer generation immunotherapies to take advantage of possible synergy. This review focuses on the current status of basic, translational, and clinical studies on mechanisms of resistance to systemic therapies in ccRCC. Mol Cancer Ther; 17(7); 1355-64. ©2018 AACR.

Sunitinib Prior to Planned Nephrectomy in Metastatic Renal Cell Carcinoma: Angiogenesis Biomarkers Predict Clinical Outcome in the Prospective Phase II PREINSUT Trial

Purpose: The PREINSUT study characterized factors predictive of response to sunitinib given before planned nephrectomy in patients with metastatic renal cell carcinoma (mRCC).Patients and Methods: This French multicenter, prospective, open-label, phase II trial (NCT00930345) included treatment-naïve patients with clear-cell mRCC. Patients received two cycles of sunitinib before nephrectomy. The primary objective was to evaluate the potential of circulating angiogenesis-related biomarkers measured before and on treatment for identifying responders based on primary renal tumor (PRT) size change. Secondary objectives were to evaluate the ability of biomarkers to predict progression-free survival (PFS) and overall survival (OS).Results: Thirty-two patients were enrolled. The median PFS was 4.5 months, and the median OS was 12.4 months. OS was significantly longer in responding patients (28.8 vs. 11.1 months; P = 0.03). Of 27 patients evaluable for PRT response, nine (33.3%) had a ≥10% decrease in PRT size. Baseline biomarkers significantly associated with outcome were endothelial progenitor cells (PRT response); vascular endothelial growth factor (VEGF)-A, stromal cell-derived factor-1 (SDF-1), soluble VEGF receptors (sVEGFR)1 and 2 (PFS); and SDF-1 and sVEGFR1 (OS). During treatment, changes in biomarkers associated with outcome were SDF-1 and platelet-derived growth factor (PDGF)-BB (PRT response), sVEGFR2 (PFS), and SDF-1 and sVEGFR1 (OS). There was no correlation between plasma sunitinib or its active metabolite steady-state trough concentrations and clinical outcome.Conclusions: Angiogenesis-related parameters that could reflect hypoxia seem to be associated with worse outcome in mRCC. As blood biomarkers are not subjected to tumor heterogeneity and allow longitudinal follow-up, circulating angiogenesis profile has a promising place in antiangiogenic therapy guidance. Clin Cancer Res; 24(22); 5534-42. ©2018 AACR.

Efficacy and safety of first-line sunitinib in Chinese patients with metastatic renal cell carcinoma

AIM

We report the first prospective study of sunitinib for metastatic renal cell carcinoma (mRCC) in China.

METHODS

Chinese mRCC patients received first-line sunitinib 50 mg daily (4/2 regimen). Overall survival (OS), progression-free survival (PFS), objective response rate and safety were assessed. Potential efficacy biomarkers were explored in post hoc analyses.

RESULTS

Median PFS was 61.7 weeks; median OS was 133.4 weeks; objective response rate was 31.1%. Most frequent adverse events (AEs) were: hand-foot syndrome (63.8%), decreased white blood cell count (52.4%), fatigue (51.4%) and decreased platelet count (51.4%). AEs were identified that predicted longer PFS and OS.

CONCLUSION

Sunitinib showed efficacy and manageable AE profile in treatment-naive Chinese mRCC patients. Larger prospective studies are required to confirm identified AEs as predictors of efficacy.

Prognostic and Predictive Factors for Renal Cell Carcinoma

Metastatic renal cell carcinoma (mRCC) is an incurable malignancy, characterized by its resistance to traditional chemotherapy, radiation, and hormonal therapy. Treatment perspectives and prognosis of patients with mRCC have been significantly improved by advances in the understanding of its molecular pathogenesis, which have led to the development of targeted therapeutics. Different molecular factors derived from the tumor or the host detected in both tissue or serum could be predictive of therapeutic benefit. Some of them suggest a rational selection of patients to be treated with certain therapies, though none have been validated for routine use. This article provides an overview of both clinical and molecular factors associated with predictive or prognostic value in mRCC and emphasizes that both should be considered in parallel to provide the most appropriate, individualized treatment and achieve the best outcomes in clinical practice.

Clinical and kinomic analysis identifies peripheral blood mononuclear cells as a potential pharmacodynamic biomarker in metastatic renal cell carcinoma patients treated with sunitinib

Background

Sunitinib is a protein tyrosine kinase (PTK) inhibitor that has immune-modulating properties. In this context, peripheral blood mononuclear cells (PBMC), mainly constituted by lymphocytes, could be a perfect surrogate tissue for identifying and assaying pharmacodynamic biomarkers of sunitinib. In this study, we investigated the changes in lymphocytes count as pharmacodynamic biomarker in metastatic renal cell carcinoma (mRCC) patients under sunitinib therapy. Thereafter, we studied the ex vivo effect of sunitinib and SU12262 (active metabolite) on PBMC from naïve mRCC patients using a high throughput kinomic profiling method.

Methods

The prognostic value of total lymphocytes count between Day 0 and Day 21 (expressed as a ratio D21/D0) was retrospectively investigated in 88 mRCC patients under sunitinib therapy. PTK PamChip^® microarrays were used to explore prospectively the ex vivo effect of sunitinib and SU12662 on PTK activity in PBMC from 21 naïve mRCC patients.

Results

In this retrospective study, D21/D0 lymphocytes ratio (Hazard Ratio, 1.83; CI95%, 1.24-2.71; p=0.0023) was independently associated with PFS. Interestingly, kinomic analysis showed that D21/D0 lymphocytes ratio and Heng prognostic model was statistically associated with the ex vivo sunitinib and SU12662 effect in PBMC.

Conclusion

The present study highlights that D21/D0 total lymphocytes ratio could be a promising pharmacodynamic biomarker in mRCC patients treated with sunitinib. Additionally, it paves the way to investigate the kinomic profile in PBMC as a prognostic factor in a larger cohort of mRCC patients under sunitinib therapy.

CXCR1 expression predicts benefit from tyrosine kinase inhibitors therapy in patients with metastatic renal cell carcinoma

PURPOSE

CXCR1 signaling promotes tumor progression in various cancers, and clinical trial has proved efficacy of CXCR1 inhibitor in metastatic breast cancer. Therefore, we investigated the prognostic value of CXCR1 in patients with metastatic renal cell carcinoma (mRCC) receiving tyrosine kinase inhibitors (TKIs) therapy.

MATERIALS AND METHODS

Patients treated with sunitinib or sorafenib were retrospectively enrolled (n = 111). CXCR1 expression was assessed by immunohistochemical staining of tissue microarrays of primary tumor, and its association with prognosis and therapeutic response were evaluated. To explore possible mechanism related to CXCR1 expression, gene set enrichment analysis was performed based on The Cancer Genome Atlas cohort.

RESULTS

High CXCR1 expression was associated with poorer overall survival (P = 0.015) and was an independent prognostic factor for patients with mRCC treated by TKIs (Hazard Ratio = 1.683, 95% Confidence Interval: 1.109-2.553, P = 0.014). CXCR1 expression was also associated with worse therapeutic response of TKIs (P = 0.017). Thirteen pathways, including hypoxia and angiogenesis, were identified to be enriched in CXCR1 positive patients.

CONCLUSIONS

High CXCR1 expression indicates reduced benefit from TKIs therapy in patients with mRCC. The mechanism may be attributed to the enriched pathways of hypoxia and angiogenesis in CXCR1 positive patients. CXCR1 may be a potential therapeutic target for mRCC, but further studies are required.

Overriding TKI resistance of renal cell carcinoma by combination therapy with IL-6 receptor blockade

Metastatic renal cell carcinoma (RCC) is a tumor entity with poor prognosis due to limited therapy options. Tyrosine kinase inhibitors (TKI) represent the standard of care for RCCs, however a significant proportion of RCC patients develop resistance to this therapy. Interleukin-6 (IL-6) is considered to be associated with poor prognosis in RCCs. We therefore hypothesized that TKI resistance and IL-6 secretion are causally connected. We first analyzed IL-6 expression after TKI treatment in RCC cells and RCC tumor specimens. Cell proliferation and signal transduction activity were then quantified after co-treatment with tocilizumab, an IL-6R inhibitor, in vitro and in vivo. 786-O RCC cells secrete high IL-6 levels after low dose stimulation with the TKIs sorafenib, sunitinib and pazopanib, inducing activation of AKT-mTOR pathway, NFκB, HIF-2α and VEGF expression. Tocilizumab neutralizes the AKT-mTOR pathway activation and results in reduced proliferation. Using a mouse xenograft model we can show that a combination therapy with tocilizumab and low dosage of sorafenib suppresses 786-O tumor growth, reduces AKT-mTOR pathway and inhibits angiogenesis in vivo more efficient than sorafenib alone. Furthermore FDG-PET imaging detected early decrease of maximum standardized uptake values prior to extended central necrosis.

Our findings suggest that a combination therapy of IL-6R inhibitors and TKIs may represent a novel therapeutic approach for RCC treatment.

Phase I Study of Dalteparin in Combination With Sunitinib in Patients With Metastatic Clear Cell Renal Carcinoma

BACKGROUND

Based on the tumor-driven concomitant activation of angiogenesis and coagulation we conducted a phase I combination study of sunitinib with the low molecular weight heparin dalteparin in patients with metastatic clear cell renal cell carcinoma (ccRCC).

MATERIALS AND METHODS

Patients received standard treatment with sunitinib (50 mg daily, 4 weeks on, 2 weeks off). During the second week of no sunitinib in the first cycle (week 6) patients received dalteparin monotherapy (in escalating doses). Combination therapy of the 2 agents was administered from the second cycle onward. Seventeen patients were enrolled at 3 dose levels of dalteparin.

RESULTS

Diarrhea and fatigue were the most frequent reported drug-related toxicities (41%). One dose-limiting toxicity (grade 3 anemia) was observed at the highest dose level of dalteparin. There were 4 partial responses (24%) and the median progression-free survival in this study was 14 months (95% confidence interval, 8.0-23.4). Anti-factor Xa levels were increased during combination therapy compared with dalteparin monotherapy.

CONCLUSIONS

Combination therapy of sunitinib with therapeutic doses of dalteparin is safe and well tolerated. The increased anti-factor Xa levels during combination treatment suggest that sunitinib might increase the anticoagulation activity of dalteparin. The positive safety profile warrants prospective evaluation of the clinical benefit of this combination strategy in patients with ccRCC.

Population Modeling Integrating Pharmacokinetics, Pharmacodynamics, Pharmacogenetics, and Clinical Outcome in Patients With Sunitinib-Treated Cancer

The tyrosine kinase inhibitor sunitinib is used as first‐line therapy in patients with metastasized renal cell carcinoma (mRCC), given in fixed‐dose regimens despite its high variability in pharmacokinetics (PKs). Interindividual variability of drug exposure may be responsible for differences in response. Therefore, dosing strategies based on pharmacokinetic/pharmacodynamic (PK/PD) models may be useful to optimize treatment. Plasma concentrations of sunitinib, its active metabolite SU12662, and the soluble vascular endothelial growth factor receptors sVEGFR‐2 and sVEGFR‐3, were measured in 26 patients with mRCC within the EuroTARGET project and 21 patients with metastasized colorectal cancer (mCRC) from the C‐II‐005 study. Based on these observations, PK/PD models with potential influence of genetic predictors were developed and linked to time‐to‐event (TTE) models. Baseline sVEGFR‐2 levels were associated with clinical outcome in patients with mRCC, whereas active drug PKs seemed to be more predictive in patients with mCRC. The models provide the basis of PK/PD‐guided strategies for the individualization of anti‐angiogenic therapies.

Sunitinib side effects as surrogate biomarkers of efficacy

With the proliferation of treatment options for the management of metastatic renal cell carcinoma (mRCC) over the past decade, predictive markers of response to therapy are becoming increasingly important. Sunitinib is commonly used in the first-line treatment of mRCC. Common mechanism-based adverse events, including hypertension, hypothyroidism, hand-foot syndrome, and neutropenia, have been explored as potential biomarkers of the clinical efficacy of sunitinib in mRCC and are reviewed in this article.

Sunitinib: Ten Years of Successful Clinical Use and Study in Advanced Renal Cell Carcinoma

The oral multikinase inhibitor sunitinib malate was approved by the U.S. Food and Drug Administration in January 2006 for use in patients with advanced renal cell carcinoma (RCC). Since then, it has been approved globally for this indication and for patients with imatinib-resistant or -intolerant gastrointestinal stromal tumors and advanced pancreatic neuroendocrine tumors. As we mark the 10-year anniversary of the beginning of the era of targeted therapy, and specifically the approval of sunitinib, it is worthwhile to highlight the progress that has been made in advanced RCC as it relates to the study of sunitinib. We present the key trials and data for sunitinib that established it as a reference standard of care for first-line advanced RCC therapy and, along with other targeted agents, significantly altered the treatment landscape in RCC. Moreover, we discuss the research with sunitinib that has sought to refine its role via patient selection and prognostic markers, improve dosing and adverse event management, and identify predictive efficacy biomarkers, plus the extent to which this research has contributed to the overall understanding and management of RCC. We also explore the key learnings regarding study design and data interpretation from the sunitinib studies and how these findings and the sunitinib development program, in general, can be a model for successful development of other agents. Finally, ongoing research into the continued and future role of sunitinib in RCC management is discussed.

THE ONCOLOGIST

2017;22:41-52 IMPLICATIONS FOR PRACTICE: Approved globally, sunitinib is established as a standard of care for first-line advanced renal cell carcinoma (RCC) therapy and, along with other targeted agents, has significantly altered the treatment landscape in RCC. Research with sunitinib that has sought to refine its role via patient selection and prognostic markers, improve dosing and adverse event management, and identify predictive efficacy biomarkers has contributed to the overall understanding and management of RCC. Key learnings regarding study design and data interpretation from the sunitinib studies and the sunitinib development program, in general, can be a model for the successful development of other agents.

Myeloid-Derived Suppressor Cell Subset Accumulation in Renal Cell Carcinoma Parenchyma Is Associated with Intratumoral Expression of IL1β, IL8, CXCL5, and Mip-1α

Purpose: Little is known about the association between myeloid-derived suppressor cell (MDSC) subsets and various chemokines in patients with renal cell carcinoma (RCC) or the factors that draw MDSC into tumor parenchyma.Experimental Design: We analyzed polymorphonuclear MDSC (PMN-MDSC), monocytic MDSC (M-MDSC), and immature MDSC (I-MDSC) from the parenchyma and peripheral blood of 48 patients with RCC, isolated at nephrectomy. We analyzed levels of IL1β, IL8, CXCL5, Mip-1α, MCP-1, and Rantes. Furthermore, we performed experiments in a Renca murine model to assess therapeutic synergy between CXCR2 and anti-PD1 and to elucidate the impact of IL1β blockade on MDSC.Results: Parenchymal PMN-MDSC have a positive correlation with IL1β, IL8, CXCL5, and Mip-1α, and I-MDSC correlate with IL8 and CXCL5. Furthermore, peripheral PMN-MDSC correlate with tumor grade. Given that PMN-MDSC express CXCR2 and parenchymal PMN-MDSC correlated with IL8 and CXCL5, we assessed the response of CXCR2 blockade with or without anti-PD1. Combination therapy reduced tumor weight and enhanced CD4⁺ and CD8⁺ T-cell infiltration. In addition, anti-IL1β decreased PMN-MDSC and M-MDSC in the periphery, PMN-MDSC in the tumor, and peripheral CXCL5 and KC. Anti-IL1β also delayed tumor growth.Conclusions: Parenchymal PMN-MDSC have a positive correlation with IL1β, IL8, CXCL5, and Mip-1α, suggesting they may attract PMN-MDSC into the tumor. Peripheral PMN-MDSC correlate with tumor grade, suggesting prognostic significance. Anti-CXCR2 and anti-PD1 synergized to reduce tumor weight and enhanced CD4⁺ and CD8⁺ T-cell infiltration in a Renca murine model, suggesting that CXCR2⁺ PMN-MDSC are important in reducing activity of anti-PD1 antibody. Finally, anti-IL1β decreases MDSC and delayed tumor growth, suggesting a potential target for MDSC inhibition. Clin Cancer Res; 23(9); 2346-55. ©2016 AACR.

Precision Oncology: Identifying Predictive Biomarkers for the Treatment of Metastatic Renal Cell Carcinoma

The recent FDA approval of multiple new pharmaceutical agents for metastatic renal cell carcinoma (RCC) has left physicians with several options for first- and second- line therapy. With limited head-to-head comparisons, however, there is a paucity of evidence to recommend the use of one agent over another. To address this knowledge gap, Voss et al. identified serum biomarkers from specimens collected during the RECORD-3 trial, a comparative study of first-line sunitinib versus first-line everolimus. Of the biomarkers identified, the 5 most strongly associated with first-line everolimus progression-free survival (PFS1L) were combined to form a composite biomarker score (CBS). The CBS was significantly associated with everolimus PFS1L in multivariate regression analysis. This study is an example of the additional value offered by a randomized trial with prospective biospecimen collection and a significant step towards identifying predictive biomarkers for the treatment of metastatic RCC. As further comparative trials are performed, it will be essential that biomarkers are appropriately identified and validated in order to further the goal of precision oncology.

Recent aspects of sunitinib therapy in patients with metastatic clear-cell renal cell carcinoma: a systematic review of the literature

Sunitinib is an orally available inhibitor of multiple tyrosine-kinase receptors approved for the treatment of advanced clear-cell renal cell carcinoma (ccRCC), a disease which has habitually had a very poor patient survival rate. Although it has become the most widely used drug for this disease, it remains not completely clear the best treatment strategy with these agent. The aim of this review is to highlight the most recent and interesting aspects of the research on treatment of advanced ccRCC with sunitinib and eventually determine alternative treatment schedule to reduce the incidence of side effects; we also wanted to review recent biomarkers able to predict response to therapy and also to point out the mechanism of acquired resistance to this drug.

Circulating biomarkers and outcome from a randomised phase II trial of sunitinib vs everolimus for patients with metastatic renal cell carcinoma

Background:

RECORD-3 assessed non-inferiority of progression-free survival (PFS) with everolimus vs sunitinib in previously untreated patients with metastatic renal cell carcinoma. Baseline plasma sample collection and randomised design enabled correlation of circulating biomarkers with efficacy.

Methods:

Samples were analysed for 121 cancer-related biomarkers. Analyses of biomarkers categorised patients as high or low (vs median) to assess association with first-line PFS (PFS1L) for each treatment arm. A composite biomarker score (CBS) incorporated biomarkers potentially predictive of PFS1L with everolimus.

Results:

Plasma samples from 442 of the 471 randomised patients were analysed. Biomarkers were associated with PFS1L for everolimus alone (29), sunitinib alone (9) or both (12). Everolimus-specific biomarkers (CSF1, ICAM1, IL-18BP, KIM1, TNFRII) with hazard ratio ⩾1.8 were integrated into a CBS (range 0–5). For CBS low (0–3, n=291) vs high (4–5, n=151), PFS1L differed significantly for everolimus but not for sunitinib. There was no significant difference in PFS1L between everolimus and sunitinib in the high CBS patient cohort.

Conclusions:

Baseline levels of multiple soluble biomarkers correlated with benefit from everolimus and/or sunitinib, independent of clinical risk factors. A similar PFS1L was observed for both treatments among patients with high CBS score.

Favorable prognostic influence of T-box transcription factor Eomesodermin in metastatic renal cell cancer patients

T-box transcription factors, T-box expressed in T cells (T-bet) encoded by Tbx21 and Eomesodermin (Eomes), drive the differentiation of effector/memory T cell lineages and NK cells. The aim of the study was to determine the prognostic influence of the expression of these transcription factors in peripheral blood (pB) in a cohort of 41 metastatic (m) RCC patients before receiving sorafenib treatment and to analyze their association with the immunophenotype in pB. In contrast to Tbx21, in the multivariate analysis including clinical features, Eomes mRNA expression was identified as an independent good prognostic factor for progression-free survival (PFS, p = 0.042) and overall survival (OS, p = 0.001) in addition to a favorable ECOG performance status (p = 0.01 and p = 0.008, respectively). Eomes expression correlated positively not only with expression of Tbx21 and TGFβ1 mRNA, but also with mRNA expression of the activation marker ICOS, and with in vivo activated HLA-DR(+) T cells. Eomes expression was negatively associated with TNFα-producing T cells. On protein level, Eomes was mainly expressed by CD56(+)CD3(-) NK cells in pB. In conclusion, we identified a higher Eomes mRNA expression as an independent good prognostic factor for OS and PFS in mRCC patients treated with sorafenib.

Sunitinib-associated hypertension and neutropenia as efficacy biomarkers in metastatic renal cell carcinoma patients

BACKGROUND

Metastatic renal cell carcinoma (mRCC) prognostic models may be improved by incorporating treatment-induced toxicities.

METHODS

In sunitinib-treated mRCC patients (N=770), baseline prognostic factors and treatment-induced toxicities (hypertension (systolic blood pressure ⩾140 mm Hg), neutropenia (grade ⩾2), thrombocytopenia (grade ⩾2), hand-foot syndrome (grade >0), and asthenia/fatigue (grade >0)) were analysed in multivariate analyses of progression-free survival (PFS) and overall survival (OS) end points.

RESULTS

On-treatment neutropenia and hypertension were associated with longer PFS (P=0.0276 and P<0.0001, respectively) and OS (P=0.0014 and P<0.0001, respectively), independent of baseline prognostic factors, including International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) criteria. By 12-week landmark analysis, neutropenia was significantly associated with longer PFS and OS (P=0.013 and P=0.0122, respectively) and hypertension or hand-foot syndrome with longer OS (P=0.0036 and P=0.0218, respectively). The concordance index was 0.65 (95% CI: 0.63-0.67) for IMDC classification alone and 0.72 (95% CI: 0.70-0.74) when combined with hypertension and neutropenia. Considering hypertension and neutropenia (developing both vs neither) changed IMDC-predicted median OS in each IMDC risk group (favourable: 45.3 vs 19.5 months; intermediate: 32.5 vs 8.0 months; poor: 21.1 vs 4.8 months).

CONCLUSIONS

On-treatment neutropenia and hypertension are independent biomarkers of sunitinib efficacy and may add prognostic accuracy to the IMDC model.

Prognostic Biomarkers for Response to Vascular Endothelial Growth Factor-Targeted Therapy for Renal Cell Carcinoma

Improved understanding of renal carcinoma disease biology has led to the discovery and approval of five novel therapies targeting specific molecules in the vascular endothelial growth factor (VEGF) biochemical pathway. Biomarker studies attempting to predict response to VEGF-targeted therapies have largely focused on circulating proteins, tissue-based molecules, and germline polymorphisms. Thus far studies have yielded conflicting results that require prospective validation; therefore no definitive biomarker has yet been integrated into the clinician's armamentarium. However, early analyses featuring genomic biomarkers have generated promising findings. This article provides an overview of available biomarkers evaluated with respect to VEGF-targeted therapies in patients with advanced renal cell carcinoma.

Association of single nucleotide polymorphisms in IL8 and IL13 with sunitinib-induced toxicity in patients with metastatic renal cell carcinoma

Purpose

Earlier, the association of single nucleotide polymorphisms (SNPs) with toxicity and efficacy of sunitinib has been explored in patients with metastatic renal cell carcinoma (mRCC). Recently, additional SNPs have been suggested as potential biomarkers. We investigated these novel SNPs for association with sunitinib treatment outcome in mRCC patients.

Methods

In this exploratory study, we selected SNPs in genes CYP3A4, NR1I2, POR, IL8, IL13, IL4-R, HIF1A and MET that might possibly be associated with sunitinib treatment outcome. Each SNP was tested for association with progression-free survival (PFS) and overall survival (OS) by Cox-regression analysis and for clinical response and toxicity using logistic regression.

Results

We included 374 patients for toxicity analyses, of which 38 patients with non-clear cell renal cell cancer were excluded from efficacy analyses. The risk for hypertension was increased in the presence of the T allele in IL8 rs1126647 (OR = 1.69, 95 % CI = 1.07–2.67, P = 0.024). The T allele in IL13 rs1800925 was associated with an increase in the risk of leukopenia (OR = 6.76, 95 % CI = 1.35–33.9, P = 0.020) and increased prevalence of any toxicity > grade 2 (OR = 1.75, 95 % CI = 1.06–2.88, P = 0.028). No significant associations were found with PFS, OS or clinical response.

Conclusions

We show that polymorphisms in IL8 rs1126647 and IL13 rs1800925 are associated with sunitinib-induced toxicities. Validation in an independent cohort is required.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-015-1935-7) contains supplementary material, which is available to authorized users.

Hypertension and Circulating Cytokines and Angiogenic Factors in Patients With Advanced Non-Clear Cell Renal Cell Carcinoma Treated With Sunitinib: Results From a Phase II Trial

BACKGROUND

We evaluated the significance of hypertension developing during vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitor (VEGFR-TKI) treatment and a group of cytokines and angiogenic factors (CAFs) in advanced non-clear cell renal cell carcinoma (nccRCC) patients treated with sunitinib in a phase II study.

MATERIALS AND METHODS

Using multiplex assays, we analyzed the levels of 38 CAFs in plasma at baseline and after 4 weeks of sunitinib therapy. Sunitinib benefit was defined as a partial response or stable disease using the Response Evaluation Criteria in Solid Tumors lasting ≥4 months. Cox proportional hazards regression models were used to assess the associations among hypertension, CAFs, and progression-free (PFS) and overall survival (OS).

RESULTS

Fifty-seven patients were evaluable; 53 had baseline CAF levels available. The median PFS and OS were 2.9 months (95% confidence interval [CI], 1.4-5.5) and 16.8 months (95% CI, 10.7-27.4), respectively. Sunitinib benefit was observed in 21 patients (37%). However, 33 patients (60%) developed hypertension during treatment, although no association was found with survival or response. Elevated baseline soluble tumor necrosis factor (TNF) receptor I, interleukin-8, growth-regulated oncogene, transforming growth factor-α, and VEGFR-2 levels were associated with an increased risk of death on multivariate analysis.

CONCLUSION

We found no association between the development of hypertension and survival or sunitinib benefit in advanced nccRCC. TNF and angiogenic/immunomodulatory mediators were identified for evaluation as markers of prognosis and VEGFR-TKI benefit in future studies.

Identifying Blood-Based Protein Biomarkers for Antiangiogenic Agents in the Clinic: A Decade of Progress

Agents that inhibit tumor angiogenesis are widely used and have provided meaningful survival benefits to patients in multiple disease settings. However, these agents differ significantly in their mechanisms of action and potential toxicities, and there are currently no prospectively validated biomarkers to guide the selection of agents for individual patients. Blood-based protein biomarkers are well suited for trials investigating antiangiogenic agents for multiple reasons. Many elements of the molecular pathways that antiangiogenic agents target are present and detectable in the circulation, sample collection is minimally invasive, and samples can be collected throughout the course of treatment. Blood-based biomarkers for antiangiogenic therapies are urgently needed to guide the development of therapeutic strategies. This review provides a brief summary of the current blood-based protein biomarkers for antiangiogenic therapies.

Predictive molecular biomarkers to guide clinical decision making in kidney cancer: current progress and future challenges

Although the past decade has seen a surfeit of new targeted therapies for renal cell carcinoma (RCC), no predictive molecular biomarker is currently used in routine clinical practice to guide personalized therapy as a companion diagnostic. Many putative biomarkers have been suggested, but none have undergone rigorous validation. There have been considerable advances in the biological understanding of RCC in recent years, with the development of accompanying molecular diagnostics that with additional validation, may be helpful for routine clinical decision making. In this review, we summarize the current understanding of predictive biomarkers in RCC management and also highlight upcoming developments of interest in biomarker research for personalizing RCC diagnostics and therapeutics.

IL8 polymorphisms and overall survival in pazopanib- or sunitinib-treated patients with renal cell carcinoma

BACKGROUND

We evaluated germline single nucleotide polymorphisms (SNPs) for association with overall survival (OS) in pazopanib- or sunitinib-treated patients with advanced renal cell carcinoma (aRCC).

METHODS

The discovery analysis tested 27 SNPs within 13 genes from a phase III pazopanib trial (N=241, study 1). Suggestive associations were then pursued in two independent datasets: a phase III trial (COMPARZ) comparing pazopanib vs sunitinib (N=729, study 2) and an observational study of sunitinib-treated patients (N=89, study 3).

RESULTS

In study 1, four SNPs showed nominally significant association (P≤0.05) with OS; two of these SNPs (rs1126647, rs4073) in IL8 were associated (P≤0.05) with OS in study 2. Because rs1126647 and rs4073 were highly correlated, only rs1126647 was evaluated in study 3, which also showed association (P≤0.05). In the combined data, rs1126647 was associated with OS after conservative multiple-test adjustment (P=8.8 × 10(-5); variant vs reference allele hazard ratio 1.32, 95% confidence interval: 1.15-1.52), without evidence for heterogeneity of effects between studies or between pazopanib- and sunitinib-treated patients.

CONCLUSIONS

Variant alleles of IL8 polymorphisms are associated with poorer survival outcomes in pazopanib- or sunitinib-treated patients with aRCC. These findings provide insight in aRCC prognosis and may advance our thinking in development of new therapies.

An update on current management of advanced renal cell cancer, biomarkers, and future directions

In the past decade, metastatic renal cell carcinoma (mRCC) treatment underwent significant advancement that resulted in an unprecedented improvement in the prognosis of this disease. This review will provide an updated review of currently approved treatment options, namely antiangiogenic and immunotherapy, as well as treatment guideline recommended by the National Comprehensive Cancer Network (NCCN). We will summarize studies ongoing in determining prognostic and predictive biomarkers in maximizing therapeutic benefit in the treatment of this disease. Lastly, we will discuss promising agents in clinical testing.

Resistance to sunitinib in renal cell carcinoma: From molecular mechanisms to predictive markers and future perspectives

The introduction of agents that inhibit tumor angiogenesis by targeting vascular endothelial growth factor (VEGF) signaling has made a significant impact on the survival of patients with metastasized renal cell carcinoma (RCC). Sunitinib, a tyrosine kinase inhibitor of the VEGF receptor, has become the mainstay of treatment for these patients. Although treatment with sunitinib substantially improved patient outcome, the initial success is overshadowed by the occurrence of resistance. The mechanisms of resistance are poorly understood. Insight into the molecular mechanisms of resistance will help to better understand the biology of RCC and can ultimately aid the development of more effective therapies for patients with this infaust disease. In this review we comprehensively discuss molecular mechanisms of resistance to sunitinib and the involved biological processes, summarize potential biomarkers that predict response and resistance to treatment with sunitinib, and elaborate on future perspectives in the treatment of metastasized RCC.

Pharmacodynamic change in plasma angiogenic proteins: a dose-escalation phase 1 study of the multi-kinase inhibitor lenvatinib

Background

Lenvatinib (E7080), an oral multi-kinase inhibitor, has inhibitory action on tumor cell proliferation and tumor angiogenesis in preclinical models. We evaluated correlations between pharmacodynamic (PD) biomarkers with patient clinical outcomes in a lenvatinib phase 1 dose-escalation study.

Methods

Plasma angiogenic proteins were evaluated as potential PD biomarkers of response to lenvatinib in a dose-escalation phase 1 study. Lenvatinib was administered to 27 patients by twice-daily dosing in 3-week cycles; 2 weeks of treatment followed by 1 week of rest until discontinuation. Blood samples for plasma proteins were collected on days 1 (baseline), 8, and 15 of cycle 1, and days 1, 8, and 15 of cycle 2. Selected clinical outcomes, including tumor shrinkage and adverse events (AEs), were used for correlative analyses of pharmacokinetic parameters and PD biomarkers.

Results

Tumor shrinkage and changes in PD biomarkers (increased vascular endothelial growth factor [VEGF] and stromal cell-derived factor 1 alpha [SDF1α] levels and decreased soluble VEGF receptor 2 [sVEGFR2] levels) significantly correlated with increasing lenvatinib exposure. Observed changes in levels of VEGF, SDF1α, and sVEGFR2 were maintained on day 15 of cycle 1, but returned to baseline during the 1-week rest period, and similar changes were induced by reinstitution of treatment in cycle 2. The worst grades of hypertension, proteinuria, and fatigue were associated with changes in VEGF and HGF at day 8 of cycle 1. Maximum tumor shrinkage was correlated with increased SDF1α levels. Decreased sVEGFR2 level was also correlated with tumor shrinkage and frequency of hypertension, proteinuria, and fatigue. Tumor shrinkage significantly correlated with the worst grade of proteinuria, but not with hypertension or fatigue.

Conclusion

PD biomarker changes observed in plasma angiogenic proteins are correlated with lenvatinib-induced tumor shrinkage and AEs. Our findings warrant further assessment of plasma proteins associated with angiogenesis as potential biomarkers of lenvatinib activity.

Trial registration

ClinicalTrial.gov: NCT00280397 (January 20, 2006).

Trial watch: Immunostimulatory cytokines in cancer therapy

Tumor-targeting immune responses provide a significant contribution to (when they do not entirely account for) the clinical activity of diverse antineoplastic regimens, encompassing not only a large panel of immunotherapeutic strategies but also conventional cytotoxic molecules, targeted anticancer agents and irradiation. In line with this notion, several approaches have been devised to elicit novel or boost existing anticancer immune responses, including the administration of immunomodulatory cytokines. Such a relatively unspecific intervention suffices to mediate clinical effects in (at least a subset of) patients bearing particularly immunogenic tumors, like melanoma and renal cell carcinoma. More often, however, immunostimulatory cytokines are administered to boost the immunogenic potential of other agents, including (but not limited to) immune checkpoint-blocking antibodies, anticancer vaccines, oncolytic viruses and immunogenic chemotherapeutics. Here, we summarize the latest advances in the clinical development of recombinant cytokines as an immunomodulatory intervention for cancer therapy.

Ramucirumab in metastatic renal cell carcinoma: The beginning or the end?

The current editorial focuses on a phase 2 study evaluating ramucirumab in patients with metastatic renal cell carcinoma (mRCC) who have received prior sunitinib and/or sorafenib therapy. The potential for further development is discussed in the context of the rapidly changing landscape of therapy for mRCC.