Dexrazoxane use in the prevention of anthracycline extravasation injury

Accidental extravasation injury from the use of the anthracycline anticancer drugs doxorubicin, daunorubicin, epirubicin and idarubicin can be a serious complication of their use. As yet, there is little consensus on the way that anthracycline extravasation injury should be clinically managed. Dexrazoxane, which is currently clinically used to reduce doxorubicin-induced cardiotoxicity, has also been shown in preclinical studies to be highly efficacious in preventing anthracycline-induced extravasation injury. Several clinical case reports of dexrazoxane for this use have also indicated positive outcomes. There are currently two multicenter Phase II/III clinical trials underway. Dexrazoxane is a prodrug analog of the metal chelator EDTA that most likely acts by removing iron from the iron–doxorubicin complex, thus preventing formation of damaging reactive oxygen species.

Dexrazoxane : a review of its use for cardioprotection during anthracycline chemotherapy

Dexrazoxane (Cardioxane, Zinecard, a cyclic derivative of edetic acid, is a site-specific cardioprotective agent that effectively protects against anthracycline-induced cardiac toxicity. Dexrazoxane is approved in the US and some European countries for cardioprotection in women with advanced and/or metastatic breast cancer receiving doxorubicin; in other countries dexrazoxane is approved for use in a wider range of patients with advanced cancer receiving anthracyclines. As shown in clinical trials, intravenous dexrazoxane significantly reduces the incidence of anthracycline-induced congestive heart failure (CHF) and adverse cardiac events in women with advanced breast cancer or adults with soft tissue sarcomas or small-cell lung cancer, regardless of whether the drug is given before the first dose of anthracycline or the administration is delayed until cumulative doxorubicin dose is > or =300 mg/m2. The drug also appears to offer cardioprotection irrespective of pre-existing cardiac risk factors. Importantly, the antitumour efficacy of anthracyclines is unlikely to be altered by dexrazoxane use, although the drug has not been shown to improve progression-free and overall patient survival. At present, the cardioprotective efficacy of dexrazoxane in patients with childhood malignancies is supported by limited data. The drug is generally well tolerated and has a tolerability profile similar to that of placebo in cancer patients undergoing anthracycline-based chemotherapy, with the exception of a higher incidence of severe leukopenia (78% vs 68%; p < 0.01). Dexrazoxane is the only cardioprotective agent with proven efficacy in cancer patients receiving anthracycline chemotherapy and is a valuable option for the prevention of cardiotoxicity in this patient population.

Metabolism of the one-ring open metabolites of the cardioprotective drug dexrazoxane to its active metal-chelating form in the rat

Dexrazoxane (ICRF-187) is clinically used as a doxorubicin cardioprotective agent and may act by preventing iron-based oxygen free radical damage through the iron-chelating ability of its fully hydrolyzed metabolite ADR-925 (N,N'-[(1S)-1-methyl-1,2-ethanediyl]-bis[(N-(2-amino-2-oxoethyl)]glycine). Dexrazoxane undergoes initial metabolism to its two one-ring open intermediates and is then further metabolized to its active metal ion-binding form ADR-925. The metabolism of these intermediates to the ring-opened metal-chelating product ADR-925 has been determined in a rat model to identify the mechanism by which dexrazoxane is activated. The plasma concentrations of both intermediates rapidly decreased after their i.v. administration to rats. A maximum concentration of ADR-925 was detected 2 min after i.v. bolus administration, indicating that these intermediates were both rapidly metabolized in vivo to ADR-925. The kinetics of the initial appearance of ADR-925 was consistent with formation rate-limited metabolism of the intermediates. After administration of dexrazoxane or its two intermediates, ADR-925 was detected in significant levels in both heart and liver tissue but was undetectable in brain tissue. The rapid rate of metabolism of the intermediates was consistent with their hydrolysis by tissue dihydroorotase. The rapid appearance of ADR-925 in plasma may make ADR-925 available to be taken up by heart tissue and bind free iron. These studies showed that the two one-ring open metabolites of dexrazoxane were rapidly metabolized in the rat to ADR-925, and thus, these results provide a mechanism by which dexrazoxane is activated to its active metal-binding form.

Feasibility and pharmacokinetic study of infusional dexrazoxane and dose-intensive doxorubicin administered concurrently over 96 h for the treatment of advanced malignancies

PURPOSE

Dexrazoxane administration prior to short infusion doxorubicin prevents anthracycline-related heart damage. Since delivery of doxorubicin by 96-h continuous intravenous infusion also reduces cardiac injury, we studied delivering dexrazoxane and doxorubicin concomitantly by prolonged intravenous infusion.

METHODS

Patients with advanced malignancies received tandem cycles of concurrent 96-h infusions of dexrazoxane 500 mg/m2 and doxorubicin 165 mg/m2, and 24 h after completion of chemotherapy, granulocyte-colony stimulating factor (5 microg/kg) and oral levofloxacin (500 mg) were administered daily until the white blood cell count reached 10,000 microl(-1). Plasma samples were analyzed for dexrazoxane and doxorubicin concentrations.

RESULTS

Ten patients were enrolled; eight patients had measurable disease. Two partial responses were observed in patients with soft-tissue sarcoma. The median number of days of granulocytopenia (<500 microl(-1)) was nine and of platelet count <20,000 microl(-1) was seven. Six patients received a single cycle because of progression (one), stable disease (four), or reversible, asymptomatic 10% decrease in cardiac ejection fraction (two). Principal grade 3/4 toxicities included hypotension (two), anorexia (four), stomatitis (four), typhlitis (two), and febrile neutropenia (seven), with documented infection (three). One death from neutropenic sepsis occurred. Dexrazoxane levels ranged from 1270 to 2800 nM, and doxorubicin levels ranged from 59.1 to 106.9 nM.

CONCLUSIONS

These results suggest that tandem cycles of concurrent 96-h infusions of dexrazoxane and high-dose doxorubicin can be administered with minimal cardiac toxicity, and have activity in patients with recurrent sarcomas. However, significant non-cardiac toxicities indicate that the cardiac sparing potential of this approach would be maximized at lower dose levels of doxorubicin.

Measurement of renal tumour and normal tissue perfusion using positron emission tomography in a phase II clinical trial of razoxane

Measurement of tumour and normal tissue perfusion in vivo in cancer patients will aid the clinical development of antiangiogenic and antivascular agents. We investigated the potential antiangiogenic effects of the drug razoxane by measuring the changes in parameters estimated from H(2)(15)O and C(15)O positron emission tomography (PET) to indicate alterations in vascular physiology. The study comprised 12 patients with primary or metastatic renal tumours >3 cm in diameter enrolled in a Phase II clinical trial of oral razoxane. Perfusion, fractional volume of distribution of water (VD) and blood volume (BV) were measured in tumour and normal tissue before and 4-8 weeks after treatment with 125 mg twice-daily razoxane. Renal tumour perfusion was variable but lower than normal tissue: mean 0.87 ml min(-1) ml(-1) (range 0.33-1.67) compared to renal parenchyma: mean 1.65 ml min(-1) ml(-1) (range 1.16-2.88). In eight patients, where parallel measurements were made during the same scan session, renal tumour perfusion was significantly lower than in normal kidney (P=0.0027). There was no statistically significant relationship between pretreatment perfusion and tumour size (r=0.32, n=13). In six patients scanned before and after razoxane administration, there was no statistically significant change in tumour perfusion: mean perfusion pretreatment was 0.81 ml min(-1) ml(-1) (range 0.46-1.26) and perfusion post-treatment was 0.72 ml min(-1) ml(-1) (range 0.51-1.15, P=0.15). Tumour VD and BV did not change significantly following treatment: mean pretreatment VD=0.66 (range 0.50-0.87), post-treatment VD=0.71 (range 0.63-0.82, P=0.22); pretreatment BV=0.18 ml ml(-1) (range 0.10-0.25), post-treatment BV=0.167 ml ml(-1) (range 0.091-0.24, P=0.55). Tumour perfusion, VD and BV did not change significantly with tumour progression. This study has shown that H(2)(15)O and C(15)O PET provide useful in vivo physiological measurements, that even highly angiogenic renal cancers have poor perfusion compared to surrounding normal tissue, and that PET can provide valuable information on the in vivo biology of angiogenesis in man and can assess the effects of antiangiogenic therapy.

The doxorubicin-cardioprotective drug dexrazoxane undergoes metabolism in the rat to its metal ion-chelating form ADR-925

PURPOSE

Dexrazoxane is clinically used as a doxorubicin-cardioprotective agent and may act by preventing iron-based oxygen free-radical damage through the iron-chelating ability of ADR-925. The metabolism of dexrazoxane (ICRF-187) to its one-ring open hydrolysis products and its rings-opened metal-chelating product ADR-925 was determined in a rat model in order to identify the mechanism by which dexrazoxane acts.

METHODS

A new fluorescence detection flow injection assay utilizing the metal-chelating dye calcein was developed to detect ADR-925 in blood plasma. Dexrazoxane and its one-ring open metabolites were determined by HPLC.

RESULTS

ADR-925 was detected within 5 min of i.v. administration of dexrazoxane to rats, suggesting that dexrazoxane is rapidly metabolized in vivo. The plasma concentrations of ADR-925 exceeded those of both one-ring open intermediates at 30 min and those of dexrazoxane by 80 min and reached a maximum at 80 min, and then slowly decreased.

CONCLUSIONS

The rapid appearance of ADR-925 in plasma may make ADR-925 available to be taken up by heart tissue and bind free iron. These results indicate that the one-ring open dexrazoxane intermediates are enzymatically metabolized to ADR-925 and provide a pharmacodynamic basis for the antioxidant cardioprotective activity of dexrazoxane.

Phase I trial of 96-hour continuous infusion of dexrazoxane in patients with advanced malignancies

Dexrazoxane is a bidentate chelator of divalent cations. Pretreatment with short infusions of dexrazoxane prior to bolus doxorubicin has been shown to lessen the incidence and severity of anthracycline-associated cardiac toxicity. However, because of rapid, diffusion-mediated cellular uptake and the short plasma half-life of dexrazoxane, combined with prolonged cellular retention of doxorubicin, dexrazoxane may be more effective when administered as a continuous infusion. Thus, a Phase I pharmacokinetic trial of a 96-h infusion of dexrazoxane was performed. Dexrazoxane doses were escalated in cohorts of 3 to 6 patients per dose level. All patients received granulocyte-colony stimulating factor at a dose of 5 microg/kg/day starting 24 h after completion of the dexrazoxane infusion. Plasma samples were collected and analyzed for dexrazoxane by high-performance liquid chromatography. Urine collections were performed at baseline and during the infusion to determine the renal clearance of dexrazoxane and the excretion rate of divalent cations. Twenty-two patients were enrolled at doses ranging from 125 to 250 mg/m(2)/day. Grade 3 and 4 toxicities included grade 4 thrombocytopenia in 2 patients treated at 250 mg/m(2)/day, grade 3 thrombocytopenia and grade 4 nausea and vomiting in 1 patient treated at 221 mg/m(2)/day, grade 4 diarrhea and grade 3 nausea and vomiting in 1 patient treated at 221 mg/m(2)/day, and grade 3 hypertension in 1 patient treated at 166.25 mg/m(2)/day. Steady-state dexrazoxane levels ranged from 496 microg/l (2.2 microM) to 1639 microg/l (7.4 microM). Dexrazoxane plasma CL(ss) and elimination t(1/2) were 7.2 +/- 1.6 l/h/m(2) and 2.0 +/- 0.8 h, respectively. The mean percentage of administered dexrazoxane recovered in the urine at steady state was 30% (range, 10-66%). Urinary iron and zinc excretion during the dexrazoxane infusion increased in 12 of 18 and 19 of 19 patients by a median of 3.7- and 2.4-fold, respectively. These results suggest that dexrazoxane as a 96-h infusion can be safely administered with granulocyte-colony stimulating factor at doses that achieve plasma levels that have been demonstrated previously to inhibit topoisomerase II activity and to induce apoptosis in vitro. Additional studies will be required to determine whether the combination of continuous infusions of dexrazoxane and doxorubicin would provide enhanced cardioprotection compared with the currently recommended bolus or short infusion schedules.

Stereoselective metabolism of dexrazoxane (ICRF-187) and levrazoxane (ICRF-186)

A chiral HPLC method has been developed to separate razoxane (ICRF-159) in blood plasma into its enantiomers dexrazoxane (ICRF-187) and levrazoxane (ICRF-186). Dexrazoxane is clinically used as a doxorubicin cardioprotective agent and little is known of its in vivo metabolism. After intravenous administration of 20 mg/kg of razoxane to rats, the razoxane was eliminated from the plasma with a half-time of approximately 20 min. The levrazoxane:dexrazoxane ratio continuously increased with time to a value of 1.5 at 150 min, indicating that dexrazoxane is metabolized faster than levrazoxane. These results, confirmed with studies on liver supernatants, are consistent with the hypothesis that dihydropyrimidine amidohydrolase in the liver and kidney is responsible for the preferential metabolism of dexrazoxane in the rat compared to levrazoxane. It is possible that on a dose-per-dose basis marginally higher therapeutic levels of levrazoxane might be achieved in the heart tissue for a longer time compared to dexrazoxane due to dihydropyrimidine amidohydrolase-based metabolism in the liver and kidney. However, given the relatively small difference in elimination of the two enantiomers, it would be difficult to predict from this study whether or not dexrazoxane or levrazoxane might be more efficacious in reducing cardiotoxicity.

Relative plasma levels of the cardioprotective drug dexrazoxane and its two active ring-opened metabolites in the rat

A postcolumn derivatization reversed-phase high-pressure liquid chromatography method has been developed to detect and separate the one-ring open intermediates of dexrazoxane (ICRF-187) in blood plasma. Dexrazoxane is clinically used as a doxorubicin cardioprotective agent and may act by preventing iron-based oxygen-free radical damage through the iron-chelating ability of its one-ring open intermediates and its fully rings opened hydrolysis product ADR-925. Little is known of the in vivo metabolism of dexrazoxane to its one-ring open intermediates, which may be two of the active forms of dexrazoxane. The one-ring open intermediates were detected within 5 min of i.v. administration of dexrazoxane to rats, suggesting that dexrazoxane is rapidly metabolized in vivo. The plasma concentrations of the one-ring open intermediates varied from 4 to 9% and 6 to 24% of the dexrazoxane concentrations at 5 and 120 min, respectively. The relatively small changes in the levels of the one-ring open intermediates with time suggest that a dynamic steady state is occurring. The ratio of the concentrations of the two one-ring open intermediates was similar to that previously seen for the in vitro dihydropyrimidine amidohydrolase-catalyzed hydrolysis of dexrazoxane. These results are consistent with the hypothesis that dihydropyrimidine amidohydrolase in the liver and kidney is responsible for the metabolism of dexrazoxane in the rat.

Dexrazoxane. A review of its use as a cardioprotective agent in patients receiving anthracycline-based chemotherapy

Dexrazoxane has been used successfully to reduce cardiac toxicity in patients receiving anthracycline-based chemotherapy for cancer (predominantly women with advanced breast cancer). The drug is thought to reduce the cardiotoxic effects of anthracyclines by binding to free and bound iron, thereby reducing the formation of anthracycline-iron complexes and the subsequent generation of reactive oxygen species which are toxic to surrounding cardiac tissue. Clinical trials in women with advanced breast cancer have found that patients given dexrazoxane (about 30 minutes prior to anthracycline therapy; dexrazoxane to doxorubicin dosage ratio 20:1 or 10:1) have a significantly lower overall incidence of cardiac events than placebo recipients (14 or 15% vs 31%) when the drug is initiated at the same time as doxorubicin. Cardiac events included congestive heart failure (CHF), a significant reduction in left ventricular ejection fraction and/or a > or = 2-point increase in the Billingham biopsy score. These results are supported by the findings of studies which used control groups (patients who received only chemotherapy) for comparison. The drug appears to offer cardiac protection irrespective of pre-existing cardiac risk factors. In addition, cardiac protection has been shown in patients given the drug after receiving a cumulative doxorubicin dose > or = 300 mg/m2. It remains to be confirmed that dexrazoxane does not affect the antitumour activity of doxorubicin: although most studies found that clinical end-points (including tumour response rates, time to disease progression and survival duration) did not differ significantly between treatment groups, the largest study did show a significant reduction in response rates in dexrazoxane versus placebo recipients. Dexrazoxane permits the administration of doxorubicin beyond standard cumulative doses; however, it is unclear whether this will translate into prolonged survival. Preliminary results (from small nonblind studies) indicate that dexrazoxane reduces cardiac toxicity in children and adolescents receiving anthracycline-based therapy for a range of malignancies. The long term benefits with regard to prevention of late-onset cardiac toxicity remain unclear. With the exception of severe leucopenia [Eastern Cooperative Oncology Group (ECOG) grade 3/4 toxicity], the incidence of haematological and nonhaematological adverse events appears similar in patients given dexrazoxane to that in placebo recipients undergoing anthracycline-based chemotherapy. Although preliminary pharmacoeconomic analyses have shown dexrazoxane to be a cost-effective agent in women with advanced breast cancer, they require confirmation.

CONCLUSIONS

Dexrazoxane is a valuable drug for protecting against cardiac toxicity in patients receiving anthracycline-based chemotherapy. Whether it offers protection against late-onset cardiac toxicity in patients who received anthracycline-based chemotherapy in childhood or adolescence remains to be determined. Further clinical experience is required to confirm that it does not adversely affect clinical outcome, that it is a cost-effective option, and to determine the optimal treatment regimen.

Clinical pharmacology of dexrazoxane

Dexrazoxane is a synthetic bisdiketopiperazine two-ringed compound which hydrolyzes to an EDTA analog. These rings undergo intracellular hydrolysis to form the single and double (ICRF-198) chelating forms of the compound by both enzymatic and non-enzymatic catalysis. These dexrazoxane metabolites are efficient at stripping the cations from the iron:anthracycline complex. The disruption of the complex prevents the oxidative damage from free radicals promoted by this anthracycline complex. Pharmacologic studies of single agent dexrazoxane (originally studied as an antineoplastic agent) demonstrates an alpha half-life of approximately 30 minutes and a beta half-life of 2 to 4 hours. When given in combination with anthracyclines (e.g. doxorubicin or epirubicin) the pharmacokinetics of dexrazoxane are unchanged. Additional studies of anthracycline metabolism when given in combination with dexrazoxane, both in single arm and randomized cross-over studies, have generally shown no change in anthracycline metabolism, including pharmacokinetic parameters of alpha, beta, and gamma half-lives, area-under-the-curve, or clearance. There is no pharmacokinetic interaction of dexrazoxane on anthracycline metabolism and, therefore, pharmacokinetics cannot account for the cardioprotective effects described for dexrazoxane.

Antineoplastic activity of continuous exposure to dexrazoxane: potential new role as a novel topoisomerase II inhibitor

Although originally developed as an antitumor agent in the 1970s, dexrazoxane (DEX) is currently used as a cardioprotective agent in combination with doxorubicin (DOX). Due to concerns about anthracycline-induced cardiotoxicity at higher cumulative doses, many investigators have chosen to administer DOX by prolonged infusion. Therefore, with the ultimate goal of combining infusional DEX and DOX, we performed a phase I study of intravenous DEX alone as a 96-hour infusion. Surprisingly, the maximum tolerated dose of DEX identified in this study was 10- to 15-fold lower than previously determined using different schedules of administration. Results of pharmacokinetic studies in support of the trial have found that steady-state DEX plasma concentrations in the range of 4 to 5 micromol/L can be achieved safely. Because previous experiments have explored the ability of DEX to inhibit the catalytic activity topoisomerase II at low micromolar concentrations and due to a lack of in vitro cytotoxicity data for long-term exposures, we performed further laboratory studies to provide a context for our pharmacokinetic findings. As a result of these correlative studies, we have found that prolonged exposures to DEX are cytotoxic to human leukemic cells at concentrations that are clinically achievable.

Dose-independent pharmacokinetics of the cardioprotective agent dexrazoxane in dogs

A randomized, four-way cross-over design was used to assess the disposition of the cardioprotective agent, dexrazoxane, in four male beagle dogs following single I.V. administration of 10, 25, 50, and 100 mg kg-1 doses. Parent drug was quantified in plasma and urine with a validated high-pressure liquid chromatographic-electrochemical assay. A two-compartment open model adequately described the dexrazoxane plasma concentration versus time data. The terminal half-life ranged between 1.1 and 1.3 h and the apparent steady-state distribution volume was 0.67 L kg-1. The systemic clearance (CL) ranged from 10.3 to 11.5 mL min-1 kg-1, while estimates of renal clearance approximated the glomerular filtration rate (GFR approximately 3.2-4.9 mL min-1 kg-1). Over the dose range evaluated, CL was dose independent (ANOVA, p = 0.33), while concentration at the end of infusion (Cend) and the area under the concentration versus time curve (AUC) were directly proportional to the dose (r > 0.999). The blood cell to plasma partitioning ratio was approximately 0.517 and drug was essentially unbound to plasma proteins (fu approximately 0.95). Dexrazoxane appeared to be subject to low organ extraction, since the hepatic and renal drug extraction ratios were on the order of 0.228 +/- 0.054 and 0.184 +/- 0.024, respectively. These results suggest a relatively small drug distribution space (approximately equal to total-body water) and low tissue and plasma protein binding. In light of the low plasma protein binding and extraction ratio exhibited by dexrazoxane, metabolic capacity and renal function would appear to be the predominant variables affecting the CL of this drug. The constancy of the half-life, CL, and VSS with increasing dose indicates dose-independent disposition for dexrazoxane. Thus a linear increase in the systemic exposure can be predicted over this dose range.

Randomized trial of the cardioprotective agent ICRF-187 in pediatric sarcoma patients treated with doxorubicin

PURPOSE

We conducted an open-label, randomized trial to determine whether ICRF-187 would reduce doxorubicin-induced cardiotoxicity in pediatric sarcoma patients.

METHODS

Thirty-eight patients were randomized to receive doxorubicin-containing chemotherapy (given as an intravenous bolus) with or without ICRF-187. Resting left ventricular ejection fraction (LVEF) was monitored serially with multigated radionuclide angiography (MUGA) scan. The two groups were compared for incidence and degree of cardiotoxicity, response rates to four cycles of chemotherapy, event-free and overall survival, and incidence and severity of noncardiac toxicities.

RESULTS

Eighteen ICRF-187-treated and 15 control patients were assessable for cardiac toxicity. ICRF-187-treated patients were less likely to develop subclinical cardiotoxicity (22% v 67%, P < .01), had a smaller decline in LVEF per 100 mg/m2 of doxorubicin (1.0 v 2.7 percentage points, P = .02), and received a higher median cumulative dose of doxorubicin (410 v 310 mg/m2, P < .05) than did control patients. Objective response rates were identical in the two groups, with no significant differences seen in event-free or overall survival. ICRF-187-treated patients had a significantly higher incidence of transient grade 1 serum transaminase elevations and a trend toward increased hematologic toxicity.

CONCLUSION

ICRF-187 reduces the risk of developing short-term subclinical cardiotoxicity in pediatric sarcoma patients who receive up to 410 mg/m2 of doxorubicin. Response rates to chemotherapy, event-free and overall survival, and noncardiac toxicities appear to be unaffected by the use of ICRF-187. Additional clinical trials with larger numbers of patients are needed to determine if the short-term cardioprotection afforded by ICRF-187 will reduce the incidence of late cardiac complications in long-term survivors of childhood cancer.

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.

Enzymatic ring-opening reactions of the chiral cardioprotective agent (+) (S)-ICRF-187 and its (-) (R)-enantiomer ICRF-186 by dihydropyrimidine amidohydrolase

The kinetics of the ring-opening reaction of the cardioprotective agent (+) (S)-ICRF-187 [(+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane, dexrazoxane] and its (-) (R)-analog ICRF-186 by the enzyme dihydropyrimidine amidohydrolase (DHPase) has been studied by HLLC. Chromatographic separation of the two single-ring opened hydrolysis products allowed an estimation of the Michaelis parameters for the opening of each individual ring on the two optical isomers. Under nonsaturating conditions, DHPase acts on ICRF-187 4 times faster than it does on ICRF-186. However, the single-ring opened hydrolysis products of both ICRF-187 and ICRF-186 are not substrates of DHPase. Because the active form of ICRF-187 is thought to be its rings-opened metal ion chelating form, these results suggest that DHPase-catalyzed hydrolysis occurring in the liver and the kidney may lead to differences in the pharmacological action and effectiveness of these two optical isomers.

[Distribution of 14C labeled at dioxopiperazine or methyl morpholine group of probimane by whole body autoradiography]

Probimane (AT-2153) is a new anticancer compound. It was first developed in this Institute. It is effective against mouse tumors S37, S180, Lewis lung carcinoma, L1210 and human pulmonary adenocarcinoma heterotransplanted into nude mice. In the present work, 14C was labeled at central dioxopiperazine or methyl morpholine group of probimane 120 mg.kg-1 was injected iv in mice bearing Lewis lung carcinoma by whole body autoradiography. The results showed that probimane was broken into at least two parts: a central part and a methyl morpholine group. The central part of compound hardly penetrated through the blood-brain barrier, but accumulated in the urinary bladder. The methyl morpholine group showed a high affinity to tumor tissue and accumulated in spleen, bone and liver.

Pharmacokinetics of the cardioprotector ADR-529 (ICRF-187) in escalating doses combined with fixed-dose doxorubicin

BACKGROUND

Although doxorubicin is an anticancer agent with a wide spectrum of activity, therapy with this anthracycline must often be discontinued at a time of benefit to the patient because of the drug's cumulative cardiotoxicity. ICRF-187 (ADR-529, dexrazoxane) is a bisdioxopiperazine compound that protects against cardiac toxicity induced by doxorubicin.

PURPOSE

Our objectives in this study were to determine the maximum tolerated dose of ADR-529 (which uses a different vehicle than ICRF-187) when given with a fixed doxorubicin dose and to determine whether ADR-529 alters doxorubicin pharmacokinetics.

METHODS

Twenty-five patients were treated with doxorubicin (60 mg/m2) preceded by administration of ADR-529 in escalating dosages (i.e., 60, 300, 600, 750, and 900 mg/m2) to groups of three to nine patients. ADR-529 was administered over a 15-minute period beginning 30 minutes before doxorubicin treatment; the protocol was repeated every 3 weeks. Blood was sampled frequently for drug levels, which were determined by high-pressure liquid chromatography with fluorescence (doxorubicin) and electrochemical detection (ADR-529).

RESULTS

Dose-limiting neutropenia occurred in four of six previously treated patients at an ADR-529 dose of 600 mg/m2; the dose ratio of ADR-529 to doxorubicin was 10:1. For three additional patients with better Eastern Cooperative Oncology Group performance status and a maximum of one prior chemotherapy regimen, 600 mg/m2 was tolerated, but grade 3 or 4 neutropenia occurred in four of six patients who received an ADR-529 dose of 900 mg/m2 and in three of four patients at a dose of 750 mg/m2. Doxorubicin's estimated terminal half-life was 39.5 +/- 18.3 (mean +/- SD) hours; the area under the curve for plasma concentration of drug x time (AUC) was 1.74 +/- 0.40 (micrograms/microL) x hour. Total-body clearance was 598 +/- 142 microL/m2 per minute (N = 20), and it did not vary with ADR-529 dose. Estimated distribution and elimination phase half-lives for plasma ADR-529 were 0.46 +/- 0.30 hours and 4.16 +/- 2.94 hours, respectively. Total-body clearance was 111 +/- 87 microL/m2 per minute (N = 18); AUC was linear (r2 = .92), and the clearance rate was constant (r2 = .18) from 60 to 900 mg/m2.

CONCLUSIONS

Myelotoxicity was dose limiting for ADR-529 at 600-750 mg/m2 when given with a fixed dose of doxorubicin at 60 mg/m2 (dose ratios of ADR-529 to doxorubicin ranged from 10:1 to 12.5:1). When used in combination, ADR-529 did not perturb doxorubicin's distribution, metabolism, or excretion; therefore, other mechanisms of cardioprotection must be involved.

IMPLICATIONS

We recommend that an ADR-529 dose of 600 mg/m2 be given with single-agent doxorubicin at a dose of 60 mg/m2 in future studies.

Phase I clinical trial and pharmacokinetics of weekly ICRF-187 (NSC 169780) infusion in patients with solid tumors

ICRF-187 was given to 62 evaluable patients with advanced solid tumors in a Phase I clinical trial. Weekly infusions were given in dosages ranging from 0.85 g/m2 to 7.42 g/m2 for a total of four weeks with a two week rest period between courses. Dose-limiting hematological toxicity was seen in heavily pretreated patients at a dose of 3.8 g/m2/week. All patients also developed reversible SGOT elevations. In patients with less prior therapy hematologic toxicity was not dose-limiting but hepatotoxicity, manifest by transient SGOT levels greater than 5 times baseline was seen at 7.42 g/m2/week even though only 3/6 patients could receive 4 consecutive weekly doses. At virtually all dose levels tested some patients developed anemia. Other toxicities, including alopecia, nausea, vomiting and reversible serum amylase elevations, were mild. Cumulative monthly doses achieved on this weekly schedule are significantly higher than a 48-hour infusion or daily times 3 or 5 schedule in adults and a daily times 3 schedule in children. Pharmacokinetic studies in eight patients indicate that the drug disappears from the plasma biphasically with a terminal t1/2 of 3.2 +/- 0.9 hr. The total clearance was 288.7 +/- 85.0 ml/hr/kg and the volume of distribution (Vda) was 1.3 +/- 0.4 l/kg. Pharmacokinetics were not dose-dependent from 3.8-7.4 g/m2 and no difference in pharmacokinetics was found in patients studied during the first and second treatments of a course. If Phase II trials of ICRF-187 are to be pursued on this schedule, appropriate doses would be 3.8 g/m2/week X 4 for heavily pretreated and 7.42 g/m2/week for "good risk" patients. Because of erratic hematologic toxicity in heavily pretreated patients, some might only tolerate three weekly doses. In good risk patients transaminitis was significant but reversible, thus, Phase II protocols should include dose escalation schemata.