Protective effect of the bispiperazinedione ICRF-187 against doxorubicin-induced cardiac toxicity in women with advanced breast cancer

Non-Hodgkin's Lymphoma in the Elderly

BACKGROUND: The incidence of non-Hodgkin's lymphoma in the elderly continues to increase. There has been a tendency among some treating physicians to minimize appropriate workup and treatment, which may product a negative effect on outcomes. METHODS: Several characteristics of non-Hodgkin's lymphoma in the elderly are reviewed, including classification and staging, pathophysiology, clinical presentation, and treatment strategies. RESULTS: The Working Formulation remains the principal classification used. In order and younger individuals, the prevalence of histologic subtypes and the stage at presentation are similar. Regardless of the regimen chosen, doxorubicin or mitoxantrone should be included if optimal responses are to be obtained. New purine analogs extend the therapeutic armamentarium. CONCLUSIONS: Advanced age and comorbidities can impair the capability for treatments to control non-Hodgkin's lymphoma. To enhance results, more studies that focus on the elderly are needed on drug combinations and the new purine analogs.

Development of the model of rat isolated perfused heart for the evaluation of anthracycline cardiotoxicity and its circumvention

1. In order to develop a predictive model for the preclinical evaluation of anthracycline cardiotoxicity and the means of preventing it, we have studied the functional parameters of perfused hearts isolated from rats receiving repeated doses of several anthracyclines. 2. The anthracyclines studied were doxorubicin, epirubicin, pirarubicin and daunorubicin, and we also studied a liposomal formulation of daunorubicin (DaunoXome) and the co-administration of dexrazoxane (ICRF-187) and doxorubicin. 3. Anthracyclines were administered i.p. at equimolar doses corresponding to 3 mg kg-1 per injection of doxorubicin, every other day for a total of six doses. Dexrazoxane was used at the dose of 30 mg kg-1 per injection and was administered either 30 min before or 30 min after doxorubicin. We evaluated any general toxicity towards the animals as well as alterations of left ventricular contractility and relaxation ex vivo. 4. Epirubicin and daunorubicin were significantly less cardiotoxic than doxorubicin, and neither pirarubicin nor DaunoXome caused significant alterations in cardiac function. There was a direct relationship between the decrease in cardiac contractility or relaxation and anthracycline accumulation in the heart, evaluated after the same treatment schedule. 5. Dexrazoxane induced a significant protection against doxorubicin-induced cardiac toxicity when administered 30 min before doxorubicin, whereas this protection was ineffective when administered 30 min after doxorubicin. Direct perfusion of DaunoXome in isolated hearts of untreated animals resulted in a 12-fold reduction of the accumulation of daunorubicin in heart tissue as compared to the perfusion of free daunorubicin, and did not cause alterations in cardiac function at a dosage for which free daunorubicin induced major alterations. 6. The isolated perfused rat heart appears to be a valuable model for screening of new anthracyclines and of strategies for circumventing anthracycline cardiotoxicity.

Pharmacology of N,N-di(n-butyl)adriamycin-14-valerate in the rat

Lipophilic N-alkylanthracyclines such as AD 198 (N-benzyladriamycin-14-valerate) or AD 201 [N,N-di(n-propyl)adriamycin-14-valerate], which exert their cytotoxicity through mechanisms which are not yet fully defined, possess inherent abilities to circumvent multidrug resistance in vitro and in vivo, possibly though alterations in normal intracellular drug trafficking. As part of structure-activity studies with this class of agent, we have now examined the pharmacology of AD 202 [N,N-di(n-butyl)adriamycin-14-valerate], another analog possessing superior antitumor activity to doxorubicin in vivo and an ability to circumvent multidrug resistance in vitro. Following the administration of AD 202 (20 mg/kg, i.v.) to anesthetized rats, rapid drug distribution (T1/2 5 min) was followed by more gradual elimination (T1/2 3.6h). Plasma clearance of AD 202 (224 +/- 63.6 ml/min per kg) and steady state volume of distribution (25.7 +/- 11.1 l/kg) were indicative of extensive tissue sequestration and/or a large degree of extra-hepatic metabolism. The parent drug predominated in plasma until 20 min, thereafter N,N-di(n-butyl)adriamycin became the principal circulating anthracycline. The systemic exposure to this biotransformation product (area under the plasma concentration-time curve from time zero to 480 min AUC(0-480) 28 1672 ng.min/ml) was > tenfold higher than for the other detected plasma products (N-butyladriamycin-14-valerate, N-butyladriamycin, and three unidentified fluorescent signals; P1-3). Total urinary elimination over 8h was limited (1.9% of dose), occurring predominantly as N,N-di(n-butyl)adriamycin (1.2% of dose), N-butyladriamycin (0.4% of dose), and their corresponding 13-carbinol metabolites (<0.1% of dose each). Low levels of adriamycin (ADR), aglycones and two unidentified products were also seen. Parental AD 202 was found in urine only up to 1h. By contrast, hepatic elimination of parent drug was seen, albeit at low levels, through 8h. Excretion by this route (22% of dose) occurred principally as N-butyl-adriamycin (8% of dose), N-butyladraimycinol (2.1% of dose) with lower levels of N,N-di(n-butyl)adriamycin (1.6% of dose), N,N-di(n-butyl)adriamycin (0.8% of dose), and aglycones (4.3% of dose, combined). Other products included ADR (1.1% of dose) and two unidentified signals (3.4% of dose, combined). The relatively poor mass balance in these studies is attributed to prolonged intracellular retention (elimination T1/2 24.2h) of N,N-di(n-butyl)adriamycin. Thus, in common with other N-alkylanthracyclines, the pharmacology of AD 202 is complex but its therapeutic properties clearly are not derived from an ADR prodrug effect. Significant differences continue to be noted as to the metabolic fate of congeners of this class of anthracycline analogs.

Role of 'catalytic' iron in an animal model of minimal change nephrotic syndrome

Treatment of minimal change disease, like most glomerulonephritides, is empirical because underlying mechanisms that cause glomerular injury are not known. We examined a pathogenic role of 'catalytic' iron in a model of minimal change nephrotic syndrome induced by injection of puromycin aminonucleoside (7.5 mg/100 g body wt) to rats. Although there was no significant change in non-heme iron content in glomeruli, the bleomycin-detectable iron (capable of catalyzing free radical reactions) was markedly increased in glomeruli from nephrotic rats when compared to control. In contrast, despite a marked and significant increase in the non-heme iron content in tubules, there was no significant change in the bleomycin-detectable iron in tubules from nephrotic rats. In a separate in vivo study, the iron chelator, deferoxamine, prevented the increase in the bleomycin-detectable iron in glomeruli and provided complete protection against proteinuria. Taken together, our data suggest an important pathogenetic role for glomerular catalytic iron in the puromycin aminonucleoside-induced minimal change nephrotic syndrome.

Cardioprotection of rat heart myocytes with amifostine (Ethyol) and its free thiol, WR-1065, in vitro

Cultured neonatal rat heart myocytes form a synchronously-contracting cell syncytium from one to two days after isolation, plating on plastic and incubation at 37 degrees C. On day 3 after plating, myocytes were exposed to the anthracycline doxorubicin, 0.1-10 micrograms/ml, for 1 h with or without a 15-min pretreatment with the thiophosphate compound amifostine (WR-2721, Ethyol) or its dephosphorylated metabolite, WR-1065. The concentration of each WR-compound was limited to 2 micrograms/ml or 10% of the maximal achievable plasma concentration of amifostine after an intravenous dose of 740 mg/m2. Both amifostine and the free thiol significantly reduced doxorubicin-induced heart-cell toxicity, measured by adenosine triphosphate content normalised to total cellular protein. A concurrent 1-h exposure to these compounds and doxorubicin was also cardioprotective, but neither compound was effective when administered after doxorubicin. Although both amifostine and WR-1065 were approximately equipotent in preventing doxorubicin-induced cardiotoxicity, only amifostine significantly increased glutathione levels in the myocytes. These results complement prior in vitro and in vivo studies in rodents showing cardioprotectant activity for amifostine and its free thiol, WR-1065, when administered prior to doxurubicin.

[Pediatric aspects of anthracycline cardiotoxicity and practical implications for prevention]

Discovered during the sixties, anthracycline antibiotics are today widely used anti-cancer drugs. Their potentially fatal cardiac toxicity, which is related in part to the total cumulative dose, has been described since 1967. The aim of this paper is to describe their biological and clinical toxic effects on the heart, especially of children, and to propose prevention guidelines. The mechanisms of cardiac toxicity, with their destructive consequences on functional myocytes reserve, are shortly recalled. Acute, sub-acute and chronic clinical aspects of anthracycline's cardiomyopathy are the subject of a literature review. In Pediatric Oncology, the prolonged survival usually observed allows delayed congestive heart failure to occur by myocardial reserve insufficiency, as hemodynamic needs are quickly increasing, especially at the end of the somatic growth. Furthermore, the frequency of cardiac abnormalities is increasing with time after therapy, reaching about half of the explored patients after 15 years. The main known methods to prevent such a toxicity are reviewed. The parcimonious use of anthracyclines is already seen in children. Every method to decrease the maximal plasma concentration of the drug (weekly schedule or prolonged infusion) has to be considered. The active cardioprotectant agent such as ICRF-187, is in clinical development. Detection, prevention, and therapy of cardiac abnormalities, which are likely to precede delayed heart failure, still remains a difficult problem in these more and more numerous children to be cured of cancer.

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.

Effects of pharmacological interventions on emetine cardiotoxicity in isolated perfused rat hearts

The cardiotoxicity of emetine continues to be a significant clinical problem. The purpose of this study was to investigate the effect of several mechanistic interventions, including ICRF-187, an iron-chelating agent which protects against doxorubicin toxicity, atropine, and fructose-1,6-bisphosphate (FBP) on the toxicity of emetine in our isolated, perfused rat heart model. The model includes functional, electrocardiographic, and biochemical determinations in the same preparation. Atropine and ICRF-187 had no effect on the time needed for emetine to induce ventricular asystole, while FBP significantly increased this time. Administration of 47 microM atropine, 300 microM FBP, or 1 mM FBP decreased the release of lactate dehydrogenase (LDH) into the coronary effluent, while ICRF-187 had no effect. These pharmacological interventions variably changed the amplitude of the biphasic response of the coronary flow to emetine. Finally, FBP was very effective in slowing the rate of QRS-waveform degeneration in the perfused hearts. Emetine caused PR- and QRS-prolongation which was not altered by FBP.

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.

Modulation of the in vitro cardiotoxicity of doxorubicin by flavonoids

Cancer therapy with the anthracycline doxorubicin (Dox) is limited by cardiomyopathy, which develops in animals and patients after cumulative dosing. Generation of free radicals by Dox may be involved in this cardiotoxicity. Dox binds strongly to metal ions, especially iron(III). This Dox-metal complex stimulates the generation of free radicals through self-reduction of the complex. We investigated the possibility of inhibiting Dox-induced cardiotoxicity by scavenging of free radicals and/or chelating metal ions. The effects of Dox, both alone and in combination with iron-chelating agents, were studied on inotropy of the isolated mouse left atrium, lipid peroxidation (LPO) in cardiac microsomal membranes, ferricytochrome c (cyt.c3+) reduction, and oxygen consumption. The flavonoids 7-monohydroxyethylrutoside (mono-HER) and 7,3',4'-trihydroxyethylrutoside (tri-HER) and the ethylenediaminetetraacetic acid (EDTA) analogue ICRF-198 and its precursor ICRF-187 were used as iron-chelating agents. The latter were used for comparison since ICRF-187 has been reported to inhibit the cardiotoxic effects of Dox both in vitro and in vivo. Only the flavonoids could inhibit the negative inotropic effect of Dox (35 microM) on the mouse left atrium; in the presence of tri-HER (500 microM) the beating force decreased by 18% instead of 50%, whereas mono-HER completely prevented the Dox-induced negative inotropic effect. ICRF-198 and both flavonoids (500 microM) completely inhibited Dox (35 microM)-induced LPO, whereas ICRF-187 provided 65% inhibition. The observation that both cyt.c3+ reduction and oxygen consumption induced by the Dox-iron(III) complex (50/16.6 microM Dox3Fe3+) could be inhibited by superoxide dismutase proved the involvement of superoxide anions (O2-.). The iron-chelating agents (50 microM) inhibited cyt.c3+ reduction by 91% (mono-HER), 43% (tri-HER), and 100% (ICRF-198). Only mono-HER and ICRF-198 (50 microM) were capable of inhibiting the oxygen consumption by 70% and 43%, respectively. It is concluded that flavonoids offer a good perspective for further studies on the prevention of Dox-induced cardiomyopathy.

Control of disease by selective iron depletion: a novel therapeutic strategy utilizing iron chelators

Recognition of the central role of iron in the generation of toxic, oxygen-derived species through the Haber-Weiss reaction, the ability of desferrioxamine (DFX) to prevent the damage associated with free radical generation in reperfusion injury, and its inhibitory effect on cell proliferation by inactivation of the iron dependent enzyme ribonucleotide reductase, resulted in an increasing number of studies exploring the novel therapeutic applications of iron chelating drugs: (a) Animal models of reperfusion injury have shown that DFX is able to decrease post-anoxic damage to the brain and heart as manifested in decreased infarct size and improved functional recovery. Iron chelators may be particularly useful in improving the preservation of organs intended for transplantation such as the heart, lung or kidney. (b) Anthracycline cardiotoxicity is aggravated by iron and inhibited by iron chelators. Because the mechanism of its antineoplastic effect differs from its cardiotoxic effect, it is possible to inhibit anthracycline cardiotoxicity without interfering with therapeutic efficacy. In vivo and in vitro animal studies have yielded encouraging results but much additional experimental work is still required before iron chelating therapy may be advocated for use in patients on anthracycline therapy. (c) Cell proliferation can be inhibited by iron chelators through the reversible inhibition of ribonucleotide reductase, a rate-limiting enzyme in DNA synthesis. This may be exploited for the treatment of malignant disease, and preliminary studies have already shown that DFX in combination with multidrug chemotherapy is effective in controlling neuroblastoma and other tumours. However, the contribution of DF to the overall clinical effect is unclear. Prospective controlled clinical studies are required in order to establish whether the antiproliferative, or cell synchronizing properties of DFX may be of practical usefulness in the control of malignant disease. (d) Control of protozoal infection: Experimental in vivo and in vitro models have shown that malarial infection may be inhibited by iron chelating therapy. This useful effect of DFX and other iron chelators is most probably related to ribonucleotide reductase inhibition. Clinical studies of asymptomatic P. falciparum malaria and of cerebral malaria have shown both an accelerated rate of parasite clearance and earlier recovery from coma. These observations lend new meaning to the term 'nutritional immunity' and open new channels for exploring the possibility of controlling infection by means of selective intracellular iron deprivation. Experimental models for studying the effect of iron chelators on other intracellular pathogens such as Toxoplasma gondii, Chlamydia psittaci, or Mycobacterium tuberculosis should be established.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytoprotection: concepts and challenges

Clinical trials with several toxicity protectors (cytoprotective or chemoprotective agents) have been performed during the past decade. These trials are quite complex since they must include sufficient dose-limiting events for study, and assessment of both toxicity (and therefore the efficacy of protection) and antitumor effects must be carried out. However, it is inevitable that with greater understanding of drug actions, one seeks to manipulate these for greater antitumor activity (biochemical modulation) or for lesser dose-limiting toxicity (cytoprotection) or for both. Examples of cytoprotective agents include dexrazoxane (ICRF-187), protecting against doxorubicin cardiotoxicity, and amifostine protecting against the myelosuppression of platinum and alkylating agents. In spite of the challenges encountered in the clinical development of these drugs, studies of cytoprotectors have led to a considerable understanding of important therapeutic issues and tangible clinical benefit in specific clinical situations.

Free radical inactivation of rabbit muscle creatinine kinase: catalysis by physiological and hydrolyzed ICRF-187 (ICRF-198) iron chelates

Creatine kinase is a sulfhydryl containing enzyme that is particularly susceptible to oxidative inactivation. This enzyme is potentially vulnerable to inactivation under conditions when it would be used as a diagnostic marker of tissue damage such as during cardiac ischemia/reperfusion or other oxidative tissue injury. Oxidative stress in tissues can induce the release of iron from its storage proteins, making it an available catalyst for free radical reactions. Although creatinine kinase inactivation in a heart reperfusion model has been documented, the mechanism has not been fully described, particularly with regard to the role of iron. We have investigated the inactivation of rabbit muscle creatine kinase by hydrogen peroxide and by xanthine oxidase generated superoxide or Adriamycin radicals in the presence of iron catalysts. As shown previously, creatine kinase was inactivated by hydrogen peroxide. Ferrous iron enhanced the inactivation. In addition, micromolar levels of iron and iron chelates that were reduced and recycled by superoxide or Adriamycin radicals were effective catalysts of creatinine kinase inactivation. Of the physiological iron chelates studied, Fe(ATP) was an especially effective catalyst of inactivation by what appeared to be a site-localized reaction. Fe(ICRF-198), a non-physiological chelate of interest because of its putative role in alleviating Adriamycin-induced cardiotoxicity, also catalyzed the inactivation. Scavenger studies implicated hydroxyl radical as the oxidant involved in iron-dependent creatine kinase inactivation. Loss of protein thiols accompanied loss of creatine kinase activity. Reduced glutathione (GSH) provided marked protection from oxidative inactivation, suggesting that enzyme inactivation under physiological conditions would occur only after GSH depletion.

Aggressive management of doxorubicin-induced cardiomyopathy associated with 'low' doses of doxorubicin

There is a dose-effect relationship between doxorubicin and the incidence of symptomatic cardiac failure. It is generally thought that doses below 500-550 mg/m2 are safe but, when objective measures of cardiac function are used, it becomes apparent that degrees of cardiac failure occur at doses below this. We present here the case histories of two patients who developed very severe cardiac failure at cumulative doses well below 500 mg/m2 but who survived their initial cardiac illness due to aggressive intervention. In one case, the patient was successfully treated by orthotopic cardiac transplantation.

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.

Doxorubicin-induced cardiomyopathy

Doxorubicin (Adriamycin; Adria Laboratories, Columbus, OH) is one of the most effective chemotherapeutic agents used in the management of pediatric neoplastic disorders during the past 20 years. However, its use has been limited by well-characterized, dose-related cardiac toxicity. Recently, cardiac dysfunction has been noted in pediatric patients who had received doxorubicin years before. This article summarizes current information regarding the pathophysiology and risk factors associated with cardiotoxicity and reviews detection methods and treatments of this condition.

Effects of ICRF-186 [(L)1,2-bis(3,5-dioxopiperazinyl-1-yl)propane] on the toxicity of doxorubicin in spontaneously hypertensive rats

An evaluation was made of the protective effects of ICRF-186 [(L)1,2-bis(3,5-dioxopiperazinyl-l-yl)propane], the L-enantiomer of ICRF-187 [(D)1,2-bis(3,5-dioxopiperazinyl-l-yl)propane], against the cardiotoxicity and nephrotoxicity induced in spontaneously hypertensive rats (SHR) by doxorubicin. SHR were given doxorubicin (1 mg/kg, i.v.), once a week for 12 weeks. Group 1 (n = 10) received doxorubicin alone; Groups 2, 3 and 4 (each, n = 5) received ICRF-186, 25 mg/kg (group 2), 12.5 mg/kg (group 3) or 6.25 mg/kg (group 4), i.p., 30 min before each dose of doxorubicin. Two groups of control animals (each, n = 5) received 12 weekly i.p. injections of saline or 25 mg/kg ICRF-186. ICRF-186 provided significant protection, in a dose-dependent manner, against the cardiotoxicity and nephrotoxicity of doxorubicin and attenuated the increases in cardiac immune effector cells (interstitial dendritic cells, cytotoxic T-helper lymphocytes and macrophages) associated with this cardiotoxicity. The results of the study were compared with those obtained with ICRF-187 under identical experimental conditions. Analysis of the cardiomyopathy scores, nephropathy scores and counts of the numbers of immune effector cells in the heart showed that, at a dose of 25 mg/kg, ICRF-186 is a somewhat less effective protectant than ICRF-187. At a dose of 12.5 mg/kg, both compounds induced generally similar degrees of protection. At a dose of 6.25 mg/kg, both had comparable, but only minimal, protective effects.

Dexrazoxane in the prevention of doxorubicin-induced cardiotoxicity

OBJECTIVE

To review doxorubicin-induced cardiotoxicity and to evaluate the use of dexrazoxane in its prevention.

DATA SOURCES

All animal and human reports involving doxorubicin-induced cardiac adverse effects were searched using MEDLINE combined with a fan search of relevant papers.

DATA EXTRACTION

Animal, in vitro cellular, and human data are thoroughly reviewed with particular emphasis on doxorubicin-induced cardiotoxicity, including clinical manifestations, risk factors, and mechanisms of toxicity. The role of dexrazoxane in the prevention of doxorubicin-induced cardiotoxicity is reviewed, including mechanism of effect, animal data, and human trials.

DATA SYNTHESIS

Anthracyclines are associated with a cumulative, dose-dependent, irreversible cardiomyopathy that can lead to congestive heart failure and death. The incidence of cardiotoxicity rises sharply at a total lifetime dose of more than 550 mg/m2. Through its semiquinone metabolite, doxorubicin appears to generate superoxide anion and superhydroxide free radicals with iron as a cofactor. Because of poor myocardial concentrations of superoxide dismutase, catalase, and glutathione peroxidase, these free radicals cause extensive lipid peroxidation and mitochondrial destruction.

CONCLUSIONS

Dexrazoxane is hydrolyzed to its active form intracellularly and binds iron to prevent the formation of superhydroxide radicals, thus preventing mitochondrial destruction. The effect of dexrazoxane on the prevention of doxorubicin-induced cardiotoxicity is impressive in both animal and human studies. Further research is needed to clearly demonstrate the effect dexrazoxane has on the antitumor effects of combination chemotherapy while defining optimal dosing strategies to minimize myelosuppression and maximize cardioprotection.

Comparison of the protective effects of desferrioxamine and ICRF-187 against doxorubicin-induced toxicity in spontaneously hypertensive rats

Since the iron-mediated formation of free radicals is considered to be a critical factor in the pathogenesis of the toxicity of doxorubicin (DXR), comparisons were made of the protective effects of two iron chelators, ICRF-187 and desferrioxamine (DFO), against the chronic cardiac and renal toxicity induced by DXR in spontaneously hypertensive rats (SHR). Two preparations of DFO were studied: DFO mesylate (DFO-M) and a polymeric form (DFO-P) in which DFO is conjugated to hydroxyethyl starch. Groups of 5 SHR each were given 12 weekly i.v. injections of 1 mg/kg DXR either alone or 30 min after the i.p. injection of 25 mg/kg ICRF-187, 50 mg/kg DFO-M, 50 mg/kg DFO-P, or 100 mg/kg DFO-P. A semiquantitative assessment was made of the cardiomyopathy (Billingham scale) and nephropathy. Renal protection was minimal with DFO-M and moderate with ICRF-187 and both doses of DFO-P. There was no cardiac protection with DFO-M. Both doses of DFO-P provided similar but modest degrees of cardiac protection. DXR-induced mortality was not prevented by either preparation of DFO. ICRF-187 provided a higher degree of protection against the cardiotoxicity and the mortality induced by DXR. Since both DFO and ICRF-187 are highly efficient chelators of iron in vitro, the differences in their in vivo protective effects are thought to be related to their cellular uptake and intracellular distribution and to the relative availability of different intracellular iron pools to these agents.

The cardioprotector ADR-529 and high-dose epirubicin given in combination with cyclophosphamide, 5-fluorouracil, and tamoxifen: a phase I study in metastatic breast cancer

The purpose of this study was to determine the maximal tolerable dose (MTD) of epirubicin and ADR-529 given in combination with cyclophosphamide, 5-fluorouracil, and tamoxifen. A total of 64 breast cancer patients with locally advanced disease or a first metastatic event were included. Using fixed doses of cyclophosphamide, 5-fluorouracil, and tamoxifen, cohorts of ten patients were treated with escalating doses of epirubicin and ADR-529. With the use of protocol criteria specifying evaluation after the first course, the MTD was not reached. Dose reductions carried out due to hematologic toxicity during the first four courses made it impossible to escalate doses of epirubicin beyond 80 mg/m2 given together with ADR-529 600 mg/m2. The vascular toxicity of ADR-529 necessitated central venous access in a number of patients. For phase III evaluation of ADR-529 given together with cyclophosphamide, epirubicin, 5-fluorouracil, and tamoxifen (CEF/TAM) we recommend using epirubicin/ADR-529 at 60/600 mg/m2. Together with evaluation of the cardioprotective properties of ADR-529, we recommend evaluating the impact of ADR-529 on the efficacy of cytotoxic therapy and investigating further the toxicity of ADR-529.

Cardiac diastolic function in pediatric patients receiving doxorubicin

The purpose of the study was to compare systolic and diastolic function in pediatric patients treated with doxorubicin. Left ventricular function was evaluated in 61 children prior to and following chemotherapy. None had clinical evidence of cardiac decompensation prior to treatment. All received relatively low cumulative doses of doxorubicin; the majority received the drug by continuous infusion. Systolic function was estimated using fractional shortening; diastolic function was estimated using A wave velocity, E wave velocity, E to A ratio, and deceleration time. There was a small but significant decline in systolic cardiac function as estimated from changes in fractional shortening that could not be appreciated in any of the measured parameters of diastolic function. A variety of reasons that could be responsible for the absence of significant changes in diastolic function are discussed. For the present, estimations of systolic function are preferred over the studied parameters of diastolic function in the evaluation of cardiac status in pediatric patients receiving doxorubicin containing regimens.

Pharmacodynamics of the hydrolysis-activation of the cardioprotective agent (+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane

The hydrolysis of the cardioprotective agent ICRF-187 [(+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane] to its presumed active form under conditions of physiologic pH and temperature were followed by HPLC chromatography. Successful chromatography of all of the hydrolysis products required the use of EDTA in the aqueous eluant to prevent metals in the HPLC flow system from binding to the strongly metal ion-binding product ADR-925. The kinetics of the hydrolysis was followed to approximately 200 h. The ring closest to the methyl group on ICRF-187 was observed to open at about twice the rate of the other ring. This product accumulates in the reaction mixture not only because it is produced more quickly but also because it decays more slowly. ICRF-187 is lost from the reaction mixture with a half-life of 9.3 h, whereas the final hydrolysis product ADR-925 is produced with a half-life of 23.0 h. Rate constants for ring opening to one-ring and two-ring opened hydrolysis products were obtained with a reaction scheme that assumed parallel and consecutive first-order reactions for these steps.

The pharmacokinetics of high-dose epirubicin and of the cardioprotector ADR-529 given together with cyclophosphamide, 5-fluorouracil, and tamoxifen in metastatic breast-cancer patients

A high-pressure liquid chromatographic method for determination of the bisdioxopiperazine derivative ADR-529 (ICRF-187), a compound proven effective in protection against anthracycline-induced cardiotoxicity, has been developed. The limit of quantitation was 5 ng/ml using a narrow-bore 5-microns silica column and UV detection. The method was used for determination of pharmacokinetic profiles of ADR-529 after a 3-weekly i.v. administration of different doses of ADR-529 (600-1000 mg/m2) together with different doses of epirubicin (E, 60-100 mg/m2), fixed-dose cyclophosphamide (C, 600 mg/m2), fixed-dose 5-fluorouracil (F, 600 mg/m2), and daily administration of tamoxifen (T, 30 mg; CEF-T) in the treatment of patients with metastatic breast cancer. Pharmacokinetic parameters for epirubicin were also determined. The aim of the study was to determine (1) whether the pharmacokinetics of ADR-529 as part of a combination with CEF-T changes with increasing doses of ADR-529 and increasing doses of epirubicin and (2) whether the pharmacokinetics of epirubicin in the same combinations is altered with the administration of increasing doses of ADR-529. A total of 82 patients were included. A crossover study including 16 of the patients showed no significant difference in epirubicin pharmacokinetic parameters when epirubicin was given with or without concomitant administration of ADR-529. Apart from minor changes in the distributional half-lives, the pharmacokinetic parameters of epirubicin were not altered with increasing doses of ADR-529, nor were the pharmacokinetic parameters of ADR-529 itself. Escalating doses of epirubicin did not significantly alter the pharmacokinetic parameters of ADR-529 with the exception of a 30% increase in the terminal half-life and a decrease in total body clearance when the epirubicin dose was raised from 60 to 100 mg/m2. We conclude that concomitant administration of ADR-529 does not alter the distribution and elimination of epirubicin in doses suitable for preventing the anthracycline-induced cardiotoxicity.

Anthracyclines and the heart

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Protracted drug infusions in cancer treatment: an appraisal of 5-fluorouracil, doxorubicin, and platinums

The feasibility to deliver chemotherapeutic agents by protracted i.v. infusion has greatly increased in the recent past. Indwelling ports, longer lasting central venous catheters requiring less than daily maintenance 'flushing', surgical expertise in placement, use in analgesia and nutrition, and 'smart' pump technology have all contributed to their increasing popularity. Justification for use of infusions in cancer chemotherapy has been slow in appearing with few studies proceeding to the comparative stage. This review will focus on three drugs in common use in cancer treatment, with the purpose of appraising the role of such infusions in cancer therapeutics and of deriving some lessons that might be applicable to other drugs or to drug development in general. For fluorouracil and doxorubicin the rationale and clinical findings favoring further development of infusion regimens is particularly strong. In the case of platinum compounds, some toxicologic advantages have emerged, but other measures designed to protect against the toxicities of cisplatin compete with infusion regimens in this regard. The therapeutic potential for this form of drug delivery, therefore, appears still confined to a subset of patients. Stronger rationales for the use of protracted infusions may be forthcoming from pharmacodynamic findings as in the case of etoposide, combined modality therapy with radiation for FU and cisplatin, biochemical modulation for FU, and reversal of multidrug resistance and its modulation for doxorubicin. While awaiting research into these areas of clinical and pre-clinical investigations, the role of infusion appears most evident in the cardiotoxicity protection of anthracyclines, and in further efficacy exploration (through dose or modulation) of FU. Both mechanistic and pharmacologic considerations could also provide additional stimulus for development of new formulations such as long circulating liposomes, and drugs more suitable for oral administration.

The role of iron and iron chelators in anthracycline cardiotoxicity

The redox cycling of anthracyclines promotes the formation of free radicals which are believed to play a central role in their cardiotoxicity. A number of observations indicate that the mechanism of the antineoplastic effect of anthracyclines is independent of their cardiotoxic effect and that it may be possible to prevent toxicity without interfering with therapeutic effect. Iron plays an important role in anthracycline toxicity by promoting the conversion of superoxide into highly toxic hydroxyl radicals through the Haber-Weiss reaction. Conversely, iron deprivation by its high-affinity binding to iron chelating compounds may inhibit anthracycline toxicity by interfering with free radical formation. ICRF-187, a bispiperazonedione which is hydrolyzed intracellularly into a bidentate chelator resembling EDTA, is able to decrease adriamycin-induced free hydroxyl radical formation and to prevent the development of clinical cardiac toxicity in patients receiving long-term anthracycline therapy. Our studies in rat heart cell cultures have shown that iron overload aggravates anthracycline toxicity and that this interaction can be prevented by prior iron chelating treatment. Since iron overload caused by multiple blood transfusions and bone marrow failure is a common condition in patients requiring anthracycline therapy, these observations may have significant clinical implications to the prevention of anthracycline cardiotoxicity.

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.

The hydrolysis product of ICRF-187 promotes iron-catalysed hydroxyl radical production via the Fenton reaction

d-1,2-Bis(3,5-dioxopiperazine-1-yl)propane (ICRF-187) (ADR-529) is a drug that ameliorates the cardiotoxicity of Adriamycin. The drug enters cells where hydrolysis leads to its diacid diamide product, dl-N,N'-dicarboxamidomethyl-N,N'-dicarboxymethyl-1,2-diamino propane (ICRF-198) (ADR-925), which is structurally similar to ethylenediaminetetraacetic acid (EDTA). The protective mechanism of ICRF-187 is unknown, but a plausible explanation is that ICRF-198 chelates iron intracellularly to prevent iron-dependent free radical reactions such as hydroxyl radical (.OH) production. We have compared Fe(ICRF-198) with Fe(EDTA) in its ability to promote .OH formation in several Fenton reaction systems. The Fenton reaction was studied with H2O2 and Fe2+ chelates or catalytic amounts of the iron chelates in the presence of Adriamycin radicals, paraquat radicals, superoxide anion radicals (O2-), and ascorbate as reducing species. .OH was detected with deoxyribose and dimethyl sulfoxide. The two methods gave comparable results. Fe(ICRF-198) was 80-100% as effective as Fe(EDTA) at promoting .OH production in the presence of the organic radicals and ascorbate, 30-70% in the presence of O2-, and 150% with non-cycling Fe2+. Fe(EDTA) is a more efficient catalyst of .OH production than physiological chelates such as ADP, ATP and citrate. Therefore, by comparing previous work which examined physiological chelates and Fe(EDTA) with the present work, Fe(ICRF-198) appears to be a better .OH catalyst than the physiological chelates. These results suggest that ICRF-198 generated in vivo from ICRF-187 would not protect against intracellular .OH production. They also imply that .OH production may not be as important in Adriamycin cardiotoxicity as other radical reactions, such as lipid peroxidation and thiol oxidation, that are inhibited by ICRF-198.

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.

The syndrome of 5-fluorouracil cardiotoxicity. An elusive cardiopathy

BACKGROUND

A case of reversible cardiogenic shock linked to 5-fluorouracil (5-FU) was observed. Recognizing the increasing use of 5-FU, the authors tried to map this syndrome.

METHODS

They reviewed 134 additional case reports, retrieved information from literature searches, focused on clinical features, and discussed possible pathophysiologic findings and prevention of this syndrome.

RESULTS

Although angina and electrocardiographic changes were common and reproducible (approximately 90% each), coronary artery disease was found in a few patients. A total of 33 patients had severe left ventricular dysfunction, 28 without evidence of myocardial infarction. The symptoms were responsive to conservative management (90%).

CONCLUSIONS

Cardiac toxicity is a little known complication of 5-FU therapy, with an unknown but significant incidence. It is highly treatable.

The role of an endogenous nonheme iron in microsomal redox reactions

Microsomal membranes contain a nonheme iron which serves in vitro for the peroxidation of unsaturated lipids or the oxidation of several other chemicals. These redox reactions are reviewed in light of a recent identification of two or more iron-binding proteins in the microsomal milieu. Indirect evidence that the microsomal iron might serve in vivo for the synthesis of heme iron is also presented and discussed. Consistent with this, the newly identified iron proteins not only participate in redox reactions but also release their bound iron upon incubation with certain intermediates of heme synthesis.

Effect of ICRF-187 on the pulmonary damage induced by hyperoxia in the rat

Histological and ultrastructural studies were made of the lungs of rats that were exposed to 100% oxygen for 60 h and were treated with either normal saline or with ICRF-187, a bis-diketopiperazine derivative of EDTA that has the capacity to chelate iron. This metal is thought to be needed to catalyze the formation of toxic oxygen free radicals. ICRF-187 (20 mg/kg) was given intraperitoneally at approximately 12 h intervals (5 doses) during the 60 h exposure. Seven of the ten saline-treated rats exposed to oxygen died prior to the end of the study whereas only one of the 10 rats in the ICRF-187-treated group died. This difference in mortality is found to be statistically significant (P less than 0.05). All saline-treated rats showed light and electron microscopic evidence of pulmonary damage. ICRF-187 attenuated the morphologic alterations observed by light microscopy (intra-alveolar edema, inflammatory exudates and bronchiolar epithelial cell swelling and hyperplasia; P less than 0.05). In addition, electron microscopic evaluation revealed that capillary thrombi, endothelial cell alterations and alveolar epithelial cell damage also were less severe in ICRF-187-treated rats. It is concluded that ICRF-187 may provide a new and useful approach for the prevention of hyperoxia-induced pulmonary damage.

Is ICRF-187 [(+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane] unusually reactive for an imide?

The hydrolysis of ICRF-187 and two model compounds, 4-methylpiperazine-2,6-dione (4-MP) and 3-methylglutarimide (3-MG), was investigated over the neutral to alkaline pH range at 25 degrees C and an ionic strength of 0.5 (sodium chloride). The purpose of the study was to correlate the influence of molecular changes to the reactivity of these imides. Additionally, an improved chromatographic resolution of all the components of the degradation and NMR confirmation of the identity of the degradation products are presented. Based on the study of 4-MP, which is essentially half of an ICRF-187 molecule, and 3-MG, which has a carbon in place of the piperazine nitrogen, several conclusions can be drawn with regard to the stability of ICRF-187. The tertiary piperazine nitrogen/s of 4-MP and ICRF-187 contributed to the base-catalyzed hydrolysis of these compounds above pH 7 and caused a significant decrease in the pKa values of the imide moiety of ICRF-187 and 4-MP compared with 3-MG. One 2,6-piperazinedione ring of ICRF-187 was shown to affect only minimally the rate of hydrolysis of the second ring. ICRF-187 hydrolyzes by parallel consecutive pathways forming two monoacids with one ring opened and, subsequently, the diacid with both rings hydrolyzed.

Roles of iron in neoplasia. Promotion, prevention, and therapy

Research and clinical observations during the past six decades have shown that: 1. Iron promotes cancer cell growth; 2. Hosts attempt to withhold or withdraw iron from cancer cells; and 3. Iron is a factor in prevention and in therapy of neoplastic disease. Although normal and neoplastic cells have similar qualitative requirements for iron, the neoplastic cells have more flexibility in acquisition of the metal. Excessive iron levels in animals and humans are associated with enhanced neoplastic cell growth. In invaded hosts, cytokine-activated macrophages increase intracellular ferritin retention of the metal, scavenge iron in areas of tumor growth, and secrete reactive nitrogen intermediates to effect efflux of nonheme iron from tumor cells. Procedures associated with lowering host intake of excess iron can assist in prevention and in management of neoplastic disease. Chemical methods for prevention of iron assimilation by neoplastic cells are being developed in experimental and clinical protocols. The antineoplastic activity of a considerable variety of chemicals, as well as of radiation, is modulated by iron. The present article focuses on recent findings and suggests directions for further cancer-iron research.

Withdrawal censoring and the sequential logrank procedure

The effects of withdrawal censoring on the power of the group sequential logrank procedure are examined in the context of survival studies. Special attention is given to an assumption that the withdrawal censoring mechanism is only conditionally independent of survival time. Simulation studies of two-sample, fixed duration trials, under random right censoring, staggered entry and exponential life times, reveal a general decrease in statistical power that is most pronounced when the withdrawals are unbalanced, the majority occurring in the group with the higher hazard rate. Generally, this decrease in power is not of practical concern under typical withdrawal rates except when conditional independence is present in which case large fluctuations in power and type I error rates can occur.