Phase III trial of satraplatin, an oral platinum plus prednisone vs. prednisone alone in patients with hormone-refractory prostate cancer

Novel therapies in genitourinary cancer: an update

In recent years, new treatment for renal cell carcinoma (RCC) has been a spotlight in the field of cancer therapeutics. With several emerging agents branded as 'targeted therapy' now available, both medical oncologists and urologists are progressively more hopeful for better outcomes. The new remedies may provide patients with improved survival and at the same time less toxicity when compared to traditional cytotoxic agents. This article will center on current and emerging treatment strategies for advanced RCC and other GU malignancies with updates from 2008 annual ASCO meeting.

Evolving perspectives of the role of novel agents in androgen-independent prostate cancer

Metastatic androgen-independent prostate cancer presents an intriguing clinical challenge, with a subtle interaction between hormone-responsive and refractory tumor cell elements. The treatment of advanced prostate carcinoma, which had remained stagnant for several decades following the understanding of the link between androgenic stimulation and carcinogenesis, has now started to make steady headway with chemotherapy and targeted approaches. Metastatic prostate cancer is almost always treated with initial androgen deprivation, in various forms. However, despite such treatment androgen-independent prostate cancer cells eventually emerge and progress to threaten life. The therapeutic objectives for treatment of metastatic prostate cancer are to maintain the quality of life and prolong survival. The out-dated nihilistic dogma of deferring chemotherapy until the most advanced stages in advanced prostate cancer is now falling by the wayside with the development of newer effective, tolerable agents.

Current status and future prospects for satraplatin, an oral platinum analogue

Platinum drugs are major chemotherapeutic agents that are used alone or in combination with other systemic agents and/or radiation therapy in the management of many human malignancies. All three platinum drugs approved by the Food and Drug Administration, cisplatin, carboplatin, and oxaliplatin, are administrated intravenously. Satraplatin is the first orally administered platinum drug under active clinical investigation. Satraplatin and its major metabolite, JM118, have shown antineoplastic activity in in vitro, in vivo, and in clinical settings. Use of satraplatin as an alternative platinum cytotoxic agent is particularly attractive because of the convenience of administration, milder toxicity profile, lack of cross-resistance with cisplatin, theoretical advantage as a radiosensitizer, and activity in cancers historically nonresponsive to platinum drugs. The most mature clinical data for satraplatin come from the recently completed phase III trial that investigated the efficacy of satraplatin and prednisone on hormone-refractory prostate cancer patients who had failed a course of other chemotherapy agents. Preliminary reports show that the combination is statistically superior to placebo and prednisone in multiple end points, including progression-free survival, prostate-specific antigen response, objective tumor response, pain response, and duration of pain response. The difference in overall survival, however, did not reach statistical significance.

Therapies in development for castrate-resistant prostate cancer

The paucity of active medical therapies for advanced prostate cancer underlies a critical need for clinical research in this area. Multiple new treatments are being evaluated, including therapies that target adrenal androgens, such as abiraterone; new chemotherapies, such as the oral platinum analog, satraplatin, and an epothilone analog, ixabepilone; combinations of chemotherapy with other agents, such as the VEGF inhibitor, bevacizumab, and calcitriol; as well as multiple immunotherapeutics, including sipuleucel-T, GVAX and ipilimumab. This review will highlight the promise of these new approaches and the challenges to their development.

Efficacy of low-dose dexamethasone in castration-refractory prostate cancer

OBJECTIVE

To evaluate the prostate-specific antigen (PSA) response rate and duration of PSA response to dexamethasone in patients with castration-refractory prostate cancer (CRPC), as corticosteroids are frequently used as second-line hormonal treatment of CRPC and there is little published evidence concerning the efficacy of low-dose dexamethasone in this setting.

PATIENTS AND METHODS

In all, 102 patients with progressive CRPC received oral dexamethasone (0.5 mg daily) between January 2003 and October 2006. The median pretreatment PSA level was 83 ng/mL. The main endpoint was the PSA response rate according to the PSA Working Group criteria.

RESULTS

In all, 50 patients (49%) had a confirmed PSA response. The median (range) time to PSA progression for the entire cohort was 7.4 (1-28) months. In responders, the median duration of the PSA response was 11.6 (1-24) months.

CONCLUSION

Low-dose dexamethasone has significant activity in CRPC. Subject to validation with more clinically meaningful endpoints, dexamethasone could become the corticosteroid of choice in the management of CRPC, and its potential for use in combination with novel agents should be explored.

Therapeutic options for hormone-refractory prostate cancer in 2007

Prostate cancer is the most commonly diagnosed cancer in American men and a major health problem. While localized disease has an excellent chance for cure, metastatic disease leads to androgen-independent progression and death within a few years. Although docetaxel represents an important therapeutic milestone and is the current standard of care for metastatic hormone-refractory prostate cancer (HRPC), most patients eventually progress because of clonal selection of therapy-resistant cells or the development of cells with a drug-resistant phenotype. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy, the rational design of targeted therapeutics is possible. Over the last few years, many gene targets that regulate apoptosis, proliferation, and cell signalling have been identified, and numerous novel compounds have entered clinical trials either as single agents or in combination with cytotoxic chemotherapy. Neoadjuvant trials in particular must be further encouraged since they allow detection of biological activity in the prostatectomy specimen. This article reviews new treatment options available for men with advanced prostate cancer. Even though HRPC remains incurable, it is not untreatable. Recent findings are very promising, but challenges remain in demonstrating effective anti-tumor activity and showing a clinically relevant survival benefit in Phase III trials.

[Promising new treatment options for metastatic androgen-independent prostate cancer]

OBJECTIVE

Review the recent advances in the treatment of androgen independent prostate cancer (AIPC).

METHODS

Review recent abstracts and literature utilizing Medline/PubMed using key words: androgen independent/hormone refractory prostate cancer, novel treatment options, Phase II, III trials and meeting abstracts/presentations.

CONCLUSION

Two pivotal trials SWOG (Southwest Oncology Group) study 9916 and Taxotere 327 have shown that survival can be improved in this population by administration of chemotherapy with docetaxel every three weeks intravenously. An overall survival of 19 months could be achieved with docetaxel/prednisone compared to 16 months with mitoxantrone/prednisone. Despite this, there is a need to improve on this survival benefit because the relapse free survival among responders is often short (6 months) and patients often would have progression of their cancer leading to death. Satraplatin, a novel platinum analogue had been found to provide an additional 1.5 week progression free survival benefit in this population in the second line setting. There is however, a need to develop less toxic drugs that would improve survival significantly.

Chemotherapy for the treatment of hormone-refractory prostate cancer

AIMS

This review aims at analysing the published literature on chemotherapy for hormone-refractory prostate cancer (HRPC) to provide recommendations for the treatment of this important patient group.

METHODS

The information for this review was compiled using the PubMed and Medline databases and the Proceedings of the American Society of Clinical Oncology annual meetings to search for articles, abstracts and presentations up to 1 March 2007. Electronic early-release publications were also included. Only articles published in English were considered. The search terms included hormone-refractory prostate cancer, docetaxel, mitoxantrone, satraplatin, ixabepilone, cyclophosphamide, vinorelbine, atrasentan, calcitriol, bevacizumab and targeted therapies. Priority was given to studies in high impact factor journals when available.

RESULTS AND CONCLUSION

Two recent trials (TAX 327 and SWOG 9916) have shown that docetaxel chemotherapy can significantly improve survival for HRPC. Docetaxel has become the standard of care for first-line chemotherapy for HRPC and has been approved for use in the United States and Europe. Many patients with HRPC will require second- and even third-line treatment upon progression and more data are required in this setting. It is likely that the future management of patients with HRPC will build on the success of docetaxel using a sequence of chemotherapy and targeted therapies to reduce the risk of death, prevent or improve disease-related symptoms and improve quality of life for this important condition.

The resurgence of platinum-based cancer chemotherapy

The accidental discovery of the anticancer properties of cisplatin and its clinical introduction in the 1970s represent a major landmark in the history of successful anticancer drugs. Although carboplatin--a second-generation analogue that is safer but shows a similar spectrum of activity to cisplatin--was introduced in the 1980s, the pace of further improvements slowed for many years. However, in the past several years interest in platinum drugs has increased. Key developments include the elucidation of mechanisms of tumour resistance to these drugs, the introduction of new platinum-based agents (oxaliplatin, satraplatin and picoplatin), and clinical combination studies using platinum drugs with resistance modulators or new molecularly targeted drugs.

Broadening the clinical use of platinum drug-based chemotherapy with new analogues. Satraplatin and picoplatin

The three platinum-containing drugs that have been thus far approved by the FDA - cisplatin, carboplatin and oxaliplatin - have had a significant effect in the treatment of patients with some malignancies such as testicular, ovarian and colorectal cancer. However, much more remains to be achieved to widen the therapeutic use of this important class of drug, either via further analogue development or by judicious use of combining the existing drugs with new molecularly targeted agents. Two analogues arising from an academic (Institute of Cancer Research)/pharmaceutical (Johnson Matthey/AnorMed) collaboration - satraplatin (JM-216) and picoplatin (JM-/AMD-473) - have recently shown promising clinical activity; satraplatin (an orally available drug) in hormone-refractory prostate cancer and picoplatin in small-cell lung cancer. There have also been advances in delivery vehicles for platinum drugs (e.g., the diaminocyclohexane [DACH]-based AP-5346 and aroplatin/liposomal cis-bis-neodecanoato-trans-(R,R)-1,2-diaminocyclohexane platinum (II) [L-NDDP] are in early clinical development). Platinum-based drugs have also been successfully combined with molecularly targeted drugs (e.g., the recent approval of the vascular endothelial growth factor monoclonal antibody bevacizumab with carboplatin and paclitaxel in patients with NSCLC).

Novel targets and approaches in advanced prostate cancer

PURPOSE OF REVIEW

The development of therapeutic resistance is the underlying cause for most cancer deaths. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in prostate cancer, the rational design of targeted therapeutics is possible. We review new treatment options for men with advanced prostate cancer.

RECENT FINDINGS

Although the taxanes currently represent the most active chemotherapeutic agents and standard of care for first-line treatment of metastatic hormone-refractory prostate cancer, most patients eventually progress because of intrinsic or acquired drug resistance. In recent years, increased knowledge of cancer progression and therapeutic resistance has identified many gene targets that regulate apoptosis, proliferation, and cell signalling. To date, numerous novel compounds have entered clinical trials as either single agents or in combination with cytotoxic chemotherapy.

SUMMARY

Even though hormone-refractory prostate cancer is still incurable, it is not untreatable. As cancer cells are proficient at adapting to therapeutic stressors, a combination regimen with drugs that target crucial cellular networks like the apoptotic rheostat may be more promising than treatment with highly selective single-target agents. Recent findings are very hopeful, but challenges remain to demonstrate effective antitumour activity in phase III trials with survival as the principal endpoint.

Preclinical antitumor activity of the oral platinum analog satraplatin

PURPOSE

Satraplatin is an orally available platinum analog. The purpose of this study was to better characterize satraplatin's preclinical antitumor efficacy in a variety of sensitive and resistant human tumor cell lines and in a prostate cancer xenograft model and to evaluate the effect of satraplatin on PSA expression and/or secretion in a prostate cancer cell line.

METHODS

Satraplatin and its primary metabolite JM-118 were preclinically tested for their cytotoxic activity in a range of cancer cells including: human prostate, those forming the NCI drug screening panel, and those resistant to anti-cancer drugs. Also, the antiproliferative efficacy of satraplatin was tested in vivo in a human prostate cancer model. The effect of satraplatin and JM-118 on PSA transcription was measured by quantitative real time PCR.

RESULTS

Satraplatin and JM-118 inhibited in vitro and in vivo the growth of prostate cancer cells in a dose-dependent fashion. The IC50 cytotoxicity values for satraplatin ranged from 1 to 3 microM for androgen-insensitive cells and was 11 microM for the androgen-sensitive cell line. Interestingly, JM-118 was up to 16-fold more potent than satraplatin. Oral administration of satraplatin to nude mouse PC-3 xenograft models inhibited the growth of these human tumors. Satraplatin had no direct effect on PSA transcription and the observed decrease in secreted PSA correlated with a decrease in cell number. When evaluated in the NCI drug-screening panel, satraplatin was most active in leukemia and small cell lung cancer cell lines. Both satraplatin and JM-118 were tested on cells resistant to chemotherapeutic agents. Satraplatin and JM-118 were equally active in the cisplatin-resistant A129cp80 ovarian carcinoma cell line, with activity comparable to that observed in the parent line. Neither expression of MDR1, BCRP, MRP1, nor altered tubulin or topoisomerase I were found to mediate resistance to satraplatin or JM-118. Although these resistance mechanisms contribute to drug resistance for a number of chemotherapeutics, they do not appear to play a role in satraplatin resistance.

CONCLUSIONS

These results demonstrate that satraplatin and JM-118 have preclinical antitumor activity in human prostate cancer and other tumor types as well, including several cell lines displaying drug resistance to cisplatin, docetaxel and mitoxantrone. In addition, the results suggest that PSA should be further evaluated as a relevant marker of clinical response in patients with prostate cancer treated with satraplatin.

IRL-1620, a tumor selective vasodilator, augments the uptake and efficacy of chemotherapeutic agents in prostate tumor rats

BACKGROUND

IRL-1620, a potent endothelin B receptor agonist, enhanced the efficacy of paclitaxel in a breast tumor model, but its effect in prostate cancer is not known. The present study was conducted to evaluate the effect of IRL-1620 on tumor perfusion, uptake of [(14)C]-doxorubicin in the tumor and efficacy of doxorubicin (DOX), and 5-flurouracil (5-FU) in a rat prostate tumor model.

METHODS

JHU-4 (Mat-Lu) cells inoculated prostate tumor model in Copenhagen rats was used for the study.

RESULTS

Administration of IRL-1620 (3 nmol/kg, i.v) significantly increased (102.8%) prostate tumor perfusion and tumor uptake of [(14)C]-doxorubicin (115%) compared to vehicle treated rats. Results of the efficacy study demonstrate that IRL-1620 administration 15 min prior to DOX (5 mg/kg) or 5-FU (50 mg/kg) on every third day for a total of four doses significantly reduced tumor volume compared to vehicle treated rats.

CONCLUSIONS

IRL-1620 significantly enhanced the uptake and efficacy of anticancer agents in prostate cancer.

Is there a role for platinum chemotherapy in the treatment of patients with hormone-refractory prostate cancer?

Docetaxel chemotherapy is the current standard of care for metastatic hormone-refractory prostate cancer (HRPC). Platinum chemotherapy drugs, such as cisplatin and carboplatin, have moderate single-agent activity in HRPC. Next-generation platinum drugs, including satraplatin and oxaliplatin, may have additional activity in the management of HRPC. Furthermore, neuroendocrine differentiation may play a role in disease progression, providing a rationale for platinum-based chemotherapy in the management of HRPC. The authors reviewed the MEDLINE database for reports related to platinum-based chemotherapy in patients with advanced prostate cancer and evaluated studies that reviewed the role of neuroendocrine differentiation in the progression of HRPC. Older studies from the 1970s and 1980s suggested a lack of activity of cisplatin and carboplatin; however, those studies were flawed at least in part by their methods of response assessment. More recent Phase II studies of carboplatin suggested a moderate level of clinical and palliative activity when it was used as a single agent. However, when carboplatin was combined with a taxane and estramustine, high response rates were observed in several recent clinical trials. In addition, a randomized trial suggested that satraplatin plus prednisone improved progression-free survival compared with prednisone alone. For patients who progressed after docetaxel, no standard options existed in the literature that was reviewed. Several preliminary reports suggested that carboplatin and oxaliplatin may have activity as second-line chemotherapy. Platinum chemotherapy drugs historically have been considered inactive in HRPC, although a review of the data suggested otherwise. Carboplatin, in particular, induced very high response rates when it was combined with estramustine and a taxane, but it also appeared to have activity in patients who progressed after docetaxel. Satraplatin plus prednisone is being investigated in a large Phase III trial as second-line chemotherapy for HRPC. Targeting neuroendocrine cells may provide a new therapeutic approach to HRPC.

Advances in the Treatment of Prostate Cancer

Several recent advances have been made in the management of prostate cancer. Active surveillance is an increasingly attractive and reasonable approach for those with low-volume, low-risk disease. For locally advanced or localized high-risk disease, neoadjuvant and adjuvant therapies are emerging as the standard of care. Innovative uses of traditional hormonal treatments can potentially limit common side effects. Recent data also support the utility of second-line hormonal therapy. For the first time, a survival advantage with the use of chemotherapy has been established. Much work is under way to augment its efficacy with novel agents such as targeted therapeutics and tumor vaccines. Recent scientific breakthroughs suggest additional strategies in treating prostate cancer.

Androgen-independent prostate cancer

Androgen-independent or hormone-refractory prostate cancer (AIPC) is prostate cancer that progresses after primary androgen-ablation therapy--either orchiectomy or a gonadotropin-releasing hormone (LHRH) agonist, followed by addition and subsequent withdrawal of an antiandrogen. In the majority of patients, AIPC appears after a median time of 18 months of hormone deprivation. Patients with AIPC have a median survival between 10 and 20 months and the prognosis can be defined by using nomograms. Standard treatment is continued castration by LHRH agonists in combination with docetaxel-containing chemotherapy. Other treatment options to palliate symptoms are hormones, other chemotherapeutic agents, radioisotopes or radiotherapy and bisphosphonates. New targeted drugs and vaccination strategies are evaluated in the treatment of AIPC.

Advances in Prostate Cancer Immunotherapies

Prostate cancer is a major cause of mortality in men in the Western world. Although treatment of early stage prostate cancer with radiation therapy or prostatectomy is efficient in most cases, some patients develop a fatal hormone-refractory disease. Treatments in this case are limited to aggressive chemotherapies, which can reduce serum prostate-specific antigen (PSA) levels in some patients. Taxane- and platinum-compound-based chemotherapies produce a survival benefit of only a few months. Therefore, it is crucial to develop novel, well tolerated treatment strategies. Over the past years, immunotherapy of hormone-refractory prostate cancer has been studied in numerous clinical trials. The fact that the prostate is a non-essential organ makes prostate cancer an excellent target for immunotherapy. Administration of antibodies targeting the human epidermal growth factor receptor-2 or the prostate-specific membrane antigen led to stabilisation of PSA levels in several patients. Vaccination of prostate cancer patients with irradiated allogeneic prostate cell lines has demonstrated that whole cell-based vaccines can significantly attenuate increases in PSA. Two different recombinant viral expression vectors have been applied in prostate cancer treatment: poxvirus and adenovirus vectors. Both vaccines have the advantages of using a natural method to induce immune responses and achieving high levels of transgene expression. Vaccinia viruses in combination with recombinant fowlpox or canarypox virus have been used to express recombinant PSA. Several studies demonstrated that this approach is safe and can lead to stabilisation of PSA values. A very promising approach in prostate cancer immunotherapy is vaccination of patients with dendritic cells. Thereby, peptides, recombinant proteins, tumour lysates or messenger RNA have been used to deliver antigens to autologous dendritic cells. Loading of dendritic cells with up to five different peptides derived from multiple proteins expressed in prostate cancer demonstrated that cytotoxic T-cell responses could be elicited in prostate cancer patients. Sipuleucel-T (APC8015), an immunotherapy product consisting of antigen-presenting cells, loaded ex vivo with a recombinant fusion protein consisting of prostatic acid phosphatase linked to granulocyte-macrophage colony-stimulating factor, demonstrated in a phase III, placebo-controlled trial an improvement in median time to disease progression. The improvement in overall survival was 4.5 months for sipuleucel-T-treated patients compared with the placebo group. Although there is a minor increase in overall survival of metastatic prostate cancer patients with some approaches, more effective therapeutic strategies need to be developed.

Hormone-Refractory Prostate Cancer

This article addresses the current status of therapeutic options in the management of hormone-refractory prostate cancer (HRPC). Following the publication of two landmark randomised trials, docetaxel chemotherapy is now the standard of care for men with metastatic HRPC. However, the benefit of this treatment is limited. Trials are now focusing on improving the efficacy of docetaxel by combining it with novel biological agents. Several new docetaxel-based combinations are under evaluation and promising results have been found for the combination of docetaxel with angiogenesis inhibitors. Early phase III trial data for atrasentan appear interesting. New cytotoxic agents such as satraplatin and ixabepilone are being investigated in several ongoing studies in order to define their role as second-line treatments of HRPC. Vaccine therapy offers an active immunological approach for combating malignancy in a targeted manner.

Current Indications for Chemotherapy in Prostate Cancer Patients

Recently, data from two randomized studies, TAX327 and SWOG 9916, which compared docetaxel-based chemotherapy to mitoxantrone-based therapy, have demonstrated that treatment with docetaxel can prolong life in a statistically significant way in patients with hormone refractory prostate cancer (HRPC). In the TAX237 trial the median overall survival rates for patients treated with docetaxel every 3 wk was 18.9 mo, compared with 16.4 mo for the patients in the control arm (p=0.009). Patients treated with the combination of docetaxel and estramustine in the SWOG trial had a significant improvement in median survival (18 mo vs 16 mo, p=0.01), longer progression-free survival (6 mo compared with 3 mo, p<0.0001), and a 20% reduction in the risk of death. The optimal timing of docetaxel-based chemotherapy is still unknown because there are no prospective clinical trials indicating whether earlier treatment is more effective than delayed treatment. There are now increasing options also for second-line therapies in the palliative treatment of HRPC, and ongoing studies on new drugs such as satraplatin and ixabepilone will define the role of these agents in this setting. Preliminary neoadjuvant and adjuvant chemotherapy studies in high-risk prostate cancer patients have demonstrated that these approaches are feasible and do not add morbidity to surgery or radiotherapy, but their impact on survival still needs to be proven in randomized studies.

Comparative nephrotoxicity of cisplatin and new octahedral Pt(IV) complexes

PURPOSE

Previously, we have reported that the newly synthesized octahedral Pt(IV) compound, trans,cis-Pt(acetato)(2)Cl(2)(1,4-butanediamine), K101 and trans,cis-Pt(trifluoroacetato)(2)Cl(2)(1,4-butanediamine), K102 showed potent antitumor activities in vitro and in vivo. In order to compare the nephrotoxicity of the newly synthesized Pt(IV) complexes, K102 and K102 with cisplatin, we performed various tests.

MATERIALS AND METHODS

We performed a single dose acute toxicity test for LD(50) values determination, biochemical assays in blood serum, acid phosphatase enzyme histochemistry and transmission electron microscopic studies in renal proximal tubular cells in mice in vivo. The route of drugs administration is intraperitoneal injection.

RESULTS

In biochemical assays, the serum levels of BUN were significantly elevated at 6 h (p < 0.001), 1 day (p < 0.05) and 3 days (p < 0.001) after injection in cisplatin treated mice (6 mg/kg, single dose, i.p.). On the other hand, the serum levels of BUN were slightly elevated at 6 h (p < 0.01) only in K101 treated mice (8.2 mg/kg, single dose, i.p.), and were significantly raised at 6 h, 1 and 3 days (p < 0.05) after injection in K102 treated mice (6.2 mg/kg, single dose, i.p.). The higher serum BUN level in K102 treated mice is considered that K102 possesses more lipophilic fluoro group than acetyl group in K101. The values of creatinine and uric acid were similar in all groups. The ultrastructural morphological changes of K101- or K102-administrated mice were less remarkable than cisplatin-administrated mice. In acid phosphatase enzyme histochemistry, cisplatin treatment induced relevant changes in the distribution pattern of enzyme activity compared with K101 or K102 treatment at 7 days after injection.

CONCLUSIONS

In conclusion, these results show that K101 is less nephrotoxic than cisplatin and a promising new platinum complex.

Molecular mechanisms of resistance and toxicity associated with platinating agents

Platinating agents, including cisplatin, carboplatin, and oxaliplatin, have been used clinically for nearly 30years as part of the treatment of many types of cancers, including head and neck, testicular, ovarian, cervical, lung, colorectal and relapsed lymphoma. The cytotoxic lesion of platinating agents is thought to be the platinum intrastrand crosslink that forms on DNA, although treatment activates a number of signal transduction pathways. Treatment with these agents is characterized by resistance, both acquired and intrinsic. This resistance can be caused by a number of cellular adaptations, including reduced uptake, inactivation by glutathione and other anti-oxidants, and increased levels of DNA repair or DNA tolerance. Here we investigate the pathways that treatment with platinating agents activate, the mechanisms of resistance, potential candidate genes involved in the development of resistance, and associated clinical toxicities. Although the purpose of this review is to provide an overview of cisplatin, carboplatin, and oxaliplatin, we have focused primarily on preclinical data that has clinical relevance generated over the past five years.

In vitro and in vivo antitumour effects of novel, orally active bile acid-conjugated platinum complexes on rat hepatoma

(NH3)2Pt(triacid) and (PPh3)2Pt(dehydrocholate)2 are novel bile acid-conjugated platinum complexes administered by oral route. The aims of the present study were to evaluate their in vitro cytotoxic activities on rat hepatoma cell line N1-S1, the in vivo antitumour effects in a syngeneic and orthotopic rat hepatoma model and the drug-related toxicities. Cisplatin, carboplatin and mitoxantrone were used as control drugs. In vitro experiments showed a concentration- and time-dependent antiproliferative activity of bile-conjugated platinum complexes. (NH3)2Pt(triacid) had similar effects on cell growth of cisplatin and carboplatin (e.g. at 48 h, IC50 0.7+/-0.05 microM vs. 0.63+/-0.28 microM and 1.1+/-0.3 microM, respectively; mean+/-S.D.). (NH3)2Pt(triacid) was able to inhibit tumour growth in a dose-dependent extent, reaching the maximum inhibitory effect at the 80 mg/kg dose (1.95+/-0.5 g vs. 13.85+/-3.9 g of control tumour weight). By contrast, despite the promising in vitro antiproliferative activity, (PPh3)2Pt(dehydrocholate)2 showed no significant in vivo antitumour effect. The toxicity profile of (NH3)2Pt(triacid) resulted favourable with minimal loss of weight and no gastrointestinal or neurological symptoms. Instead, (PPh3)2Pt(dehydrocholate)2 showed dose-dependent signs of severe weight loss and neurological alterations. In conclusion (NH3)2Pt(triacid) is a tolerable and active platinum derivative endowed by a preclinical antitumour activity by oral route.

Chemotherapy for advanced prostate cancer: docetaxel and beyond

To place appropriately into context the current status of chemotherapy as a management option for patients with hormone-refractory metastatic prostate cancer, it is important to reflect on the widely held historical belief that advanced prostate cancer is a chemotherapeutic-insensitive neoplasm. This article focuses on three disease subsets: (1)metastatic, hormone-refractory, chemotherapy-naive prostate cancer;(2) metastatic, hormone-refractory, progressive prostate cancer after frontline chemotherapy; and (3) locally advanced prostate cancer. Yagoda and Petrylak evaluated the results of 26 phase II trials of antineoplastics in advanced prostate cancer published between 1987 and 1991 and found the average objective response rate was less than 10% with only a few studies having response rates in the 10% to 20%range.

Management of the Spectrum of Hormone Refractory Prostate Cancer

INTRODUCTION

In its advanced stages, hormone refractory prostate cancer (HRPC) is an incurable condition which consists of a spectrum of disease. This requires an integrated multidisciplinary approach by an uro-oncologic team supported by radiologists, skeletal surgeons and palliative care. Aim of this review was to critically evaluate the current and potential approaches to patients affected by HRPC.

MATERIALS AND METHODS

A comprehensive evaluation of available published data included analysis of published full-length papers that were identified with Medline and Cancerlit from January 1981 to January 2006. Official proceedings of internationally known scientific societies held in the same time period were also assessed.

RESULTS

Most men with hormone refractory prostate cancer will die of their disease in the absence of intercurrent illness, and the various conditions arising as a consequence of local and distal cancer progression commonly lead to a spectrum of morbidity requiring treatment. Recent data regarding docetaxel-based chemotherapy have shown small but significant improvements in survival and improvement in quality of life in men receiving treatment. However, this therapy may not be suitable for all patients. New agents used alone or in combination with docetaxel currently are under trial in an attempt to provide much needed improvements in outcome. Bone-targeted treatments, particularly late-generation bisphosphonates, have added to the range of options, reducing the incidence of skeletal complications in some men. Further work is needed to target their use more effectively, to explore their efficacy in combination with existing proven therapies and to develop new approaches to treat bone metastases. Complications arising as a consequence of upper and lower tract dysfunction, haematologic, neurologic and psychologic disorders are common. These complications often are amenable to effective treatment, but interventions may engender difficult clinical and ethical decisions.

CONCLUSIONS

Although HRPC is incurable, it is not untreatable, and that the clinical management embraces not just chemotherapy, but many interventional and supportive therapies. A holistic and supportive approach to patient care is vital for optimal management, and is best provided by a coordinated, multidisciplinary team including urologists and oncologists.

New molecular targets in advanced prostate cancer

Classically, advanced prostate cancer has been treated with hormonal therapy and, most recently, chemotherapy. This treatment clearly demonstrated a survival benefit, but never a cure. With the ever-expanding understanding of the pathophysiology of prostate cancer, there has been a recent explosion in the potential molecular targets and novel therapeutic approaches to both advanced and potentially localized prostate cancer. This review will focus on what the author perceives to be the most promising of these new strategies. The endothelin pathway has been identified as pivotal in the viscous cycle of tumorigenesis in bone, leading to the development of endothelial receptor antagonists. Vaccine therapy using autologous granulocyte-macrophage colony-stimulating factor-producing prostate cancer cells has been effective in producing both immune and clinical responses. Randomized clinical trials of the immunotherapy cell product APC8015 (Provenge) have demonstrated improved survival in the hormone-refractory setting. The development of antisense oligonucleotides to segments of mRNA critical to the progression to androgen-independent disease has emerged as one further tool in the expanding armamentarium of potential therapies being tested. Clearly, headway is being made in improving outcomes in this most prevalent health problem.

Satraplatin: an orally available platinum analog for the treatment of cancer

Satraplatin is a novel, orally bioavailable, platinum anticancer drug. Platinum analogs form the mainstay of treatment for a number of cancers, including lung, ovarian, colorectal and head and neck cancer. A disadvantage of the currently marketed platinum analogs is that they must all be administered via intravenous infusion. In addition, their utility is often limited by toxicity, particularly neurotoxicity, ototoxicity and renal toxicity. Satraplatin has preclinical antitumor activity comparable with that of cisplatin and, clinically, has a more manageable side-effect profile. Satraplatin is active in lung, ovarian and prostate cancer, and appears to have good efficacy in combination with radiation for lung and head and neck cancer. Preclinical data suggest it may also be effective for the treatment of certain cisplatin-refractory tumors. A large, randomized Phase III trial is currently evaluating satraplatin in combination with prednisone for the treatment of patients with hormone-refractory prostate cancer whose disease has progressed following prior systemic therapy. Positive results from this trial would support regulatory approval for satraplatin for this indication. The availability of an active oral platinum agent, such as satraplatin, with few of the serious toxicities associated with traditional intravenous platinum compounds makes satraplatin an alternative to other platinum agents and a new treatment option in the oncologist's armamentarium.

The development of platinum compounds and their possible combination

Cisplatin plays a central role in cancer chemotherapy in spite of its toxicity. To circumvent this toxicity and to enhance its therapeutic index a lot of preclinical and clinical studies have been conducted and several thousand analogues have been synthesized. Much more analysis remains to be done, but nowadays, the absence of any definitive, biologically interpretable molecular predictor of activity is consistent with the idea that platinum compounds have multiple intracellular targets and that cells can have multiple mechanisms of resistance. This review analyses a part of these platinum compounds analyzed to date, their mechanism of action, resistance and the future trends in this sector.

Comparative anti-tumor efficacy of two orally administered platinum(IV) drugs in nude mice bearing human tumor xenografts

The oral anti-tumor activity of a novel platinum(IV) complex, coded as LA-12, with a bulky adamantylamine ligand was evaluated and compared with another platinum(IV) complex satraplatin. The human carcinoma xenografts of colon HCT116, prostate PC3, and ovarian A2780 and A2780/cisR (resistant to cisplatin) were used to evaluate the in-vivo anti-tumor activity. The daily x 5 repeated dose regimen in equimolar doses of LA-12 and satraplatin, administered in 2 cycles, was selected for this evaluation. All doses of LA-12 and satraplatin were significantly effective in comparison with the control. The activities of LA-12 in all doses and all used tumor xenografts were higher than equimolar doses of satraplatin. The highest effect was reached with LA-12 at a dose of 60 mg/kg. The shapes of growth curves of ovarian carcinoma A2780 and its subline resistant to cisplatin after therapy with LA-12 were very similar. This shows that LA-12 is able to overcome resistance to cisplatin.

The changing pattern of management for hormone-refractory, metastatic prostate cancer

Prostate cancer responds initially to hormonal manipulation by androgen withdrawal and peripheral androgen blockade. The inevitable progression to a hormone-refractory state is accompanied by an exacerbation of local symptoms and metastatic spread, principally to the bones, which has a considerable impact on quality of life and survival. Treatment of hormone-refractory prostate cancer is palliative, and surgery and radiotherapy are used for the relief of lower urinary tract symptoms and localized painful bony metastases. Systemic treatments are not widely accepted in this setting, but clinical trials have demonstrated the potential for bone targeting agents such as strontium-89 and the bisphosphonates to palliate painful bone metastases and to delay progression in certain settings. Chemotherapy with mitozantrone in combination with steroids has previously been shown to have palliative benefits and to delay progression. The additional costs incurred by the use of chemotherapy or bone-targeting therapies may be offset by gains in overall care with fewer in-patient admissions compared with steroid monotherapy. Recent clinical trials have demonstrated that docetaxel significantly improves patient quality of life, and importantly, increases survival. Future studies investigating the timing of chemotherapy, combinations with existing treatments or other novel therapies are underway.

Management of prostate cancer. Part 3: metastatic disease

Despite the increased detection of prostate cancer at an early stage, men are still dying of this disease. Management of advanced disease focuses on controlling the disease process, palliation of symptoms and improving quality of life. In this review, the basis for androgen deprivation in hormone-dependent disease is discussed and the role of maximum and intermittent androgen deprivation, as well as management options for hormone-refractory disease is addressed. Local radiotherapy continues to be of importance in pain control and the maintenance of quality of life. Radiopharmaceuticals and bisphosphonates also have a role to play, the latter particularly in the reduction of skeletal-related events. Chemotherapy in hormone-refractory disease is now well established following pivotal trials demonstrating a survival benefit with docetaxel. The emergence of novel agents targeting growth factors, angiogenesis and immunotherapy present exciting possibilities for future treatment.

Novel mechanisms of platinum drug resistance identified in cells selected for resistance to JM118 the active metabolite of satraplatin

PURPOSE

The goal of this study was to identify molecular determinants of sensitivity and resistance to JM118, the active metabolite of satraplatin, an orally bioavailable cisplatin analog that has activity in prostate cancer.

EXPERIMENTAL DESIGN

Human ovarian carcinoma 2008/JM118 cells were derived from parental 2008 cells by repeated exposure to JM118; the revertant 2008/JM118/REV subline was isolated from the 2008/JM118 cells by growth in the absence of drug. Drug sensitivity was determined by clonogenic assay and Pt levels were measured by ICP-MS.

RESULTS

Eight sequential rounds of selection yielded the 2008/JM118 subline that was 4.9-fold resistant to JM118 and cross-resistant at varying levels to satraplatin, cisplatin, carboplatin, and oxaliplatin. Cross-resistance to the other Pt drugs was lost as resistance to JM118 waned. The same parental 2008 cells selected for resistance to cisplatin were partially cross-resistant to JM118. The 2008/JM118 cells accumulated significantly more Pt than the 2008 cells when exposed to low concentrations of either JM118 or cisplatin indicating a detoxification process that involves intracellular sequestration. In contrast, 2008 cells selected for cisplatin resistance accumulated less cisplatin and less JM118 reflecting a mechanism involving reduced accumulation. The 2008 and 2008/JM118 cells did not differ in their uptake or efflux of 64Cu, expression of Cu efflux transporters ATP7A or ATP7B or their glutathione content. The 2008/JM118 cells exhibited 3.0-7.7-fold hypersensitivity to docetaxel, paclitaxel and doxorubicin. Expression profiling identified 4 genes that were significantly up-regulated and 19 that were down-regulated in the 2008/JM118 cells at a false discovery rate of 1 gene.

CONCLUSIONS

While the cellular defense mechanisms that protect cells against JM118 also mediate resistance to the other Pt drugs, these mechanisms are quite different from those commonly found in cells selected for resistance to cisplatin. JM118-resistant cells accumulate more rather than less Pt and rely on an intracellular detoxification mechanism different from that involved in cisplatin resistance. This is consistent with clinical evidence suggesting that satraplatin has activity in diseases in which cisplatin does not. In this model, JM118 resistance is associated with substantial collateral hypersensitivity to docetaxel, paclitaxel, and doxorubicin.

Response to second-line chemotherapy in patients with hormone refractory prostate cancer receiving two sequences of mitoxantrone and taxanes

OBJECTIVES

Clinical trials have demonstrated a survival benefit with docetaxel chemotherapy, but limited data exist regarding the activity of second-line chemotherapy.

METHODS

We retrospectively identified all patients at one institution who received at least two chemotherapy regimens for hormone-refractory prostate cancer, one mitoxantrone-based and the other taxane-based, either including docetaxel or paclitaxel. Patients were evaluated using criteria modified from the Prostate-Specific Antigen Working Group.

RESULTS

A total of 68 patients were analyzed; 33 patients received mitoxantrone followed by taxane-based treatment, and 35 received taxane-based chemotherapy followed by mitoxantrone. The median patient age was 66 and 58 years and the median prostate-specific antigen at the start of treatment was 23 and 24 ng/mL in the mitoxantrone-first and taxane-first group, respectively. The response rates to taxane-based chemotherapy were greater whether it was used first or second (P <0.0001). Progression-free survival (PFS) was longer with taxanes than with mitoxantrone, whether used first or second (P <0.05). However, the corresponding total PFS from start of the first regimen to progression during the second regimen was similar at 39.9 and 38.7 weeks (P = 0.67). Overall survival was also not significantly different (15.2 and 17.1 months, P = 0.97). Neither age nor the interval from diagnosis to chemotherapy influenced the differences in PFS.

CONCLUSIONS

Taxane-based chemotherapy is active before or after mitoxantrone. Although PFS was longer with taxane-based chemotherapy, the total PFS and overall survival were equivalent for both sequences in this retrospective analysis, suggesting that taxane-based chemotherapy retains activity, even if delayed. Although responses were seen with mitoxantrone after taxanes, the median PFS was short, and new agents are needed after taxane-based chemotherapy.

Octahedral Pt(IV) complex K101 induces apoptosis via ERK1/2 activation and the p53 pathway in human colon cancer cells

Recently, the synthesized octahedral Pt(IV) compound trans,cis-Pt(acetato)2Cl2(1,4-butanediamine), K101, showed potent anti-tumor activity in vitro and in vivo. For the further investigation of K101-induced anti-cancer activity, we tested cytotoxicity against various cancer cell lines and performed the histoculture drug response assay (HDRA) against human colorectal tumor tissues in vitro. We investigated the signaling pathway of K101-induced apoptosis via expression of p53 and ERK1/2 in the human colon cell line HCT116. The cytotoxicity and the three-dimensional HDRA of K101 were evaluated using the MTT assay. To study the K101-induced apoptosis pathway, we performed FACS analysis and immunoblotting of p53, p21, Bax, Fas and ERK1/2 in HCT116 cells treated with or without K101. The cytotoxic IC50 values of K101 ranged from 1.15 to 2.38 micromol/l, compared to cisplatin ranging from 2.13 to 13.1 micromol/l. Among several cancer cell lines, K101 showed greater potency than cisplatin in colon cancer cell lines. In the HDRA, K101 showed 80.0-91.4% efficacy rates compared with 48.6% for cisplatin against colorectal cancer patient tissues. In the signaling pathway, the expression of p53 and phospho-ERK1/2 was increased in a time-dependent manner by treatment with K101 in the HCT116 cells. When K101 was treated with MEK inhibitor U0126, the cell death rate was increased. The octahedral Pt(IV) complex K101 could be an attractive candidate as a chemotherapeutic agent against colon cancer. ERK1/2 activation and the p53 pathway may play significant functions in mediating K101-induced apoptosis in human colon cancer cells.