Reduction of daunomycin toxicity by razoxane

Dexrazoxane Protects against Myelosuppression from the DNA Cleavage–Enhancing Drugs Etoposide and Daunorubicin but not Doxorubicin

PURPOSE

The anthracyclines daunorubicin and doxorubicin and the epipodophyllotoxin etoposide are potent DNA cleavage-enhancing drugs that are widely used in clinical oncology; however, myelosuppression and cardiac toxicity limit their use. Dexrazoxane (ICRF-187) is recommended for protection against anthracycline-induced cardiotoxicity.

EXPERIMENTAL DESIGN

Because of their widespread use, the hematologic toxicity following coadministration of dexrazoxane and these three structurally different DNA cleavage enhancers was investigated: Sensitivity of human and murine blood progenitor cells to etoposide, daunorubicin, and doxorubicin +/- dexrazoxane was determined in granulocyte-macrophage colony forming assays. Likewise, in vivo, B6D2F1 mice were treated with etoposide, daunorubicin, and doxorubicin, with or without dexrazoxane over a wide range of doses: posttreatment, a full hematologic evaluation was done.

RESULTS

Nontoxic doses of dexrazoxane reduced myelosuppression and weight loss from daunorubicin and etoposide in mice and antagonized their antiproliferative effects in the colony assay; however, dexrazoxane neither reduced myelosuppression, weight loss, nor the in vitro cytotoxicity from doxorubicin.

CONCLUSION

Although our findings support the observation that dexrazoxane reduces neither hematologic activity nor antitumor activity from doxorubicin clinically, the potent antagonism of daunorubicin activity raises concern; a possible interference with anticancer efficacy certainly would call for renewed attention. Our data also suggest that significant etoposide dose escalation is perhaps possible by the use of dexrazoxane. Clinical trials in patients with brain metastases combining dexrazoxane and high doses of etoposide is ongoing with the aim of improving efficacy without aggravating hematologic toxicity. If successful, this represents an exciting mechanism for pharmacologic regulation of side effects from cytotoxic chemotherapy.

Dexrazoxane in combination with anthracyclines lead to a synergistic cytotoxic response in acute myelogenous leukemia cell lines

In an attempt to improve current therapeutic strategies for acute myelogenous leukemia (AML), we studied the effects of a commercially available drug, dexrazoxane (DEX), which protects against anthracycline-induced cardiotoxicity. The rationale was that DEX would permit higher doses of cardiotoxic drugs to be given. The drug itself may have therapeutic potential as well. Finally, there are concerns that the drug may, as a protective agent, diminish the effectiveness of various chemotherapeutics. To help resolve the question about potential drug antagonism, we undertook a series of in vitro analyses of DEX and various combinations with anthracyclines and other agents. Colony-forming assays were used to evaluate stem-cell renewal of myeloid cells in vitro, and median-effect analysis was used to evaluate antagonism, synergism, and additivity. The anthracyclines doxorubicin, daunorubicin, and idarubicin were individually combined with DEX to study in vitro effects in leukemic myeloid cell lines. In the hope, we could extend the findings to non-anthracyclines, etoposide and cytosine arabinoside were also evaluated in combination with DEX using the same in vitro model and method. We found that the effects of DEX in combination with any of the anthracyclines were schedule dependent. The antitumor effect was greater for each combination than for any anthracycline alone except when DEX was administered 24h before doxorubicin or daunorubicin. These data were corroborated through median-effect analysis. Etoposide in combination with DEX was synergistic for all combinations and schedules, and the combination of cytosine arabinoside and DEX was effective depending on the schedule used. DEX appears to be a promising drug in the treatment of AML and warrants further clinical study involving novel drug combinations.

In vitro effects of dexrazoxane (Zinecard) and classical acute leukemia therapy: time to consider expanded clinical trials?

Anthracyclines have been the backbone of acute leukemia therapy in the adult for many years, but little attention has been paid to the long-term toxicity of these agents in this disease because of the poor survival of this population of patients. Recent studies have examined dose-intensified daunorubicin with dosages as high as 95 mg/m2 daily x 3 in this population with the attendant concerns of both acute and chronic toxicity. We have examined three human leukemia cell lines in vitro, treated with either daunorubicin, mitoxantrone, with or without cytosine arabinoside in the presence of dexrazoxane to determine whether such treatment would be synergistic or antagonistic. AML-193, CRF-SB, and Molt-4 cell lines were grown to confluence, plated into microtiter dishes and incubated for 72 h with varying concentrations of the above drugs. Cytotoxicity was determined by the MTT assay, and synergy or antagonism by median effect analysis. Dexrazoxane demonstrated additive or synergistic cytotoxic effects (CI <1) under most conditions. The triplet of daunorubicin, cytosine arabinoside, and dexrazoxane showed profound synergy in all three cell lines. These effects occurred at clinically achievable levels. If high dosages of anthracyclines are contemplated in this population, these preclinical data suggest that the addition of dexrazoxane to classical therapy is not antagonistic and thus may allow an investigation of the role of dexrazoxane as a cardiac protectant.

Chemoprotectants: a review of their clinical pharmacology and therapeutic efficacy

Dose-limiting toxicity secondary to antineoplastic chemotherapy is due to the inability of cytotoxic drugs to differentiate between normal and malignant cells. The consequences of this may include impairment of patient quality of life, because of toxicity, and reduced tumour control because of the inability to deliver adequate dose-intensive therapy against the cancer. Specific examples of toxicity against normal tissues include cisplatin-related neurotoxicity and nephrotoxicity, myelotoxicity secondary to treatment with alkylating agents and carboplatin, oxazaphosphorine-induced haemorrhagic cystitis, and cumulative dose-related cardiac toxicity secondary to anthracycline treatment. Chemoprotectants have been developed as a means of ameliorating the toxicity associated with cytotoxic agents by providing site-specific protection for normal tissues, without compromising antitumour efficacy. Clinical trials with toxicity protectors must include sufficient dose-limiting events for study, and assessment of both toxicity (allowing for measurement of efficacy of protection) and antitumour effect. Several chemoprotective compounds have now been extensively investigated, including dexrazoxane, amifostine, glutathione, mesna and ORG 2766. Dexrazoxane appears to complex with metal co-factors including iron, to reduce the incidence of anthracycline-induced cardiotoxicity, allowing the delivery of higher cumulative doses of anthracyclines without the expected consequence of cardiomyopathy. Numerous studies have demonstrated that sulfur-containing nucleophiles, including amifostine, glutathione, and mesna can specifically bind cisplatin- or alkylating agent-generated free radicals or alkylating agent metabolites to reduce the incidence of cisplatin-associated neurotoxicity and nephrotoxicity, or alkylating agent-associated myelosuppression and urothelial toxicity. These studies, in the majority of instances, have not revealed any evidence of reduction in antitumour efficacy. Further randomised trials are required to identify the optimal role of chemoprotectants when used alone or in combination with other toxicity modifiers including haemopoietic growth factors.

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.

Antagonistic effect of the cardioprotector (+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane (ICRF-187) on DNA breaks and cytotoxicity induced by the topoisomerase II directed drugs daunorubicin and etoposide (VP-16)

The effect of the bisdioxopiperazine cardioprotector ICRF-187 (ADR-529, dexrazoxan) on drug-induced DNA damage and cytotoxicity was studied. Using alkaline elution assays, ICRF-187 in a dose-dependent manner inhibited the formation of DNA single strand breaks (SSBs) as well as DNA-protein cross-links induced by drugs such as VP-16 (etoposide), m-AMSA [4'-(9-acridinylamino)-methanesulfon-m-anisidide], daunorubicin and doxorubicin (Adriamycin) which are known to stimulate DNA-topoisomerase II cleavable complex formation. Thus, 50% inhibition of DNA SSBs induced by 5 microM doxorubicin occurred already at equimolar ICRF-187. In contrast, ICRF-187 did not affect DNA SSBs induced by H2O2. In clonogenic assay, ICRF-187 in non-toxic doses antagonized both VP-16 and daunorubicin cytotoxicity in a dose-dependent manner. Our results indicate that the previously described acute in vivo protection by ICRF-187 against anthracycline toxicity may be due to inhibition of topoisomerase II activity. The antagonistic effect of ICRF-187 on daunorubicin cytotoxicity should be taken into consideration when planning clinical trials.

Cardioprotection by ICRF187 against high dose anthracycline toxicity in children with malignant disease

OBJECTIVE

A pilot study to assess the efficacy of ICRF187 as a protective agent against the cardiotoxic effects of anthracycline drugs used to treat childhood malignancies.

DESIGN

A study of cardiac function in children treated receiving ICRF187 ((s)-(+)-1,2 bis (3,5-dioxopiperazenyl) propane) in addition to anthracycline therapy compared with contemporary controls selected retrospectively on the basis of anthracycline dose matching.

PATIENTS

Five children in whom recurrence of malignant disease was re-treated with chemotherapy containing anthracycline drugs and additional ICRF187 (supplied on a compassionate-use basis) (cumulative anthracycline doses 550-1650 mg/m2). Five more children with recurrence of malignant disease were re-treated to similar cumulative anthracycline doses (600-1150 mg/m2) without ICRF187.

METHODS

Cardiac function was assessed clinically and echocardiographically throughout treatment. Clinical and echocardiographic state were compared before treatment and after completion of therapy within and between groups treated with and without ICRF187.

RESULTS

Two patients treated without ICRF187 developed symptomatic congestive cardiac failure from which one died. Another developed considerable but as yet asymptomatic left ventricular dysfunction. No patient receiving additional ICRF187 developed cardiac failure or left ventricular dysfunction. There were no significant differences in cumulative anthracycline dose, dose increase, type of anthracycline used, survival rate, or length of survival between groups. Left ventricular shortening fraction fell by a mean of 1.0% in patients receiving ICRF187 and by a mean of 11% in the patients treated without it (p = 0.04).

CONCLUSIONS

ICRF187 seems to have provided highly effective cardioprotection to this small group of children with end-stage malignancy. Severe cardiotoxicity was seen in a similar group treated with comparable anthracycline doses but without ICRF187.

Timing of treatment with ICRF-187 and its effect on chronic doxorubicin cardiotoxicity

Studies were conducted to evaluate whether the timing of administration of ICRF-187 [(+)-1,2-bis(3,5 dioxopiperazinyl-1-yl)propane] would influence the degree of cardioprotection provided by this agent against the development of doxorubicin-induced chronic cardiomyopathy. Beagle dogs (8.5-14 kg) received either doxorubicin alone (1.75 mg/kg, i.v., n = 8), doxorubicin (1.75 mg/kg) simultaneously with ICRF-187 (35 mg/kg, i.v., n = 8), or doxorubicin (1.75 mg/kg) followed 2 h later by ICRF-187 (35 mg/kg, n = 8). Control animals received ICRF-187 (35 mg/kg, n = 4) or saline (n = 4). All animals received a course of seven treatments, each given 3 weeks apart, and were killed 3 weeks after the last treatment. Semiquantitative grading of histologic sections of myocardium showed that as compared with animals treated with doxorubicin alone, the incidence and the severity of the doxorubicin-induced myocardial lesions were reduced in the two groups of animals given doxorubicin plus ICRF-187. However, protection was significantly better in dogs receiving ICRF-187 and doxorubicin simultaneously than in those given ICRF-187 2 h after doxorubicin. These observations were interpreted as indicating that the timing of administration of ICRF-187 with respect to that of doxorubicin is an important factor in determining the degree of cardioprotection and that there is a "time window" in which ICRF-187 exerts optimal effects.

Antitumor activity of MST-16, a novel derivative of bis(2,6-dioxopiperazine), in murine tumor models

We studied the antitumor activity of newly synthesized bis(1-acyloxymethyl) derivatives of 4,4'-(1,2-ethanediyl)bis(2,6-piperazinedione) using i.p.-i.p. models of P388 leukemia and B16 myeloma. As a result, we found 4,4'-(1,2-ethanediyl)bis(1-isobutoxycarbonyloxymethyl-2,6-piperazi nedione) (MST-16) to possess considerable therapeutic activity. MST-16 showed not only marked life-prolonging effects in both P388 leukemia- and B16 melanoma-bearing mice but also a greater therapeutic ratio than did its parent compounds, ICRF-154 and ICRF-159. Further studies revealed that MST-16 has considerable therapeutic activity against a number of other tumors such as ascitic forms of L1210 leukemia, colon 26 adenocarcinoma, and MH-134 hepatoma and solid forms of B16 melanoma, Lewis lung carcinoma, colon 38 adenocarcinoma, and M5076 fibrosarcoma. These results suggest that MST-16 is very promising as an antitumor agent.

Evidence of the selective alteration of anthracycline activity due to modulation by ICRF-187 (ADR-529)

Anthracyclines are powerful anticancer drugs whose use is limited by the development of chronic cardiotoxicity. The bisdioxopiperazine compound ICRF-187 (ADR-529) specifically abrogates this toxicity both in preclinical animal models and in humans. It does this without effecting either the acute toxicities or the anticancer activity. Therefore, with a specific antagonist, the mechanism of activity of the anthracyclines can be explored. This review discusses recent clinical trials and animal models addressing this issue and concludes by hypothesizing a mechanism of action.

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

Studies in animals suggest that the bispiperazinedione ICRF-187 can prevent the development of dose-related doxorubicin-induced cardiac toxicity. In a randomized trial in 92 women with advanced breast cancer, we compared treatment with fluorouracil, doxorubicin, and cyclophosphamide (FDC), given every 21 days, with the same regimen preceded by administration of ICRF-187 (FDC + ICRF-187). Patients were withdrawn from the study when cardiac toxicity developed or the cancer progressed. The mean cumulative dose of doxorubicin tolerated by patients withdrawn from study was 397.2 mg per square meter of body-surface area in the FDC group and 466.3 mg in the FDC + ICRF-187 group (no significant difference). Eleven patients on the FDC + ICRF-187 arm received cumulative doxorubicin doses above 600 mg per square meter, whereas one receiving FDC was able to remain in the study beyond this dose. Antitumor response rates were similar (FDC vs. FDC + ICRF-187, 3 vs. 4 complete responses; 17 vs. 17 partial responses; and 9.3 vs. 10.3 months to disease progression). Although myelosuppression was slightly greater in the FDC + ICRF-187 group, the incidence of fever, infections, alopecia, nausea and vomiting, or death due to toxicity did not differ between the groups. Cardiac toxicity was evaluated by clinical examination, determination of the left ventricular ejection fraction by multigated nuclear scans, and endomyocardial biopsy. In comparisons of the FDC group with the FDC + ICRF-187 group, clinical congestive heart failure was observed in 11 as compared with 2 patients; the mean decrease in the left ventricular ejection fraction was 7 vs. 1 percent when the cumulative dose of doxorubicin was 250 to 399 mg per square meter (P = 0.02), 16 vs. 1 percent at 400 to 499 mg (P = 0.001), and 16 vs. 3 percent at 500 to 599 mg (P = 0.003); and the Billingham biopsy score was 2 or more in 5 of 13 patients undergoing biopsy vs. none of 13 (P = 0.03). We conclude that ICRF-187 offers significant protection against cardiac toxicity caused by doxorubicin, without affecting the antitumor effect of doxorubicin or the incidence of noncardiac toxic reactions.

Effect of high dose mitozantrone with Cronassial on the Lewis lung carcinoma and L1210 leukaemia

Mice given mitozantrone (MTZ) in doses close to the LD100 (high dose, HD) all survive if they also receive at the same time a mixture of four defined gangliosides--Cronassial (CRN). The protective action of CRN against the toxic effects of MTZ is not accompanied by a reduction of the antitumour activity of MTZ; on the contrary the reduced toxicity permits higher doses of MTZ to be given with the result that better antitumour activity can be achieved. This is illustrated by the highly effective action of MTZ and CRN in preventing the appearance of Lewis lung carcinoma (3LL) metastases, a tumour against which MTZ when used alone is inactive even at maximum tolerated doses (MTD). However, the effect of the combination on the primary 3LL is less pronounced. HD-MTZ and CRN are also more effective than MTD-MTZ alone in preventing dissemination and proliferation of L1210 leukaemia. Although the mechanism of the CRN protective effect is as yet unclear it appears that CRN prevents the lethal effects of necrotizing enteritis produced by HD-MTZ. It is concluded that CRN by reducing MTZ toxicity without interfering with its activity increases the therapeutic index of MTZ and permits an expanded exploration of its dose response curve against a variety of malignancies.

Mitigation of an anthracycline-induced cardiomyopathy by pretreatment with razoxane: a quantitative morphological assessment

A quantitative evaluation of structural modifications was undertaken in the myocardium of daunorubicin (DNR)-treated and razoxane (RZ)-protected mice. BDF1 mice were injected with DNR, 15 mg/kg; a second group of mice was subjected to the same conditions but, in addition, received a pretreatment of RZ, 200 mg/kg. Representative cubes of myocardial tissue were processed for viewing with the electron microscope. Five hundred myocardial cells in each group were examined for the presence of lesions which had been categorized as early, moderate, or advanced. Contrasting the total number of demonstrable lesions in each group revealed a statistically significant reduction of 38% in abnormalities present in RZ-protected mice. By category, RZ-pretreated mice showed a mitigation in the appearance of early and moderate alterations and a striking reduction in the incidence of advanced, irreversible lesions. These results indicate that the cardiomyopathy associated with DNR administration can be ameliorated by pretreatment with RZ; this protective effect is markedly exerted by preventing the development of severe, irreversible lesions in the murine myocardium; the initial, non-transient structural alteration subsequent to DNR-exposure appears to affect the myocardial sarcoplasmic reticulum.

The influence of inosine on adriamycin-induced cardiomyopathy in rats

The effect of inosine on adriamycin-induced cardiomyopathy was studied. Total adriamycin (ADR) dose of 25 mg/kg i.p. injected in 15 equal partial doses 3 times a week for five following weeks evoked fully developed cardiomyopathy in rats. Inosine 200 mg/kg i.p. injected 5 times a week parallel to ADR diminished ADR cardiotoxicity evaluated by electrocardiographic recordings and histopathological examination. Moreover lower cytostatic toxicity was observed as judged by less-expressed leucopenia and lower SGOT activities in inosine treated animals.

Interaction of razoxane and radiation on cultured Chinese hamster cells

Razoxane [(+/-)-1,2-bis(3,5-dioxopiperazine-1-yl)propane] was investigated for its effects on the survival of irradiated Chinese hamster fibroblasts in vitro. Razoxane alone produced cytotoxicity that was dependent upon drug concentration and pulse exposure time, with a preferential lethality for cells treated while in the DNA-synthetic phase. Razoxane enhanced radiation-induced cell killing when used as either a pulse exposure or a continuous treatment. In asynchronous populations of cells, this was expressed as an increase in the slope and a reduction in the shoulder of the radiation dose-survival curve. In synchronous populations of cells, a modest increase in cell killing was observed for those cells treated in G1 and G2, with a greater enhancement for cells treated in the S-phase. Overall, razoxane may potentiate the radiation-induced killing of cultured mammalian cells by a number of mechanisms: 1) a blockade of cell cycle progression causing an accumulation of cells in radiosensitive phases of the cell cycle; 2) selective cytotoxicity of cells in radioresistant phases of the cell cycle; 3) inhibition of the accumulation of sublethal radiation damage; or 4) interaction of the damages induced by each agent so as to produce an enhanced effect. These mechanisms may need to be considered if razoxane and radiation therapy are to be used in combined modality therapeutic approaches.

Mitigating effects of ICRF-159 (razoxane) on a daunomycin-induced cardiomyopathy in mice

In an attempt to induce in mice the cardiomyopathy associated with daunomycin treatment and to ameliorate this disorder by a protective pretreatment with ICRF-159 (razoxane), young male BDF 1 mice were injected with daunomycin, 6 mg/kg, in multiple doses. A second group of mice were pretreated by injection with razoxane, 200 mg/kg, 24 hours before each daunomycin administration. Within three weeks of the third daunomycin injection one half of the unprotected mice were moribund and were sacrificed. Mice pretreated with razoxane survived the length of the experiment without exhibiting any disabilities. Myocardial tissue of all mice was processed for light and electron microscopic examination. The myocardial ultrastructure of daunomycin-toxic mice showed foci of incipient changes, characterized by sarcoplasmic translucency, vacuolation of membrane-limited components, degeneration of mitochondria and lysosomal aggregates. Evaluation of mice pretreated with razoxane either failed to reveal ultrastructural alterations or demonstrated only minimal changes in the myocardium.

Antitumor activities and schedule dependence of orally administered MST-16, a novel derivative of bis(2,6-dioxopiperazine)

We studied bioavailability, treatment schedule dependence, and therapeutic efficacy of orally administered MST-16, a novel derivative of bis(2,6-dioxopiperazine), against murine tumors and human tumor xenografts. The rate of its intestinal absorption was about 50%, and it was immediately metabolized to its parent compound, ICRF-154. Therapeutic efficacy of MST-16 was heavily dependent on the treatment schedule: 9 daily oral administrations and treatment every 4 h on day 1 only were much more effective against s.c.-implanted L1210 leukemia than a single dose or five daily administrations giving the same total dose. Orally administered MST-16 showed potent life-prolonging effects (196%, 219% and 148%) in mice inoculated i.p. with P388, L1210 leukemia, and C-26 colon adenocarcinoma, respectively, but had no effect on B16 melanoma inoculated in the same way. MST-16 inhibited more than 80% growth of Lewis lung carcinoma, B16 melanoma, and C-38 colon adenocarcinoma implanted s.c., but had only a minor effect on M5076 fibrosarcoma. Lung metastasis of Lewis lung carcinoma was also effectively suppressed. Furthermore, MST-16 significantly inhibited growth of human colon, lung and breast cancers implanted s.c. in nude mice. We also made a kinetic analysis of the in vitro cell-killing effect by ICRF-154, the active form of MST-16 in vivo. It demonstrated a cell cycle phase-specific and time-dependent action, providing a reasonable explanation for the schedule-dependent therapeutic effect of MST-16.