Cardioxane--ICRF-187 towards anticancer drug specificity through selective toxicity reduction

New Iron Metabolic Pathways and Chelation Targeting Strategies Affecting the Treatment of All Types and Stages of Cancer

There is new and increasing evidence from in vitro, in vivo and clinical studies implicating the pivotal role of iron and associated metabolic pathways in the initiation, progression and development of cancer and in cancer metastasis. New metabolic and toxicity mechanisms and pathways, as well as genomic, transcription and other factors, have been linked to cancer and many are related to iron. Accordingly, a number of new targets for iron chelators have been identified and characterized in new anticancer strategies, in addition to the classical restriction of/reduction in iron supply, the inhibition of transferrin iron delivery, the inhibition of ribonucleotide reductase in DNA synthesis and high antioxidant potential. The new targets include the removal of excess iron from iron-laden macrophages, which affects anticancer activity; the modulation of ferroptosis; ferritin iron removal and the control of hyperferritinemia; the inhibition of hypoxia related to the role of hypoxia-inducible factor (HIF); modulation of the function of new molecular species such as STEAP4 metalloreductase and the metastasis suppressor N-MYC downstream-regulated gene-1 (NDRG1); modulation of the metabolic pathways of oxidative stress damage affecting mitochondrial function, etc. Many of these new, but also previously known associated iron metabolic pathways appear to affect all stages of cancer, as well as metastasis and drug resistance. Iron-chelating drugs and especially deferiprone (L1), has been shown in many recent studies to fulfill the role of multi-target anticancer drug linked to the above and also other iron targets, and has been proposed for phase II trials in cancer patients. In contrast, lipophilic chelators and their iron complexes are proposed for the induction of ferroptosis in some refractory or recurring tumors in drug resistance and metastasis where effective treatments are absent. There is a need to readdress cancer therapy and include therapeutic strategies targeting multifactorial processes, including the application of multi-targeting drugs involving iron chelators and iron-chelator complexes. New therapeutic protocols including drug combinations with L1 and other chelating drugs could increase anticancer activity, decrease drug resistance and metastasis, improve treatments, reduce toxicity and increase overall survival in cancer patients.

Advances on Chelation and Chelator Metal Complexes in Medicine

Metal ions such as iron, copper and zinc are essential for life. Chelators (Chele, greek χειλή-claw of a crab) are organic molecules possessing specific ligands which have high affinity and can bind/carry metal ions and play very important roles in living systems e.g., haemoglobin, transferrin, phytochelators and microbial siderophores [...].

Trastuzumab in the treatment of HER2 positive breast cancer

Objective. To provide a comprehensive review of the preclinical and clinical pharmacology and toxicology of the monoclonal antibody trastuzumab, with particular reference to its use in its approved indication, HER2/neu-overexpressing breast cancer.

Data sources. A MEDLINE search was conducted using the terms ‘trastuzumab’ and ‘Herceptin’ for the period 1995-2001. The reference lists from retrieved articles were reviewed and other relevant papers identified. The abstract books from the annual meetings of the American Society of Clinical and Oncology and the European Society of Medical Oncology were also reviewed.

Data extraction. The aim of the review was to be comprehensive and descriptive. All studies containing information deemed to be of interest were reviewed by the author; none were excluded on grounds of quality.

Data summary. Trastuzumab is a chimeric monoclonal antibody with a hypervariable region of murine origin inserted into a human IgG1 skeleton. Trastuzumab recognizes p185HER2/neu, the 185-kDa product of the HER2/neu protooncogene. This gene is overexpressed in around 20% of breast cancers and encodes for a trans-membrane protein that has extensive structural homology with the EGFR. HER2/neu overexpression is prognostic of short relapse-free and overall survival and, possibly, of poor response to certain hormonal and cytotoxic treatments. Trastuzumab inhibits the growth of HER2/neu-overexpressing tumour cells grown in tissue culture or as xeno-grafts in mice. It also potentiates the action of certain cytotoxic drugs against such cells. These properties stimulated clinical trials of trastuzumab in women with HER2/neu-positive breast cancer. Used alone, in women with heavily pretreated HER2/neu-positive breast cancer, trastuzumab stabilized disease in 35% of cases and induced regression in a further 22%. Its use was associated with prolonged stabilization of quality of life. When used in combination with paclitaxel, or anthracycline-based chemotherapy, as a first-line treatment for metastatic breast cancer, it increased response rates, time to disease progression and survival. Unfortunately, when used in conjunction with anthracyclines, trastuzumab has been associated with an unacceptable incidence of cardiotoxicity. For this reason, it is currently approved for use alone or in combination with paclitaxel. When added to paclitaxel as a first-line treatment, it increased the median time to disease progression from 3.0 to 6.9 months (P= 0.0001) and the 1-year survival rate from 62% to 73%, with little toxicity except occasional and, generally, mild infusion reactions.

Review : Amifostine and other chemoprotective agents in cancer chemotherapy: A brief review

Objective. Cytotoxic chemotherapy is a frequently, and increasingly, used treatment for malignant disease and is associated with substantial toxicity. A number of drugs have been developed in recent years for the prevention and treatment of chemotherapy-induced toxicity. Most are specific to one group of drugs, eg, mesna and the oxazophosphorines, or one type of toxicity, eg, the 5-HT3 antagonist antiemetics. The first multiorgan cytoprotective, amifostine, recently was launched, and another, glutathione, is under development. The purpose of this review is to con sider the agents currently available for the manage ment of cytotoxic drug-induced toxicity and their place in treatment. Special attention is directed to amifostine and drugs in development, including glu tathione, Ossirene (Baker Norton), ORG-2766, and dexrazoxane and less to agents in routine clinical use.

Data sources. A variety of sources were used, including manual and on-line (Medline) literature searching. Approved and other drug names were used as the primary search terms, linked with cytotoxic chemotherapy where limitation was required. Medi cal information departments of drug companies also were used where appropriate.

Study selection. Particular attention was directed to randomized clinical trials, but nonrandomised and animal studies were considered where appropriate.

Conclusions. Over the past decade significant advances have been made in the control of chemo therapy-induced toxicity and new agents promise even greater control. This is important, not only because they may improve the quality of life of conventionally treated cancer patients, but also be cause they should allow the dose-response relation ship for cytotoxic drug treatment to be fully explored. Unfortunately, the data available at present are insuf ficient to determine the extent to which this promise will be fulfilled.

Physical and chemical stability of reconstituted and diluted dexrazoxane infusion solutions

BACKGROUND AND PURPOSE

Dexrazoxane is used clinically to prevent anthracycline-associated cardiotoxicity. Hydrolysis of dexrazoxane prior to reaching the cardiac membranes severely hampers its mode of action; therefore, degradation during the preparation and administration of intravenous dexrazoxane admixtures demands special attention. Moreover, the ongoing national shortage of one dexrazoxane formulation in the United States has forced pharmacies to dispense other commercially available dexrazoxane products. However, the manufacturers' limited stability data restrict the flexibility of dexrazoxane usage in clinical practice. The aims of this study are to determine the physical and chemical stability of reconstituted and diluted solutions of two commercially available dexrazoxane formulations.

METHODS

The stability of two dexrazoxane products, brand and generic name, in reconstituted and intravenous solutions stored at room temperature without light protection in polyvinyl chloride bags was determined. The concentrations of dexrazoxane were measured at predetermined time points up to 24 h using a validated reversed phase high-performance liquid chromatography with ultraviolet detection assay.

RESULTS

Brand (B-) and generic (G-) dexrazoxane products, reconstituted in either sterile water or 0.167 M sodium lactate (final concentration of 10 mg/mL), were found stable for at least to 8 h. Infusion solutions of B-dexrazoxane, prepared according to each manufacturer's directions, were stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. Infusion solutions of G-dexrazoxane, prepared in either 5% dextrose or 0.9% sodium chloride following the manufacturer's guidelines, were also stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. All tested solutions were found physically stable up to 24 h at room temperature.

CONCLUSION

The stability of dexrazoxane infusion solutions reported herein permits advance preparation of dexrazoxane intravenous admixtures, facilitating pharmacy workflow and clinical operations. However, due to the potential risks of fluid overload when these intravenous solutions are administered to patients, caution is advised to ensure patient safety.

Protective effect of selected flavonoids on in vitro daunorubicin-induced cardiotoxicity

Flavonoids are an ubiquitous group of polyphenolic substances with varied chemical structures present in foods of plant origin and act as free radical scavenging and chelating agents with a variety of biological activities. Using a model of spontaneously beating, cultured adult rat cardiomyocytes, this study examined the cardioprotective role of quercetin, naringenin, pycnogenol and a model antioxidant, trolox, against daunorubicin-induced toxicity. Cardiomyocyte protection was assessed by MTT test and extracellular lactate dehydrogenase detection. Protection of cardiomyocytes was concentration/dose dependent for quercetin > naringenin > pycnogenol > trolox. Quercetin (10(-4)-10(-6) mol/L) after 24 h of co-incubation with daunorubicin significantly increased the cardiomyocyte survival in all tested concentrations (p < 0.001). The cytoprotective effect of naringenin (10(-4)-10(-6) mol/L) was similar to those of quercetin (p < 0.001 and p < 0.01, respectively). Pycnogenol was the least effective of the flavonoids studied. On the other hand, all tested flavonoids had significantly better protective effects than trolox. The leakage of lactate dehydrogenase induced by daunorubicin was also prevented by the studied compounds and was in accordance with their cytoprotective activity.

Long-term serial echocardiographic examination of late anthracycline cardiotoxicity and its prevention by dexrazoxane in paediatric patients

The authors conducted an 8-year prospective non-randomised study to determine whether dexrazoxane (ICRF-187) would reduce late anthracycline-induced cardiotoxicity in patients treated in childhood for haematological malignancy. The authors examined prospectively 75 patients (40 male/35 female) aged 2-17 years (median 6.5 years) at the time of diagnosis. The cardioprotection was given to 53 patients (26 male/17 female) and the standard protocol was used in 22 patients (14 male/8 female). The prospective echocardiographic evaluation was done before and after the chemotherapy and every year during the follow-up period. Dynamic stress echocardiography (DSE) was assessed in the final year. The clinical cardiotoxicity was not diagnosed. Higher cumulative doses of anthracycline were given in the dexrazoxane group (234+/-58 mg/m(2), median 240 mg/m(2) versus 203+/-86 mg/m(2), median 210 mg/m(2), P <0.04) and a significantly higher percentage of patients received cumulative doses >240 mg/m(2) of anthracycline ( P <0.05). During the follow-up period, the fractional shortening (FS) declined in the no-dexrazoxane group only in the 8th year and was significantly lower compared to the dexrazoxane group ( P <0.05). The pathological decrease in FS was present in 24% of patients; 41% in the no-dexrazoxane and 17% in the dexrazoxane groups, respectively ( P <0.05). DSE demonstrated lower rest EF and cardiac index (CI) in the no-dexrazoxane group ( P <0.05); however, neither the response of EF and CI to the stress echocardiography nor the exercise tolerance significantly differed between sub-groups. A higher number of patients in the dexrazoxane group had very good exercise tolerance (ET) >3 Watts/kg ( P <0.05) and a lower number responded with a decreased ET <2 Watts/kg ( P <0.05) compared to the no-dexrazoxane group.

CONCLUSION

Dexrazoxane seems to reduce the risk of late subclinical cardiotoxicity. Dexrazoxane-treated patients revealed better exercise tolerance; however the haemodynamic response to the stress was no different in both sub-groups.

Modulation by Melatonin of the Cardiotoxic and Antitumor Activities of Adriamycin

In this study, we investigated the effects of melatonin on adriamycin-induced cardiotoxicity both in vivo in rats and in vitro, and on the antitumor activities of adriamycin on MDA-231 and NCI breast cancer cells. Rats that received a single intraperitoneal injection of 25 mg/kg adriamycin showed a mortality rate of 86%, which was reduced to 20% by melatonin treatment (10 mg/kg, SC for 6 days). Melatonin attenuated adriamycin-induced body-weight loss, hemodynamic dysfunction, and the morphologic and biochemical alterations caused by adriamycin. Melatonin also reduced adriamycin-induced nuclear DNA fragmentation, as assessed by the comet assay. In addition, the antitumor activity of adriamycin could be maintained using lower doses of this drug in combination with melatonin. Melatonin treatment in the concentration range of 0.1-2.5 mM inhibited the growth of human breast cancer cells. In terms of oncolytic activity, the combination of adriamycin and melatonin improved the antitumor activity of adriamycin, as indicated by an increase in the number of long-term survivors as well as decreases in body-weight losses resulting from adriamycin treatment. These results indicate that melatonin not only protects against adriamycin-induced cardiotoxicity but also enhances its antitumor activity. This combination of melatonin and adriamycin represents a potentially useful regimen for the treatment of human neoplasms because it allows the use of lower doses of adriamycin, thereby avoiding the toxic side effects associated with this drug.

Late anthracycline cardiotoxicity protection by dexrazoxane (ICRF-187) in pediatric patients: echocardiographic follow-up

BACKGROUND

The authors conducted a retrospective study to determine whether dexrazoxane (ICRF-187) would reduce late anthracycline-induced cardiotoxicity in patients treated in childhood for hematological malignancy.

PATIENTS AND METHODS

The authors examined 108 patients (63 male, 45 female) 5-29 years old, (median 15 years). All patients were in long-term remission of their malignancy. The cardioprotection was given to 68 patients (39 male, 29 female), and standard treatment was used in 40 patients (24 male, 16 female). Dexrazoxane (cardioxane, Chiron Company, The Netherlands) was given in 20:1 ratio to anthracycline. The follow-up time was 2-20 years (mean 7 years). The control group consisted of 41 volunteers (22 males, 19 females) 4-31 years old (median 18 years). The cardiotoxicity has been defined as the presence of heart failure or the decline of shortening fraction below 30% or ejection fraction (EF) below 55%. The end-systolic wall stress (ESS), myocardial performance index (MPI; Tei index), and parameters of left ventricular diastolic filling were also assessed.

RESULTS

The anthracycline cardiomyopathy with the presence of heart failure was diagnosed in only one patient treated with a standard regimen. The pathological decline of fractional shortening was present in three (5%) and six (15%) patients with and without cardioprotection given, respectively. Similarly, none of the patients with cardioprotection revealed a pathological value of EF, while four (10%) patients without cardioprotection showed an EF decrease. Finally, ESS and isovolumic relaxation time were pathologically increased in the group without cardioprotection in comparison to the controls and to the group with cardioprotection. However, the MPI was significantly increased in both groups of patients.

CONCLUSIONS

Dexrazoxane reduces the risk of late clinical and subclinical cardiotoxicity and does not affect the response rates to chemotherapy and overall survival during the median follow-up period of 7 years (follow-up period 2-20 years).

A comparative study between catalase gene therapy and the cardioprotector monohydroxyethylrutoside (MonoHER) in protecting against doxorubicin-induced cardiotoxicity in vitro

Cardiotoxicity is the main dose-limiting side effect of doxorubicin in the clinic. Being a free radical producer, doxorubicin affects the heart specifically because of its low antioxidant capacity. Among those antioxidants, catalase is present in very low levels in the heart compared to other organs. Since catalase is an essential enzyme in detoxifying hydrogen peroxide, the aim of the present study was to investigate the protective effect of catalase as delivered by an adenovirus vector against doxorubicin-induced cardiotoxicity in cultured neonatal rat cardiac myocytes (NeRCaMs). 7-Monohydroxyethylrutoside (MonoHER), a potent cardioprotector currently under clinical investigations, was included in the study as a reference. Neonatal rat cardiac myocytes were infected with different multiplicity of infections (MOIs) of adenovirus encoding catalase (AdCat). A control infection with an adenovirus vector encoding a nonrelated protein was included. The activity and content of catalase in infected cells were determined during 3 days postinfection. One group of NeRCaMs was infected with AdCat before treatment with doxorubicin (0–50 μM). The second and third group were treated with doxorubicin (0–50 μM) with and without 1 mM monohydroxyethylrutoside (monoHER), respectively. The LDH release and viability of treated cells were measured 24 and 48 h after doxorubicin treatment. The beating rate was followed in three other groups of cells receiving the same treatments within 3 days after doxorubicin (0–100 μM) treatment. Catalase activity increased in AdCat-infected cells, with different MOIs, starting from the second day after infection as compared to the mock-infected cells (P<0.03). At the third day of infection, an MOI of more than 50 caused cytopathic effects, which hampered the use of higher viral titres. With an MOI of 50, catalase activity increased 3.5-fold in AdCat-infected cells 3 days postinfection (P=0.021) compared to mock-infected cells. The beating rate and survival of NeRCaMs decreased in a concentration and time-dependent manner after doxorubicin treatment (P<0.0005). This cytotoxicity was associated with an increase in the LDH release from the treated cells (P<0.0005). The cells stopped beating 24 h after treatment with >50 μM doxorubicin. A 3.5-fold increase in the activity of catalase did not protect NeRCaMs against any of the cytotoxic effects of doxorubicin on NeRCaMs. In contrast, monoHER (1 mM) significantly protected NeRCaMs against the lethal effects of doxorubicin on the survival, LDH release and the beating rate of NeRCaMs (P<0.004) during 48 h after doxorubicin treatment. This protection resulted in a prolongation of the beating of doxorubicin-treated cells after the end of the experiment (i.e. >72 h). The present study (1) illustrates that the cytotoxicity of high MOI of AdCat (>50) limited the possibility to increase catalase activity more than 3.5-fold, which was not enough to protect infected NeRCaMs against doxorubicin-induced cardiotoxicity and (2) confirms the efficacy of monoHER as a cardioprotector. Thus, the use of monoHER proves more suitable for the prevention of doxorubicin-induced cardiotoxicity than catalase gene transfer employing adenovirus vectors.

Lecithinized copper,zinc-superoxide dismutase as a protector against doxorubicin-induced cardiotoxicity in mice

Production of superoxide radicals from doxorubicin is widely accepted to be the cause of the cardiotoxicity induced by this antitumor agent. Pretreatment with superoxide dismutase could improve the therapeutic application. Aim of the present study was to determine whether lecithinized superoxide dismutase (PC-SOD) can serve as a cardioprotective drug during doxorubicin treatment. The protective potential of PC-SOD on doxorubicin-induced cardiotoxicity was investigated in BALB/c mice. The possible influence of PC-SOD on the antitumor activity of doxorubicin was investigated in vitro as well as in vivo. Mice were treated intravenously with doxorubicin (4 mg x kg(-1)) or doxorubicin and PC-SOD (5000, 20000 or 80000 U x kg(-1)) weekly x 6 and appropriate controls were included. Cardiotoxicity was monitored for 8 weeks by ECG measurement. The influence of PC-SOD on the antitumor activity of doxorubicin was evaluated in three human malignant cell lines. Nude mice bearing OVCAR-3 human ovarian cancer xenografts were treated intravenously with doxorubicin (8 mg x kg(-1)) alone or preceded by PC-SOD 20000 or 80000 U x kg(-1) weekly x 2 and appropriate controls were included. PC-SOD prevented doxorubicin-induced cardiotoxicity already at 5000 U x kg(-1) whereas 20000 and 80000 U x kg(-1) were equally protective. No toxicity was observed in mice treated with PC-SOD. PC-SOD did not interfere with the antiproliferative effects of doxorubicin in vitro. In vivo, PC-SOD had no negative effect on the inhibition of xenograft growth induced by doxorubicin. It can be concluded that PC-SOD protects the heart, but not the tumor against doxorubicin. These data suggest that PC-SOD may be a suitable cardioprotector during doxorubicin treatment.

Benefits and risks of deferiprone in iron overload in Thalassaemia and other conditions: comparison of epidemiological and therapeutic aspects with deferoxamine

Deferiprone is the only orally active iron-chelating drug to be used therapeutically in conditions of transfusional iron overload. It is an orphan drug designed and developed primarily by academic initiatives for the treatment of iron overload in thalassaemia, which is endemic in the Mediterranean, Middle East and South East Asia and is considered an orphan disease in the European Union and North America. Deferiprone has been used in several other iron or other metal imbalance conditions and has prospects of wider clinical applications. Deferiprone has high affinity for iron and interacts with almost all the iron pools at the molecular, cellular, tissue and organ levels. Doses of 50-120 mg/kg/day appear to be effective in bringing patients to negative iron balance. It increases urinary iron excretion, which mainly depends on the iron load of patients and the dose of the drug. It decreases serum ferritin levels and reduces the liver and heart iron content in the majority of chronically transfused iron loaded patients at doses >80 mg/kg/day. It is metabolised to a glucuronide conjugate and cleared through the urine in the metabolised and a non-metabolised form, usually of a 3 deferiprone: 1 iron complex, which gives the characteristic red colour urine. Peak serum levels of deferiprone are observed within 1 hour of its oral administration and clearance from blood is within 6 hours. There is variation among patients in iron excretion, the metabolism and pharmacokinetics of deferiprone. Deferiprone has been used in more than 7500 patients aged from 2-85 years in >50 countries, in some cases daily for >14 years. All the adverse effects of deferiprone are considered reversible, controllable and manageable. These include agranulocytosis with frequency of about 0.6%, neutropenia 6%, musculoskeletal and joint pains 15%, gastrointestinal complains 6% and zinc deficiency 1%. Discontinuation of the drug is recommended for patients developing agranulocytosis. Deferiprone is of similar therapeutic index to subcutaneous deferoxamine but is more effective in iron removal from the heart, which is the target organ of iron toxicity and mortality in iron-loaded thalassaemia patients. Deferiprone is much less expensive to produce than deferoxamine. Combination therapy of deferoxamine and deferiprone has been used in patients not complying with subcutaneous deferoxamine or experiencing toxicity or not excreting sufficient amounts of iron with use of either drug alone. New oral iron-chelating drugs are being developed, but even if successful these are likely to be more expensive than deferiprone and are not likely to become available in the next 5-8 years. About 25% of treated thalassaemia patients in Europe and more than 50% in India are using deferiprone. For most thalassaemia patients worldwide who are not at present receiving any form of chelation therapy the choice is between deferiprone and fatal iron toxicity.

The protective effect of cardiac gene transfer of CuZn-sod in comparison with the cardioprotector monohydroxyethylrutoside against doxorubicin-induced cardiotoxicity in cultured cells

Doxorubicin-induced cardiotoxicity is related to its production of free radicals that specifically affect heart tissue because of its low antioxidant status. Monohydroxyethylrutoside (monoHER), a potent antioxidant flavonoid, is under development as a protector against doxorubicin-induced cardiotoxicity. The overexpression of high levels of superoxide dismutase (sod) protects against free radical damage in transgenic mice. Seeking alternatives besides the few cardioprotectors that are presently under investigation, the aim of the present study was to investigate the protective effect of cardiac gene transfer of CuZn-sod compared with that of the presently most promising cardioprotector monoHER against doxorubicin-induced cardiotoxic effects on neonatal rat cardiac myocytes (NeRCaMs) in vitro. NeRCaMs were infected with different multiplicity of infections (MOIs) of adenovirus encoding CuZn-sod (AdCuZn-sod). A control infection with an adenovirus vector encoding a nonrelated protein was included. The overexpression of CuZn-sod was characterized within 3 days postinfection. For doxorubicin treatment, NeRCaMs were divided into three groups. The first group was infected with AdCuZn-sod before treatment with doxorubicin (0-50 microM). The second and third groups were treated with doxorubicin (0-50 microM) alone and with 1 mM monoHER, respectively. The LDH release and survival of treated cells were measured 24 and 48 hours after doxorubicin treatment. The beating rate was followed during the 3 days after doxorubicin (0-100 microM) treatment. At the third day after infection with an MOI of 25 plaque-forming unit (PFU) of AdCuZn-sod/cell, the activity of CuZn-sod significantly increased (five-fold, P=.029). Higher MOI produced cytopathic effects (CPEs). Doxorubicin alone produced significant concentration- and time-dependent reduction in NeRCaMs beating rate and survival (P < .0005). Doxorubicin (> or =50 microM)-treated cells ceased to beat after 24 hours. This cytotoxicity was associated with an increase in the LDH release from the treated cells (P <.0005). The five-fold increase in the activity of CuZn-sod did not protect against any of the cytotoxic effects of doxorubicin on NeRCaMs. In contrast, monoHER (1 mM) protected against the lethal effects of doxorubicin on the survival, LDH release and the beating rate of NeRCaMs (P <.004) during 48 hours after doxorubicin treatment. Doxorubicin-treated (< or =100 microM) cells continued beating for >72 hours in the presence of monoHER. The present study showed the lack of adenoviral CuZn-sod gene-transfer to protect myocardiocytes against doxorubicin-induced toxicity and confirms the efficacy of monoHER cardioprotection. Thus, a gene-therapy strategy involving overexpression of CuZn-sod to protect against doxorubicin-induced cardiotoxicity is not feasible with the currently available adenovirus vectors.

Melatonin as an effective protector against doxorubicin-induced cardiotoxicity

The present study was designed to explore the protective effects of melatonin and its analogs, 6-hydroxymelatonin and 8-methoxy-2-propionamidotetralin, on the survival of doxorubicin-treated mice and on doxorubicin-induced cardiac dysfunction, ultrastructural alterations, and apoptosis in mouse hearts. Whereas 60% of the mice treated with doxorubicin (25 mg/kg ip) died in 5 days, almost all the doxorubicin-treated mice survived when melatonin or 6-hydroxymelatonin (10 mg/l) was administered in their drinking water. Perfusion of mouse hearts with 5 microM doxorubicin for 60 min led to a 50% suppression of heart rate x left ventricular developed pressure and a 50% reduction of coronary flow. Exposure of hearts to 1 microM melatonin or 6-hydroxymelatonin reversed doxorubicin-induced cardiac dysfunction. 8-Methoxy-2-propionamidotetralin had no protective effects on animal survival and on in vitro cardiac function. Infusion of melatonin or 6-hydroxymelatonin (2.5 microg/h) significantly attenuated doxorubicin-induced cardiac dysfunction, ultrastructural alterations, and apoptosis in mouse hearts. Neither melatonin nor 6-hydroxymelatonin compromised the antitumor activity of doxorubicin in cultured PC-3 cells. These results suggest that melatonin protect against doxorubicin-induced cardiotoxicity without interfering with its antitumor effect.

Cytoprotection in the treatment of pediatric cancer: review of current strategies in adults and their application to children

BACKGROUND

The protection of patients from the acute and/or chronic toxicity of antineoplastic therapy has become a major concern of oncology centers around the world. However, most of the effort has been directed toward the adult population, and limited studies have been performed in the group that may gain the most from such strategies, namely, children.

PROCEDURES

The MedLine and CancerLit databases were surveyed, and the relevant biomedical literature on cytoprotection during antineoplastic treatment was analyzed.

RESULTS

Cytotoxicity from antineoplastic therapy customarily is addressed by altering dosing schedules, a technique that can seriously impact the efficacy of the therapy. Colony stimulating factors have been used posttherapy to stimulate recovery from neutropenia, and various agents have been proposed as pretherapy cytoprotectors. Trials in adults have produced mixed results, and, to date, only amifostine and dexrazoxane have been approved as cytoprotectors for very narrow indications. Few trials have been performed in children, although these patients often can look forward to long-term remission.

CONCLUSIONS

To prevent permanent toxicities from antineoplastic therapies that impact long-term pediatric survivors, the experience gained in adults should be extended more aggressively to children, and formal, randomized trials should be performed to determine the type of protection most suitable for the pediatric population.

Comparative open, randomized, cross-over bioequivalence study of two intravenous dexrazoxane formulations (Cardioxane and ICRF-187) in patients with advanced breast cancer, treated with 5-fluorouracil-doxorubicin-cyclophosphamide (FDC)

The purpose of this study was to compare the pharmacokinetic disposition of two intravenous dexrazoxane formulations, and their effects on doxorubicin's kinetics and metabolism. Plasma concentration versus time curves and pharmacokinetic parameters of dexrazoxane given as Cardioxane (dexrazoxane hydrochloride salt) and ICRF-187 reference formulation (dexrazoxane base) were determined and compared. Both formulations were administered as a single intravenous infusion prior to 5-fluorouracil-doxorubicin-cyclophosphamide administration. In addition, the pharmacokinetics of doxorubicin and its metabolites were studied after dexrazoxane administration. A total of 15 patients with advanced breast cancer participated in this open, randomized, cross-over study and 12 patients were evaluable. Plasma concentrations of dexrazoxane, doxorubicin and doxorubicin metabolites were determined by high-performance liquid chromatography in samples obtained in the 72 h after drug administration. No statistically significant differences were found in the tested kinetic parameters when the two products were compared by analysis of variance (ANOVA) on log-transformed data. Cardioxane fulfilled the bioequivalence criteria when compared with ICRF-187 reference formulation for all of the investigated parameters (AUC, t1/2beta, Vdss, Cl(tot), Cl(ren)). The parametric 90% confidence intervals were contained within the bioequivalence interval (0.8-1.25). Pharmacokinetic parameters and metabolism of doxorubicin were not different after the administration of either Cardioxane or ICRF-187 formulation. From the results of this study it can be concluded that the two formulations can be considered bioequivalent with regard to extent of absorption (AUC and Vdss) and elimination (t1/2beta, Cl(tot) and Cl(ren)).

Dexrazoxane: A New Cardioprotective Agent

Objective:

To review the literature discussing the use of dexrazoxane (e.g., Zinecard, ICRF-187) to prevent doxorubicin-induced cardiotoxicity.

Data Sources:

Pertinent English-language reports of studies in humans were retrieved from a MEDLINE search (January 1980-January 1997); search terms included chelating agents, razoxane, dexrazoxane, Zinecard, ICRF-187, ADR-529, and ICRF-159.

Study Selection:

Representative articles discussing the chemistry, pharmacology, pharmacokinetics, dosing, and administration of dexrazoxane and those discussing clinical trials were selected.

Data Extraction:

Data were extracted and analyzed if the information was relevant and consistent. Studies were selected for review in the text on the basis of study design and clinical end points.

Data Synthesis:

Dexrazoxane is a chemoprotective agent developed to prevent cardiac tissue toxicity. Dexrazoxane exerts a cardioprotective effect with some clinically significant toxicities; it may also interfere with the antitumor activity of doxorubicin. Until there are sufficient data to support its use in first-line supportive care therapy, dexrazoxane should be reserved for use in patients responding to doxorubicin-based chemotherapy but who have risk factors for cardiac toxicity or have received a cumulative doxorubicin bolus dose of 300 mg/m2.

Conclusions:

The management of doxorubicin-induced cardiotoxicity has led to the development of supportive care drugs that specifically counteract the dose-limiting toxicities. Dexrazoxane may not completely eliminate the concern about doxorubicin-induced cardiotoxicity, but it may open new avenues for continuing doxorubicin-based chemotherapy.

Anthracyclines in haematology: pharmacokinetics and clinical studies

The activity of anthracyclines in the treatment of a wide spectrum of haematological malignancies has long been established. Differences in the pharmacokinetic and pharmacodynamic properties of these drugs have resulted in the selection of individual compounds for particular indications while the recent reformulation of anthracyclines in liposomal preparations seems likely to significantly alter their range of activity and toxicity. The problems related to cumulative cardiotoxicity secondary to anthracycline exposure can be ameliorated by the use of dexrazoxane and a number of agents may prove to have a role in altering their cellular resistance to their cytotoxic actions.

Anthracyclines in haematology: preclinical studies, toxicity and delivery systems

The anthracyclines are widely used in the treatment of haematological and non-haematological malignancy and there is now more than 30 years' clinical experience with these agents but despite this, their mechanism of action is incompletely understood. The anthracyclines have been shown to intercalate with DNA and indirectly inhibit the activity of the enzyme topoisomerase II, resulting in DNA strand breaks. More recently, workers have focused on induction of apoptosis and have shown that daunorubicin stimulates production of the apoptotic mediator, ceramide and that the activity of doxorubicin can be blocked by inhibitors of CD95 (fas). One of the major problems with anthracycline therapy is the development of resistance which may be mediated by p-glycoprotein or by other mechanisms. Much recent research has concentrated on methods to modulate the drug-resistant phenotype and these include development of new analogues and use of specific reversal agents. The toxicity profile of the anthracyclines includes bone marrow suppression, severe local reaction following extravasation, radiation recall, alopecia, gastrointestinal and hepatic effects, development of secondary malignancies and significant cardiac toxicity. The risk factors for the development of anthracycline-related cardiac toxicity are well documented and several methods have been exploited in attempts at prevention. Finally, a number of drug delivery systems have been developed in order to improve therapeutic response and reduce toxicity to normal tissues, including the use of liposomal preparations.

Modulation of transferrin receptor expression by dexrazoxane (ICRF-187) via activation of iron regulatory protein

Dexrazoxane (ICRF-187) has recently been demonstrated to reduce cardiac toxicity induced by chemotherapy with anthracyclines, although the reason for this phenomenon has remained obscure thus far. In order to investigate whether ICRF-187 might exert its effects by modulating iron metabolism, we studied the drug's potential to influence the maintenance of iron homeostasis in two human cell lines. We demonstrate that ICRF-187 enhanced the binding affinity of iron regulatory protein (IRP), the central regulatory factor for posttranscriptional iron regulation, to RNA stem loop structures, called iron responsive elements (IRE), in THP-1 myelomonocytic as well as K562 erythroleukemic cells. Increased IRE/IRP interaction was paralleled by an elevation of transferrin receptor (trf-rec) mRNA levels which, according to the well-established mechanism of posttranscriptional iron regulation, was likely due to stabilisation of trf-rec mRNA by IRP. Subsequently, ICRF-187 treatment of cells increased trf-rec surface expression and enhanced cellular iron uptake. All these events, i.e. IRP activation, stabilisation of trf-rec mRNA and increased surface expression of the protein in response to ICRF-187, follow a dose-response relationship. Increased cellular uptake and sequestration of iron in response to ICRF-187 may contribute to the protective activity of ICRF-187 by reducing the iron-anthracycline complex and iron-catalysed generation of hydroxyl radicals via the Haber-Weiss reaction.

A QSAR study comparing the cytotoxicity and DNA topoisomerase II inhibitory effects of bisdioxopiperazine analogs of ICRF-187 (dexrazoxane)

A series of twelve structurally related bisdioxopiperazines that included ICRF-187 (dexrazoxane), ICRF-159 (razoxane), ICRF-193, and ICRF-154 were examined both for their ability to inhibit the growth of Chinese hamster ovary (CHO) cells and their ability to inhibit the catalytic activity of mammalian DNA topoisomerase II. The bisdioxopiperazines exhibited a wide range in both growth inhibitory effects (30,000-fold), and in their ability to inhibit the catalytic activity of topoisomerase II (150-fold). The cytotoxicity of the bisdioxopiperazines toward CHO cells was highly correlated (correlation coefficient r = 0.86, P = 0.0003) with their inhibition of the catalytic activity of DNA topoisomerase II. This result strongly suggests that DNA topoisomerase II is the functional target of the bisdioxopiperazines. The stereoisomers (+)-ICRF-187 and (-)-ICRF-186 were observed to be equally cytotoxic and equally inhibitory toward DNA topoisomerase II. This result indicates that the bisdioxopiperazine binding site on DNA topoisomerase II is large enough or flexible enough to accommodate either form of the drug. The strongly metal-ion binding fully rings-opened hydrolysis product of ICRF-187, ADR-925, demonstrated no measurable inhibitory activity toward DNA topoisomerase II or cytotoxicity toward CHO cells.

Monohydroxyethylrutoside as protector against chronic doxorubicin-induced cardiotoxicity

1. The clinical use of the antitumour agent, doxorubicin, is largely limited by the development of a cumulative dose-related cardiotoxicity. This toxicity is generally believed to be caused by the formation of oxygen free radicals. In earlier studies it was established that flavonoids, naturally occurring antioxidants, can provide some degree of protection. In this study we investigated whether 7-monohydroxyethylrutoside (monoHER), a powerful antioxidative flavonoid with extremely low toxicity, can provide protection to an extent comparable to the clinically successful Cardioxane (ICRF-187). 2. Balb/c mice of 20-25 g were equipped i.p. with a telemeter to measure ECG. They were given 6 i.v. doses of doxorubicin (4 mg kg-1) at weekly intervals. ICRF-187 (50 mg kg-1) or monoHER (500 mg kg-1) were administered i.p. 1 h before doxorubicin administration. In the 2 monoHER groups the treatment continued with either 1 or 4 additional injections per week. A saline and monoHER treated group served as controls. After these 6 weeks, they were observed for another 2 weeks. 3. At the end of this study (week 8) the ST interval had increased by 16.7 +/- 2.7 ms (mean +/- s.e. mean) in doxorubicin-treated mice. At that time, the ST interval had increased by only 1.8 +/- 0.9 ms in ICRF-187 co-mediated mice and in monoHER co-medicated mice by only 1.7 +/- 0.8 and 5.1 +/- 1.7 ms (5- and 2-day schedule, respectively, all P < 0.001 relative to doxorubicin and not significantly different from control). The ECG of the control animals did not change during the entire study. The QRS complex did not change in either group.4. It can be concluded that monoHER protects against doxorubicin-induced cardiotoxicity and merits further evaluation in this respect.

Iron: mammalian defense systems, mechanisms of disease, and chelation therapy approaches

During the past 6 decades, much attention has been devoted to understanding the uses, metabolism and hazards of iron in living systems. A great variety of heme and non-heme iron-containing enzymes have been characterized in nearly all forms of life. The existence of both ferrous and ferric ions in low- and high-spin configuration, as well as the ability of the metal to function over a wide range of redox potentials, contributes to its unique versatility. Not surprisingly, the singular attributes of iron that permit it to be so useful to life likewise render the metal dangerous to manipulate and to sequester. All vertebrate animals are prone to tissue damage from exposure to excess iron. In order to protect them from this threat, a complex system has evolved to contain and detoxify this metal. This is known as the iron withholding defense system, which mainly serves to scavenge toxic quantities of iron and also for depriving microbial and neoplastic invaders of iron essential for their growth. Since 1970, medical scientists have become increasingly aware of the problems involved in cellular iron homeostasis and of the disease states related to its malfunctioning. Scores of studies have reported that excessive iron in specific tissue sites is associated with development of infection, neoplasia, cardiomyopathy, arthropathy and a variety of endocrine and neurologic deficits. Accordingly, several research groups have attempted to develop chemical agents that might prevent and even eliminate deposits of excess iron. A few of these drugs now are in clinical use, e.g. deferiprone (L1). In the present review, we focus on recent developments in (i) selected aspects of the iron withholding defense system, and (ii) pharmacologic methods that can assist the iron-burdened patient.

Metabolism of the cardioprotective agents dexrazoxane (ICRF-187) and levrazoxane (ICRF-186) by the isolated hepatocyte

1. The metabolism of dexrazoxane (ICRF-187) and its optical isomer levrazoxane (ICRF-186) by the isolated rat hepatocyte was studied by hplc. 2. 4-Chlorobenzenesulphonamide, which is a strong inhibitor of dihydropyrimidine amidohydrolase (DHPase), caused 82% inhibition of the loss of dexrazoxane from the hepatocyte suspension. 3. Dexrazoxane was metabolized at an initial rate by isolated hepatocytes that was 1.8 times faster than levrazoxane. This ratio is close to that found for purified DHPase, suggesting that DHPase present in the hepatocyte catalyses the ring-opening hydrolysis of these drugs. 4. The ratios of the rates at which each of the one-ring open intermediates of dexrazoxane and levrazoxane were produced in the hepatocyte suspension are also consistent with DHPase being primarily responsible for the metabolism of dexrazoxane and levrazoxane. 5. Thus, the DHPase-catalysed formation of the one-ring opened intermediates enhances the rate at which the presumably active metal-ion binding forms of dexrazoxane are produced in the hepatocyte. 6. The DHPase content of the hepatocyte was estimated to be 1.2 nmol/kg of total hepatocyte mass, or equivalently 5700 molecules of DHPase per hepatocyte.

The one-ring open hydrolysis product intermediates of the cardioprotective agent ICRF-187 (dexrazoxane) displace iron from iron-anthracycline complexes

The ability of the cardioprotective agent ICRF-187 (dexrazoxane), its one-ring open hydrolysis products, and its two-ring open hydrolysis product, ADR-925, to displace Fe3+ from its complex with doxorubicin, daunorubicin, epirubicin and idarubicin have been studied. At pH 7.4, ICRF-187 at a concentration of 100 microM ICRF-187 slowly but completely displaced Fe3+ from its anthracycline complexes with half-times ranging from 230 to 450 min. The one-ring open intermediate hydrolysis products were also shown to be chelating agents and were also able to displace quickly and completely Fe3+ from its anthracycline complexes with half-times ranging from 1.7 to 16.7 min. Molecular modeling of Fe3+ complexes with the one-ring open intermediates showed that these intermediates were likely acting as tetradentate ligands. Since these intermediates are such good chelating agents, they may also be pharmacologically active species in preventing oxygen-radical derived iron-based anthracycline-induced cardiotoxicity. Since these one-ring open intermediates are produced by hydrolysis from the parent ICRF-187 more quickly than is ADR-925, the formation of pharmacologically active species might be occurring more quickly than previously thought. The displacement of Fe3+ from its anthracycline complexes by the two-ring open hydrolysis product ADR-925 also took place quickly and completely with half-times ranging from 1 to 3 min.

Present status and future prospects of oral iron chelation therapy in thalassaemia and other diseases

In the last few years we have witnessed the emergence of oral chelation which is a new form of therapy for transfusional iron-loaded patients in thalassaemia and other refractory anaemias. The need for a cheap, non-toxic, orally effective iron chelator is paramount because it could potentially save the lives of many thousands of patients. At present, less than 10% of the patients requiring iron chelation therapy worldwide receive the widely used chelating drug desferrioxamine (DF) because of its high cost, oral inactivity and toxicity. The most promising oral iron chelator is 1, 2-dimethyl-3-hydroxypyrid-4-one (L1 or INN: Deferiprone), which has so far been taken by over 450 patients in 15 countries, and in some cases daily for over 4 years with very promising results. L1 was shown at 50-100 mg/kg/day to be effective in bringing patients to negative iron balance. It increases urinary iron excretion, decreases serum ferritin levels and reduces liver iron in multi-transfused iron-loaded patients. Toxic side effects were mainly encountered at high doses (80-100 mg/kg/day) and include transient agranulocytosis (5 cases), transient musculoskeletal and joint pains (10-20%), gastric intolerance (2-6%) and zinc deficiency (1%). The incidence of these toxic side effects was reduced by using lower doses of 50-75 mg/kg/day. The overall efficacy and toxicity of L1 is comparable to that of DF in animals and humans. Further work is required for identifying susceptible individuals to L1 toxicity, and also optimum dose protocols of L1 which can maximise iron excretion and minimise the incidence of toxic side effects.

The removal of metal ions from transferrin, ferritin and ceruloplasmin by the cardioprotective agent ICRF-187 [(+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane] and its hydrolysis product ADR-925

The ability of the metal ion binding rings-opened hydrolysis product of the anthracycline cardioprotective agent ICRF-187 [dexrazoxane; (+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane] to remove iron from transferrin and ferritin, and copper from ceruloplasmin was examined. ADR-925 completely removed Fe3+ from transferrin at below physiological pH but was unreactive at pH 7.4. ADR-925 slowly removed copper from ceruloplasmin at physiological pH (68% removal after 4.8 days). ADR-925 was capable of removing 18% of the iron from ferritin in 7.0 days. All of the metalloproteins displayed saturation behavior in their initial rates of metal ion removal by ADR-925. ICRF-187 may be, in part, preventing doxorubicin-induced cardiotoxicity by depleting iron and copper from these storage and transport proteins or by scavenging metal ions released from these proteins, thus inhibiting hydroxyl radical production by iron-doxorubicin complexes.

Systemic therapy of advanced breast cancer

Many cytotoxic agents have demonstrated activity in advanced breast cancer, the more active agents being cyclophosphamide and the anthracyclines doxorubicin and epirubicin. Combinations of drugs are generally superior to single agents in terms of response rate, duration of response and survival. The treatment of advanced breast cancer can be continued either until treatment failure, or for a limited time from either initiation of therapy or from the observation of complete response. Although these are issues of significant concern, data from randomised trials are limited, and so the question of optimal treatment duration remains open. Randomised trials comparing regimens that differ by a dose intensity factor of less than 2 have failed to demonstrate significant differences in efficacy between the dose levels. With higher doses, as applied in combination with colony-stimulating factors and bone marrow transplantation, response rates seem to increase, but whether this translates into improved survival has not yet been answered by the results of randomised trials. Approximately 30% of patients respond to endocrine therapy. From the results of randomised trials, which have compared the efficacies and toxicities of different endocrine modalities including combined endocrine therapy, single-agent tamoxifen is generally considered as the preferred first-line treatment, leaving progestins and aromatase inhibitors as alternatives for second-line endocrine therapy in responders. In the majority of trials, chemotherapy combined with endocrine therapy has given improved response rates compared with chemotherapy alone, but the differences have not generally been translated into prolonged survival with combined modalities. This gives rise to the question of the optimal sequence of chemotherapy and endocrine therapy, a subject needing further evaluation in future trials.