Pazopanib: an antiangiogenic drug in perspective

Atomic Layer Deposition Coating on the Surface of Active Pharmaceutical Ingredients to Reduce Surface Charge Build-Up

Active pharmaceutical ingredients (APIs) typically consist of solid therapeutic particles that may acquire electrostatic charge during milling and grinding operations. This may result in the agglomeration of particles, thereby reducing the flowability and affecting the homogeneity of the drug formulation. Electrostatic charge build-up may also lead to fire explosions. To avoid charge build-up, APIs are often coated with polymers. In this paper, atomic layer deposition (ALD) using metal oxides such as Al2O3 and TiO2 on APIs, namely, palbociclib and pazopanib HCl, has been utilized to demonstrate a uniform coating that results in a significant reduction in the surface charge of the drug particles. Kelvin probe force microscopy (KPFM) shows a 4-fold decrease in the surface contact potential of uncoated pazopanib HCl (2.3 V) to 0.52 and 0.82 V in TiO2-and Al2O3-coated APIs, respectively. Also, the ζ potential indicated a 4-fold decrease in the surface charge on coating pazopanib HCl, i.e., from -32.9 mV to -7.51 and -8.51 mV in Al2O3 and TiO2, respectively. Surface morphology, thermal stability, dissolution studies, and cytotoxicity of the drug particles after coating were also examined. Thermal analysis indicated no change in the melting temperature (Tm) after coating. ALD coating was found to be uniform and conformal as observed in images obtained from scanning electron microscopy (SEM) and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). The rate of dissolution was found to be delayed by the coating, and thus ALD offers slower drug release. Coating APIs with TiO2 and Al2O3 did not induce statistically significant cytotoxicity compared to the uncoated samples. The results presented in this study demonstrate that ALD coating can be used to reduce surface charge build-up and enhance the bulk properties of the drug particles without affecting their physicochemical properties.

Biomolecular interaction mechanism of an anticancer drug, pazopanib with human serum albumin: a multi-spectroscopic and computational approach

Pazopanib (PZP) is a multi-targeting tyrosine kinase inhibitor and is currently approved by FDA for the treatment of soft tissue sarcoma and renal cancer. Molecular interaction mechanism of PZP with human serum albumin (HSA) was explored under simulated physiological conditions (pH = 7.4), using fluorescence and UV absorption spectroscopy along with computational methods. Based on the inverse correlation between the Stern-Volmer constant (K_sv) and temperature, it was concluded that PZP quenched the protein fluorescence through static quenching mechanism. This was also confirmed from the UV-vis absorption spectral results. Moderate binding affinity between PZP and HSA was evident from the K_a values (5.51 - 1.05 × 10⁵ M^-1) while PZP-HSA complex formation was driven by hydrophobic and van der Waals interactions as well as hydrogen bonds, as revealed by positive entropy change (ΔS = +98.37 J mol^-1 K^-1) and negative enthalpy change (ΔH = -60.31 kJ mol^-1). Three-dimensional fluorescence spectral results disclosed microenvironmental perturbations around Trp and Tyr residues of the protein upon PZP binding. Interestingly, the addition of PZP to HSA significantly protected the protein against thermal stress. Competitive drug displacement results obtained with warfarin, phenylbutazone and diazepam elucidated Sudlow's Site I, positioned in subdomain IIA of HSA, as the preferred binding site of PZP which was well supported by molecular docking analysis, while molecular dynamics simulation results suggested the stability of the PZP-HSA complex.Communicated by Vsevolod Makeev.

Pazopanib, a novel multi-kinase inhibitor, shows potent antitumor activity in colon cancer through PUMA-mediated apoptosis

Colon cancer is still the third most common cancer which has a high mortality but low five-year survival rate. Novel tyrosine kinase inhibitors (TKI) such as pazopanib become effective antineoplastic agents that show promising clinical activity in a variety of carcinoma, including colon cancer. However, the precise underlying mechanism against tumor is unclear. Here, we demonstrated that pazopanib promoted colon cancer cell apoptosis through inducing PUMA expression. Pazopanib induced p53-independent PUMA activation by inhibiting PI3K/Akt signaling pathway, thereby activating Foxo3a, which subsequently bound to the promoter of PUMA to activate its transcription. After induction, PUMA activated Bax and triggered the intrinsic mitochondrial apoptosis pathway. Furthermore, administration of pazopanib highly suppressed tumor growth in a xenograft model. PUMA deletion in cells and tumors led to resistance of pazopanib, indicating PUMA-mediated pro-apoptotic and anti-tumor effects in vitro and in vivo. Combing pazopanib with some conventional or novel drugs, produced heightened and synergistic antitumor effects that were associated with potentiated PUMA induction via different pathways. Taken together, these results establish a critical role of PUMA in mediating the anticancer effects of pazopanib in colon cancer cells and provide the rationale for clinical evaluation.

The role of pazopanib on tumour angiogenesis and in the management of cancers: A review

Pazopanib is a relatively new compound to be introduced into the chemotherapy field. It is thought to have decent anti-angiogenic properties, which gives an additional hope for the treatment of certain types of cancers. A systematic review solely discussing about pazopanib and its anti-angiogenic effect is yet to be published to date, despite several relevant clinical trials being conducted over the recent years. In this review, we aim to investigate the mechanism of pazopanib's anti-angiogenic effect and its effectiveness in treating several cancers. We have included, in this study, findings from electronically searchable data from randomized clinical trials, clinical studies, cohort studies and other relevant articles. A total of 352 studies were included in this review. From the studies, the effect of pazopanib in various cancers or models was observed and recorded. Study quality is indefinite, with a few decent quality articles. The most elaborately studied cancers include renal cell carcinoma, solid tumors, advanced solid tumors, soft tissue sarcoma, breast cancer and gynecological cancers. In addition, several less commonly studied cancers are included in the studies as well. Pazopanib had demonstrated its anti-angiogenic effect based on favorable results observed in cancers, which are caused by angiogenesis-related mechanisms, such as renal cell carcinoma, solid tumors, advanced solid tumors and soft tissue sarcoma. This review was conducted to study, analyze and review the anti-angiogenic properties of pazopanib in various cancers. The results obtained can provide a decent reference when considering treatment options for angiogenesis-related malignancies. Furthermore, the definite observations of the anti-angiogenic effects of pazopanib could provide newer insights leading to the future development of drugs of the same mechanism with increased efficiency and reduced adverse effects.

Overview of fundamental study of pazopanib in cancer

Angiogenesis is an indispensible process for tumor growth and metastasis. Anti-angiogenesis based therapy is one of the most promising treatments for inhibiting cancer progression. Through the exploration of inhibitors of vascular endothelial growth factor receptor (VEGFR)-2, deemed as the major angiogenesis pathway, pazopanib was found as a small molecular pan-VEGFR and pan-platelet-derived growth factor receptor (PDGFR) inhibitor, with suitable pharmacodynamic and pharmacokinetic parameters to be an oral drug. In an vitro study, pazopanib exerted anti-tumor effect through mechanisms including the Raf-MAPK/ERK (MEK)-extracellular signal-regulated kinase (ERK) pathway, and directly targeted on v-raf murine sarcoma viral oncogene homolog B (B-raf) as well. It inhibited the proliferation of cell lines, such as DU-145 and HRC-45 in hepatocellular carcinoma, through mechanisms like "cell cycle arrest." In vivo xenograft studies and phase I/II clinical trials revealed a series of plasma cytokine and angiogenic factors, such as interleukin (IL)-6, IL-12, hepatocyte growth factor (HGF), and soluble VEGFR2, which have significant association with clinical curative effect. Pazopanib has been shown to be effective in solid tumors and some hematological malignancies. Future studies should focus on the exploration of biomarkers to screen sensitive patients and concomitant or metronomic dosage with other kinds of medicines.

A phase I open-label study of the safety, tolerability, and pharmacokinetics of pazopanib in combination with irinotecan and cetuximab for relapsed or refractory metastatic colorectal cancer

BACKGROUND

Pazopanib is a multi-targeted tyrosine kinase inhibitor shown to be clinically active in the treatment of various cancer types. This study aimed to evaluate the maximum tolerated regimen (MTR), safety, and pharmacokinetics of pazopanib in combination with irinotecan and cetuximab in adult patients with relapsed or refractory metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

This was a Phase I, 3 + 3 design, open-label, dose-escalation study (NCT0050943; VEG108925) conducted in sequential cohorts to determine the MTR of pazopanib and irinotecan administered with cetuximab. Twenty-five patients received treatment in three dosing cohorts and were evaluated for safety and tolerability of the combination and pharmacokinetics of individual drugs.

RESULTS

The MTR was determined to be 400 mg pazopanib per day orally in combination with 150 mg/m(2) irinotecan biweekly and 250 mg/m(2) cetuximab weekly by infusion. Neutropenia was the main dose-limiting toxicity. Pharmacokinetic results suggested that the overall systemic exposure to SN-38, the active metabolite of irinotecan, was affected by pazopanib to a greater extent than was the systemic exposure to irinotecan itself.

CONCLUSIONS

This study provided evidence for the manageable safety profile and feasibility of using the novel triplet combination of pazopanib, irinotecan, and cetuximab in patients with refractory mCRC. Further large-scale Phase II studies are warranted.

Current and future systemic treatments for renal cell carcinoma

Systemic treatment of renal cell carcinoma has changed dramatically since 2007, with the development and approval of six new agents, which target complex molecular pathways regulating tumour angiogenesis and cell proliferation and survival. These treatments have significantly improved survival times in metastatic renal cell carcinoma, but remain palliative. A number of newer agents are in clinical development, which offer theoretical advantages over existing treatments, and research methodologies are adapting with the aim of defining an individualised approach to therapy which exploits the underlying tumour biology. This review will provide an overview of current and emerging systemic treatments and how they might be integrated with surgical therapy, with a particular focus on advanced, clear cell metastatic renal cell carcinoma.

Increased activation of the PI3K/AKT pathway compromises decidualization of stromal cells from endometriosis

CONTEXT

Endometriosis affects approximately 10% of women in the United States and causes pain and infertility. Decidualization of endometrial stromal cells from women with endometriosis is aberrant.

OBJECTIVE

The objective of this study was to investigate a potential mechanism for the inadequate decidual response in stromal cells from ovarian endometriomas.

DESIGN

Stromal cells of the endometrium from women without endometriosis (HSC) or from ovarian endometriomas (OsisSC) were grown in culture and treated with 10 μm LY294002 or 250 nm MK2206, 100 nm medroxyprogesterone acetate (M), and 0.5 mm dibutyryl cAMP (A) or infection with 100 multiplicity of infection adenoviral constructs containing wild-type Forkhead box O1 or triple-mutant FOXO1. Real-time PCR was used to measure the expression of FOXO1, IGF binding protein-1 (IGFBP1), and prolactin (PRL) mRNA, and Western blot and immunohistochemical staining were used to detect the levels of progesterone receptor (PR), FOXO1, AKT, and p(Ser473)-AKT protein in vitro or in vivo.

RESULTS

Expression of the decidua-specific genes, IGFBP1 and PRL, were significantly lower in OsisSC compared with normal HSC in response to M+A treatment. Basal expression levels of PRA, PRB, and FOXO1 proteins were dramatically lower in OsisSC. Overexpression of triple-mutant FOXO1 increased mRNA levels of IGFBP1 and PRL in OsisSC in the presence of M+A, whereas the overexpression of wild-type FOXO1 had no effect. AKT was highly phosphorylated in OsisSC compared with HSC and inhibition of phosphatidylinositol 3-kinase, with LY294002, increased levels of FOXO1 protein as well as IGFBP1 mRNA in the presence of M+A. Moreover, inhibition of AKT with MK2206, an allosteric AKT inhibitor, dramatically increased the accumulation of nuclear FOXO1 as well as expression of IGFBP1. Finally, immunohistochemical staining demonstrated higher p(Ser473)-AKT and lower FOXO1 levels in endometriosis tissues, compared with normal endometrial tissues.

CONCLUSIONS

In endometriotic stromal cells, overactivation of the phosphatidylinositol 3-kinase/AKT signaling pathway contributes to the reduced expression of the decidua-specific gene, IGFBP1, potentially through reduced levels of nuclear FOXO1.

Delivering preventive, predictive and personalised cancer medicine for renal cell carcinoma: the challenge of tumour heterogeneity

Recent years have seen major advances in the management of metastatic renal cell carcinoma (mRCC). The tyrosine kinase and mammalian target of rapamycin inhibitors have resulted in disease control and improved survival for many patients with mRCC, but they have not led to preventive, predictive or personalised medicine (PPPM). Failure to achieve this rests ultimately with inadequate knowledge of tissue and molecular heterogeneity; discovery of these drugs was based upon identification of pathogenic molecular pathways in RCC, but research into molecular factors which underpin drug response, resistance and selection of therapy for individual patients has lagged well behind clinical trials of drug development. This review will provide an overview of the development of targeted drug therapies for mRCC, will discuss the challenges which currently impede the delivery of PPPM, including identification of biomarkers, drug resistance and molecular heterogeneity, and will propose research methodologies and technologies required to overcome these obstacles.

New targeted therapies for renal cell carcinoma

INTRODUCTION

The aim of treatment in metastatic renal cell carcinoma is palliation. In the last 5 years, multiple targeted agents have been developed which have resulted in prolongation of patients' lives, but complete responses remain rare. New therapies and approaches are required to further improve the prognosis for patients with this disease.

AREAS COVERED

This review discusses the molecular targets in renal cell carcinoma relevant to the development of new treatments and describes the progress of novel therapies. The evidence is compiled from the PubMed database and proceedings of scientific meetings, searched up to December 2010.

EXPERT OPINION

A multitude of experimental agents are in clinical development and offer theoretical advantages over those currently in use. It is hoped that these treatments will result in better long-term control of metastatic renal cell carcinoma, with improved side effect profiles, but curative treatment in this disease remains elusive until the mechanisms underlying response and resistance to therapy are elucidated. Progress in the field has been limited by inadequate tissue collection within clinical trials; current and future clinical trial design will incorporate a larger translational component in an attempt to establish predictive biomarkers.

Pazopanib: a multikinase inhibitor with activity in advanced renal cell carcinoma

Treatment options for patients with metastatic renal cell carcinoma (RCC) have changed dramatically, and a new paradigm has evolved. IFN-alpha and IL-2 were previously mainstays of therapy, but since December 2005, six new agents have been approved in the USA for the treatment of advanced RCC. Three of these new agents are multitargeted kinase inhibitors, including sunitinib, sorafenib, and recently pazopanib, two target the mTOR (temsirolimus and everolimus), and one is a humanized monoclonal antibody (bevacizumab in combination with IFN-alpha) that targets VEGF. Sunitinib has emerged as the standard of care for treatment-naive RCC patients, with the recently approved bevacizumab and IFN-alpha combination providing an additional option for this population. The recent approval of pazopanib, based on the results from sequential Phase II and III clinical trials demonstrating improved overall response rates and progression-free survival, provides yet another option for front-line therapy. The current article examines the pazopanib preclinical and clinical data, provides an overview of the development of this tyrosine kinase inhibitor, and provides some speculation concerning its role in RCC therapy.

Systemic therapy for metastatic renal cell carcinoma in treatment naïve patients: a risk-based approach

IMPORTANCE OF THE FIELD

Kidney cancer is the ninth most common cancer in the USA, with an annual incidence of approximately 55,000 cases per year. Over 13,000 patients are estimated to die from this disease annually. Cloning of the VHL gene, recognition of the associated abnormalities in sporadic clear-cell carcinoma, and its role as a regulator of the hypoxic response, were important milestones in our understanding of renal-cell carcinoma (RCC) biology and the recognition of the vascular endothelial growth factor (VEGF) dependency of RCC. A variety of clinical features, including histologic features, prognostic factors, and patient history of comorbid illness, provide the framework in which the results of recent clinical trials and regulatory approvals of these agents are utilized to develop treatment recommendations for the largest metastatic patient RCC group, the therapy naïve individual.

AREAS COVERED IN THIS REVIEW

The rationale for use of VEGF-targeted therapy in advanced RCC patients and the recently developed treatment options for these individuals are reviewed. Regulatory approval of sorafenib for the treatment of metastatic RCC (mRCC), was followed by the approval of sunitinib, temsirolimus, bevacizumab plus interferon (IFNα), everolimus, and--most recently--pazopanib. These licences were granted from late 2005 through late 2009, a very short span of 4 years. In treatment-naïve mRCC patients, sunitinib, sorafenib, pazopanib, bevacizumab + IFNα, and temsirolimus were approved by the Food and Drug Administration (FDA) and/or the European Medicines Agency (EMEA). The clinical trials and data supporting these approvals are reviewed.

WHAT WILL THE READER GAIN

This review examines these developments and provides the reader an overview and understanding of available current systemic therapy options for treatment-naïve mRCC patients.

TAKE HOME MESSAGE

As multiple treatment options are now available for treatment-naïve mRCC patients, an understanding of how to utilize this group of agents is required. The use of various clinical features allows a rational approach to therapy selection. These features include prior treatment status, histologic subtype, and prognostic group. Further refinement of therapy selection is required and will require further biologic information as well as comparative randomized trials.

Pazopanib reveals a role for tumor cell B-Raf in the prevention of HER2+ breast cancer brain metastasis

PURPOSE

Brain metastases of breast cancer contribute significantly to patient morbidity and mortality. We have tested pazopanib, a recently approved antiangiogenic drug that targets VEGFR1, VEGFR2, VEGFR3, PDGFRβ, PDGFRα, and c-kit, for prevention of experimental brain metastases and mechanism of action.

EXPERIMENTAL DESIGN

In vitro assays included B-Raf enzymatic assays, Western blots, and angiogenesis assays. For in vivo assays, HER2 transfectants of the brain seeking sublines of MDA-MB-231 cells (231-BR-HER2) and MCF7 cells (MCF7-HER2-BR3, derived herein) were injected into the left cardiac ventricle of mice and treated with vehicle or pazopanib beginning on day 3 postinjection. Brain metastases were counted histologically, imaged, and immunostained.

RESULTS

Treatment with 100 mg/kg of pazopanib resulted in a 73% decline in large 231-BR-HER2 metastases (P < 0.0001) and a 39% decline in micrometastases (P = 0.004). In vitro, pazopanib was directly antiproliferative to 231-BR-HER2 breast cancer cells and inhibited MEK and ERK activation in vitro despite B-Raf and Ras mutations. Enzymatic assays demonstrated that pazopanib directly inhibited the wild type and exon 11 oncogenic mutant, but not the V600E mutant forms of B-Raf. Activation of the B-Raf targets pERK1/2 and pMEK1/2 was decreased in pazopanib-treated brain metastases whereas blood vessel density was unaltered. In the MCF7-HER2-BR3 experimental brain metastasis model, pazopanib reduced overall brain metastasis volume upon magnetic resonance imaging (MRI) by 55% (P = 0.067), without affecting brain metastasis vascular density.

CONCLUSIONS

The data identify a new activity for pazopanib directly on tumor cells as a pan-Raf inhibitor and suggest its potential for prevention of brain metastatic colonization of HER2(+) breast cancer.