A Preliminary Clinical Experience with Reduced Glutathione as Protector against Cisplatin-Toxicity

Dietary phytochemicals with anti-oxidant and pro-oxidant activities: A double-edged sword in relation to adjuvant chemotherapy and radiotherapy?

Many advances have been made in the development and introduction of new anti-cancer drugs to the clinic. However, limited attention has been paid to improving the efficacy of currently available treatments through complementary phytochemical interventions that affect cellular reactive oxygen species (ROS) levels, which are important for the etiology of certain cancers and the effectiveness of radiotherapy and some chemotherapy. In this regard, the maintenance of redox homeostasis may be influenced by the intake of anti-oxidant and pro-oxidant compounds from dietary sources. Interestingly, certain dietary phytochemicals exhibit both anti-oxidant and pro-oxidant activities, depending on their concentration and cellular microenvironment. There is evidence that concurrent administration of some dietary phytochemicals enhances the efficacy of certain cancer treatments by increasing intracellular ROS accumulation. Paradoxically, consumption of the same dietary phytochemicals under conditions that result in the scavenging of ROS might also negatively affect the outcome of ROS-dependent cancer treatments. This review discusses the potential impact of consuming dietary phytochemicals with anti-oxidant and/or pro-oxidant activities on the effectiveness of concurrent chemotherapy and/or radiotherapy in cancer patients.

A Phase II Study of Combination Chemotherapy in Advanced Ovarian Carcinoma with Cisplatin and Cyclophosphamide plus Reduced Glutathione as Potential Protective Agent against Cisplatin Toxicity

Aims and Backgroud

The clinical use of cisplatin (CDDP)„ one of the most active agents in advanced ovarian cancer, is limited by nephrotoxicity and cumulative neurotoxicity. In preclinical studies, reduced glutathione (GSH) demonstrated a protective action against CDDP nephrotoxicity. We treated 20 patients with advanced ovarian carcinoma, with polichemotherapy containing CDDP + GSH, to assess the protective action of GSH against CDDP nephrotoxicity.

Methods

Between January 1988 and December 1989, 20 patients, with advanced ovarian carcinoma (St. III-IV-FIGO), not pretreated received CDDP: 45 mg/m2 i.v., on day 1-2, + cyclophosphamide (CPA): 900 mg/m2 i.v. on day 2 + GSH 2500 mg i.v. in normal saline 100 ml (in 15 min), before CDDP, every 21-28 days.

Results

A pathologic complete response rate (PCR) of 55 % (11/20) was observed (7/14 patients with bulky disease). Median survival was 26.5 months and 5 patients were still alive and disease free at 35 months. Toxicity was limited, without any case of nephrotoxicity.

Conclusions

On the basis of our previous experience with the same regimen without GSH, this study suggests that also in the clinical setting, GSH has no negative interference on CDDP activity and that GSH might improve the therapeutic index of CDDP. However, our data need to be confirmed by large randomized clinical studies.

A Feasibility Study of High-Dose Cisplatin and 5-Fluorouracil with Glutathione Protection in the Treatment of Advanced Colorectal Cancer

On the basis of previous studies supporting that glutathione (GSH) reduced cisplatin nephrotoxicity we have designed a new regimen in the treatment of advanced colorectal cancer, which included GSH as a modulator of cisplatin-induced toxicity. Eleven untreated patients with measurable metastatic colorectal cancer received 5-fluorouracil (750 mg/m2, daily continuous infusion for days 1-5) and cisplatin (40 mg/m2 1 hour-infusion for days 6-8) given every 4 weeks. Reduced glutathione (2.5 g) was delivered i.v. prior to each cisplatin infusion. Toxicity was minimal and reversible and included nausea/vomiting (11 cases), mild neurotoxicity (4 cases) and leukopenia (2 cases); only 2 patients showed moderate and transient increases of serum creatinine « 2 mg/dl) and BUN. Renal function impairment was also monitored by magnesemia levels and urinary marker enzymes indicating minimal cumulative nephrotoxicity. Out of 10 evaluable patients, only 2 partial responses were observed. The median survival was 9 months (range 5-26). The study was closed, since the preliminary results do not suggest any therapeutic advantage in adding cisplatin to 5-fluorouracil in the present schedule, even using an intensive regimen. Indirect evidence suggests that these disappointing results are not the consequence of interference of GSH on the cytotoxic efficacy of cisplatin. The lack of incidence of severe toxicity of this regimen supports the role of reduced glutathione as a potential protective against cisplatin nephrotoxicity. Although these preliminary results suggest that further studies with the present regimen in this disease are not warranted, in view of its safety this program deserves evaluation in the treatment of neoplastic diseases responsive to 5-fluorouracil/cisplatin.

Antioxidants as precision weapons in war against cancer chemotherapy induced toxicity - Exploring the armoury of obscurity

Cancer is the leading cause of mortality worldwide, accounting for almost 13% of deaths in the world. Among the conventional cancer treatments, chemotherapy is most frequently carried out to treat malignant cancer rather than localised lesions which is amenable to surgery and radiotherapy. However, anticancer drugs are associated with a plethora of side effects. Each drug, within every class, has its own set of adverse reactions which may cause patient incompliance and deterioration of the quality of life. One of the major causes of adverse reactions, especially for drugs targeting DNA, is the excessive production of reactive oxygen species (ROS) and subsequent build up of oxidative stress. To curb these undesired side effects, several dietary supplements have been tested, amongst which antioxidants have gained increasing popularity as adjuvant in chemotherapy. However, many oncologists discourage the use of antioxidant rich food supplements because these may interfere with the modalities which kill cancer by generating free radicals. In the present review, all studies reporting concomitant use of several antioxidants with chemotherapy are indiscriminately included and discussed impartially.

The effect of supplementation of thirteen different antioxidants and their analogues as a single agent or in combination with chemotherapy has been compiled in this article. The present review encompasses a total of 174 peer-reviewed original articles from 1967 till date comprising 93 clinical trials with a cumulative number of 18,208 patients, 56 animal studies and 35 in vitro studies. Our comprehensive data suggests that antioxidant has superior potential of ameliorating chemotherapeutic induced toxicity. Antioxidant supplementation during chemotherapy also promises higher therapeutic efficiency and increased survival times in patients.

Systematic review: generating evidence-based guidelines on the concurrent use of dietary antioxidants and chemotherapy or radiotherapy

The risk-benefit ratio for concurrent use of dietary antioxidants with chemotherapy or radiation therapy is a controversial topic. In this review, the medical literature on concurrent antioxidant use with chemotherapy or radiotherapy was assessed and further steps for generating evidence-based guidelines are suggested. The clinical cancer research community should cooperate and focus new studies on the use of a specific combination of antioxidant and chemotherapy or radiotherapy, and determine optimal doses for a specific cancer setting. Mechanistic studies on the interaction between antioxidants and conventional cancer therapy could lead to novel biomarkers for assessing dose adequacy.

L-2-oxothiazolidine-4-carboxylate influence on age- and heat exposure-dependent redox changes in rat's blood plasma

In the present study, we investigated both the age- and heat exposure-related redox changes of blood plasma by analyzing GSH, thiol status and carbonyl groups. Our results clearly indicated that the plasma redox balance shifted toward oxidation during both aging and acute heat exposure. To further confirm this age- and heat exposure-related redox shift, we quantified the changes in thiol content. The total thiol level was found to be significantly decreased in the aged group. A similar pattern can be explained by low levels of serum GSH in old rats compared to young rats. The significance of the present study are the data showing increased oxidative stress in plasma during aging, attributed to a decrease in major antioxidant components in serum. OTC treatment, in relation to C=O regarded as a marker of oxidative damage was probably much more effective in increasing of GSH synthesis than in prevention of protein oxidation.

Protective role of Ipomoea obscura (L.) on cyclophosphamide-induced uro- and nephrotoxicities by modulating antioxidant status and pro-inflammatory cytokine levels

Cyclophosphamide (CP) is widely used, alone or in combination with other chemotherapeutic agents, for the treatment of neoplastic diseases. Its urotoxicity may cause dose-limiting side-effects, for example haemorrhagic cystitis. This urotoxicity may lead to nephrotoxicity. In the present study, we investigated the protective role of Ipomoea obscura against CP-induced uro- and nephrotoxicities in animal models. Swiss albino mice were treated with an acute dose of CP (1.5 mmol/kg body wt ip) in the presence and absence of alcoholic extract of I. obscura (10 mg/kg, body wt, ip) for 5 days. The toxicities caused by CP were reversed by the extract administration as evident from the decrease in BUN, serum creatinine levels as well as an increase in body weight. A significant increase in kidney antioxidant system such as, GSH, SOD, CAT, and GPx was also observed in extract-treated animals. Histopathological analysis of urinary bladder and kidney indicated that CP-induced tissue damage was significantly reduced in animals treated with I. obscura. The lowered levels of cytokines IFN-γ and IL-2, after CP treatment were found to be increased in treated animals. At the same time the level of proinflammatory cytokine TNF-α, which was elevated during CP administration, was significantly reduced by extract administration. This study clearly demonstrates that I. obscura can ameliorate CP-induced bladder and renal toxicities by modulating antioxidant status and proinflammatory cytokine levels.

Diagnosis, management, and evaluation of chemotherapy-induced peripheral neuropathy

Peripheral neuropathy induced by cancer chemotherapy represents a large unmet need for patients due to the absence of treatment that can prevent or mitigate this common clinical problem. Chemotherapy-induced peripheral neuropathy (CIPN) diagnosis and management is further compounded by the lack of reliable and standardized means to diagnose and monitor patients who are at risk for, or who are symptomatic from, this complication of treatment. The pathogenesis and pathophysiology of CIPN are not fully elucidated, but there is increasing evidence of damage or interference with tubulin function. The diagnosis of CIPN may present a diagnostic dilemma due to the large number of potential toxic etiologies and conditions, which may mimic some of the clinical features; the diagnosis must be approached with care in such patients. The incidence and severity of CIPN is commonly under-reported by physicians as compared with patients. The development of new and reliable methods for the assessment of CIPN as well as safe and effective treatments to prevent this complication of treatment would represent important medical advancements for cancer patients.

Protective effects of Emblica officinalis Gaertn. in cyclophosphamide-treated mice

Cyclophosphamide (CP) is one of the most popular alkylating anticancer drugs in spite of its toxic side effects including immunotoxicity, hematotoxicity, mutagenicity and a host of others. The present study was undertaken to assess the protective effects of total aqueous extract of a medicinal plant, Indian gooseberry (Emblica officinalis Gaertn.) in mice treated with CP. These protective effects were studied on immunological parameters and kidney and liver antioxidants. Plant extract treatment at a dose of 100 mg/kg body weight per os (p.o.) for 10 days resulted in the modulation of these parameters in normal as well as CP (50 mg/kg)-treated animals. Plant extract in particular was very effective in reducing CP-induced suppression of humoral immunity. Plant extract treatment in normal animals modulated certain antioxidants of kidney and liver. In CP-exposed animals, plant pretreatment provided protection to antioxidants of kidney. Not only were the reduced glutathione levels significantly (p<0.001) increased but plant extract treatment resulted in restoration of antioxidant enzymes in CP-treated animals. It is suggested that E. officinalis or its medicinal preparations may prove to be useful as a component of combination therapy in cancer patients under CP treatment regimen.

Dietary antioxidants during cancer chemotherapy: impact on chemotherapeutic effectiveness and development of side effects

Several studies suggest that dietary supplementation with antioxidants can influence the response to chemotherapy as well as the development of adverse side effects that results from treatment with antineoplastic agents. Administration of antineoplastic agents results in oxidative stress, i.e., the production of free radicals and other reactive oxygen species (ROS). Oxidative stress reduces the rate of cell proliferation, and that occurring during chemotherapy may interfere with the cytotoxic effects of antineoplastic drugs, which depend on rapid proliferation of cancer cells for optimal activity. Antioxidants detoxify ROS and may enhance the anticancer effects of chemotherapy. For some supplements, activities beyond their antioxidant properties, such as inhibition of topoisomerase II or protein tyrosine kinases, may also contribute. ROS cause or contribute to certain side effects that are common to many anticancer drugs, such as gastrointestinal toxicity and mutagenesis. ROS also contribute to side effects that occur only with individual agents, such as doxorubicin-induced cardiotoxicity, cisplatin-induced nephrotoxicity, and bleomycin-induced pulmonary fibrosis. Antioxidants can reduce or prevent many of these side effects, and for some supplements the protective effect results from activities other than their antioxidant properties. Certain side effects, however, such as alopecia and myelosuppression, are not prevented by antioxidants, and agents that interfere with these side effects may also interfere with the anticancer effects of chemotherapy.

Renal toxicity caused by cisplatinum in glutathione-depleted metallothionein-null mice

To elucidate the protective role of metallothionein (MT) and glutathione (GSH) in renal toxicity caused by cisplatinum (cis-DDP), we examined the sensitivity of GSH-depleted MT-null mice to the renal toxicity of cis-DDP. Blood urea nitrogen and creatinine values in the serum, and histopathological change in the kidney were utilized as indicators of nephrotoxicity caused by cis-DDP. Although cis-DDP exerted renal toxicity in MT-null mice and wild-type mice, the toxicity was more conspicuous in the MT-null mice than in the wild-type mice. Moreover, renal toxicity caused by cis-DDP was enhanced significantly by a decrease in the renal GSH level by buthionine sulfoximine (BSO) pretreatment in both kinds of mice. The cis-DDP-caused nephrotoxicity that was enhanced by BSO-mediated GSH depletion was much more severe in the MT-null mice than in the wild-type mice. However, preadministration of zinc sulfate cancelled the BSO-enhanced, cis-DDP-dependent renal toxicity in the wild-type mice, but not in the MT-null mice. In the present study, we found that MT and GSH play an important, cooperative role in detoxification of severe kidney damage caused by cis-DDP. Moreover, the renal MT preinduced by zinc could protect mice from cis-DDP nephrotoxicity enhanced by GSH depletion.

Protection by extracellular glutathione against sulfur mustard induced toxicity in vitro

1. The present study characterizes the role of extracellularly added glutathione in protection against sulfur mustard (HD) toxicity in a macrophage monocyte cell line J774. 2. Toxic effects of HD depend on dose and duration of exposure with an ED50 of 50 and 75 microM for dividing and confluent cells respectively. 3. Exposure to HD, 100-200 microM caused approximately 15% decrease in the cellular glutathione (GSH) content 2 h after exposure, pretreatment with GSH, 0.2-10 mM, elevated cellular GSH approximately x 1.5. 4. GSH pretreatment increased cell viability after HD 2-3-fold. Similar protective effects of GSH treatment were found in a human epidermoid carcinoma cell line (KB). 5. Protection by post treatment with GSH was apparent even 60 min post HD exposure. 6. No protection was afforded when the intracellular GSH concentration was elevated prior to exposure and the extracellular GSH had been washed out. However, GSH depleted cells were more sensitive to HD than normal cells, and were also protected by addition of GSH to the growth medium, although the intracellular GSH content remained low. 7. We conclude that it is essential for the GSH to be present extracellularly in order to protect cells from HD toxicity. 8. Our findings have therapeutic implications in particular for the protection of lungs after inhalation exposure to HD vapor.

The effect of treatment with high dose melphalan, cisplatin or carboplatin on levels of glutathione in plasma, erythrocytes, mononuclear cells and urine

Glutathione(GSH) has been implicated as an important factor in the detoxification of many electrophilic xenobiotics, including agents used in cytotoxic chemotherapy. Maintenance of high levels of GSH in normal tissues is believed to be important in the prevention of drug-induced toxicity. Previous studies have indicated that exposure of cells to some toxic electrophiles both in vitro and in vivo can cause a temporary decrease in intracellular levels of GSH. In this paper we report that in a series of 22 children and young adults treated with high dose melphalan (ten courses studied, all 200 mg/m2), cisplatin (eight courses, 80-104 mg/m2) or carboplatin (seven courses, 507-750 mg/m2) there was no significant alteration in the level of plasma, erythrocyte or urine GSH in the period immediately following drug administration. Fluctuations in the level of GSH in mononuclear cells were observed in some patients but did not follow any consistent pattern and were similar to those observed in a series of nine normal adult controls over the same time course. These results suggest that for melphalan, cisplatin and carboplatin, drug-GSH adduct formation is insufficient to cause a measurable decrease in intracellular GSH levels in normal peripheral haematopoietic cells during the course of treatment.

Attenuation of gentamicin ototoxicity by glutathione in the guinea pig in vivo

The effect of glutathione co-therapy on the expression of gentamicin ototoxicity was tested in pigmented guinea pigs. The first group of animals was injected with gentamicin (100 mg/kg body weight/day) for two weeks followed by 10 weeks of rest. A second group received glutathione by gastric gavage immediately prior to each gentamicin injection. Two groups of controls were treated either with saline injections or glutathione gavage alone. Auditory brainstem responses, taken at 2-week intervals, revealed a progressive gentamicin-induced hearing loss reaching a 30 to 40 dB threshold shift at 2 kHz, approximately 60 dB at 8 kHz and 80 dB at 18 kHz. Glutathione co-therapy slowed the progression of hearing loss and significantly attenuated the final threshold shifts by 20 to 40 dB. Morphological evaluation confirmed hair cell loss after gentamicin treatment and protection by glutathione. Drug serum levels were assayed at 2 and 7 days of treatment. There were no differences between the gentamicin (mean = 183 micrograms/ml; range, 90 to 300) and the gentamicin/glutathione group (mean = 164 micrograms/ml; range, 80 to 320). Antimicrobial activity of gentamicin was tested against Staphylococcus aureus and Pseudomonas aeruginosa. A 30-fold molar excess of glutathione did not influence the efficacy of gentamicin. These studies suggest that glutathione protects against ototoxicity by interfering with the cytotoxic mechanism.

Patterns of hearing loss resulting from cis-platinum therapy

The purpose of this study was to provide a clinically useful classification of the hearing loss that occurs with chemotherapy using cis-diamminedichloroplatinum (cis-platinum). Serial audiometric testing was performed on 66 patients who underwent cis-platinum chemotherapy (2 to 6 courses, 100 mg/m2). Subsequent hearing losses were classified according to (1) whether hearing loss occurred after the first or second course of chemotherapy, (2) the magnitude of loss, and (3) the frequencies affected. Of 39 patients who could be classified, 21 (54%) had no loss or mild loss, 14 (36%) had early loss, and 4 (10%) had late loss. Different patterns of hearing loss were observed. The observation that different patterns of hearing loss occur implies that different mechanisms of hearing loss exist. Some mechanisms must be more important in different patients. Our data are important with regard to continuation of chemotherapy treatment after hearing loss occurs. Most significant hearing loss (90%) occurred early or not at all. If early hearing loss occurred and treatment was continued, the speech frequencies were eventually affected in 71% of patients. Recognition of the patterns of hearing loss are important considerations when discontinuation of therapy is being considered.

Role of glutathione for cisplatin nephrotoxicity in young and adult rats

Investigations were done in 10- and 55-day-old Wistar rats. Glutathione (GSH) level in kidney was decreased by 8 mmol buthionine sulfoximine (BSO)/100 g BW. There was no effect on the renal function and nephrotoxicity of cisplatin (0.6 mg CP/100 g BW) in adult rats. In young rats BSO treatment was followed by nephrotoxic effects. Pt concentration remained unaffected by BSO in young and adult rats. GSH concentration in kidney was increased by 100 mg acetyl-cysteine (accys)/100 g BW. CP nephrotoxicity was lower in young as well as in adult ac-cys-treated rats. Pt levels in renal tissue were significantly decreased in rats from both age groups. From our results we conclude that the beneficial effect of high GSH concentration in renal tissue on CP nephrotoxicity is the result of decreased Pt concentration in kidney.

Weekly 5-fluorouracil and folinic acid plus escalating doses of cisplatin with glutathione protection in patients with advanced head and neck cancer

Twenty-two patients with advanced head and neck carcinoma were treated with 5FU 400 mg-2 m-1 week and folinic acid 500 mg m-2 week-1 plus CDDP in escalating doses from 20 to 40 mg m-2 week-1 without forced diuresis. Reduced glutathione at the dose of 1.5 g m-2 was employed to protect patients from CDDP-related nephrotoxicity. The aims of the study were: a) to evaluate the therapeutic efficacy of this schedule, and b) to evaluate reduced glutathione as uroprotector. Out of 20 evaluable patients 14 (70%) had a major objective response. A CR with a mean duration of 9.0+ months was achieved in 15% of the patients, a PR of 5.8+ months in 55% of the patients, while 3 patients had stable disease and 4 progressed. It was possible to escalate CDDP up to 35 mg m-2 week-1, but at the dose of CDDP 40 mg m-2 week-1 the occurrence of grade 2 renal toxicity provoked a severe reduction of dose-intensity. Overall, this treatment has been very well tolerated by most patients with few cases of grade 3 gastrointestinal or hematological toxicity. In conclusion, the schedule seems effective and may be safely given to patients with advanced head and neck cancer on outpatient basis. Reduced glutathione seems to be able to reduce, at least partially, CDDP-related nephrotoxicity permitting the delivery of higher CDDP doses.

Cisplatin-based chemotherapy in a renal transplant recipient

Cisplatin-based chemotherapy is the treatment of choice for metastatic testicular cancer; however, the safety of conventional regimens in renal transplant recipients has been questioned. The authors report the course of a renal transplant recipient successfully treated with a cisplatin-based chemotherapy regimen for testicular seminoma and review three additional cases that have been reported in the English language literature to date. Emphasis is placed on review of the safety, optimal administration, and appropriate monitoring of cisplatin and controversy regarding the need for continued administration of immunosuppressive therapy.

High-dose intravenous glutathione in man. Pharmacokinetics and effects on cyst(e)ine in plasma and urine

Parenteral glutathione has therapeutic potential for targeted delivery of cysteine equivalents. Thus, high doses of reduced glutathione (GSH) protect from the nephrotoxic and urotoxic effects of cisplatinum and oxazaphosphorines. In order to elucidate the underlying mechanisms the kinetics and the effect of glutathione on plasma and urine sulphydryls were studied in 10 healthy volunteers. Following the intravenous infusion of 2 g m-2 of glutathione the concentration of total glutathione in plasma increased from 17.5 +/- 13.4 mumol l-1 (mean +/- SD) to 823 +/- 326 mumol l-1. The volume of distribution of exogenous glutathione was 176 +/- 107 ml kg-1 and the elimination rate constant was 0.063 +/- 0.027 min-1 corresponding to a half-life of 14.1 +/- 9.2 min. Cysteine in plasma increased from 8.9 +/- 3.5 mumol l-1 to 114 +/- 45 mumol l-1 after the infusion. In spite of the increase in cysteine, the plasma concentration of total cyst(e)ine (i.e. cysteine, cystine, and mixed disulphides) decreased, suggesting an increased uptake of cysteine from plasma into cells. Urinary excretion of glutathione and of cyst(e)ine was increased 300-fold and 10-fold, respectively, in the 90 min following the infusion. The present data suggest that the concentration of sulphydryls in the urinary tract and, more importantly, the intracellular availability of cysteine increase markedly following parenteral glutathione. The high intracellular concentration of cysteine may protect against cisplatinum and oxazaphosphorine toxicity either directly or indirectly by supporting the synthesis of glutathione.

Relative effectiveness of some compounds for the control of cisplatin-induced nephrotoxicity

Several procedures which have been reported as effective for the control of cisplatin induced nephrotoxicity were compared in the Sprague-Dawley rat using the same dose of cisplatin. The treatments examined were based on the use of sodium thiosulfate, sodium diethyldithiocarbamate (DDTC), glutathione (GSH), sodium N-methyl-D-glucamine dithiocarbamate (NaG) and S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721). The differences in the effectiveness of the procedures were assessed using BUN and serum creatinine values, histopathological examination, body weight changes, and renal platinum levels as indices. The effect of such treatments on the antineoplastic activity of cisplatin were examined with both the Walker 256 carcinosarcoma in the rat and the L1210 murine leukemia in mice. Under the conditions used, GSH was found to be more effective than the other nucleophiles in protecting against the nephrotoxicity of cisplatin while providing the least amount of interference with the antitumor activity as measured against the Walker 256 carcinosarcoma and the L1210 murine leukemia. Simultaneous i.v. administration of cisplatin and any of the sulfur-containing nucleophiles leads to a significant protection against the nephrotoxicity but reduced the anti-neoplastic activity of cisplatin when measured against the Walker 256 carcinosarcoma.

Efficacy and safety of high-dose cisplatin and cyclophosphamide with glutathione protection in the treatment of bulky advanced epithelial ovarian cancer

Recent efforts to improve the response rates in advanced ovarian cancer with the use of high-dose cisplatin have been limited by unacceptable toxicity. Based on experimental and clinical studies indicating that reduced glutathione (GSH) is a protective agent against cisplatin-induced toxicity, a new high-dose regimen including GSH as a chemoprotector was designed in an attempt to improve the efficacy and therapeutic index of cisplatin. A total of 40 consecutive patients with stage III (bulky) and IV ovarian carcinoma were treated with cisplatin (40 mg/m2 daily for 4 consecutive days) and cyclophosphamide (600 mg/m2 i.v. on day 4). The treatment was repeated every 3-4 weeks for five courses unless progression or severe toxicity occurred. Before each cisplatin administration, patients received GSH (1,500 mg/m2) i.v. over 15 min, with a standard i.v. hydration (2,000 ml fluid) without diuretics. Debulking surgery was initially attempted in 18 patients and, after 2-3 courses, in 16 patients; it could not be carried out in 6 patients. Three patients were not evaluable for response because they prematurely discontinued their treatment. In all, 23 patients (62%) achieved complete clinical remission (negative second-look laparotomy in 16), with an overall (complete + partial) response rate of 86%; 2 patients achieved disease-free status following second surgery. Nausea/vomiting was the most severe acute toxic effect; myelosuppression was acceptable. Renal impairment was effectively prevented by GSH. Neurotoxicity that was not associated with motor dysfunction was the most significant cumulative toxicity in patients (24/32) receiving 4-5 courses. The results of this study indicate that the use of GSH is a safe new method for high-dose cisplatin administration. This regimen is well-tolerated and very effective in ovarian cancer patients with bulky disease and warrants further evaluation.

L-methionine antagonism of cis-platinum nephrotoxicity

L-Methionine administered simultaneously with cis-platinum (CDDP) iv results in a significant reduction of the nephrotoxicity normally associated with CDDP without any apparent effect on the antineoplastic activity for rats bearing the Walker 256 carcinosarcoma. CDDP given with L-methionine at a 1:20 mole ratio can be administered to rats at doses up to 35 mg/kg iv with the survival of all treated animals (3/3) and up to 56 mg/kg iv (bolus injection) with the survival of 3/6 animals, while CDDP administered alone at these levels is lethal. A reduced level of protection against the nephrotoxicity was also achieved at lower mole ratios of L-methionine to CDDP. Renal function was monitored using BUN and serum creatinine levels, and gastrointestinal toxicity by weight changes during the course of the experiments. A histopathological examination of the kidneys was also performed to evaluate the protection provided by L-methionine. Under the conditions used, the reaction between L-methionine and CDDP does not appear to proceed so rapidly as to interfere with the antitumor activity of the CDDP. The examination of structural analogs as agents for the control of CDDP-induced nephrotoxicity revealed that the C-S-C-group is the essential group for the protective action in these structures. Although L-methionine can provide renal protection in rats given high doses of CDDP, it does not prevent the accumulation of platinum in the kidney.

Protective effect of reduced glutathione against cisplatin-induced renal and systemic toxicity and its influence on the therapeutic activity of the antitumor drug

Reduced glutathione has been shown to be an effective protector against cisplatin-induced nephrotoxicity of potential clinical value, since it does not reduce antitumor activity of the cytotoxic drug. This paper extends previous observations on the protective potential of reduced glutathione against cisplatin-induced nephrotoxicity, in different rodent models. Following i.v. administration, glutathione protection against cisplatin-induced nephrotoxicity was found to be critically dependent on timing of thiol administration. Whereas the sulfhydryl compound provided almost complete protection in CD rats, the protective effect against toxic renal damage was only partial in mice of different strains. In spite of the modest protection against kidney toxicity, glutathione reduced lethal toxicity in the mouse. Under the same experimental conditions at protective dose levels, the tripeptide thiol did not interfere with the antitumor effectiveness of cisplatin, in any of the tumor models examined. The kidney content of non-protein sulfhydryls of CD rats produced by the effective dose of glutathione was markedly higher than that found in the mouse treated with the same dose. This finding is consistent with a differential protection provided by glutathione against cisplatin-induced renal toxicity in these species.