Anti-angiogenesis therapy:concepts and importance of dosing schedules in clinical trials

The comparative study of serum iron, copper, and zinc levels between bladder cancer patients and a control group

OBJECTIVE

A relatively wide range of trace elements are known to play important roles in biological processes, including the oxidative processes. Oxidative processes are one of the mechanisms involved in both incidence and recurrence of bladder cancer. In the present study, the concentration of iron (Fe), copper (Cu) and zinc (Zn) were determined in the serum of patients with bladder cancer in comparison to healthy subjects.

MATERIALS AND METHODS

This cross-sectional study was conducted on 51 patients with bladder cancer and 58 healthy volunteers after age, sex, and smoking habits were matched. After overnight fasting, samples were collected. The concentrations of Fe, Cu, and Zn were measured by flame atomic absorption spectroscopy and comparisons were made using Student's t-test.

RESULTS

There was a significant increase in mean Cu and Cu/Zn serum level in bladder cancer patients compared to the control group (P < 0.001). In contrast, the serum zinc level in patients having bladder cancer was significantly lower than in the control group (P < 0.05). Moreover, the serum iron level was significantly lower in the patients than the control group (P < 0.001).

CONCLUSIONS

In the present study, a relationship was seen between the level of trace elements and the occurrence of bladder cancer, suggesting that an increase in the serum level of Cu and a decrease in the levels of Zn and Fe might be important causes of bladder cancer occurrence; however, defining such a cause-and-effect relationship needs several prospective studies to be done, which seems necessary with regard to the high prevalence of this cancer.

Metronomic antiangiogenic therapy with capecitabine and celecoxib in advanced tumor patients--results of a phase II study

BACKGROUND

Combined therapy of continuous low dose capecitabine and high dose celecoxib targeting angiogenesis was used in a phase II trial to treat advanced cancer patients. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was used to monitor antiangiogenic effects.

MATERIAL AND METHODS

37 Patients (21 men, 16 women), mean age 60 years, with advanced and progressive cancer of various tumor types were included. Therapy consisted of 2 x 500 mg oral capecitabine/ day and 2 x 400 mg oral celecoxib/day continuously until progression of disease. To monitor antiangiogenic effects, DCE-MRI measurements were performed at baseline, after 1 month, and after 3 months of therapy. Tumor assessment was performed according to RECIST criteria, toxicity was evaluated according to the CTC version 2.0 catalogue.

RESULTS

Therapy was well tolerated without grade 3 and 4 toxicities. The mean number of treatment cycles was 4 (range: 1-15+). Disease stabilization after 3 cycles was seen in 11 patients. 6 patients were stable over long periods. The mean number of treatment cycles in this group was 10 (range: 7-15+). DCE-MRI demonstrated a reduction of tumor vessel permeability and blood flow in patients who reached stable disease or some minor regression.

CONCLUSION

Continuous dosing of the combination of capecitabine and celecoxib was well tolerated, produced antiangiogenic effects, and has antitumor activity. Patients with rapid progression did not benefit.

PAC fixed dose: pharmacokinetics of a 1-hour paclitaxel infusion and comparison to BSA-normalized drug dosing

BACKGROUND

The aim of this study was to determine the pharmacokinetics (PKs) of a 175-mg fixed dose of paclitaxel (PAC) after a 1-h infusion in cancer patients and to compare them with the PK parameters from a study with a dose normalized to the body surface area (BSA) (100 mg/m2).

PATIENTS AND METHODS

PAC PKs were studied during the first course of therapy in 13 patients. A fixed dose of 175 mg PAC was administered weekly by a 1-h infusion to patients with advanced cancer. Total PAC in serum was quantified by high-performance liquid chromatography (HPLC). PK parameters were calculated by non-compartmental and model-dependent methods.

RESULTS

The mean BSA of 12 patients (1 patient excluded from all analyses because of prolonged infusion duration) was 1.79 m2 (coefficient of variation (CV) 7.8%), the mean dose referred to the individual BSAs was 98.3 mg/m2 (CV 8.3%). The mean area under the curve (AUC) was 6,193 ng/ml x h (CV 46%), the mean plasma clearance (Clp) was 19.7 l/h/m2 (CV 45%), and the volume of distribution at steady state (Vss) was 121.6 l/m2 (CV 52%). The mean residence time (MRT) was 7.6 h (CV 46%), the mean distribution half-life (t1/2 alpha) of PAC(tot) was 0.4 h (CV 62%), and the elimination half-life (t1/2 beta) 10.0 h (CV 42%). Maximum plasma concentration Cmax was 3,161 ng/ml (CV 36%). The mean time above 0.05 microM (42.7 ng/ml) was 19.7 h, and the mean time above 0.1 microM (85.4 ng/ml) was 10.6 h.

CONCLUSIONS

In this study, a fixed dose of PAC of 175 mg corresponds to a mean BSA-normalized dose of 98.3 mg/m2 (range 88.8-117.4 mg/m2). A higher variability of PK parameters was observed compared to previously published results of a PK study with BSA-normalized dosing of 100 mg/m2. However, the AUC and the time above threshold concentrations did not depend on the dose. Therefore, a fixed dose of 175 mg weekly could be an option for palliative treatment with PAC and may offer a simple but effective schedule for PAC treatment.

Phase II clinical trial results involving treatment with low-dose daily oral cyclophosphamide, weekly vinblastine, and rofecoxib in patients with advanced solid tumors

PURPOSE

Preclinical studies indicate that conventional chemotherapeutic agents given continuously at low doses (metronomic chemotherapy) may provide an improved therapeutic index. Cyclophosphamide and vinblastine have been best studied in experimental models, where tumor growth inhibition is achieved, at least in part, through antiangiogenic mechanisms.

EXPERIMENTAL DESIGN

Fifty patients with advanced solid tumors were enrolled in this phase II trial, 43 of whom had received at least one prior chemotherapy regimen. Patients were required to have Eastern Cooperative Oncology Group performance status of < or = 2, a life expectancy of >3 months, and at least one measurable lesion. All patients received oral cyclophosphamide (50 mg) and rofecoxib (25 mg) daily in addition to weekly injections of vinblastine (3 mg/m2). Half of the patients also received minocycline (100 mg) orally twice daily with the intent of further inhibiting tumor angiogenesis. The primary end point of the study was clinical benefit, defined as the percentage of patients experiencing an objective response or exhibiting stable disease for at least 6 months.

RESULTS

For the 47 eligible patients, there were two (4%) complete responses and four (9%) partial responses, for an overall objective response rate of 13%. An additional eight patients achieved disease stabilization (stable disease > or = 6 months) (17%). The primary end point of clinical benefit was therefore 30%, (95% confidence interval, 16-44%). The median progression-free survival for all patients was 103 days and 289 days for patients experiencing clinical benefit. The incidence of patients experiencing grade 3/4 toxicities were as follows: neutropenia (10/2), anemia (2/0), and thrombocytopenia (1/0). No patients developed grade 3 or 4 nausea, vomiting, mucositis, or alopecia.

CONCLUSIONS

This low-dose regimen consisting of daily oral cyclophosphamide and weekly vinblastine injections given concurrently with rofecoxib is associated with minimal toxicity and provides significant clinical benefit to patients with advanced solid tumors. These results are particularly encouraging given the nature of the study population and indicate that this approach merits further investigation in specific disease site studies.

Phase I clinical and pharmacokinetic study of PTK/ZK, a multiple VEGF receptor inhibitor, in patients with liver metastases from solid tumours

The family of VEGF receptors are important mediators of angiogenesis, which is essential for tumour growth and metastasis. PTK/ZK is a multiple VEGF receptor inhibitor that blocks the activity of all known VEGF receptor tyrosine kinases. This phase I/II trial evaluated the safety, pharmacokinetics and efficacy of PTK/ZK in patients with liver metastases from solid tumours. Patients were administered oral PTK/ZK monotherapy once daily at doses of 300-1200 mg/day in 28-day cycles until unacceptable toxicity or tumour progression occurred. Twenty-seven patients were enrolled and treatment with PTK/ZK was generally well tolerated. The most frequently reported adverse events were fatigue, nausea, dizziness, and vomiting (mostly National Cancer Institute Common Toxicity Criteria grade 1 or 2). The area under the concentration-time curve (AUC) of PTK/ZK increased between 300 and 1000 mg/day with no further increase from 1000 to 1200 mg/day; the AUC decreased by 50% between day 1 and day 15. The DCE-MRI showed a statistically significant early reduction of tumour blood supply (measured as Ki) at day 2 at doses > or = 750 mg/day. Disease progression was significantly correlated with percent change from baseline Ki. Thirteen patients had stable disease for at least two cycles (56 days). Median overall survival was 11.8 months (95% CI = 6.6, 17.1 months). Long-term therapy with PTK/ZK demonstrated predictable pharmacokinetics, was safe and feasible in patients with metastatic disease, and showed promising clinical activity. The minimum biologically active dose was established at 750 mg/day whereas the recommended dose for phase III studies is 1200 mg/day.

Anti-vascular tumor therapy: recent advances, pitfalls and clinical perspectives

Anti-vascular tumor therapy represents a promising new strategy for cancer treatment. Anti-vascular treatment may be divided in anti-angiogenic and vascular targeting therapy. Whereas anti-angiogenic drugs aim on the inhibition of new vessel formation, vascular targeting compounds are designed to selectively destruct preexisting tumor blood vessels leading to secondary tumor cell death. Both anti-angiogenic drugs and vascular targeting agents have proven effective anti-tumoral activity in numerous preclinical studies over the last decade. In vivo, a combination with anti-vascular tumor therapy enhances the effects of other treatment modalities as chemo- and radiotherapy. Phase I clinical studies revealed a number of well-tolerated candidates. As monotherapy, however, anti-angiogenic treatment lacked efficacy in randomized clinical studies so far. In contrast, combination of anti-angiogenic therapy with chemotherapy was highly effective in an encouraging, large randomized phase III trial on metastatic colorectal cancer. This review will outline recent advances in the preclinical and clinical development of anti-vascular therapy with focus on vascular targeting. Conceptual differences between anti-angiogenic and vascular targeting therapies will be discussed with emphasis on specific problems and pitfalls in the conversion into the clinic.

Resistance to cytotoxic and anti-angiogenic anticancer agents: similarities and differences

Intrinsic resistance to anticancer drugs, or resistance developed during chemotherapy, remains a major obstacle to successful treatment. This is the case both for resistance to cytotoxic agents, directed at malignant cells, and for resistance to anti-angiogenic agents, directed at non-malignant endothelial cells. In this review, we will discuss mechanisms of resistance which have a bearing on both these conceptually different classes of drugs. The complexity of drug resistance, involving drug transporters, such as P-glycoprotein, as well as resistance related to the tissue structure of solid tumors and its consequences for drug delivery is discussed. Possible mechanisms of resistance to endothelial cell-targeted drugs, including inhibitors of the VEGF receptor and EGF receptor family, are reviewed. The resistance of cancer cells as well as endothelial cells related to anti-apoptotic signaling events initiated by cell integrin-matrix interactions is discussed. Current strategies to overcome resistance mechanisms are summarized; they include high-dose chemotherapy, tumor targeting of cytotoxics to improve tumor uptake, low-dose protracted (metronomic) chemotherapy and combinations of classical agents with anti-angiogenic agents. This review discusses primarily literature published in 2001 and 2002.

Inhibition of integrin alpha5beta1 function with a small peptide (ATN-161) plus continuous 5-FU infusion reduces colorectal liver metastases and improves survival in mice

Integrin alpha(5)beta(1) is expressed on activated endothelial cells and plays a critical role in tumor angiogenesis. We hypothesized that a novel integrin alpha(5)beta(1) antagonist, ATN-161, would inhibit angiogenesis and growth of liver metastases in a murine model. We further hypothesized that combining ATN-161 with 5-fluorouracil (5-FU) chemotherapy would enhance the antineoplastic effect. Murine colon cancer cells (CT26) were injected into spleens of BALB/c mice to produce liver metastases. Four days thereafter, mice were given either ATN-161 (100 mg/kg, every 3rd day) or saline by intraperitoneal injection, with or without combination of continuous-infusion 5-FU (100 mg/kg/2 weeks), which was started on day 7. On day 20 after tumor cell inoculation, mice were killed and liver weights and number of liver metastases were determined. A follow-up study on survival was also conducted in which mice were randomized to receive ATN-161, 5-FU or ATN-161+5-FU. Combination therapy with ATN-161+5-FU significantly reduced tumor burden (liver weight) and number of liver metastases (p<0.02). Liver tumors in the ATN-161 and ATN-161+5-FU groups had significantly fewer microvessels (p<0.05) than tumors in the control or 5-FU-treated groups. Unlike treatment with either agent alone, ATN-161+5-FU significantly increased tumor cell apoptosis and decreased tumor cell proliferation (p<0.03) and improved overall survival (p<0.03, log-rank test). Targeting integrin alpha(5)beta(1) in combination with 5-FU infusion reduced liver metastases formation and improved survival in this colon cancer model. The enhancement of antineoplastic activity from the combination of anti-angiogenic therapy and chemotherapy may be a promising approach for treating metastatic colorectal cancer.

The interface between ErbB and non-ErbB receptors in tumor invasion: clinical implications and opportunities for target discovery

The molecular switches by which malignant cancer cells evolve from a confined to an invasive state are poorly understood, but seem to involve a progressive activation of a signaling network shared by several growth factor receptors and non-receptor molecules. Abnormal expression of ErbB tyrosine kinase receptors, commonly seen in cancer, is an early event in the invasive process, which makes these receptors exciting targets for drug discovery. The past few years have been full of promise for ErbB targeting in the context of receptor overexpression, but also fraught with disappointment as clinical efficacy has often been hampered by potential problems such as the heterogeneity of receptor expression within the same tumor, and the extensive cooperative signaling among ErbB and non-ErbB receptors. Cooperative signaling is a common characteristic of invasive cancer cells, and is believed to dictate the genetic program that controls invasion switches. Molecular studies on the combinatorial signaling involved in tumor invasion are becoming a fertile area for target discovery in cancer. This review discusses how cooperative signaling between ErbB and non-ErbB receptors regulates tumor invasion and hence provides multiple opportunities for drug discovery, and how current therapies and investigational drugs could pave the way to even more potent alternative combinatorial therapeutic approaches for invasive cancers.

Minimizing long-term tumor burden: the logic for metronomic chemotherapeutic dosing and its antiangiogenic basis

The general utility of the maximum tolerated dose (MTD) paradigm, a strategy aimed at optimizing the chance of total tumor cell eradication, is here questioned. Evidence to date suggests that for many tumors the potential for eradication is in fact remote, with patients consistently demonstrating tumor cell presence subsequent to MTD treatments having eradicative intent. The failure to eradicate is attributed largely to the heterogeneous nature of the tumor. Heterogeneous cell populations demonstrate short-term refractoriness to up-front dose delivery, but "resensitize" as part of dose recovery, showing increased overall susceptibility to a given series of doses when delivered more evenly spaced. It is demonstrated: (1) that the minimization of total tumor burden, rather than complete eradication, may often be the more practical objective; and (2) that regularly spaced, "metronomic" dosing is the best way to achieve it. As a corollary, it is found that the more efficient ability of the tumor endothelial cells to resensitize following dosing predicts a targeting bias towards the endothelial compartment of a tumor when metronomic dosing is employed. This lends theoretical support to recent empirical studies showing that regularly spaced dosing schedules with no extended rest periods act more antiangiogenically, thereby delaying or avoiding the onset of acquired resistance.

Emerging cancer-targeted therapies

There is reason to believe that the unfolding revolution in molecular biology and translational research will allow selective targeting of tumor cells, and radically change the way general practitioners and pediatric oncologists treat and follow children with cancer. This article highlights some of the most promising approaches being tested in the field. By learning about the underlying biology, the remaining hurdles, the projected timeline, and the possible impact of new therapies on the practice of pediatric oncology, health care professionals and patients should be better prepared for the future of pediatric oncology.

A doxorubicin-CNGRC-peptide conjugate with prodrug properties

There is increasing interest in the exploitation of molecular addresses for the targeting of tumor imaging or therapeutic agents. A recent study demonstrated anticancer activity in human xenografts of doxorubicin (DOX)-peptide conjugates targeted to the tumor vascular endothelium, among them DOX coupled to the cyclic pentapeptide CNGRC [Science 279 (1998) 377]. In order to learn more about the mechanism of action of this type of DOX-peptide conjugates, we have studied the interaction of DOX-CNGRC with primary human umbilical cord vein endothelial cells (HUVEC) and tumor cells under defined in vitro conditions. We used a DOX conjugate, in which the cyclic CNGRC peptide, for which an in vivo endothelial address has recently been identified as aminopeptidase N (APN)/CD13, has been coupled via a hydrolysable spacer to the C-14 anthracycline-side chain. First we determined that the t(1/2) of DOX-CNGRC conjugate in human blood was 442 min (at 37 degrees ) allowing sufficient time for endothelial targeting when administered i.v. When cultured cells were exposed for 30 min to DOX-CNGRC a more cytoplasmic localization of fluorescent drug was seen when compared to DOX exposure and intracellular DOX-CNGRC was identified after extraction from the cells. This revealed differences in the cellular uptake process of the conjugate compared to DOX. The antiproliferative effect of DOX-CNGRC was determined by 30 min exposure in medium with a high protein content in order to mimick the in vivo targeting situation. In this medium, the IC(50) was 1.1 microM for highly CD13 expressing HT-1080, 1.45 microM for CD13 negative SK-UT-1 sarcoma cells and 6.5 microM for CD13 positive HUVEC. The IC(50) of DOX for these cells were 1.0, 2.0 and 7.3 microM, respectively. Although DOX-CNGRC inhibited the peptidase activity of CD13 up to 50%, our data do not favor an important role for the enzyme inhibition in the cytotoxic effect of the conjugate. The antitumor activity was tested in nude mice bearing human ovarian cancer xenografts (OVCAR-3). A weekly i.v. administration (3mg/kg DOX-equivalent, 3x) showed a minor (40%) growth delay, which does not indicate efficacy better than that expected for free DOX. In conclusion, this study indicates that the antiproliferative and anti-angiogenic effects of DOX-CNGRC as reported before, are likely caused by the cytostatic effects of intracellularly released parent drug DOX, independent of CD13 expression/activity. More research is needed to identify the optimal specific chemical configuration of DOX-peptide conjugates for in vivo targeting and receptor-mediated cellular uptake.

Inhibition of tumor angiogenesis by non-steroidal anti-inflammatory drugs: emerging mechanisms and therapeutic perspectives

Chronic intake of non steroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced risk of developing gastrointestinal tumors, in particular colon cancer. Increasing evidence indicates that NSAID exert tumor-suppressive activity on pre-malignant lesions (polyps) in humans and on established experimental tumors in mice. Some of the tumor-suppressive effects of NSAIDs depend on the inhibition of cyclooxygenase-2 (COX-2), a key enzyme in the synthesis of prostaglandins and thromboxane, which is highly expressed in inflammation and cancer. Recent findings indicate that NSAIDs exert their anti-tumor effects by suppressing tumor angiogenesis. The availability of COX-2-specific NSAIDs opens the possibility of using this drug class as anti-angiogenic agents in combination with chemotheapy or radiotherapy for the treatment of human cancer. Here we will briefly review recent advances in the understanding of the mechanism by which NSAIDs suppress tumor angiogenesis and discuss their potential clinical application as anti-cancer agents.