Therapeutic targeting of angiopoietins in tumor angiogenesis and cancer development

The formation and progression of tumors in humans are linked to the abnormal development of new blood vessels known as neo-angiogenesis. Angiogenesis is a broad word that encompasses endothelial cell migration, proliferation, tube formation, and intussusception, as well as peri-EC recruitment and extracellular matrix formation. Tumor angiogenesis is regulated by angiogenic factors, out of which some of the most potent angiogenic factors such as vascular endothelial growth factor and Angiopoietins (ANGs) in the body are produced by macrophages and other immune cells within the tumor microenvironment. ANGs have a distinct function in tumor angiogenesis and behavior. ANG1, ANG 2, ANG 3, and ANG 4 are the family members of ANG out of which ANG2 has been extensively investigated owing to its unique role in modifying angiogenesis and its tight association with tumor progression, growth, and invasion/metastasis, which makes it an excellent candidate for therapeutic intervention in human malignancies. ANG modulators have demonstrated encouraging outcomes in the treatment of tumor development, either alone or in conjunction with VEGF inhibitors. Future development of more ANG modulators targeting other ANGs is needed. The implication of ANG1, ANG3, and ANG4 as probable therapeutic targets for anti-angiogenesis treatment in tumor development should be also evaluated. The article has described the role of ANG in tumor angiogenesis as well as tumor growth and the treatment strategies modulating ANGs in tumor angiogenesis as demonstrated in clinical studies. The pharmacological modulation of ANGs and ANG-regulated pathways that are responsible for tumor angiogenesis and cancer development should be evaluated for the development of future molecular therapies.

Investigating the Anticancer Activity of Isatin/Dihydropyrazole Hybrids

A series of isatin-dihydropyrazole hybrids have been synthesized in order to assess their potential as anticancer agents. In particular, 12 compounds were evaluated for their antiproliferative activity toward A549, IGR39, U87, MDA-MB-231, MCF-7, BT474, BxPC-3, SKOV-3, and H1299 cell lines, and human foreskin fibroblasts. Four compounds exhibited interesting antiproliferative activity and were further examined to determine their EC₅₀ values toward a panel of selected tumor cell lines. The best compounds were then investigated for their induced mechanism of cell death. Preliminary structure-activity relationship indicates that the presence of a substituent such as a chlorine atom or a methyl moiety in position 5 of the isatin nucleus is beneficial for the antitumor activity. EMAC4001 proved the most promising compound within the studied series with EC₅₀ values ranging from 0.01 to 0.38 μM.

Structural and Functional View of Polypharmacology

Protein domains mediate drug-protein interactions and this principle can guide the design of multi-target drugs i.e. polypharmacology. In this study, we associate multi-target drugs with CATH functional families through the overrepresentation of targets of those drugs in CATH functional families. Thus, we identify CATH functional families that are currently enriched in drugs (druggable CATH functional families) and we use the network properties of these druggable protein families to analyse their association with drug side effects. Analysis of selected druggable CATH functional families, enriched in drug targets, show that relatives exhibit highly conserved drug binding sites. Furthermore, relatives within druggable CATH functional families occupy central positions in a human protein functional network, cluster together forming network neighbourhoods and are less likely to be within proteins associated with drug side effects. Our results demonstrate that CATH functional families can be used to identify drug-target interactions, opening a new research direction in target identification.

Ongoing Screening and Treatment to Potentially Reduce Tyrosine Kinase Inhibitor-Related Fatigue in Renal Cell Carcinoma

CONTEXT

Renal cell carcinoma (RCC) represents 1% to 4% of adult malignancies, and approximately 33% of patients with RCC present with metastatic disease and have a poor prognosis. Better understanding of RCC tumor biology has led to the development of several molecularly targeted agents, such as tyrosine kinase inhibitors (TKIs), to manage advanced disease. Although evolving data suggest these drugs may be beneficial in RCC, they are associated with significant toxicities. Cancer-related fatigue (CRF) is one of the most common toxicities associated with the TKIs used in RCC.

OBJECTIVES

To review the incidence, pathophysiology, and management of CRF in patients with RCC who are undergoing targeted therapy with TKIs.

METHODS

A comprehensive database search was performed using PubMed, Ovid, Embase, and MEDLINE. References of all cited articles also were reviewed. Data from articles published between 1975 and June 2014 were considered. A narrative review regarding the incidence, pathophysiology, and management of CRF in patients with RCC undergoing targeted therapy with TKIs was performed.

RESULTS

CRF is one of the most common TKI toxicities in patients with metastatic RCC and often is the dose-limiting toxicity. Management of TKI-related CRF can be difficult and may necessitate various nonpharmacologic and pharmacologic interventions.

CONCLUSION

TKI-related CRF in patients with RCC is a highly distressing complication of cancer therapy. CRF can substantially influence drug compliance, the ability to maximally treat, and quality of life. It is important to recognize this common, yet frequently underdiagnosed complication and initiate appropriate management strategies, to increase the likelihood for optimal outcomes.

Current management of patients with gastrointestinal stromal tumor receiving the multitargeted tyrosine kinase inhibitor sunitinib

BACKGROUND

Gastrointestinal stromal tumor (GIST), a form of soft tissue sarcoma, is often detected incidentally or at an advanced stage. The tyrosine kinase inhibitor sunitinib malate (Sutent * ) is established as second-line treatment for the management of GIST after disease progression on, or intolerance to, first-line imatinib treatment. Several published reviews give guidance on management of side effects in patients with advanced renal cell carcinoma treated with sunitinib, but fewer publications cover side-effect management in patients with GIST.

SCOPE

Using published articles and abstracts, prescribing information, and personal experience in managing patients with GIST at a specialized center of excellence for cancer care, I review side-effect management recommendations for patients with GIST treated with sunitinib and provide an overview of GIST.

FINDINGS

Sunitinib has a well described side-effect profile: most side effects occurring in patients with GIST can be easily managed by standard medical intervention and/or dose modification.

CONCLUSION

Care of patients with GIST can be enhanced through communication, support, knowledge, and education, with the goal of providing effective therapy and optimal symptom control.

Risk of mucocutaneous toxicities in patients with solid tumors treated with sunitinib: a critical review and meta analysis

INTRODUCTION

we performed a systematic review and meta-analysis of mucocutaneous toxicities associatedwith sunitinib, an oral multi-tyrosine kinase inhibitor.

METHODS

eligible studies included randomized Phase II and III trials of patients with solid tumors on sunitinib daily, describing events of hand-foot syndrome, skin rash, stomatitis, and skin and hair discoloration.

RESULTS

the relative risk (RR) of all-grade hand-foot skin reaction, skin rash, stomatitis, skin and hair discoloration were 2.12 (95% CI: 1.28-3.51; p < 0.004), 1.33 (95% CI: 1.15-1.54; p < 0.0002), 1.88 (95% CI: 1.36-2.59; p = 0.0001), 16.6 (95% CI: 4.18-64.94 p < 0.003), 4.42 (95% CI: 0.8-24.5; p < 0.09); respectively.

CONCLUSIONS

our meta-analysis has demonstrated that sunitinib is associated with a higher risk of developing all-grade hand-foot skin reaction, skin rash, stomatitis and skin discoloration compared with control. Clinicians should be aware of these risks and perform regular clinical monitoring.

Learning experiences with sunitinib continuous daily dosing in patients with pancreatic neuroendocrine tumours

Molecular strategies to improve outcomes for patients with pancreatic neuroendocrine tumours (nets) have focused on targeting vascular endothelial growth factor, platelet-derived growth factor, and mtor (the mammalian target of rapamycin). This approach has led to the regulatory approval of two molecularly targeted agents for advanced pancreatic nets: sunitinib, a multi-targeted tyrosine kinase inhibitor, and everolimus, an mtor inhibitor. Initial experience with sunitinib in advanced pancreatic net was gained from the phase iii registration trial, which used a continuous daily dosing (cdd) schedule instead of daily drug administration for 4 consecutive weeks every 6 weeks (schedule 4/2), the approved schedule for advanced renal cell carcinoma (rcc) and gastrointestinal stromal tumour (gist). Clinical experience gained with schedule 4/2 in rcc and gist shows that, using a therapy management approach, patients can start and be maintained on the recommended dose and schedule, thus optimizing treatment outcomes. Here, we discuss challenges that can potentially be faced by physicians who use sunitinib on the cdd schedule, and we use clinical data and real-life clinical experience to present therapy management approaches that support cdd in advanced pancreatic net.

Risk of cardiovascular toxicities in patients with solid tumors treated with sunitinib, axitinib, cediranib or regorafenib: an updated systematic review and comparative meta-analysis

BACKGROUND

We performed a systematic review and comparative meta-analysis of cardiovascular toxicities associated with sunitinib, axitinib, cediranib or regorafenib; oral multi tyrosine kinase inhibitors.

PATIENTS AND METHODS

Eligible studies included randomized phase II and III trials of patients with solid tumors on sunitinib, axitinib, cediranib or regorafenib describing daily events of hypertension, left ventricular dysfunction, bleeding or thrombosis.

RESULTS

Patients treated with these four agents had a significantly increased risk of all-grade hypertension and bleeding. The RR of all-grade hypertension, bleeding, thrombosis and cardiac dysfunction were 2.78 (95% CI 2.03-3.81; p<0.00001), 1.93 (95% CI 1.41-2.64; p<0.00001), 0.85 (95% CI 0.60-1.19; p=0.50), 2.36 (95% CI 0.95-5.87; p=0.06), respectively. Exploratory subgroup analysis showed no effect of the agent used (sunitinib vs. axitinib vs. cediranib) in the risk of hypertension; while for bleeding, only the sunitinib subgroup RR was significant compared to axitinib or cediranib.

CONCLUSIONS

Our meta-analysis has demonstrated that sunitinib, axitinib, cediranib and regorafenib are associated with a higher risk of developing all grade and high grade hypertension compared with control. While for bleeding, only the sunitinib subgroup RR was significant compared to axitinib or cediranib. Clinicians should be aware of these risks and perform regular cardiovascular monitoring.

Drug-eluting beads loaded with antiangiogenic agents for chemoembolization: in vitro sunitinib loading and release and in vivo pharmacokinetics in an animal model

PURPOSE

The combination of embolic beads with a multitargeted tyrosine kinase inhibitor that inhibits tumor vessel growth is suggested as an alternative and improvement to the current standard doxorubicin-eluting beads for use in transarterial chemoembolization. This study demonstrates the in vitro loading and release kinetics of sunitinib using commercially available embolization microspheres and evaluates the in vitro biologic efficacy on cell cultures and the resulting in vivo pharmacokinetics profiles in an animal model.

MATERIALS AND METHODS

DC Bead microspheres, 70-150 µm and 100-300 µm (Biocompatibles Ltd., Farnham, United Kingdom), were loaded by immersion in sunitinib solution. Drug release was measured in saline in a USP-approved flow-through apparatus and quantified by spectrophotometry. Activity after release was confirmed in cell culture. For pharmacokinetics and in vivo toxicity evaluation, New Zealand white rabbits received sunitinib either by intraarterial injection of 100-300 µm sized beads or per os. Plasma and liver tissue drug concentrations were assessed by liquid chromatography-tandem mass spectroscopy.

RESULTS

Sunitinib loading on beads was close to complete and homogeneous. A total release of 80% in saline was measured, with similar fast-release profiles for both sphere sizes. After embolization, drug plasma levels remained below the therapeutic threshold (< 50 ng/mL), but high concentrations at 6 hours (14.9 µg/g) and 24 hours (3.4 µg/g) were found in the liver tissue.

CONCLUSIONS

DC Bead microspheres of two sizes were efficiently loaded with sunitinib and displayed a fast and almost complete release in saline. High liver drug concentrations and low systemic levels indicated the potential of sunitinib-eluting beads for use in embolization.

[Renal toxicity of anti-VEGF (corrected) targeted therapies]

For a few years, new targeted therapies have been used for metastatic cancers, targeting VEGF and its receptors and improving patients' survival for metastatic carcinoma (kidney, GIST, breast, colorectal). The objective of these treatments is to block either circulating VEGF (bevacizumab; VEGF-Trap), or tyrosine kinase receptors (especially the VEGF receptor) (sorafenib, sunitinib, brivanib, imatinib, etc.). Indeed, VEGF stimulates endothelial cell proliferation and then tumour growth and metastasis. However, all these antiangiogenic drugs share similar side effects, most frequently gastrointestinal disturbance, skin toxicity and hypertension. Hypertension seems to be especially frequent in case of good response. Renal side effects have probably been underestimated in the first place and their exact frequency is not known, needing some specific trials and registries. Proteinuria, thrombotic microangiopathies and acute renal failures have been reported: renal biopsies might be necessary for precise evaluation of renal damages. Physiopathology seems very close to preeclampsia. Good collaboration between oncologists, nephrologists and cardiologists is therefore crucial in order to continue these targeted therapies safely for the patients.

Sunitinib in advanced pancreatic neuroendocrine tumors: latest evidence and clinical potential

Based on preclinical data available in the RIP1-Tag2 transgenic mouse model, sunitinib is an inhibitor of angiogenesis in pancreatic neuroendocrine tumors blocking vascular endothelial growth factor receptors and platelet-derived growth factor receptors in endothelial cells and pericytes, respectively. Evidence of objective response in phase I trials justified the initiation of a large phase II/III program using sunitinib in patients with advanced/metastatic well-differentiated pancreatic neuroendocrine tumors. In the phase II study, sunitinib showed potent antitumor activity and a safe toxicity profile. In a recent double-blind placebo-controlled randomized phase III trial, sunitinib doubled the progression-free survival of patients, induced objective responses, and reduced the risk of death of patients with advanced/metastatic well-differentiated tumors. These data allowed the approval of sunitinib in several countries including Europe and the United States of America. These recent data provide hope for patients with well-differentiated pancreatic neuroendocrine tumors and will change standards of care in this disease.

Oral adverse events associated with tyrosine kinase and mammalian target of rapamycin inhibitors in renal cell carcinoma: a structured literature review

BACKGROUND

Oral adverse events (OAEs) associated with multitargeted tyrosine kinase inhibitors (TKIs) and mammalian target of rapamycin inhibitors (mTORIs) are underestimated but frequent and novel presentations of mucosal manifestations. Because optimal antitumor activity requires maintaining the optimal dose, it is essential to avoid unintended treatment delays or interruptions.

METHODS

We review the reported prevalence and appearance of OAEs with TKIs and mTORIs and the current oral assessment tools commonly used in clinical trials. We discuss the correlations between OAEs and hand-foot skin reaction (HFSR) and rash.

RESULTS

The reported prevalence of oral mucositis/stomatitis of any grade is 4% for pazopanib, 28% for sorafenib, 38% for sunitinib, 41% for temsirolimus, and 44% for everolimus. Oral lesions associated with these agents have been reported to more closely resemble aphthous stomatitis than OM caused by conventional agents. In addition, these agents may result in symptoms such as oral mucosal pain, dysgeusia, and dysphagia, in the absence of clinical lesions. Because of these factors, OAEs secondary to targeted agents may be underreported. In addition, a correlation between OAEs and HFSR was identified.

CONCLUSIONS

OAEs caused by TKIs and mTORIs may represent dose-limiting toxicities, especially considering the fact that even low grades of OAEs may be troubling to the patient. We discuss how these novel AEs can be assessed because current mucositis assessment tools have limitations. Prospective studies investigating the pathogenesis, risk factors, and management of OAEs are needed in order to minimize the impact on patient's health-related quality of life.

Residual renal function after partial or radical nephrectomy for renal cell carcinoma

Renal cell carcinoma (RCC) is often detected incidentally and early. Currently, open partial nephrectomy and laparoscopic total nephrectomy form competing technologies. The former is invasive, but nephron-sparing; the other is considered less invasive but with more loss of renal mass. Traditionally, emphasis has been placed on oncologic outcomes. However, a patient with an excellent oncologic outcome may suffer from morbidity and mortality related to renal failure. Animal models with hypertension and diabetic renal disease indicate accelerated progression of pre-existing disease after nephrectomy. Patients with RCC are older and they have a high prevalence of diabetes and hypertension. The progression of renal failure may also be accelerated after a nephrectomy. Our analysis of the available literature indicates that renal outcomes in RCC patients after surgery are relatively poorly defined. A strategy to systematically evaluate the renal function of patients with RCC, with joint discussion between the nephrologist and the oncologic team, is strongly advocated.

Characteristics of human Ewing/PNET sarcoma models

Ewing/PNET (peripheral neuroepithelioma) tumors are rare aggressive bone sarcomas occurring in young people. Rare-disease clinical trials can require global collaborations and many years. In vivo models that as accurately as possible reflect the clinical disease are helpful in selecting therapeutics with the most promise of positive clinical impact. Human Ewing/PNET sarcoma cell lines developed over the past 45 years are described. Several of these have undergone genetic analysis and have been confirmed to be those of Ewing/PNET sarcoma. The A673 Ewing sarcoma line has proven to be particularly useful in understanding the biology of this disease in the mouse. The chromosomal translocation producing the EWS/FLI1 fusion transcript characterizes clinical Ewing sarcoma. Cell lines that express this genetic profile are confirmed to be those of Ewing sarcoma. The A673 Ewing sarcoma line grows in culture and as a xenograft in immunodeficient mice. The A673 model has been used to study Ewing sarcoma angiogenesis and response to antiangiogenic agents. Many Ewing sarcoma clinical specimens express the cell surface protein endosialin. Several Ewing sarcoma cell lines, including the A673 line, also express cell surface endosialin when grown as subcutaneous tumor nodules and as disseminated disease; thus the A673 is a useful model for the study of endosialin biology and endosialin-directed therapies. With the advent of tools that allow characterization of clinical disease to facilitate optimal treatment, it becomes imperative, especially for rare tumors, to develop preclinical models reflecting disease subsets. Ewing PNET sarcomas are a rare disease where models are available.

Sunitinib malate for the treatment of pancreatic neuroendocrine tumors

BACKGROUND

The multitargeted tyrosine kinase inhibitor sunitinib has shown activity against pancreatic neuroendocrine tumors in preclinical models and phase 1 and 2 trials.

METHODS

We conducted a multinational, randomized, double-blind, placebo-controlled phase 3 trial of sunitinib in patients with advanced, well-differentiated pancreatic neuroendocrine tumors. All patients had Response Evaluation Criteria in Solid Tumors-defined disease progression documented within 12 months before baseline. A total of 171 patients were randomly assigned (in a 1:1 ratio) to receive best supportive care with either sunitinib at a dose of 37.5 mg per day or placebo. The primary end point was progression-free survival; secondary end points included the objective response rate, overall survival, and safety.

RESULTS

The study was discontinued early, after the independent data and safety monitoring committee observed more serious adverse events and deaths in the placebo group as well as a difference in progression-free survival favoring sunitinib. Median progression-free survival was 11.4 months in the sunitinib group as compared with 5.5 months in the placebo group (hazard ratio for progression or death, 0.42; 95% confidence interval [CI], 0.26 to 0.66; P<0.001). A Cox proportional-hazards analysis of progression-free survival according to baseline characteristics favored sunitinib in all subgroups studied. The objective response rate was 9.3% in the sunitinib group versus 0% in the placebo group. At the data cutoff point, 9 deaths were reported in the sunitinib group (10%) versus 21 deaths in the placebo group (25%) (hazard ratio for death, 0.41; 95% CI, 0.19 to 0.89; P=0.02). The most frequent adverse events in the sunitinib group were diarrhea, nausea, vomiting, asthenia, and fatigue.

CONCLUSIONS

Continuous daily administration of sunitinib at a dose of 37.5 mg improved progression-free survival, overall survival, and the objective response rate as compared with placebo among patients with advanced pancreatic neuroendocrine tumors. (Funded by Pfizer; ClinicalTrials.gov number, NCT00428597.).

The incidence and mechanism of sunitinib-induced thyroid atrophy in patients with metastatic renal cell carcinoma

BACKGROUND

To elucidate the incidence and mechanisms of sunitinib-induced thyroid atrophy, we investigated serial volumetric and functional changes, and evaluated histological changes of the thyroid gland in metastatic renal cell carcinoma patients who received sunitinib.

METHODS

Thyroid volume (by computed tomography volumetry) and thyroid function were measured at baseline, during the treatment, and at post-treatment periods. Histological evaluation of the thyroid gland was performed in four autopsied patients.

RESULTS

The median reduction rate in thyroid volume at last evaluation during sunitinib treatment was 30% in all 17 patients. The incidence of hypothyroidism during sunitinib treatment was significantly higher in the high reduction rate group (n=8; more than 50% reduction in volume) than in the low reduction rate group (n=9; less than 50% reduction in volume). Half of the patients in the high reduction rate group exhibited a transient thyroid-stimulating hormone suppression, suggesting thyrotoxicosis during sunitinib treatment. Histological evaluation demonstrated atrophy of thyroid follicles and degeneration of follicular epithelial cells without critical diminution of vascular volume in the thyroid gland.

CONCLUSION

Thyroid atrophy is frequently observed following sunitinib treatment and may be brought about by sunitinib-induced thyrotoxicosis or the direct effects of sunitinib that lead to degeneration of thyroid follicular cells.

Nilotinib in patients with GIST who failed imatinib and sunitinib: importance of prior surgery on drug bioavailability

PURPOSE

To evaluate the efficacy of nilotinib in patients with advanced gastrointestinal stromal tumors (GISTs) resistant or intolerant to both imatinib and sunitinib and to explore the potential relationship between nilotinib pharmacokinetics and clinical outcomes.

PATIENTS AND METHODS

We analyzed the efficacy, tolerability and pharmacokinetic parameters of nilotinib (400 mg twice daily) in 17 GIST patients with histories of prior gastrointestinal surgery.

RESULTS

Median patient age was 59 years (range, 35-71 years), 14 of 17 patients (82.4%) were male, and mean body weight was 59.4 kg. Of the 17 patients, 2 (11.8%) had partial responses (PR), 10 (58.8%) had stable disease (SD), and 5 (29.4%) had progressive disease (PD), with a clinical benefit rate (CR + PR + SD) at 24 weeks of 47.0%. Median progression-free survival (PFS) and overall survival (OS) were 23.6 weeks (95% confidence interval [CI] 0.0-50.6 weeks) and 74.0 weeks (95% CI 27.4-120.6 weeks), respectively. Most observed adverse events were mild (grade 1, 41.2%; grade 2, 52.9%), with no grade 3/4 events. Pharmacokinetic parameters of nilotinib were as follows: C (max) of 1,754 ± 970 μg/L, T(1/2) of 13.4 ± 8.94 h and AUC (0-12 h) of 14,190 ± 6,853 h μg/L. The AUC (0-12 h) of nilotinib was significantly lower in the 4 patients with prior major (total or subtotal) gastrectomy than in the other 13 patients (8,526 ± 7,869 h μg/L vs. 15,930 ± 5,759 h μg/L, P = 0.014). Of the 4 gastrectomized patients, two (50%) showed markedly decreased nilotinib exposure (AUC (0-12 h) of 1,914 and 3,194 h μg/L) and rapid disease progression (PFS of 4.6 and 7.1 weeks).

CONCLUSION

Nilotinib was active and safe in patients with advanced GIST resistant to both imatinib and sunitinib. Major gastrectomy decreased the bioavailability of nilotinib and, in some patients, lowered its clinical activity.

Off-tumor target--beneficial site for antiangiogenic cancer therapy?

Antiangiogenic cancer therapy is based on agents that target blood vessels of the tumor to inhibit its growth. However, experience from the clinic demonstrates that survival benefits following antiangiogenic therapy do not always correlate with tumor size and growth inhibition. Emerging evidence shows that delivery of antiangiogenic drugs might induce systemic alterations of the vasculature that modulate the function of various tissues and organs. Normalization of tissues and organs by antiangiogenic therapy may be an important mechanism underlying the survival benefits seen in patients with cancer who suffer cancer-associated systemic syndromes. This new concept has been validated in preclinical tumor models, and responses in patients have positively correlated with clinical benefits.

Sunitinib paves the way for targeted therapies in neuroendocrine tumors

Sunitinib demonstrating efficacy in pancreatic islet cell carcinomas will pave the way for further trials in other neuroendocrine tumor types such as carcinoid, poorly differentiated neuroendocrine disease, and several other endocrine tumors that are dependent on VEGF/VEGFR for angiogenesis. In addition, other drugs with distinct mechanisms of action, such as mTOR inhibitors, currently investigated in phase III trials, may also supply novel options in those diseases to control tumor growth and metastasis.