Multi-targeted tyrosine kinase inhibitors in clinical development: focus on XL-184 (cabozantinib)

XL-184 (cabozantinib) is a novel, small-molecule, multitargeted receptor tyrosine kinase inhibitor with particular activity against hepatocyte growth factor receptor (tyrosine-protein kinase Met), vascular endothelial growth factor receptor 2 (VEGFR-2) and proto-oncogene tyrosine-protein kinase receptor Ret. There is ample evidence of Met, VEGFR-2 and Ret signaling in several tumor types. Preclinical data suggest that XL-184 has activity in tumors derived from both epithelial and mesenchymal origins. Phase I and II clinical studies support significant antitumor activity, particularly in medullary thyroid cancer and cancers metastatic to the bone. This review will evaluate XL-184's preclinical pharmacology, pharmacokinetics, drug interactions and clinical activity in phase I through phase III studies.     

Vandetanib: in medullary thyroid cancer

Vandetanib, an orally active, small-molecule, multitargeted tyrosine kinase inhibitor, demonstrates potent inhibitory activity against vascular endothelial growth factor receptor (VEGFR)-2 and -3, epidermal growth factor receptor (EGFR) and the rearranged during transfection (RET) tyrosine kinase receptor. The large (n=331), randomized, double-blind, multinational ZETA trial compared vandetanib at a dosage of 300 mg once daily with placebo in patients with unresectable, locally advanced or metastatic, hereditary or sporadic, medullary thyroid cancer. During a median follow-up period of 2 years, vandetanib demonstrated statistically significant clinical benefits over placebo with respect to the primary endpoint, namely progression-free survival (PFS), and a range of secondary endpoints, which included objective response rate, disease control rate, time to worsening of pain and calcitonin biochemical response rate. The PFS benefit with vandetanib was mostly consistent across patient subgroups based on baseline characteristics and disease status. Although the correlation between RET mutation status and clinical outcome could not be clearly evaluated in this trial, it is notable that, among patients with sporadic disease, vandetanib not only demonstrated a PFS benefit in the subgroup confirmed as having a RET mutation, but also in the subgroup for whom the RET mutation status was unknown. Vandetanib was generally well tolerated in the ZETA trial; the majority of adverse events were manageable according to standard clinical practice alone or in combination with vandetanib dose reductions. The adverse event of most concern is corrected QT interval prolongation, particularly in view of the long terminal elimination half-life of the drug.     

Vandetanib: An overview of its clinical development in NSCLC and other tumors

Vandetanib is an oral inhibitor of vascular endothelial growth factor receptor 2 (VEGFR-2), epidermal growth factor receptor (EGFR) and Ret tyrosine kinases involved in tumor growth, progression and angiogenesis. Phase I studies indicated that the recommended dose of vandetanib as a single agent is 300 mg/day. Rash, diarrhea, hypertension and asymptomatic Q-Tc prolongation were the most common adverse events. Four randomized phase III clinical trials evaluated the efficacy of vandetanib in non-small cell lung cancer (NSCLC) in combination with docetaxel (ZODIAC), pemetrexed (ZEAL) or as a single agent (ZEST and ZEPHYR). Only the ZODIAC trial met its primary endpoint (progression-free survival [PFS]), while no study showed an advantage in overall survival with vandetanib. No significant antitumor activity has been observed in small cell lung cancer, advanced ovarian, colorectal, breast, prostate cancer and multiple myeloma. In advanced metastatic medullary thyroid cancer, one randomized phase III clinical trial has demonstrated that vandetanib can significantly improve response rate, PFS and time to worsening of pain. Several key questions remain to be addressed regarding the identification of clinical or molecular biomarkers predictive of response, the choice of the optimal dose or schedule of vandetanib and the safety of long-term administration. The results of ongoing trials in untreated patients with advanced NSCLC and other tumors should better define the optimal clinical application of vandetanib.     

Epidermal growth factor receptor inhibitors in non-small-cell lung cancer

The epidermal growth factor receptor (EGFR) is a cell membrane receptor that plays a key role in cancer development and in the progression of many human malignancies, including non-small-cell lung cancer (NSCLC). EGFR-dependent signaling is involved in cancer cell proliferation, apoptosis, angiogenesis, invasion and metastasis. Targeting the EGFR is a valuable molecular approach in cancer therapy. This receptor is overexpressed in up to 80% of NSCLC cases. Thus, several molecules inhibiting this critical biologic pathway have been synthesized and tested as a single agent or in combination with other anticancer modalities in a wide of clinical trials, including reversible and irreversible small tyrosine kinase inhibitors, such as gefitinib and erlotinib, dual vascular endothelial growth factor receptor EGFR tyrosine kinase inhibitors, such as vandetanib (ZD-6474), and monoclonal antibodies, such as cetuximab, which have shown promising activity in patients with NSCLC. This review focuses on the preclinical and clinical results available with EGFR inhibitors in the treatment of NSCLC patients.     

Vandetanib for the treatment of non-small-cell lung cancer

INTRODUCTION: The use of targeted therapies in the treatment of advanced non-small-cell lung cancer (NSCLC) is increasing, especially as conventional chemotherapy affords relatively small benefits at a cost of increased toxicity. Two of the more established therapeutic targets in NSCLC are the vascular endothelial growth factor receptor (VEGFR) and epidermal growth factor receptor (EGFR). Vandetanib is an orally available inhibitor of VEGFR and EGFR signalling and is an attractive therapeutic agent owing to the simultaneous inhibition of both pathways. AREAS COVERED: This review encompasses the clinical efficacy, safety and tolerability of vandetanib in advanced NSCLC. Of particular interest are the randomized Phase III clinical trials, which did not show clinically significant overall survival benefit for vandetanib monotherapy or in combination with standard chemotherapy regimens. EXPERT OPINION: Vandetanib has anti-tumour activity in NSCLC, with improved objective responses and disease control. However, significant survival benefits were not demonstrated in Phase III clinical trials and at present vandetanib is not in further development for use in NSCLC.     

Vandetanib for the treatment of non-small-cell lung cancer

Introduction: The use of targeted therapies in the treatment of advanced non-small-cell lung cancer (NSCLC) is increasing, especially as conventional chemotherapy affords relatively small benefits at a cost of increased toxicity. Two of the more established therapeutic targets in NSCLC are the vascular endothelial growth factor receptor (VEGFR) and epidermal growth factor receptor (EGFR). Vandetanib is an orally available inhibitor of VEGFR and EGFR signalling and is an attractive therapeutic agent owing to the simultaneous inhibition of both pathways.

Areas covered: This review encompasses the clinical efficacy, safety and tolerability of vandetanib in advanced NSCLC. Of particular interest are the randomized Phase III clinical trials, which did not show clinically significant overall survival benefit for vandetanib monotherapy or in combination with standard chemotherapy regimens.

Expert opinion: Vandetanib has anti-tumour activity in NSCLC, with improved objective responses and disease control. However, significant survival benefits were not demonstrated in Phase III clinical trials and at present vandetanib is not in further development for use in NSCLC.     

Targeting RET for thyroid cancer therapy

The limited efficacy of conventional treatments in progressive thyroid carcinomas indicates the need for new therapeutic options. Activating mutations of the receptor tyrosine kinase-encoding RET gene have been identified as driving oncogenic events in subsets of papillary (PTC) and medullary (MTC) thyroid carcinomas suggesting the interest of targeted therapy. The role of RET oncogenes and the encoded constitutively active oncoproteins as potential targets has been investigated by different strategies including gene therapy and pharmacological approaches, but targeted treatment for RET-driven cancers is not clinically available in current therapy. Small molecule tyrosine kinase inhibitors, including sorafenib, sunitinib, motesanib and vandetanib, which have already shown efficacy against other neoplastic diseases, are being evaluated in clinical trials for treatment of thyroid carcinomas. Most of them, also described as Ret inhibitors, are multi-kinase inhibitors with antiangiogenic activity related to inhibition of receptor tyrosine kinases, such as the vascular endothelial growth factor receptors. Preclinical evidence supports the relevance of Ret oncoproteins as therapeutic targets for a subset of thyroid neoplastic diseases and, although targeting the original causal genetic change may not be sufficient to control the disease efficiently, the available knowledge outlines therapeutic opportunities for exploiting Ret inhibition.     

索拉非尼的药理及临床研究

索拉非尼是一种新型口服多靶点的抗肿瘤药,通过抑制Raf-1激酶从而靶向于细胞间信号传导通路直接抑制肿瘤生长,并通过抑制血管内皮生长因子受体-2(VEGF-2)和血小板衍生生长因子(PDGF)受体,阻断肿瘤血管生成途径。主要用于肾细胞癌的治疗。现综述其药理作用、药动学、临床研究、药物相互作用及不良反应的研究进展。     

国产创新药安罗替尼抗肿瘤治疗的研究进展

血管新生是恶性肿瘤细胞增殖、生长、转移过程中的重要环节,抗肿瘤血管新生药物在肿瘤治疗中起重要作用。安罗替尼是我国自主研发的多靶点小分子酪氨酸激酶抑制剂,其主要作用于血管内皮生长因子受体(VEGFR)-1、VEGFR-2、VEGFR-3、血小板衍生生长因子受体、成纤维细胞生长因子受体、c-Kit、Ret等多个靶点,可以阻断肿瘤血管生成并抑制肿瘤生长。多项临床试验证实安罗替尼在非小细胞肺癌、软组织肉瘤、小细胞肺癌、甲状腺髓样癌、肾癌和结直肠癌中均具有良好的疗效和安全性。     

Lapatinib: a novel EGFR/HER2 tyrosine kinase inhibitor for cancer

Lapatinib is an oral dual tyrosine kinase inhibitor that targets epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor-2 (HER2), both frequently overexpressed in human cancer. Preclinical data have shown that lapatinib is a potent and selective inhibitor of the tyrosine kinase domain of EGFR and HER2, and tumor cells that overexpress these receptors are growth inhibited by lapatinib both in vitro and in vivo. Phase I clinical trials have shown that lapatinib is well tolerated, with mild diarrhea and rash the most frequent toxicities, and early evidence of clinical efficacy has been reported especially in HER2-positive breast cancer. Phase II studies have shown activity for lapatinib in trastuzumab-refractory breast cancer either alone or in combination with trastuzumab. When used as first-line monotherapy for advanced breast cancer, objective tumor responses have been seen in 28% of patients with untreated HER2-positive advanced breast cancer. An extensive phase III program in advanced breast cancer is now in progress both for refractory disease and as first-line therapy in combination with chemotherapy with and without trastuzumab, and with endocrine therapy. Phase II studies have also been conducted in a variety of other tumors, including renal cell cancer. Parallel biomarker studies are starting to elucidate predictive molecular phenotypes that may indicate likelihood of response to lapatinib, and these may direct future trials with this oral tyrosine kinase inhibitor.     

ZD-6474. AstraZeneca

ZD-6474, one of a series of inhibitors of vascular endothelial growth factor receptor tyrosine kinase, which also has activity against the epidermal growth factor receptor tyrosine kinase, is under development by AstraZeneca for the potential treatment of solid tumors. Phase II trials in non-small-cell lung cancer, small-cell lung cancer and myeloma were ongoing in January 2003.     

Vascular endothelial growth factor receptor 2 inhibition in-vivo affects tumor vasculature in a tumor type-dependent way and downregulates vascular endothelial growth factor receptor 2 protein without a prominent role for miR-296

The precise molecular effects that antiangiogenic drugs exert on tumor vasculature remain to be poorly understood. We therefore set out to investigate the molecular and architectural changes that occur in the vasculature of two different tumor types that both respond to vascular endothelial growth factor receptor 2 (VEGFR2) inhibitor therapy. Mice bearing Lewis lung carcinoma (LLC) or B16.F10 melanoma were treated with vandetanib (ZD6474), a VEGFR2/epidermal growth factor receptor (EGFR)/REarranged during Transfection (RET) kinase inhibitor, resulting in a significant 80% reduction in tumor outgrowth. Although in LLC the vascular density was not affected by vandetanib treatment, it was significantly decreased in B16.F10. In LLC, vandetanib treatment induced a shift in vascular gene expression toward stabilization, as demonstrated by upregulation of Tie2 and N-cadherin and downregulation of Ang2 and integrin β3. In contrast, only eNOS and P-selectin responded to vandetanib treatment in B16.F10 vasculature. Strikingly, vandetanib reduced protein expression of VEGFR2 in both models, whereas mRNA remained unaffected. Analysis of miR-296 expression allowed us to exclude a role for the recently proposed microRNA-296 in VEGFR2 posttranslational control in LLC and B16.F10 in vivo. Our data demonstrate that VEGFR2/EGFR inhibition through vandetanib slows down both LLC and B16.F10 tumor growth. Yet, the underlying molecular changes in the vasculature that orchestrate the antitumor effect differ between tumor types. Importantly, in both models, vandetanib treatment induced loss of its pharmacological target, which was not directly related to miR-296 expression. Validation of our observations in tumor biopsies from VEGFR2 inhibitor-treated patients will be essential to unravel the effects of VEGFR2 inhibitor therapy on tumor vasculature in relation to therapeutic efficacy.     

Monoclonal antibodies targeting the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR, HER1) autocrine pathway contributes to a number of highly relevant processes in cancer development and progression, including cell proliferation, regulation of apoptotic cell death, angiogenesis and metastatic spread. The crucial role that EGFR plays in human cancers has led to an extensive search for selective inhibitors of its signaling pathway. The results of a large body of preclinical studies and clinical trials thus far conducted suggest that targeting the EGFR could bring a significant contribution to cancer therapy. A variety of different approaches are currently being used to target the EGFR. The most promising strategies in clinical development include monoclonal antibodies, to prevent ligand binding, and small molecules inhibitors of the tyrosine kinase enzymatic activity, that inhibit autophosphorylation and downstream intracellular signaling. Several blocking monoclonal antibodies against the EGFR have been developed. Among these, IMC-225 is a chimeric human-mouse monoclonal IgG1 antibody that has been the first anti-EGFR targeted therapy to enter clinical evaluation in cancer patients in Phase II and III studies, alone or in combination with conventional radiotherapy and chemotherapy. However, other antibodies against EGFR have demonstrated antitumor activity in several preclinical models of human cancer and are currently under investigation in the clinical setting, such as ICR62, ABX-EGF and EMD72000. This review will focus on all the preclinical data available on monoclonal antibodies engineered against the EGF receptor.     

Pazopanib,a potent orally administered small-molecule multitargeted tyrosine kinase inhibitor for renal cell carcinoma

Background: The recent approvals of sunitinib, sorafenib and temsirolimus have revolutionized the management of renal cell carcinoma (RCC). Pazopanib (GW-786034) is a second-generation multitargeted tyrosine kinase inhibitor against VEGFR-1, 2 and 3, platelet-derived growth factor receptor (PDGFR)-α, PDGFR-β and c-kit. Objective: Data supporting the development of pazopanib for RCC are reviewed. Methods: Preclinical and clinical data available for pazopanib are presented. Results: Preclinical evaluation has revealed excellent anti-angiogenic and anti-tumor activity in several mouse models. A Phase II clinical trial of pazopanib in untreated or cytokine/bevacizumab pretreated RCC has demonstrated promising activity accompanied by a favorable toxicity profile. A placebo-controlled Phase III trial is ongoing in untreated or cytokine-treated patients with RCC. Ongoing trials are further evaluating pazopanib in a variety of other malignancies.     

Molecularly targeted therapy for gastrointestinal cancer

Receptor and non-receptor tyrosine kinases (TKs) have emerged as clinically useful drug target molecules for treating gastrointestinal cancer. Imatinib mesilate (STI-571, Gleevec(TM)), an inhibitior of bcr-abl TK, which was primarily designed to treat chronic myeloid leukemia is also an inhibitor of c-kit receptor TK, and is currently the drug of choice for the therapy of metastatic gastrointestinal stromal tumors (GISTs), which frequently express constitutively activated forms of the c-kit-receptor. The epidermal growth factor receptor (EGFR), which is involved in cell proliferation, metastasis and angiogenesis, is another important target. The two main classes of EGFR inhibitors are the TK inhibitors and monoclonal antibodies. Gefitinib (ZD1839, Iressa(TM)) has been on trial for esophageal and colorectal cancer (CRC) and erlotinib (OSI-774, Tarceva(TM)) on trial for esophageal, colorectal, hepatocellular, and biliary carcinoma. In addition, erlotinib has been evaluated in a Phase III study for the treatment of pancreatic cancer. Cetuximab (IMC-C225, Erbitux(TM)), a monoclonal EGFR antibody, has been FDA approved for the therapy of irinotecan resistant colorectal cancer and has been tested for pancreatic cancer. Vascular endothelial growth factor (VEGF) and its receptor (VEGFR) are critical regulators of tumor angiogenesis. Bevacizumab (Avastin(TM)), a monoclonal antibody against VEGF, was efficient in two randomized clinical trials investigating the treatment of metastatic colorectal cancer. It is also currently investigated for the therapy of pancreatic cancer in combination with gemcitabine. Other promising new drugs currently under preclinical and clinical evaluation, are VEGFR2 inhibitor PTK787/ZK 222584, thalidomide, farnesyl transferase inhibitor R115777 (tipifarnib, Zarnestra(TM)), matrix metalloproteinase inhibitors, proteasome inhibitor bortezomib (Velcade(TM)), mammalian target of rapamycin (mTOR) inhibitors, cyclooxygenase-2 (COX-2) inhibitors, platelet derived growth factor receptor (PDGF-R) inhibitors, protein kinase C (PKC) inhibitors, mitogen-activated protein kinase kinase (MEK) 1/2 inhibitors, Rous sarcoma virus transforming oncogene (SRC) kinase inhibitors, histondeacetylase (HDAC) inhibitors, small hypoxia-inducible factor (HIF) inhibitors, aurora kinase inhibitors, hedgehog inhibitors, and TGF-beta signalling inhibitors.     

Targeting angiogenesis from multiple pathways simultaneously: BIBF 1120, an investigational novel triple angiokinase inhibitor

Angiogenesis is considered one of the major components of tumor progression and metastasis. Interfering with the formation and stabilization of tumor blood vessels could increase tumor response rates and may translate into improved clinical outcomes in cancer patients. The clinical efficacy demonstrated in phase III trials with bevacizumab, a monoclonal antibody that targets vascular endothelial growth factor ligand, suggests that targeting angiogenesis is a rational approach to cancer management. Agents that target additional proangiogenic intracellular signaling pathways also have the potential to contribute to our anticancer armamentarium. Novel targeted agents that have antiangiogenic properties have been developed in recent years such as sorafenib, sunitinib, vandetanib, and others. Many of them inhibit additional pathways beyond vascular endothelial growth factor signaling. One of these investigational targeted agents is a triple angiokinase inhibitor known as BIBF 1120. This compound targets not only vascular endothelial growth factor receptors, but also fibroblast growth factor receptors, and platelet-derived growth factor receptors. The preliminary clinical efficacy of BIBF 1120 is discussed in the context of the most relevant clinical data in several malignancies including non-small cell lung cancer.     

Molecular design and clinical development of VEGFR kinase inhibitors

Vascular angiogenesis has been shown to play a key role in many solid tumors. The vascular endothelial growth factor (VEGF) isoforms and their tyrosine kinase receptors (VEGFRs) have been under intense research for effective anticancer drug candidates. Epidermal growth factor (EGF) and its receptor (EGFR) provide another pathway critical in monitoring angiogenesis. VEGF exerts its effect through binding to tyrosine kinase receptors, mainly VEGFR-1 (Flt-1, the fms-like tyrosine kinase-1) and VEGFR-2 (Flk-1/KDR, fetal liver kinase-1). This paper reviews the progress, mechanism, and binding modes of recently approved kinase inhibitors, such as sunitinib (Sutent), sorafenib (Nexavar) and dasatinib (Sprycel), as well as other inhibitors that are still under clinical development. Recent clinical treatments suggest that most inhibitors of VEGFR (and/or EGFR) exert their therapeutic effect through not only targeting the VEGFR (and/or EGFR) pathway, but also inhibiting other pathways, such as RAF/MEK/ERK pathway. A new pharmacophore model for second generation of type II tyrosine kinase inhibitors and recent advances in the combination of VEGFR tyrosine kinase inhibitors and other chemotherapeutics are also covered.     

Synthesis and discovery of pyrazine-pyridine biheteroaryl as a novel series of potent vascular endothelial growth factor receptor-2 inhibitors

Pathological angiogenesis is associated with disease states such as cancer, diabetic retinopathy, rheumatoid arthritis, endometriosis, and psoriasis. There is much evidence that direct inhibition of the kinase activity of vascular endothelial growth factor receptor-2 (VEGFR-2) will result in the reduction of angiogenesis and the suppression of tumor growth. Attempts to optimize a cyclin-dependent kinase-1 (CDK1) inhibitor by using palladium-catalyzed C-C bond, C-N bond formation reactions to assemble diverse biheteroaryl molecules led to the unexpected discovery of a pyrazine-pyridine biheteroaryl as a novel series of potent VEGFR-2 inhibitors. Compound 15, which had IC(50) = 0.084 microM at VEGFR-2, showed very modest selectivity against fibroblast growth factor receptor-2 (IC(50) = 0.21 microM), platelet-derived growth factor receptor (IC(50) = 0.36 microM), and glycogen synthase kinase-3 (IC(50) = 0.478 microM), while it exhibited more than 10-fold selectivity against epidermal growth factor receptor (IC(50) = 1.36 microM) and insulin-R kinase (IC(50) = 1.69 microM). On the other hand, compound 15 exhibited more than 100-fold selectivity against calmodulin kinase 2; casein kinase-1 and -2; CDK1 and -4; mitogen-activated protein kinase; and protein kinase A, Cbeta2, and Cgamma (IC(50) >10 microM). Compound 15 also displayed high inhibitory potency on VEGF-stimulated human umbilical vein endothelial cell (HUVEC) proliferation (IC(50) = 0.005 microM) and good selectivity against cell lines such as HUVEC, human aortic smooth muscle cells, and MRC5 lung fibroblasts. Molecular docking studies were conducted in an attempt to rationalize the unexpected high VEGFR-2 selectivity of 15.     

Targeting signaling pathways in ovarian cancer

Background: Ovarian cancer is the most lethal gynecological cancer in western countries. Prognosis is poor for patients who relapse after platinum- and taxane-based therapy and additional treatment options besides second-line chemotherapy are necessary. Signaling pathways form promising novel candidates for pinpoint cancer treatment and thus much effort has been made to establish signal transduction as target for therapy. Objective: Tyrosine kinases, as crucial parts of the transduction pathways, have become important objects in successful treatment of various cancers. This review aims to examine the role of tyrosine kinase inhibition in treatment of ovarian cancer. Methods: Based on results of various clinical Phase I – III trials and preclinical basic research this review focuses on inhibition of growth factor receptors like human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR), and vascular endothelial growth factor (VEGFR), including presentations from the American Society of Clinical Oncology (ASCO) annual meeting 2007. Conclusions: Although various agents show activity in ovarian cancer results are variable and mostly disappointing. Clinical value may be relevant only for an immunohistologically defined subgroup of patients. These questions have to be examined in larger Phase III trials.     

Novel investigational drugs for gastric cancer

Background: Gastric cancer still represents a leading cause of death worldwide. Several cytotoxic agents have demonstrated activity and combination regimens improve progression-free survival, overall survival and quality of life. Nevertheless, now there is no standard therapy for advanced gastric cancer patients. Objective: To evaluate the role of new investigational agents. Methods: We analysed Phase I, II and III studies that evaluated tailored drugs directed against the epidermal growth factor receptor (EGFR), the c-erbB2, the vascular endothelial growth factor (VEGF), the vascular endothelial growth factor receptor (VEGFR), the matrix metalloproteinases (MMP) and the mammalian target of rapamycin (mTOR). Conclusion: Data from Phase II trials indicate the potential of improved efficacy of chemotherapy when administered in combination with bevacizumab and cetuximab. Trastuzumab results are ongoing, while marimastat has not obtained clinical developments even if it has demonstrated to be an active drug in this setting of patients.