The B-Raf status of tumor cells may be a significant determinant of both antitumor and anti-angiogenic effects of pazopanib in xenograft tumor models

Biological functions and research progress of eIF4E

The eukaryotic translation initiation factor eIF4E can specifically bind to the cap structure of an mRNA 5' end, mainly regulating translation initiation and preferentially enhancing the translation of carcinogenesis related mRNAs. The expression of eIF4E is closely related to a variety of malignant tumors. In tumor cells, eIF4E activity is abnormally increased, which stimulates cell growth, metastasis and translation of related proteins. The main factors affecting eIF4E activity include intranuclear regulation, phosphorylation of 4EBPs, and phosphorylation and sumoylation of eIF4E. In this review, we summarize the biological functions and the research progress of eIF4E, the main influencing factors of eIF4E activity, and the recent progress of drugs targeting eIF4E, in the hope of providing new insights for the treatment of multiple malignancies and development of targeted drugs.

New Oxazolo[5,4-d]pyrimidines as Potential Anticancer Agents: Their Design, Synthesis, and In Vitro Biological Activity Research

Cancer is a large group of diseases in which the rapid proliferation of abnormal cells generally leads to metastasis to surrounding tissues or more distant ones through the lymphatic and blood vessels, making it the second leading cause of death worldwide. The main challenge in designing a modern anticancer therapy is to develop selective compounds that exploit specific molecular targets. In this work, novel oxazolo[5,4-d]pyrimidine derivatives were designed, synthesized, and evaluated in vitro for their cytotoxic activity against a panel of four human cancer cell lines (lung carcinoma: A549, breast adenocarcinoma: MCF7, metastatic colon adenocarcinoma: LoVo, primary colon adenocarcinoma: HT29), along with their P-glycoprotein-inhibitory ability and pro-apoptotic activity. These oxazolo[5,4-d]pyrimidine derivatives, which are structurally similar to nucleic purine bases in general, are characterized by the presence of a pharmacologically favorable isoxazole substituent at position 2 and aliphatic amino chains at position 7 of the condensed heterocyclic system. In silico analysis of the obtained compounds identified their potent inhibitory activity towards human vascular endothelial growth factor receptor-2 (VEGFR-2). Molecular docking was performed to assess the binding mode of new derivatives to the VEGFR-2 active site. Then, their physicochemical, pharmacokinetic, and pharmacological properties (i.e., ADME-administration, distribution, metabolism, and excretion) were also predicted to assess their druglikeness. In particular, compound 3g (with a 3-(N,N-dimethylamino)propyl substituent) was found to be the most potent against the HT29 cell line, with a 50% cytotoxic concentration (CC₅₀) of 58.4 µM, exceeding the activity of fluorouracil (CC₅₀ = 381.2 μM) and equaling the activity of cisplatin (CC₅₀ = 47.2 µM), while being less toxic to healthy human cells (such as normal human dermal fibroblasts (NHDFs)) than these reference drugs. The results suggest that compound 3g is a potentially promising candidate for the treatment of primary colorectal cancer.

Durable response achieved using Pazopanib for germ tumor cells: A case report

Germ cell tumors with somatic-type malignancy (GCTSTM) are rare, and patients with GCTSTM have extremely poor prognoses with a median survival of nine months. Somatic-type malignancy, which are mainly sarcomas, usually exhibit chemoresistance. The recommended therapy for GCTSTM is radical resection; however, Pazopanib, which is a multityrosine kinase inhibitor, has indicated therapeutic effects for some soft tissue sarcoma components. The current study reports the case of a 21-year-old Asian man who presented with GCTSTM after combined chemotherapy for a primary mediastinal germ cell tumor with multiple lung metastases. Despite the metastases, his disease was stable after continuous administration of Pazopanib for two years and then stopping the medication for four years. To the best of our knowledge, the current report is the first report of a durable response by Pazopanib for GCTSTM, which is a rare outcome.

Introduction of Mercaptoethyl at Sorafenib Pyridine-2-Amide Motif as a Potentially Effective Chain to Further get Sorafenib-PEG-DGL

The crystal structure of the sorafenib and B-RAF complex indicates that the binding cavity occupied by the pyridine-2-carboxamide in sorafenib has a large variable space, making it a reasonable modification site. In order to identify novel compounds with anti-cancer activity, better safety and polar groups for further application, five sorafenib analogs with new pyridine-2-amide side chains were designed and synthesized. Preliminary pharmacologic studies showed that these compounds displayed much lower toxicities than that of sorafenib. Among them, compound 10b bearing mercaptoethyl group kept relevant antiproliferation potency compared to sorafenib in Huh7 and Hela cell lines with values of IC₅₀ 58.79 and 63.67 μM, respectively. As a small molecule inhibitor targeting protein tyrosine kinases, thiol in compound 10b would be an active group to react with maleimide in a mild condition for forming nanoparticles Sorafenib-PEG-DGL, which could be developed as a delivery vehicle to improve the concentration of anti-tumor therapeutic agents in the target cancer tissue and reduce side effects in the next study.

Novel potent substituted 4-amino-2-thiopyrimidines as dual VEGFR-2 and BRAF kinase inhibitors

In the present study, we report the discovery of a novel class of substituted 4-amino-2-thiopyrimidines as antiangiogenic and antiproliferative agents. Structural hybridization between 4-substituted aminopyrimidines (VEGFR-2 inhibitors) and 2-thioxopyrimidines (BRAF inhibitors) was carried out to afford substituted 4-amino-2-thiopyrimidines as type II dual VEGFR-2/BRAF inhibitors. Our design strategy was tailored such that the 4-amino-2-thiopyrimidine scaffold is to be accommodated in the central gate area of the inactive DFG-out conformation of both enzymes. On one side, the hydrophobic substituent on the 4-amino group would occupy the hydrophobic back pocket and on the other side the substituent on the sulfide moiety should extend to fit in the hinge region (front pocket). Molecular docking simulations confirmed the ability of the designed compounds to accomplish the key interactions in VEGFR-2 and BRAF active sites. Most of the synthesized substituted 4-amino-2-thiopyrimidines demonstrated potent VEGFR-2 inhibitory activity at submicromolar concentrations. Compounds 8a, 8d, 9c and 9e showed IC₅₀ = 0.17, 0.12, 0.17 and 0.19 μM, respectively against VEGFR-2 in comparison to sorafenib (I) IC₅₀ = 0.10 μM and regorafenib (II) IC₅₀ = 0.005 μM. While compounds 9c, 9d and 10a showed IC₅₀ = 0.15, 0.22 and 0.11 μM, respectively against BRAF-WT. At 10 μM concentration 9c revealed promising in vitro broad-spectrum antiproliferative activity against cancer cell lines with growth inhibition percent ranging from 10 to 90%. Moreover, compounds 7b, 8d, 9a, 9b, 9c and 9d showed potent activity against MCF7 cell line (IC₅₀ = 17.18, 17.20, 19.98, 19.61, 13.02 and 16.54 μM, respectively). On the other hand, compounds 9c, 9d and 10d were found to be the most potent compounds against T-47D cell line (IC₅₀ = 2.18, 8.09 and 4.36 μM, respectively). Studying the effect of the most potent compounds on VEGFR-2 level in MCF7 cell line revealed that 9c and 9d showed inhibition percent of 84 and 80%, respectively, in comparison to sorafenib (I) (% inhibition = 90%).

Pazopanib in advanced soft tissue sarcomas

Pazopanib is the first and only tyrosine kinase inhibitor currently approved for the treatment of multiple histological subtypes of soft tissue sarcoma (STS). Initially developed as a small molecule inhibitor of vascular endothelial growth factor receptors, preclinical work indicates that pazopanib exerts an anticancer effect through the inhibition of both angiogenic and oncogenic signaling pathways. Following the establishment of optimal dosing and safety profiles in early phase studies and approval for the treatment of advanced renal cell carcinoma, pazopanib was investigated in STS. A landmark phase III randomized study demonstrated improved progression-free survival with pazopanib compared to that with placebo in pretreated patients with STS of various subtypes. The efficacy of pazopanib in specific STS subtypes has been further described in real-world-based case series in both mixed and subtype-specific STS cohorts. At present, there are no clinically validated predictive biomarkers for use in selecting patients with advanced STS for pazopanib therapy, limiting the clinical effectiveness and cost-effectiveness of the drug. In this review, we summarize the preclinical and clinical data for pazopanib, outline the evidence base for its effect in STS and explore reported studies that have investigated putative biomarkers.

Paclitaxel with or without trametinib or pazopanib in advanced wild-type BRAF melanoma (PACMEL): a multicentre, open-label, randomised, controlled phase II trial

BACKGROUND

Advanced melanoma treatments often rely on immunotherapy or targeting mutations, with few treatment options for wild-type BRAF (BRAF-wt) melanoma. However, the mitogen-activated protein kinase pathway is activated in most melanoma, including BRAF-wt. We assessed whether inhibiting this pathway by adding kinase inhibitors trametinib or pazopanib to paclitaxel chemotherapy improved outcomes in patients with advanced BRAF-wt melanoma in a phase II, randomised and open-label trial.

PATIENTS AND METHODS

Patients were randomised (1 : 1 : 1) to paclitaxel alone or with trametinib or pazopanib. Paclitaxel was given for a maximum of six cycles, while 2 mg trametinib and 800 mg pazopanib were administered orally once daily until disease progression or unacceptable toxicity. Participants and investigators were unblinded. The primary end point was progression-free survival (PFS). Key secondary end points included overall survival (OS) and objective response rate (ORR).

RESULTS

Participants were randomised to paclitaxel alone (n = 38), paclitaxel and trametinib (n = 36), or paclitaxel and pazopanib (n = 37). Adding trametinib significantly improved 6-month PFS [time ratio (TR), 1.47; 90% confidence interval (CI) 1.08-2.01, P = 0.04] and ORR (42% versus 13%; P = 0.01) but had no effect on OS (P = 0.25). Adding pazopanib did not benefit 6-month PFS; (TR 1.36; 90% CI 0.96-1.93; P = 0.14), ORR, or OS. Toxicity increased in both combination arms.

CONCLUSION

In this phase II trial, adding trametinib to paclitaxel chemotherapy for BRAF-wt melanoma improved PFS and substantially increased ORR but did not impact OS.This study was registered with the EU Clinical Trials Register, EudraCT number 2011-002545-35, and with the ISRCTN registry, number 43327231.

Pharmacokinetic drug evaluation of pazopanib for the treatment of uterine leiomyosarcomas

INTRODUCTION

Uterine leiomyosarcomas (ULMS) represent 1.3% of all uterine malignant tumors. Surgery is the curative treatment for patients with early stage disease. In case of advanced, persistent or recurrent tumor, chemotherapy represents the standard of care, but these patients have a poor prognosis. As the results with available therapies are far from being satisfactory, research is focusing on identification of new compounds. In 2012 the Food and Drug Administration (FDA) licensed pazopanib for the treatment of advanced soft-tissue sarcomas failing previous chemotherapy. Areas covered: The aim of this article is to review the literature on the pharmacokinetics, pharmacodynamics, clinical efficacy and safety of the tyrosine kinase inhibitor (TKI), pazopanib in the treatment of ULMS. Expert opinion: The discovery of some relevant signalling pathways in LMS cells led to the development of new targeted drugs with promising results in the management of these tumors. Pazopanib is a multi-target second-generation TKI with activity against growth factors involved in angiogenesis. It has shown promising results both in terms of efficacy and safety, as shown in the EORTC 62043 Study and the PALETTE trial. Further studies are awaited to evaluate its efficacy in uterine leiomyosarcomas.

Limited Tumor Tissue Drug Penetration Contributes to Primary Resistance against Angiogenesis Inhibitors

Resistance mechanisms against antiangiogenic drugs are unclear. Here, we correlated the antitumor and antivascular properties of five different antiangiogenic receptor tyrosine kinase inhibitors (RTKIs) (motesanib, pazopanib, sorafenib, sunitinib, vatalanib) with their intratumoral distribution data obtained by matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). In the first mouse model, only sunitinib exhibited broad-spectrum antivascular and antitumor activities by simultaneously suppressing vascular endothelial growth factor receptor-2 (VEGFR2) and desmin expression, and by increasing intratumoral hypoxia and inhibiting both tumor growth and vascularisation significantly. Importantly, the highest and most homogeneous intratumoral drug concentrations have been found in sunitinib-treated animals. In another animal model, where - in contrast to the first model - vatalanib was detectable at homogeneously high intratumoral concentrations, the drug significantly reduced tumor growth and angiogenesis. In conclusion, the tumor tissue penetration and thus the antiangiogenic and antitumor potential of antiangiogenic RTKIs vary among the tumor models and our study demonstrates the potential of MALDI-MSI to predict the efficacy of unlabelled small molecule antiangiogenic drugs in malignant tissue. Our approach is thus a major technical and preclinical advance demonstrating that primary resistance to angiogenesis inhibitors involves limited tumor tissue drug penetration. We also conclude that MALDI-MSI may significantly contribute to the improvement of antivascular cancer therapies.

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.

Pazopanib in sarcomas: expanding the PALETTE

PURPOSE OF REVIEW

After failure of standard therapy, few effective treatment options exist for adult patients with metastatic sarcomas, and median survival remains dismal at approximately 1 year. Pazopanib, a multitargeted tyrosine kinase inhibitor, has recently been approved for nonadipocytic soft tissue sarcomas refractory to chemotherapy. In this review, we will revisit the efficacy of pazopanib in sarcomas, and present a patient case that illustrates two of many unanswered questions: which sarcoma patients are most likely to benefit from pazopanib therapy, and what criteria are best suited to accurately detect benefit in clinical trials?

RECENT FINDINGS

Pazopanib has been tested in sarcoma patients in a phase II and phase III study, and was shown to prolong progression-free survival by 3 months relative to placebo. Although histology has been the primary stratification variable for subgroup analysis in large sarcoma trials, the PALETTE study did not demonstrate superior response within histologic cohorts. Ongoing trials seek to explore efficacy of pazopanib in previously excluded histologies, as well as include correlative studies to identify histologic and molecular biomarkers to predict patients likely to benefit.

SUMMARY

Pazopanib has been proven to provide modest benefit overall to nonadipocytic soft tissue sarcoma patients, but we have yet to identify the molecular basis for those patients who derive exceptional benefit.

Pazopanib inhibits the activation of PDGFRβ-expressing astrocytes in the brain metastatic microenvironment of breast cancer cells

Brain metastases occur in more than one-third of metastatic breast cancer patients whose tumors overexpress HER2 or are triple negative. Brain colonization of cancer cells occurs in a unique environment, containing microglia, oligodendrocytes, astrocytes, and neurons. Although a neuroinflammatory response has been documented in brain metastasis, its contribution to cancer progression and therapy remains poorly understood. Using an experimental brain metastasis model, we characterized the brain metastatic microenvironment of brain tropic, HER2-transfected MDA-MB-231 human breast carcinoma cells (231-BR-HER2). A previously unidentified subpopulation of metastasis-associated astrocytes expressing phosphorylated platelet-derived growth factor receptor β (at tyrosine 751; p751-PDGFRβ) was identified around perivascular brain micrometastases. p751-PDGFRβ(+) astrocytes were also identified in human brain metastases from eight craniotomy specimens and in primary cultures of astrocyte-enriched glial cells. Previously, we reported that pazopanib, a multispecific tyrosine kinase inhibitor, prevented the outgrowth of 231-BR-HER2 large brain metastases by 73%. Here, we evaluated the effect of pazopanib on the brain neuroinflammatory microenvironment. Pazopanib treatment resulted in 70% (P = 0.023) decrease of the p751-PDGFRβ(+) astrocyte population, at the lowest dose of 30 mg/kg, twice daily. Collectively, the data identify a subpopulation of activated astrocytes in the subclinical perivascular stage of brain metastases and show that they are inhibitable by pazopanib, suggesting its potential to prevent the development of brain micrometastases in breast cancer patients.

Potential biofluid markers and treatment targets for renal cell carcinoma

Renal cell carcinoma (RCC) is the 13th most common cancer in the world and one of the few cancers for which incidence is increasing. This disease is generally asymptomatic at an early stage and is highly metastatic. Frequently discovered by physicians in the process of working up other diseases such as acute kidney injury, RCC is often discovered in an advanced form and many patients have metastases at the time of diagnosis. Given that life expectancy with currently approved therapies for metastatic RCC is approximately 1-2 years, biomarkers for RCC that will enable early detection are urgently needed. Although it is unlikely that highly sensitive and specific biomarkers will be identified in the near future that are useful for screening the general population, a noninvasive marker or set of markers could soon be used in general medicine, nephrology, and urology clinics to screen patients at increased risk of RCC. In addition to the ongoing need for RCC biomarkers, the frequent resistance reported with currently available targeted therapies makes the identification of new therapeutic targets similarly important. Many promising leads for new targeted therapies have come to light; some of these therapies are in clinical trials and others are still being evaluated in the laboratory.

Concise drug review: pazopanib and axitinib

Pazopanib and axitinib are both U.S. Food and Drug Administration approved ATP-competitive inhibitors of the vascular endothelial growth factor receptor. Pazopanib and axitinib have been shown to be effective and tolerable treatment options for patients with metastatic renal cell cancer and therefore have enlarged the armamentarium for this disease. This concise drug review discusses the clinical benefits, clinical use, mechanism of action, bioanalysis, pharmacokinetics, pharmacogenetics, pharmacodynamics, drug resistance, toxicity, and patient instructions and recommendations for supportive care for these two drugs.