Suramin: a novel growth factor antagonist with activity in hormone-refractory metastatic prostate cancer

Drug-Induced Peripheral Neuropathy: Diagnosis and Management

Peripheral neuropathy comes in all shapes and forms and is a disorder which is found in the peripheral nervous system. It can have an acute or chronic onset depending on the multitude of pathophysiologic mechanisms involving different parts of nerve fibers. A systematic approach is highly beneficial when it comes to cost-effective diagnosis. More than 30 causes of peripheral neuropathy exist ranging from systemic and auto-immune diseases, vitamin deficiencies, viral infections, diabetes, etc. One of the major causes of peripheral neuropathy is drug induced disease, which can be split into peripheral neuropathy caused by chemotherapy or by other medications. This review deals with the latest causes of drug induced peripheral neuropathy, the population involved, the findings on physical examination and various workups needed and how to manage each case.

Suramin Targets the Conserved Ligand-Binding Pocket of Human Raf1 Kinase Inhibitory Protein

Suramin was initially used to treat African sleeping sickness and has been clinically tested to treat human cancers and HIV infection in the recent years. However, the therapeutic index is low with numerous clinical side-effects, attributed to its diverse interactions with multiple biological macromolecules. Here, we report a novel binding target of suramin, human Raf1 kinase inhibitory protein (hRKIP), which is an important regulatory protein involved in the Ras/Raf1/MEK/ERK (MAPK) signal pathway. Biolayer interference technology showed that suramin had an intermediate affinity for binding hRKIP with a dissociation constant of 23.8 µM. Both nuclear magnetic resonance technology and molecular docking analysis revealed that suramin bound to the conserved ligand-binding pocket of hRKIP, and that residues K113, W173, and Y181 play crucial roles in hRKIP binding suramin. Furthermore, suramin treatment at 160 µM could profoundly increase the ERK phosphorylation level by around 3 times. Our results indicate that suramin binds to hRKIP and prevents hRKIP from binding with hRaf1, thus promoting the MAPK pathway. This work is beneficial to both mechanistically understanding the side-effects of suramin and efficiently improving the clinical applications of suramin.

Neurotoxicity of antineoplastic drugs: Mechanisms, susceptibility, and neuroprotective strategies

This review summarizes the adverse effects on the central and/or peripheral nervous systems that may occur in response to antineoplastic drugs. In particular, we describe the neurotoxic side effects of the most commonly used drugs, such as platinum compounds, doxorubicin, ifosfamide, 5-fluorouracil, vinca alkaloids, taxanes, methotrexate, bortezomib and thalidomide. Neurotoxicity may result from direct action of compounds on the nervous system or from metabolic alterations produced indirectly by these drugs, and either the central nervous system or the peripheral nervous system, or both, may be affected. The incidence and severity of neurotoxicity are principally related to the dose, to the duration of treatment, and to the dose intensity, though other factors, such as age, concurrent pathologies, and genetic predisposition may enhance the occurrence of side effects. To avoid or reduce the onset and severity of these neurotoxic effects, the use of neuroprotective compounds and/or strategies may be helpful, thereby enhancing the therapeutic effectiveness of antineoplastic drug.

Hormone Refractory Prostate Cancer (Hrpc): Present and Future Approaches of Therapy

The mainstay of therapy for patients with advanced prostate cancer still remains androgen deprivation, although response to this is invariably temporary. Most of the patients develop hormone-refractory disease resulting in progressive clinical deterioration and, ultimately, death. Until recently there has been no standard chemotherapeutic approach for hormone refractory prostate cancer (HRPC), the major benefits of chemotherapy being only palliative. The studies combining mitoxantrone plus a corticosteroid demonstrated that chemotherapy could be given to men with symptomatic HRPC with minimal toxicity and a significant palliation could be provided. Recently, results from 2 phase III randomized clinical trials demonstrating that a combination of docetaxel plus prednisone can improve survival in men with HRPC have propelled docetaxel-based therapy into the forefront of treatment options for these patients as the new standard of care. There is a promising activity of new drug combinations such as taxanes plus vinca alkaloids; bisphosphonates are assuming a prominent role in prostate therapy through their ability to prevent skeletal morbidity. Combinations of classic chemotherapeutic agents and biological drugs began to be tested in phase II-III trials and the first results appear interesting. This article focuses on combinations recently evaluated or under clinical development for the treatment of HRPC.

Is There a Standard Chemotherapeutic Regimen for Hormone-Refractory Prostate Cancer? Present and Future Approaches in the Management of the Disease

Prostate cancer that no longer responds to hormonal manipulation can be defined as hormone-refractory prostate cancer. Until recently, there has been no standard chemotherapeutic approach for hormone-refractory prostate cancer. The major benefits of chemotherapy in the treatment of the disease are palliative in nature, in terms of reduction of pain and use of analgesics and improvement of performance status, as followed in the most recent trials. Phase III studies are necessary to better evaluate the efficacy of the different regimens, because several old studies suffer for methodological deficits. There is a promising activity of new drug combinations, such as vinca alkaloids and taxanes. Phase I and II trial are testing combinations of classic chemotherapeutic agents and biologic drugs, and the first results appear interesting. In this article, recent advances in the treatment of hormone-refractory prostate cancer using chemotherapeutic regimens are critically reviewed.

Vinorelbine and Prednisone in older Cancer Patients with Hormone-Refractory Metastatic Prostate Cancer a Phase II Study

Aims and Background

Prostate cancer is a common disease in older men. Since it is hormone resistant, no treatment may improve survival. In patients with hormone-refractory prostate cancer, clinical benefit is an important treatment end point.

Study Design

This study evaluated the efficacy and toxicity of a vinorelbine and prednisone combination in hormone-refractory prostate cancer patients. Vinorelbine was administered at the dose of 25 mg/m2 on days 1 and 8, every three weeks; prednisone was administered orally at the dose of 12 mg/day. Thirty consecutive patients, 65 years or older, with progressive (PSA increase or increase in bidimensionally measurable lesion) metastatic prostate adenocarcinoma were enrolled. Four patients (13%) had a partial response and 14 (46%) stable disease. Time to progression for the entire group was 4.5 months (range, 2–13) and 7.5 months for the group of responders (range, 3–13). A PSA decrease >50% was registered in 36% of the patients. Pain reduction was recorded in 44.4% of the patients and stability in 14.8%.

Results

The treatment was well tolerated and grade 3 toxicity was found in 2 cases of anemia and 2 cases of leukopenia without fever.

Conclusions

The schedule is able to control the evolution of hormone-refractory prostate cancer and to give a clinical benefit. These results provide information for further clinical trials in a large series of elderly cancer patients.

Suramin-Induced Neurotoxicity: Preclinical Models and Neuroprotective Strategies

Suramin is a trypan blue analogon originally developed to treat protozoan infections, which was found to have diverse antitumor effects. One of the most severe side effects in clinical trials was the development of a peripheral sensory-motor polyneuropathy. In this study, we aimed to investigate suramin-induced neuropathy with a focus on calcium (Ca²⁺) homeostasis as a potential pathomechanism. Adult C57Bl/6 mice treated with a single injection of 250 mg/kg bodyweight suramin developed locomotor and sensory deficits, which were confirmed by electrophysiological measurements showing a predominantly sensory axonal-demyelinating polyneuropathy. In a next step, we used cultured dorsal root ganglia neurons (DRGN) as an in vitro cell model to further investigate underlying pathomechanisms. Cell viability of DRGN was significantly decreased after 24-hour suramin treatment with a calculated IC₅₀ of 283 µM. We detected a suramin-induced Ca²⁺ influx into DRGN from the extracellular space, which could be reduced with the voltage-gated calcium channel (VGCC) inhibitor nimodipine. Co-incubation of suramin and nimodipine partially improved cell viability of DRGN after suramin exposure. In summary, we describe suramin-induced neurotoxic effects on DRGN as well as potentially neuroprotective agents targeting intracellular Ca²⁺ dyshomeostasis.

Treatment of hormone-refractory prostate cancer

Objective. An increasing number of patients with prostate cancer develop hormone-refractory disease after standard treatment modalities. In these patients, early clinical trials with chemotherapy produced disappointing response rates. However, clinical trials that employ response criteria such as prostate-specific antigen (PSA) and clinical benefit response have produced encouraging responses. This article reviews current and future treatment options for the management of hormone-refractory prostate cancer.

Data Sources. A MEDLINE search for the years 1978 to 1998 was completed. The following terms were used in our search: prostate cancer, hormone-refractory, treatment, and chemotherapy. Relevant articles referenced in the literature obtained in our MEDLINE search were reviewed.

Study Selection. Randomized and nonrandomized clinical trials were used in our review. Clinical trials using prostate-specific antigen or a palliation of symptoms as primary criteria for response were given priority.

Data Synthesis. Several genetic alterations, including the overexpression of bcl-2 or mutations in p53, may lead to the development of hormone-refractory prostate cancer. Agents such as estramustine and taxanes, which affect microtubule function and potentially modulate bcl-2, appear to be particularly active in the treatment of hormone-refractory prostate cancer. In addition, mitoxantrone as well as other agents has been shown to be beneficial in improving the quality of life in patients with hormone-refractory prostate cancer.

Conclusion. Hormone-refractory prostate cancer is not a chemotherapy-resistant disease as once believed; significant progress in the treatment of hormone-refractory prostate cancer has been made with new combinations of chemotherapy agents. Promising new treatments are currently under evaluation to assess their potential benefit over the standard treatment modalities that are currently available.

The beneficial effect of suramin on monocrotaline-induced pulmonary hypertension in rats

BACKGROUND

Pulmonary hypertension (PH) is a progressive disorder characterized by an increase in pulmonary artery pressure and structural changes in the pulmonary vasculature. Several observations indicate that growth factors play a key role in PH by modulating pulmonary artery smooth muscle cell (PA-SMC) function. In rats, established monocrotaline-induced PH (MCT-PH) can be reversed by blocking platelet-derived growth factor receptors (PDGF-R), epidermal growth factor receptors (EGF-R), or fibroblast growth factor receptors (FGF-R). All these receptors belong to the receptor tyrosine kinase (RTK) family.

METHODS AND RESULTS

We evaluated whether RTK blockade by the nonspecific growth factor inhibitor, suramin, reversed advanced MCT-PH in rats via its effects on growth-factor signaling pathways. We found that suramin inhibited RTK and ERK1/2 phosphorylation in cultured human PA-SMCs. Suramin inhibited PA-SMC proliferation induced by serum, PDGF, FGF2, or EGF in vitro and ex vivo. Treatment with suramin from day 1 to day 21 after monocrotaline injection attenuated PH development, as shown by lower values for pulmonary artery pressure, right ventricular hypertrophy, and distal vessel muscularization on day 21 compared to control rats. Treatment with suramin from day 21 to day 42 after monocrotaline injection reversed established PH, thereby normalizing the pulmonary artery pressure values and vessel structure. Suramin treatment suppressed PA-SMC proliferation and attenuated both the inflammatory response and the deposition of collagen.

CONCLUSIONS

RTK blockade by suramin can prevent MCT-PH and reverse established MCT-PH in rats. This study suggests that an anti-RTK strategy that targets multiple RTKs could be useful in the treatment of pulmonary hypertension.

The FGF family: biology, pathophysiology and therapy

The family of fibroblast growth factors (FGFs) regulates a plethora of developmental processes, including brain patterning, branching morphogenesis and limb development. Several mitogenic, cytoprotective and angiogenic therapeutic applications of FGFs are already being explored, and the recent discovery of the crucial roles of the endocrine-acting FGF19 subfamily in bile acid, glucose and phosphate homeostasis has sparked renewed interest in the pharmacological potential of this family. This Review discusses traditional applications of recombinant FGFs and small-molecule FGF receptor kinase inhibitors in the treatment of cancer and cardiovascular disease and their emerging potential in the treatment of metabolic syndrome and hypophosphataemic diseases.

Current status and perspective of antiangiogenic therapy for cancer: urinary cancer

Angiogenesis is considered a prerequisite for solid tumor growth. Antiangiogenic therapy reduces tumor size and extends host survival in a number of preclinical animal models. However, in humans antiangiogenic therapy is a poor promoter of tumor regression and has shown minimal effect on patient survival. In urinary cancers, such as renal cell cancer, prostate cancer, and bladder cancer, advanced refractory disease is a good candidate for antiangiogenic therapy because of its resistance to ordinary chemotherapy, radiotherapy, and hormonal therapy. Unique characteristics of molecular mechanisms underlie the induction of angiogenesis in urinary cancers. In this review, we summarize these unique mechanisms and review the results of clinical trials of antiangiogenic therapy for these cancers, discussing prospects and problems relating to antiangiogenic therapy.

Antiangiogenic and antitumoral properties of a polysaccharide isolated from the seaweed Sargassum stenophyllum

The potential antiangiogenic and antitumoral properties of SargA, a polysaccharide extracted from the brown marine alga Sargassum stenophyllum, were studied in assays carried out in chick embryos and mice. Gelfoam plugs containing SargA (2-1500 microg/plug) implanted in vivo into fertilized 6-day-old chicken eggs induced dose-related antiangiogenic activity in the chorioallantoic membrane (CAM). By day 8, the highest dose of SargA alone decreased the vessel number in the CAM by 64%, but coadministered with hydrocortisone (156 microg/plug, which alone caused 30% inhibition) failed to potentiate its antiangiogenic effect. Combined with basic fibroblast growth factor (50 ng/plug), SargA (1500 microg/plug) abolished angiogenesis stimulated by this factor in both chick embryo CAM and in subcutaneous (s.c.) Gelfoam plugs implanted in the dorsal skin of Swiss mice (measured as plug hemoglobin content). Repeated s.c. injections of SargA (1.5 or 150 microg per animal per day for 3 days) close to B16F10 melanoma cell tumors in the dorsal skin of mice markedly decreased tumor growth in a dose-related fashion (by 40% and 80% at 2 weeks after the first injection, respectively), without evident signs of toxicity. SargA caused graded inhibitions of migration and viability of cultured B16F10 cells and also displayed antithrombotic activity in human plasma (5 mg/ml increased thrombin time 2.5-fold relative to saline). Thus, SargA exhibits pronounced antiangiogenic as well as antitumoral properties. Although the latter action of SargA might be related to the inhibition of angiogenesis, the polysaccharide also exerts cytotoxic effects on tumor cells. Because of its chemical characteristics and polyanionic constituents, we postulate that the polysaccharide SargA might modulate the activity of heparin-binding angiogenic growth factors.

Heparan sulfate proteoglycans and heparanase--partners in osteolytic tumor growth and metastasis

This review summarizes a series of studies demonstrating that heparan sulfate proteoglycans act to promote the growth and metastasis of myeloma and breast tumors, two tumors that home to, and grow within, bone. Much of the growth-promoting effect of proteoglycans in these tumors may reside in the shed form of syndecan-1 that acts to favorably condition the tumor microenvironment. Moreover, the interplay between heparan sulfate and the extracellular enzyme heparanase-1 also has important regulatory implications. Recent studies indicate that the activity of heparanase, which likely releases heparin sulfate-bound growth factors and generates highly active heparan sulfate fragments, also promotes growth and metastasis of myeloma and breast tumors. Understanding the role of heparan sulfate and heparanase in the regulation of tumor behavior may lead to new therapeutic approaches for treating cancer.

Clinical trials in metastatic prostate cancer – Has there been real progress in the past decade?

Hormone refractory prostate cancer remains a challenge. While only palliative treatment strategies were available for the past several decades, many promising agents have been investigated over the past decade. Of those the taxanes appeared with significant anti-tumor activity and recently, two large randomized controlled trials demonstrated for the first time, a survival and palliative benefit with docetaxel based chemotherapy. In the current era, recurrent disease after local treatment for localized disease is diagnosed long before evidence of systemic disease. With earlier institution of hormonal treatments, patients are becoming "hormone refractory" earlier in the course of their disease with considerable long life expectancy. Hence, there is a greater need than ever for more treatment options for this expanding group of patients. A number of new systemic therapies have recently emerged, based on a deeper understanding of prostate cancer biology. Novel chemotherapeutics such as the epothilones, molecularly targeted therapies against angiogenesis, the proteosome and endothelin receptor antagonists, as well as biological agents such as anti-sense oligonucleotides are being tested as part of the armamentarium. Key to progress in the therapy of this fatal disease is the commitment and timely enrolment of prostate cancer patients in clinical trials.

Combination chemotherapy with docetaxel, estramustine and suramin for hormone refractory prostate cancer

PURPOSE

To investigate more effective chemotherapy against hormone refractory prostate cancer (HRPC) with the combination of estramustine (EM), docetaxel, and suramin.

PATIENTS AND METHODS

A total of 42 patients with symptomatic, progressive HRPC were included in this study. We evaluated the activity of the following schedule: EM 10 mg/kg orally daily on Days 1 to 21 every 28 days, docetaxel 70 mg/m(2) IV on Day 2 every 28 days and a total doses of 2150 mg of suramin in every cycle. Treatment was continued until disease progression or excessive toxicity.

RESULTS

Median follow-up was 23.4 months. A median of 8.8 consecutive cycles was administered per patient. In the 25 patients with lymphadenopathy, there were three (12%) complete and 18 (72%) partial responses for a measurable disease response rate of 84%. Levels of prostatic specific antigen (PSA) decreased by greater than 50% in 100% of patients and by greater than 90% in 76.2%. The median time to progression was 57 weeks and median overall survival was 132 weeks. A decline in PSA of > or =50% lasting > or =30 days was significantly associated with a prolonged median time to progression and median overall survival. Tumor volume reduction and/or antitumor treatment effects were observed in 88% of patients. A significant decrease in mean pain score from 7.8 (range, 6-10) to 2.2 (range, 0-4) (P < 0.001) was achieved in 78%. Of patients with bone metastasis, 30.5% demonstrated a partial response. The mean Eastern Cooperative Oncology Group (ECOG) performance score improved from 2.8 to 1.5 at the end of treatment period. There was no therapy-related death. The predominant toxicities were Grade 3 or 4 leukopenia in 33.3%, anemia in 21%, thrombocytopenia in 21.4%, cardiac ischemia in 4.7%, and rash in 4.7%.

CONCLUSION

The combination of docetaxel, EM, and suramin is a highly effective regimen for HRPC. Although hematologic and gastrointestinal toxicities were modest, these were easily managed medically.

Angiogenesis-targeted therapies in prostate cancer

Most patients with metastatic prostate cancer will respond initially to ablation of gonadal androgen production. Eventually, all patients will develop progressive disease despite continued androgen suppression, a condition called androgen-independent or hormone-refractory prostate cancer. Hormone-refractory prostate cancer is characterized by virulent biologic and clinical behavior. Recently, docetaxel-based chemotherapy has been shown to improve survival and quality of life in this disease when compared with mitoxantrone-based therapy. However, results remain suboptimal. Recently, there have been remarkable advances in the delineation of the mechanisms of cancer growth, metastasis, and the intricate interactions between tumor cells and the surrounding normal tissues. The accumulated evidence has confirmed the importance of angiogenesis in these processes and validated the theory that inhibition of neovascularization is a promising therapeutic anticancer strategy. Currently, dozens of compounds that interfere with different steps of the angiogenic cascade are in preclinical and clinical development. Some of these agents have exhibited promising antitumor activity in hormone-refractory prostate cancer. This review summarizes the molecular mechanisms implicating angiogenesis in the development and progression of advanced-stage prostate cancer, as well as the drug development efforts that are targeting this process.

Management of patients with hormone refractory prostate cancer

Prostate cancer is the second most common cancer in men in the UK, and the incidence of prostate cancer has increased dramatically over the past two decades. Although most men are diagnosed at early stage, more than 50% develop locally advanced or metastatic disease. Androgen ablation with luteinising hormone-releasing hormone (LHRH) agonists alone, or in combination with anti-androgens, is the standard treatment for men with metastatic prostate cancer. Unfortunately, almost all men develop progressive disease after a variable time period, despite the maximal androgen blockade. The management of hormone refractory prostate cancer (HRPC) is challenging, as there is no uniformly accepted strategy. Various treatment options, including second-line hormone therapy, are discussed. Chemotherapy is being increasingly used and, importantly, docetaxel and estramustine may play an important role in the near future. The role of radiotherapy, strontium-89, bisphosphonates, novel agents and future therapies are also outlined.

Suramin sensitizing cells to ionizing radiation by inactivating DNA-dependent protein kinase

Here we report that suramin sensitizes LM217, MDA-MB-468, T98G and A431 cells to ionizing radiation. Suramin sensitized cells to X radiation in a dose-dependent fashion, and longer exposure to suramin before X irradiation resulted in more efficient sensitization. The dose-modifying factors calculated from the survival curves were 1.18 in LM217 cells and 1.37 in MDA-MB-468 cells. Suramin did not sensitize Scid cells that had no DNA-dependent protein kinase activity. Suramin inhibited DNA-dependent protein kinase activity in vitro and in vivo. The concentration of suramin resulting in 50% inhibition in vitro was 1.7 microM in LM217 cells and 2.4 microM in MDA-MB-468 cells. Exposure of LM217 and MDA-MB-468 cells to suramin did not affect the level of Ku70 (G22P1) or Ku80 (XRCC5), but it increased the level of DNA-PKcs(PRKDC). Suramin did not sensitize LM217 or MDA-MB-468 cells to UV radiation. Suramin's effects were not caused by accumulation of cells in a specific phase of the cell cycle. These results suggest that suramin sensitizes cells to ionizing radiation by inhibiting DNA-dependent protein kinase activity.

An autocrine mechanism for constitutive Wnt pathway activation in human cancer cells

Autocrine Wnt signaling in the mouse mammary tumor virus model was the first identified mechanism of canonical pathway activation in cancer. In search of this transformation mechanism in human cancer cells, we identified breast and ovarian tumor lines with upregulation of the uncomplexed transcriptionally active form of beta-catenin without mutations afflicting downstream components. Extracellular Wnt antagonists FRP1 and DKK1 caused a dramatic downregulation of beta-catenin levels in these tumor cells associated with alteration of biological properties and increased expression of epithelial differentiation markers. Colorectal carcinoma cells with knockout of the mutant beta-catenin allele retained upregulated beta-catenin levels, which also could be inhibited by these Wnt antagonists. Together, these findings establish the involvement of autocrine Wnt signaling in human cancer cells.

Phase II study of CI-958 in patients with hormone refractory prostate carcinoma

A phase II trial of CI-958 (NSC #635371), a new benzothiopyranoindazole was performed in patients with hormone refractory prostate carcinoma using prostate specific antigen (PSA) levels for response assessment. Twenty-two patients were entered on this study and twenty one were eligible. Toxicity consisted mainly of granulocytopenia (71% grade 3 or 4), but there were no significant infections. Two patients were removed from study due to asymptomatic decreases in cardiac ejection fraction. Of 21 evaluable patients, there were four responders (19%, CI 0-35%).

Suramin and radiotherapy in newly diagnosed glioblastoma: phase 2 NABTT CNS Consortium study

Suramin is a polysulfonated naphthylurea that inhibits the function of growth factors and growth factor receptors implicated in glioma progression, angiogenesis, and radioresistance. The safety and benefits of combining inhibitors of angiogenesis and growth factors with cytotoxic therapies in patients with neoplasms of the central nervous system remain unclear. The objectives of this phase 2 study were to determine the safety of administering suramin with standard cranial radiotherapy (RT) and to estimate survival using this approach in patients with newly diagnosed glioblastoma multiforme (GBM). Fifty-five patients with newly diagnosed GBM (Karnofsky performance status >or= 60) were enrolled in this multicenter phase 2 study. Patients received suramin by a conventional intermittent fixed-dosing regimen for 1 week prior to and during cranial RT (60 Gy in 30 fractions, weeks 2-7). Patients with stable or responsive disease at week 18 received an additional 4 weeks of suramin (weeks 19-22). The median survival for suramin-treated patients was 11.6 months, with 1-year and 18-month survival rates of 49% (95% confidence interval [CI], 36%-62%) and 18% (95% CI, 8%-28%), respectively. Overall, 55% of the patients (30/55) had greater than grade 2 toxicity at least possibly related to suramin therapy. Two patients died of possibly related neurologic events (i.e., stroke, elevated intracranial pressure). Otherwise, toxicities were generally transient and self-limited. Administration of suramin using an intermittent fixed-dosing regimen during cranial RT was generally well tolerated. However, overall survival is not significantly improved when compared with the New Approaches to Brain Tumor Therapy GBM database or other comparable patient populations.

A Phase II trial of suramin monthly × 3 for hormone-refractory prostate carcinoma

BACKGROUND

The goal of the current study was to determine the prostate-specific antigen (PSA) and objective response rates and the pharmacokinetics associated with a monthly x 3 one-hour infusion of suramin in 58 patients with hormone-refractory prostate carcinoma.

METHODS

A PSA response was defined as a > 50% reduction in the PSA level from baseline for at least 3 consecutive evaluations over a minimum of 6 weeks. The suramin dose was 2400 mg/m(2) taken intravenously on Day 1, 1620 mg/m(2) on Day 29, and 1292 mg/m(2) on Day 57. All patients received 0.5 mg dexamethasone twice daily.

RESULTS

Among 56 evaluable patients (median entry PSA level, 229.5 ng/mL), there were 21 PSA responders (37.5%). Among 27 patients with measurable disease, there were 5 responders (4 partial and 1 complete). The median overall survival time was 15.3 months. Grade III fatigue (14.1%) was the predominant toxicity observed. Suramin plasma levels remained high even 3 months after treatment was discontinued. Among the 12 evaluable patients who previously had received chemotherapy, the PSA response rate was 42%; one response was observed among 4 patients with measurable disease, and the median survival was 12 months.

CONCLUSIONS

Monthly bolus suramin was well tolerated, reduced PSA levels, and induced objective responses, even in patients who previously had received chemotherapy.

Inhibition of heparanase activity and heparanase-induced angiogenesis by suramin analogues

Heparanase, a heparan sulfate-specific endo-beta-D-glucuronidase, plays an important role in tumor cell metastasis through the degradation of extracellular matrix heparan sulfate proteoglycans (ECM HSPG). Heparanase activity correlates with the metastatic propensity of tumor cells. Suramin, a polysulfonated naphthylurea, is an inhibitor of heparanase with suramin analogues shown to possess antiangiogenic and antiproliferative properties. We investigated the effects of selected suramin analogues (NF 127, NF 145 and NF 171) on heparanase activity and heparanase-driven angiogenesis. Studies of the ability of cellular extracts and purified heparanase from human, highly invasive and brain-metastatic melanoma (70W) cells revealed that heparanase expressed by these cells was effectively inhibited by suramin analogues in a dose-dependent manner. These analogues possessed more potent heparanase inhibitory activities than suramin: The concentrations required for 50% heparanase inhibition (IC(50)) were 20-30 microM, or at least 2 times lower than that for suramin. One hundred percent inhibition was observed at concentrations of 100 microM and higher. Of relevance, these compounds significantly decreased (i) the invasive capacity of human 70W cells by chemoinvasion assays performed with filters coated with purified HSPG or Matrigel trade mark, and (ii) blood vessel formation by in vivo angiogenic assays, thus linking their antiangiogenic properties with impedance of heparanase-induced angiogenesis. Specifically, inhibition of invasion by NF 127, NF 145 and NF 171 was found at 10 microM concentrations of compounds with a significant decrease of invasive values at concentrations as low as 1.5 microM. In addition, NF 127, NF 145 and NF 171 promoted nearly complete inhibition of heparanase-induced angiogenesis at values ranging from 236 microM (for NF 145) to 362 microM (for NF 127). These results further emphasize the importance of heparanase in invasive and angiogenic mechanisms and the potential clinical application of heparanase inhibitors such as suramin analogues in cancers and angiogenesis-dependent diseases.

Fibroblast growth factors and their receptors in urological cancers: basic research and clinical implications

Because therapeutical options for advanced urological cancers are limited, the understanding of key elements responsible for invasion and metastasis is very important. It has been hypothesized that progression to malignant growth is associated with a dysregulation of growth factors and/or their receptors. In the last few years, signaling pathways of the fibroblast growth factor (FGF) family have been subject to intense investigation. Fibroblast growth factors constitute one of the largest families of growth and differentiation factors for cells of mesodermal and neuroectodermal origin. The family comprises two prototypic members, acidic FGF (aFGF) and the basic FGF (bFGF), as well as 21 additionally related polypeptide growth factors that have been identified to date. FGFs are involved in many biological processes during embryonic development, wound healing, hematopoesis, and angiogenesis. In prostate, bladder, and renal cancers, FGFs regulate the induction of metalloproteinases (MMP) that degrade extracellular matrix proteins, thus facilitating tumor metastasis. Probably due to their potent angiogenic properties, aFGF and bFGF have received the most attention. However, there is increasing evidence that other FGFs also play crucial roles in tumors of the prostate, bladder, kidney, and testis. This review will discuss the different elements involved in FGF signaling and summarize the present knowledge of their biological and clinical relevance in urological cancers.

Suramin modulates wound healing of rabbit conjunctiva after trabeculectomy: comparison with mitomycin C

PURPOSE

To investigate and compare the effects of suramin and mitomycin C on conjunctival wound healing after trabeculectomy in a rabbit model.

MATERIALS AND METHODS

Thirty New Zealand White rabbits were divided into three groups, and trabeculectomy was performed on the left eyes under general anesthesia. During the surgery, suramin (250 mg/ml) and mitomycin C (0.4 mg/ml) were applied to the scleral flap site for 2 minutes in groups 1 and 2, respectively. The control animals (group 3) received no pharmacological treatment during trabeculectomy. Intraocular pressure (IOP) measurements were recorded before surgery and every 3 days after the operation, starting from postoperative day 1. Three animals from each group were sacrificed on days 15, 20, and 25, yielding a total of 27 eyes for histopathological study. Each specimen was histochemically and immunohistochemically (CD3, CD20, CD68, and collagen III) evaluated, and graded.

RESULTS

Bleb failure time was significantly longer in both the suramin (15.0 +/- 4.7 days) and mitomycin C (16.7 +/- 5.1 days) groups than in the controls (10.3 +/- 4.2 days) (p < 0.05). Starting from postoperative day 9, the IOP in the suramin and mitomycin C groups was significantly lower than that in the control group (p < 0.05). This difference continued to be significant until day 18 for the suramin group, and until day 24 in the mitomycin C group. Histopathological evaluation showed lower degrees of cellularity, fibrosis, collagen III deposition, and CD3 density in the suramin- and mitomycin C-treated eyes compared to control eyes at all time points (p < 0.05). There was also no significant difference between the suramin and mitomycin C groups concerning these histopathological findings and CD3 density (p > 0.05). Although there were trends towards reduced mean elastic fiber deposition and lower CD20 and CD68 density in both groups of treated eyes, the differences between the treated and control groups were not significant (p > 0.05).

CONCLUSIONS

The results of the current study suggest that suramin has beneficial effects on wound healing in glaucoma surgery, and effectively prolongs bleb survival in rabbits. Suramin may be a promising alternative to anti-metabolite therapy in glaucoma surgery.

A phase I study of intravesical suramin for the treatment of superficial transitional cell carcinoma of the bladder

PURPOSE

Suramin is a polysulfonated naphthylurea that inhibits proliferation and DNA synthesis of transitional cell carcinoma cell lines. Its large molecular size and negative charge inhibit bladder absorption, making suramin an excellent candidate for intravesical chemotherapy. Intravesical suramin was evaluated in a phase I study to define dose limiting toxicity and systemic absorption, determine a starting dose and regimen for phase II studies and provide a preliminary assessment of in vivo antitumor activity.

MATERIALS AND METHODS

Intravesical suramin treatment was administered in 9 patients with histologically identified transitional cell carcinoma (Tcis, Ta or T1) in whom at least 1 course of standard intravesical chemotherapy (bacillus Calmette-Guerin, thiotepa or mitomycin C) had failed. Suramin was administered once weekly for 6 weeks. Patients were treated in groups of 3 using a 60 cc volume and intrapatient dose escalation schedule. Suramin doses of 0.3 to 614.4 mg./ml. were administered intravesically. The last group was treated with the same weekly dose for 6 weeks.

RESULTS

The 9 patients underwent 54 treatments with suramin. Plasma suramin concentration after treatment was 1.9 to 38.0 microg./ml. and was not related to treatment dose. The dose escalation phase was limited by the solubility of suramin in solution. Complications included self-limited bladder spasms (less than 24 hours) in 4 of 54 treatments (7%) and new or worsening vesicoureteral reflux in 3 ureters (17%). Another patient who was treated after the Foley balloon was inflated in the urethra experienced bladder spasms, skin flushing and fever (39C). Mean bladder capacity before and after treatment was 600 and 540 ml., respectively. At followup 7 patients had stage Ta tumors and 2 had carcinoma in situ.

CONCLUSIONS

An intravesical suramin dose of 153 mg./ml was defined as a safe treatment parameter with acceptable plasma concentrations and minimal side effects. Phase II studies are needed to assess the antitumor activity of suramin in patients with transitional cell carcinoma of the bladder.

Randomized study of three different doses of suramin administered with a fixed dosing schedule in patients with advanced prostate cancer: results of intergroup 0159, cancer and leukemia group B 9480

PURPOSE

To test the hypothesis that the efficacy and toxicity of suramin in the treatment of patients with hormone-refractory prostate cancer was dose dependent.

PATIENTS AND METHODS

Patients were randomized with equal probability to receive low-, intermediate-, or high-dose suramin (total doses 3.192, 5.320, and 7.661 g/m(2), respectively). Overall survival, time to progression, and response rate (prostate-specific antigen [PSA] and objective) for each treatment arm were compared. Relationships between plasma suramin concentrations and response, toxicity, and survival were also evaluated.

RESULTS

Three hundred ninety patients were randomized. For the low-, intermediate-, and high-dose arms, the median survival time was 16, 14, and 13 months, respectively (P =.49). The objective response rate was 9%, 7%, and 15%, respectively (P =.10). PSA response rates were 24%, 28%, and 34%, respectively (P =.082). Landmark analyses of a 50% decline in PSA at 20 weeks showed a significant correlation with survival. There was a dose-response relationship between dose and toxicity. After adjusting for treatment arm, the measured suramin concentration was not associated with clinical response, PSA response, survival, or toxicity.

CONCLUSION

Although high-dose suramin was associated with higher objective and PSA response rates, these were not statistically significant. Overall, no dose-response relationship was observed for survival or progression-free survival, but toxicity was increased with the higher dose. Patients treated with the low-dose level experienced modest toxicity, making it the preferred arm on this study. The lack of a dose-response relationship and the toxicity profile observed raise questions regarding the utility of suramin, particularly high-dose suramin, as administered on this schedule.

Nature of Interaction between basic fibroblast growth factor and the antiangiogenic drug 7,7-(carbonyl-bis[imino-N-methyl-4,2-pyrrolecarbonylimino[N-methyl-4,2-pyrrole]-carbonylimino])-bis-(1,3-naphtalene disulfonate). II. Removal of polar interactions affects protein folding

Fibroblast growth factor-2 (basic FGF), a potent inducer of angiogenesis, and the naphthalene sulfonic distamycin A derivative, 7,7-(carbonyl-bis[imino-N-methyl-4,2-pyrrolecarbonylimino[N-methyl-4,2-pyrrole]-carbonylimino])-bis-(1,3-naphtalene disulfonate) (PNU145156E), which exhibits in vivo antiangiogenic activity, form a tight reversible (1:1) complex. PNU145156E binds to the heparin and the selenate-binding sites on bFGF. The cis bFGF-heparin (2:1) complex, essential for the activation of the angiogenic process, is thus prevented. The nature of the forces involved in bFGF:PNU145156E complex, using the wild-type and the K128Q, K138Q, K134Q, and K128Q-K138Q point mutated bFGFs was sought. Based on thermodynamic analysis of the complexation constants, protein temperature stability profiles by ultraviolet absorption, circular dichroism measurements, fluorescence Förster energy-transfer, and anisotropy studies, in harmony with the published x-ray crystallographic structure, the following molecular interactions are proposed: reduced coulombic interactions, hence loosening of the complex by the removal of charged polar groups from the bFGF-heparin binding cleft resulted in decreased binding constants and in a change in the binding mode from polar to nonpolar. Concomitantly, upon mutation, the protein was rendered more compact, less flexible, and less aqueously exposed compared with the wild type. These were further pronounced with the double mutant: weaker dominantly nonpolar protein-drug interactions were accompanied by conspicuous folding. With heparin, however, wild-type bFGF forms a tighter complex with a more compact structure.

Suramin's development: what did we learn?

Suramin, a polysulphonated napthylurea, has been extensively evaluated over the past 10 years as an anticancer agent, with the most interest in the treatment of prostate cancer. Early clinical results were promising with response rates of up to 70% being reported. However, a recent double-blind study showed only modest palliative effect in patients with androgen independent prostate cancer. In retrospect, it appears those initial reports failed to control for confounding variables such as antiandrogen withdrawal and hydrocortisone. Suramin causes numerous reversible toxicities (lethargy, rash, fatigue, anemia, hyperglycemia, hypocalcemia, coagulopathies, neutropenia, renal and hepatic complications). Neurotoxicity has been the most significant complication and appears to be related to the intensity of the dosing regimen. An optimal therapeutic dose has not been determined, but it is clear that adaptive controls add little benefit. Aside from moderate toxicities and the low therapeutic index in patients with prostate cancer, suramin's development has taught us some valuable lessons (i.e., anti-androgen withdrawal was noted during suramin's development, the use of PSA as an indicator of tumor burden was initiated during the evaluation of suramin). These lessons can be applied to all clinical trials in hormone refractory prostate cancer. Suramin has significantly enhanced the evolution of our knowledge in several areas of prostate cancer biology and treatment.

The treatment challenge of hormone-refractory prostate cancer

BACKGROUND

Both the demographics and treatment of hormone-refractory prostate cancer (HRPC) are changing. Patients are younger and healthier, with fewer comorbidities. The "no treatment until symptoms" approach is disappearing. Chemotherapy is increasingly being utilized.

METHODS

The authors review the steps involved in hormone management before chemotherapy is considered. The roles for chemotherapy in current clinical trials are examined.

RESULTS

Effective hormonal management of the prostate cancer patient incorporates an understanding of the stages of hormone sensitivity and prescribing additional interventions beyond simple castration. Once hormone refractoriness is established, the combination of mitoxantrone and prednisone has become a standard chemotherapeutic approach. New agents such as docetaxel are being tested in phase III trials against mitoxantrone plus prednisone.

CONCLUSIONS

HRPC is now regarded as a chemotherapy-sensitive tumor. The goals of chemotherapy in HRPC are to decrease PSA level and improve quality of life. New agents and combinations are needed to improve survival.

Fixed higher dose schedule of suramin plus hydrocortisone in patients with hormone refractory prostate carcinoma a multicenter Phase II study

BACKGROUND

Using a fixed higher-dose schedule, the efficacy and toxicity of suramin plus hydrocortisone were assessed in patients with metastatic hormone-refractory prostate carcinoma (HRPC).

METHODS

Fifty consecutive patients with HRPC (including those in whom hormonotherapy was withdrawn) and an Eastern Cooperative Oncology Group performance status of 0-2 were recruited. Treatment was comprised of a bolus intravenous infusion of 200 mg of suramin followed by suramin (500 mg/m(2) intravenously [i.v.] over 24 hours) given daily over 5 days as a loading course, followed by suramin (350 mg/m(2) i.v. over 2 hours) administered weekly for 12 weeks. This 12-week course was repeated at 6-month intervals. All patients received concomitant hydrocortisone.

RESULTS

Five hundred fifty weekly doses of therapy were delivered over the course of the entire study. A partial response, based on a > 50% decrease in the prostate specific antigen (PSA) level, was achieved in 27 patients (54%; 95% confidence interval [95% CI], 44.7-65.0%), 16 of whom (32%; 95%CI, 23.9-43.2%) had a > 75% decrease in their PSA levels. The measurable disease objective response rate was 18% (95% CI, 2.3-51.8%). Of the 37 patients with bone pain requiring analgesia, 27 patients (73%; 95% CI, 55.9-86.2%) reduced their medication consumption to a lower level on the World Health Organization analgesic ladder. The median duration of response was 15.5 weeks (range, 6-70 weeks), the median time to disease progression was 13 weeks, and the median overall survival time was 11 months. Treatment generally was well tolerated. Fatigue and severe lymphopenia were the most commonly reported significant toxicities. In addition, there was 1 septic toxic death reported, and 10% of the patients were found to have NCI Grade 3-4 neurotoxicity.

CONCLUSIONS

The results of the current study demonstrated that the fixed-dose suramin regimen administered herein showed high, although short-lived, activity and a good tolerance profile in HRPC patients.

The treatment of prostate cancer: an overview of current options

PURPOSE

The purpose of this report is to discuss the current treatment options available to the patient with prostate cancer in all stages of the disease.

OVERVIEW

With the exception of skin cancer, prostate cancer is the most common cancer in men in the United States. Most patients in the current era will present with organ-confined disease, amenable to curative treatment. Treatment for organ-confined disease includes watchful waiting, radical prostatectomy, radiation therapy, and cryosurgery in selective cases. Hormone therapy is the cornerstone of treatment of patients with advanced prostate cancer. There is no curative treatment for hormone-refractory prostate cancer.

CLINICAL IMPLICATIONS

The availability of several therapeutic options for localized prostate cancer warrants careful consideration when planning treatment with curative intent. Patients need to be active participants in decision making, and they must be aware of the benefits and possible complications of the different types of treatment. Patients with advanced prostate cancer need to be aware that hormone treatment will provide temporization and palliation in the majority of cases. Hormone-resistant prostate cancer is refractory to most forms of conventional and experimental therapy.

Toxicity, efficacy, and pharmacology of suramin in adults with recurrent high-grade gliomas

PURPOSE

To determine the toxicity, efficacy, and pharmacology of suramin in patients with recurrent or progressive recurrent high-grade gliomas.

PATIENTS AND METHODS

Fifty adults were to receive suramin. However, if no responses were seen in the first ten patients, the study was to be terminated. A total of 12 patients were enrolled onto this trial. Ten patients had glioblastoma multiforme, and 11 had received prior nitrosoureas.

RESULTS

Drug-related toxicities were modest and reversible. Three patients developed grade 3 to 4 neutropenia, constipation, diarrhea, or nausea. No CNS bleeding was observed. Median time to progression was 55 days (range, 17 to 242 days) and median survival was 191 days (range, 42 to 811 days). No partial or complete responses were seen at 12 weeks. However, the clinical outcome of three patients suggests that evidence of suramin activity may be delayed. One patient who "progressed" after 12 weeks of suramin had a subsequent marked reduction in tumor size and has maintained an excellent partial response for over 2 years without other therapy. Two others had disease stabilization and lived for 16 and 27 months. Pharmacokinetics from 11 patients revealed that all reached target suramin concentrations.

CONCLUSION

This study demonstrates that suramin is well tolerated by patients with recurrent high-grade gliomas and may have efficacy in this disease. Its pharmacology seems unaffected by anticonvulsants. As a result of this data, suramin and radiation are now being administered concurrently to patients with newly diagnosed glioblastoma multiforme, with survival as the primary outcome.

General aspects of anti-angiogenesis and cancer therapy

Angiogenesis is the outgrowth of new vessels from pre-existing ones. Tumour growth and metastasis is dependent on angiogenesis and many stimulatory and inhibitory factors have been described which play an active role in this process. Inhibition of tumour neovasculature may be one strategy to inhibit tumour growth. Naturally occurring inhibitors of angiogenesis have been discovered and synthetic agents have been designed. Many of these inhibitors are currently being evaluated in clinical trials for the treatment of cancer. This review discusses the mechanism of action of these anti-angiogenics as well as a description of the clinical trials in which they are being evaluated.

Examining new models for the study of autocrine and paracrine mechanisms of angiogenesis through FGF2-transfected endothelial and tumour cells

Angiogenesis is the process of generating new capillary blood vessels. Uncontrolled endothelial cell proliferation is observed in tumour neovascularization. Several growth factors and cytokines have been shown to stimulate endothelial cell proliferation in vitro and in vivo and among them FGF2 was one of the first to be characterised. FGF2 is a Mr 18,000 heparin-binding cationic polypeptide that induces proliferation, migration, and protease production in endothelial cells in culture and neovascularization in vivo. FGF2 interacts with endothelial cells through two distinct classes of receptors, the high affinity tyrosine-kinase receptors (FGFRs) and low affinity heparan sulfate proteoglycans (HSPGs) present on the cell surface and in the extracellular matrix. Besides experimental evidence for paracrine mode of action for FGF2, some observations raise the hypothesis that FGF2 may also play an autocrine role in endothelial cells. FGF2 may therefore represent a target for anti-angiogenic therapies. In order to assess the angiostatic potential of different classes of compounds, novel experimental models have been developed based on the autocrine and/or the paracrine capacity of FGF2.

Prostate Cancer Old Problems and New Approaches. Part III. Prevention and Treatment

In Part Three of this review, we begin with an analysis of prevention strategies for prostate cancer followed by a discussion of the clinical use of molecular techniques for the evaluation and treatment of patients with clinically localized prostate cancer. New developments in neutron and photon therapy of prostate cancer are addressed as well as the use of systemic radiotherapy for the treatment of bone metastases. Finally, we conclude with the role of hormonal therapy in the treatment of prostate cancer and the current status of development of chemo therapeutic regimens for the treatment of prostate cancer.

Suramin analogs inhibit human angiogenesis in vitro

BACKGROUND

Suramin is a polysulfonated naphthylurea that inhibits tumor cell proliferation and angiogenesis, but the widespread use of this drug has been limited by significant neurologic toxicity. A series of suramin analogs that may exhibit less toxicity in vivo have been synthesized. We hypothesized that these novel analogs would have antiangiogenic properties equal to or greater than those of suramin when evaluated in an in vitro human placental vein angiogenesis model.

METHODS

Human placental veins (n = 72 per group) were cultured in a 0.3% fibrin clot for a period of 14 days. Three suramin analogs (NF 145, NF 248, NF 293) and suramin were tested at 56 and 560 microM concentrations to determine their effect on the development of an angiogenic response. Experiments were repeated for each analog on veins from three different placentas. The percentage of wells that initiated an angiogenic response was calculated and compared with initiation in a control group (n = 141).

RESULTS

The three suramin analogs inhibited angiogenesis in a dose-dependent fashion, with all compounds exhibiting near-complete inhibition of angiogenesis at 560 microM. The effects of these analogs were equal to or greater than those of suramin.

CONCLUSION

Suramin analogs with structural alterations inhibit human angiogenesis at concentrations equivalent to those seen in vivo. These analogs may be more effective antiangiogenic agents than suramin and may have less potential for toxicity.

Suramin therapy for patients with symptomatic hormone-refractory prostate cancer: results of a randomized phase III trial comparing suramin plus hydrocortisone to placebo plus hydrocortisone

PURPOSE

Suramin is a novel agent that has demonstrated preliminary evidence of antitumor activity in hormone-refractory prostate cancer (HRPC). A prospective randomized clinical trial was designed to evaluate pain and opioid analgesic intake as surrogates for antitumor response in HRPC patients with significant, opioid analgesic-dependent pain.

PATIENTS AND METHODS

A double-blind, placebo-controlled trial randomized patients to receive a 78-day, outpatient regimen of either suramin plus hydrocortisone (HC, 40 mg/d) or placebo plus HC. Treatment assignment was unblinded when either disease progression or dose-limiting toxicity occurred; placebo patients were allowed to cross-over to open-label suramin plus HC. In addition to pain and opioid analgesic intake, prostate-specific antigen (PSA) response, time to disease progression, quality of life, performance status, and survival were compared.

RESULTS

Overall mean reductions in combined pain and opioid analgesic intake were greater for suramin plus HC (rank sum P =.0001). Pain response was achieved in a higher proportion of patients receiving suramin than placebo (43% v 28%; P =.001), and duration of response was longer for suramin responders (median, 240 v 69 days; P =.0027). Time to disease progression was longer (relative risk = 1.5; 95% confidence interval, 1.2 to 1.9) and the proportion of patients with a greater than 50% decline in PSA was higher (33% v 16%; P =.01) in patients who received suramin. Neither quality of life nor performance status was decreased by suramin treatment, and overall survival was similar. Most adverse events were of mild or moderate intensity and were easily managed medically.

CONCLUSION

Outpatient treatment with suramin plus HC is well tolerated and provides moderate palliative benefit and delay in disease progression for patients with symptomatic HRPC.

Chemotherapy for prostate cancer

The development of chemotherapy for prostate cancer has been limited by the toxicity of treatment in an elderly population. The evaluation of newer agents in the 1990's has allowed chemotherapy to be given which has fewer side effects, and has improved life quality. The investigation of adjuvant treatment may be warranted in an attempt to improve the outlook of this condition.

Androgen deprivation and four courses of fixed-schedule suramin treatment in patients with newly diagnosed metastatic prostate cancer: A Southwest Oncology Group Study

PURPOSE

To assess the feasibility of administering a combination of suramin and hydrocortisone in addition to androgen deprivation in a cooperative group setting; to assess the feasibility of treatment with multiple courses of suramin; and to assess progression-free and overall survival in patients with newly diagnosed metastatic prostate cancer who underwent such treatment.

PATIENTS AND METHODS

Patients with newly diagnosed metastatic prostate cancer who had adequate hematologic, hepatic, renal, neurologic, and coagulation parameters were treated by combined androgen deprivation and suramin plus hydrocortisone. Suramin was administered on a 78-day fixed dosing schedule (one cycle), and suramin treatment cycles were repeated every 6 months for a total of four cycles. The statistical design was developed on the basis of the feasibility of administering suramin, as judged by the number of patients who developed neurotoxicity of grade 3 or higher or by treatment interruption of 4 weeks or longer due to any persistent suramin-related toxicity.

RESULTS

Of the 62 patients enrolled onto the study between August 1994 and January 1997, 59 were eligible and assessable for toxicity on the first cycle. Thirty-two (54%) of 59 patients received a second cycle, 13 (22%) of 59 patients received a third cycle, and only five patients (8%) received a fourth cycle. During the first cycle, 27 patients were removed from the study: 17 because of toxicity, five because of disease progression, two who had died, and three because of other reasons. There was one therapy-related death. Grade 4 toxicities were noted in 11 and three patients during first and second courses, respectively. Neurotoxicity of grade 3 or higher was observed in nine and seven patients during the first and second cycles, respectively. Fifteen patients had treatment interruptions of 4 weeks or longer. Overall, only 54% (95% confidence interval, 41% to 67%) of the patients demonstrated acceptable limits of toxicity.

CONCLUSION

Suramin plus hydrocortisone and androgen deprivation has limited applicability in the treatment of patients with newly diagnosed metastatic prostate cancer.