Antiangiogenic tyrosine kinase inhibition related gastrointestinal perforations: a case report and literature review

Anti-VEGF (vascular endothelial growth factor) therapy with the monoclonal antibody bevacizumab can cause gastrointestinal (GI) perforations. In recent years it became apparent that GI perforations also occur during treatment with antiangiogenic tyrosine kinase inhibitors (TKIs). It is of clinical importance to consider (vague) abdominal complaints during antiangiogenic treatment as a sign of a GI perforation. To illustrate this serious complication, we report four cases of antiangiogenic treatment related GI perforations. In three cases this was due to antiangiogenic TKI treatment. Reported risk factors of GI perforations due to bevacizumab include the presence of a primary tumor in situ and recent history of endoscopy or abdominal radiotherapy. Pathology assessments of surgical removal of the perforated intestinal part reveal that perforations are predominantly seen at the tumor or anastomotic site, in case of carcinomatosis or diverticulitis or when GI obstruction or an intra-abdominal abscess is present. Whether the same risk factors may be involved in antiangiogenic TKI related GI perforations is unknown. The underlying mechanisms responsible for GI perforation during antiangiogenic treatment is unknown, but disturbance of host cell homeostasis of immune cells as well as platelet-endothelial cell interactions may play an important role. In conclusion, while clinical awareness that antiangiogenic treatment can cause GI perforations is critical for current medical practice, it is also very important to get more insight in its underlying mechanisms so that this life-threatening complication may be prevented in the near future.

Understanding the molecular-based mechanism of action of the tyrosine kinase inhibitor: sunitinib

Sunitinib is an orally available small-molecule multikinase inhibitor. This agent potently inhibits the vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and c-Kit in addition to other kinases in biochemical and cell-based assays. In several relevant preclinical cancer models, sunitinib exerts significant antiangiogenesis and antitumor effects. In phase I studies, using intermittent dosing schedules, oral administration of doses up to 50 mg/day were reasonably well tolerated and resulted in plasma concentrations in the range of targeted levels needed for sustained kinase inhibition. Biomarker and functional imaging studies showed modulation of circulating markers of angiogenesis as well as a reduction in tumor metabolism. Sunitinib showed clinical activity in patients with renal cell cancer and in patients with imatinib-resistant gastrointestinal stromal tumors. Definitive randomized clinical trials showed significant clinical activity in these two indications leading to regulatory approval. In addition, this drug has showed activity in a variety of other tumor types such as breast, colon, and lung cancer and is being explored in combination with standard drugs in these diseases. The observation that biological and functional imaging effects are reduced during drug-free intervals has prompted the evaluation of protracted dosing schedules. A better understanding of mechanisms involved in resistance to sunitinib provides the rationale for combination strategies that hopefully will result in better clinical effect. Ongoing studies will elucidate the overall role of this drug in cancer treatment.

A phase I pharmacokinetic and pharmacodynamic study of CKD-732, an antiangiogenic agent, in patients with refractory solid cancer

We conducted a phase I trial of the antiangiogenic agent 6-O-(4-dimethylaminoethoxy) cinnamoyl fumagillol hemioxalate (CKD-732). Our aims were to determine the maximum tolerated dose (MTD), pharmacokinetics (PK), and safety profiles as well as identify the biologically active dose (BAD) from ex vivo pharmacodynamics (PD) and biomarkers of CKD-732. Using a dose escalation schedule, 19 patients with refractory solid tumors were enrolled at dose levels of CKD-732 ranging from 1 to 15 mg/m(2) given twice weekly for 2 weeks followed by a 1-week rest. No treatment-related deaths occurred in this study. Confusion and insomnia were dose-limiting toxicities (DLTs), and MTD was 15 mg/m(2). The area under the concentration-time curve (AUC) and maximum concentration (Cmax) increased dose dependently with increasing doses. The BAD was 5 mg/m(2) according to ex vivo PD. A decrement in soluble vascular endothelial growth factor receptor-3 (sVEGF-3) level was correlated with a reduction in tumor size (r = 0.54, P = 0.045). The results from this study showed an MTD of 15 mg/m(2) and a BAD of 5 mg/m(2).

Platelet-derived growth factor receptor inhibition and chemotherapy for castration-resistant prostate cancer with bone metastases

PURPOSE

To further assess preclinical and early clinical evidence that imatinib mesylate, a platelet-derived growth factor receptor (PDGFR) inhibitor, modulates taxane activity in prostate cancer and bone metastases, a randomized study was conducted.

EXPERIMENTAL DESIGN

Men with progressive castration-resistant prostate cancer with bone metastases (n = 144) were planned for equal randomization to i.v. 30 mg/m(2) docetaxel on days 1, 8, 15, and 22 every 42 days with 600 mg imatinib daily or placebo, for an improvement in median progression-free survival from 4.5 to 7.5 months (two-sided alpha = 0.05 and beta = 0.20). Secondary end points included differential toxicity and bone turnover markers, tumor phosphorylated PDGFR (p-PDGFR) expression, and modulation of p-PDGFR in peripheral blood leukocytes.

RESULTS

Accrual was halted early because of adverse gastrointestinal events. Among 116 evaluable men (57 docetaxel + imatinib; 59 docetaxel + placebo), respective median times to progression were 4.2 months (95% confidence interval, 3.1-7.5) and 4.2 months (95% confidence interval, 3.0-6.8; P = 0.58, log-rank test). Excess grade 3 toxicities (n = 23) in the docetaxel + imatinib group were principally fatigue and gastrointestinal. Tumor p-PDGFR expression was observed in 12 of 14 (86%) evaluable bone specimens. In peripheral blood leukocytes, p-PDGFR reduction was more likely in docetaxel + imatinib-treated patients compared with docetaxel + placebo (P < 0.0001), as were reductions in urine N-telopeptides (P = 0.004) but not serum bone-specific alkaline phosphatase (P = 0.099).

CONCLUSIONS

These clinical and translational results question the value of PDGFR inhibition with taxane chemotherapy in prostate cancer bone metastases and are at variance with the preclinical studies. This discordance requires explanation.

Sorafenib and sunitinib: novel targeted therapies for renal cell cancer

Renal cell cancer (RCC) is a relatively uncommon malignancy, with 51,190 cases expected to be diagnosed in 2007. Localized disease is curable by surgery; however, locally advanced or metastatic disease is not curable in most cases and, until recently, had a limited response to drug treatment. Historically, biologic response modifiers or immunomodulating agents were tested in clinical trials based on observations that some cases of RCC can spontaneously regress. High-dose aldesleukin is approved by the United States Food and Drug Administration as a treatment for advanced RCC; however, the drug is associated with a high frequency of severe adverse effects. Responses have been observed with low-dose aldesleukin and interferon alfa, but with little effect on overall survival. Sorafenib and sunitinib are novel therapies that target growth factor receptors known to be activated by the hypoxia-inducible factor and the Ras-Raf/MEK/ERK pathways. These pathways are important in the pathophysiology of RCC. Sorafenib and sunitinib have shown antitumor activity as first- and second-line therapy in patients with cytokine-refractory metastatic RCC who have clear-cell histology. Although complete responses are not common, both drugs promote disease stabilization and increase progression-free survival. This information suggests that disease stabilization may be an important determinant for response in RCC and possibly other cancers. Sorafenib and sunitinib are generally well tolerated and are considered first- and second-line treatment options for patients with advanced clear cell RCC. In addition, sorafenib and sunitinib have shown promising results in initial clinical trials evaluating antitumor activity in patients who are refractory to other antiangiogenic therapy. The most common toxicities with both sorafenib and sunitinib are hand-foot syndrome, rash, fatigue, hypertension, and diarrhea. Research is directed toward defining the optimal use of these new agents.

Protein kinases as targets for cancer treatment

In various types of malignancies, conventional forms of therapy (surgery, radiation and chemotherapy) are often ineffective, as well as harmful. In the last few years, a convergence of scientific advances has enabled the identification of molecular targets and signaling pathways specific to cancer cells, resulting in therapies with enhanced selectivity and efficacy and reduced toxicity. Compound validation has relied on target validation first, although some of the most successful drugs often have effects outside of their postulated mechanism. Protein kinases represent such molecular targets; considerable research effort has been devoted to the development of targeted drugs that inhibit the action of pathogenic kinases, and clinical studies performed so far have validated the positive effects of kinase inhibitors for cancer treatment. In this review, the specificity, mechanism of action and antitumor activity of several new small-molecule inhibitors of tyrosine and serine/threonine kinases are discussed.

Vascular endothelial growth factor-targeted therapy in renal cell carcinoma: current status and future directions

Renal cell carcinoma is a highly vascular tumor associated with expression of vascular endothelial growth factor (VEGF). Recently, VEGF-targeted therapies have been identified as a promising therapeutic approach. Three agents targeting the VEGF pathway have shown clinical activity as monotherapy in metastatic renal cell carcinoma: the anti-VEGF monoclonal antibody, bevacizumab, and small-molecule VEGF receptor tyrosine kinase inhibitors, sorafenib and sunitinib. This article explores these agents in terms of their mechanisms of action, clinical efficacy, and toxicity profiles. This article also reviews future development strategies, including combination regimens and drug sequencing, trial design considerations, and patient selection opportunities.

Wirksamkeit von Multikinaseinhibitoren in der Therapie des fortgeschrittenen Nierenzellkarzinoms

Due to the chemoresistance of renal cell cancer, cytokine-based therapeutic approaches were considered the standard treatment for patients with metastatic disease. At present, data that are available from a few phase II/III studies, dealing both with the first- and second-line treatment of patients suffering from systemic progression of RCC, indicate the significantly higher clinical efficacy of multikinase inhibitors when compared with cytokine-based therapeutic regimens. In this context, sorafenib (Nexavar, BAY 43-9006) and sunitinib (Sutent, SU 011248) are the most frequently applied and most intensively investigated substances. In Germany, with regard to a phase III study reported at the ASCO congress in 2006, sunitinib received approval for the first-line therapy of metastatic RCC. The application of multikinase inhibitors follows the principle of targeting such mediators that are considered to be substantially involved in the pathogenesis and particularly progression of renal cell cancer within relatively well-defined molecular pathways. The aim of the present paper is to address and to critically discuss the clinical data that are currently available regarding the therapeutic efficacy of kinase inhibitors during the treatment of metastatic RCC.

Sunitinib: from rational design to clinical efficacy

Sunitinib (SU011248) is an oral small molecular tyrosine kinase inhibitor that exhibits potent antiangiogenic and antitumor activity. Tyrosine kinase inhibitors such as SU6668 and SU5416 (semaxanib) demonstrated poor pharmacologic properties and limited efficacy; therefore, sunitinib was rationally designed and chosen for its high bioavailability and its nanomolar-range potency against the antiangiogenic receptor tyrosine kinases (RTKs)--vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR). Sunitinib inhibits other tyrosine kinases including, KIT, FLT3, colony-stimulating factor 1 (CSF-1), and RET, which are involved in a number of malignancies including small-cell lung cancer, GI stromal tumors (GISTs), breast cancer, acute myelogenous leukemia, multiple endocrine neoplasia types 2A and 2B, and familial medullary thyroid carcinoma. Sunitinib demonstrated robust antitumor activity in preclinical studies resulting not only in tumor growth inhibition, but tumor regression in models of colon cancer, non-small-cell lung cancer, melanoma, renal carcinoma, and squamous cell carcinoma, which were associated with inhibition of VEGFR and PDGFR phosphorylation. Clinical activity was demonstrated in neuroendocrine, colon, and breast cancers in phase II studies, whereas definitive efficacy has been demonstrated in advanced renal cell carcinoma and in imatinib-refractory GISTs, leading to US Food and Drug Administration approval of sunitinib for treatment of these two diseases. Studies investigating sunitinib alone in various tumor types and in combination with chemotherapy are ongoing. The clinical benchmarking of this small-molecule inhibitor of members of the split-kinase domain family of RTKs will lead to additional insights regarding the biology, potential biomarkers, and clinical utility of agents that target multiple signaling pathways in tumor, stromal, and endothelial compartments.

Present strategies in the treatment of metastatic renal cell carcinoma: an update on molecular targeting agents

The understanding of cellular processes underlying tumour biology has allowed the development of novel molecular-targeted drugs with optimistic results in renal cell carcinoma (RCC). Mutations in the von Hippel-Lindau gene are found in 75% of sporadic RCCs, which results in upregulation of several genes involved in angiogenesis, e.g. vascular endothelial growth factor and platelet-derived growth factor. Other activated pathways in RCC are the epidermal growth factor receptor and the mTOR pathway, which regulate survival and cell growth. In addition to temsirolimus (an mTOR inhibitor) two different strategies have been studied to inhibit these targets: monoclonal antibodies, e.g. bevacizumab, and small molecule tyrosine-kinase inhibitors such as sorafenib, sunitinib and AG 013736. Phase II studies with these drugs reported substantial clinical activity in advanced RCC. Survival benefit was reported with temsirolimus, sunitinib and sorafenib in randomized trials, which led to the accelerated approval of sorafenib and sunitinib for advanced RCC by regulatory authorities in the USA and Europe. Nevertheless, as new therapies develop, new challenges arise for the optimum use of these targeted drugs. We discuss the rationale and the clinical development of these novel molecular-targeted agents, with special emphasis on updated information presented at recent meetings because of the relevance of the data reported and the potential future impact in the management of patients with RCC.

Targeted therapy for metastatic renal cell carcinoma

The discovery of a relationship for the VHL tumor suppressor gene, hypoxia inducible factor-1 alpha, and vascular endothelial growth factor in the growth of clear-cell renal cell carcinoma (RCC) has identified a pathway for novel targeted therapy. This study evaluated the impact of these agents on metastatic RCC (mRCC), and highlights recent phase II and III trials. A systematic review examined the clinical data for novel targeted agents in mRCC, with a focus on randomized phase II and III trials of the novel targeted agents sunitinib, temsirolimus, sorafenib, and bevacizumab. Several agents, including the small-molecule targeted inhibitors sunitinib, temsirolimus, sorafenib, and the monoclonal antibody bevacizumab, have demonstrated antitumor activity in randomized trials. Superior activity was found with sunitinib and temsirolimus versus cytokines in first-line therapy. Improved progression-free survival was reported with sorafenib and bevacizumab given second-line compared with placebo. Targeted therapies show promising activity in this disease, and they have been changing patient management. Sunitinib and sorafenib were recently approved by the US Food and Drug Administration for treatment of mRCC, These drugs are currently included in clinical practice.