Effects of the modulating agent WR2721 and its main metabolites on the formation and stability of cisplatin-DNA adducts in vitro in comparison to the effects of thiosulphate and diethyldithiocarbamate

Alpha-thiol deoxynucleotide triphosphates (S-dNTPs) as radioprotective agents: A novel approach

In this study, the ability of a mixture of four different alpha-thiol deoxynucleotide triphosphates (S-dNTPs) each at a concentration of 10μM when incorporated into the genomic DNA of proliferating human HL-60 and Mono-Mac-6 (MM-6) cells in vitro to provide protection from 2, 5, and 10 Gy of gamma radiation was investigated. Incorporation of the four different S-dNTPs into nuclear DNA at 10 μM concentration for five days was validated by agarose gel electrophoretic band shift analysis. S-dNTP-treated genomic DNA reacted with BODIPY-iodoacetamide demonstrated a band shift to higher molecular weight to confirm the presence of sulfur moieties in the resultant phosphorothioate DNA backbones. No overt signs of toxicity or obvious morphologic cellular differentiation were noted in the presence of 10 μM S-dNTPs even after 8 days in culture. Significantly reduced radiation-induced persistent DNA damage measured at 24 and 48 h post-exposure by γ-H2AX histone phosphorylation using FACS analysis in S-dNTP incorporated HL-60 and MM6 cells indicated protection against radiation-induced direct and indirect DNA damage. Statistically significant protection by S-dNTPs was noted at the cellular level by CellEvent™ Caspase-3/7 assay, which assess the extent of apoptotic events, and by trypan blue dye exclusion to assed cell viability. The results appear to support an innocuous antioxidant thiol radioprotective effect built into genomic DNA backbones as the last line of defense against ionizing radiation and free radical-induced DNA damage.

Advances in Toxicological Research of the Anticancer Drug Cisplatin

Cisplatin is one of the most widely used chemotherapeutic agents for various solid tumors in the clinic due to its high efficacy and broad spectrum. The antineoplastic activity of cisplatin is mainly due to its ability to cross-link with DNA, thus blocking transcription and replication. Unfortunately, the clinical use of cisplatin is limited by its severe, dose-dependent toxic side effects. There are approximately 40 specific toxicities of cisplatin, among which nephrotoxicity is the most common one. Other common side effects include ototoxicity, neurotoxicity, gastrointestinal toxicity, hematological toxicity, cardiotoxicity, and hepatotoxicity. These side effects together reduce the life quality of patients and require lowering the dosage of the drug, even stopping administration, thus weakening the treatment effect. Few effective measures exist clinically against these side effects because the exact mechanisms of various side effects from cisplatin remain still unclear. Therefore, substantial effort has been made to explore the complicated biochemical processes involved in the toxicology of cisplatin, aiming to identify effective ways to reduce or eradicate its toxicity. This review summarizes and reviews the updated advances in the toxicological research of cisplatin. We anticipate to provide insights into the understanding of the mechanisms underlying the side effects of cisplatin and designing comprehensive therapeutic strategies involving cisplatin.

Has vitamin E any shreds of evidence in cisplatin-induced toxicity

Cisplatin is one of the highly consumed and effective antitumor agents whose clinical application is accompanied by nephrotoxicity adverse reaction. Also, other complications such as ototoxicity and hepatotoxicity are a matter of concern. Today, it is suggested that cisplatin-associated toxicities are mainly induced by free radicals production, which will result in oxidative organ injury. The evidence is growing over the protective effects of antioxidants on cisplatin-induced adverse reactions especially nephrotoxicity. The possible protective effects of vitamin E and its derivative in cisplatin-induced nephrotoxicity and ototoxicity are reviewed here at the light of pertinent results from basic and clinical research. Administration of vitamin E alone or in combination with other antioxidant agents could cause amelioration in oxidative stress biomarkers such as decreasing the level of malondialdehyde, reducing serum urea and creatinine, and also enhancing the activities of renal antioxidant enzymes including renal catalase, glutathione-S-transferase, and superoxide dismutase. Although the data from most of the studies are in favors of protective effects of vitamin E against cisplatin-induced toxicity, more clinical trials are needed to clarify the clinical importance of vitamin E administration as an antioxidant during cisplatin therapy in cancer condition.

Development of Second-Generation CDK2 Inhibitors for the Prevention of Cisplatin-Induced Hearing Loss

There are currently no FDA-approved therapies to prevent the hearing loss associated with the usage of cisplatin in chemotherapeutic regimens. We recently demonstrated that the pharmacologic inhibition with kenpaullone or genetic deletion of CDK2 preserved hearing function in animal models treated with cisplatin, which suggests that CDK2 is a promising therapeutic target to prevent cisplatin-induced ototoxicity. In this study, we identified two lead compounds, AT7519 and AZD5438, from a focused library screen of 187 CDK2 inhibitors, performed in an immortalized cell line derived from neonatal mouse cochleae treated with cisplatin. Moreover, we screened 36 analogues of AT7519 and identified analogue 7, which exhibited an improved therapeutic index. When delivered locally, analogue 7 and AZD5438 both provided significant protection against cisplatin-induced ototoxicity in mice. Thus, we have identified two additional compounds that prevent cisplatin-induced ototoxicity in vivo and provided further evidence that CDK2 is a druggable target for treating cisplatin-induced ototoxicity.

Progress in the Development of Preventative Drugs for Cisplatin-Induced Hearing Loss

Cisplatin is a highly effective treatment for malignant cancers and has become a cornerstone in chemotherapeutic regimens. Unfortunately, its use in the clinic is often coupled with a high incidence of severe hearing loss. Over the past few decades, enormous effort has been put forth to find protective agents that selectively protect against the ototoxic side effects of cisplatin and do not interfere with its antitumoral activity. Many therapies have been successful in preclinical work, but only a few have shown any protection in the clinic, and none have been approved by the FDA. This review summarizes the clinical and preclinical studies of the most effective small-molecule candidates currently in clinical trials, while also detailing their molecular mechanisms of action, to gain insight for future drug development in the field.

Normal tissue radioprotection by amifostine via Warburg-type effects

The mechanism of Amifostine (WR-2721) mediated radioprotection is poorly understood. The effects of amifostine on human basal metabolism, mouse liver metabolism and on normal and tumor hepatic cells were studied. Indirect calorimetric canopy tests showed significant reductions in oxygen consumption and of carbon dioxide emission in cancer patients receiving amifostine. Glucose levels significantly decreased and lactate levels increased in patient venous blood. Although amifostine in vitro did not inhibit the activity of the prolyl-hydroxylase PHD2, experiments with mouse liver showed that on a short timescale WR-1065 induced expression of the Hypoxia Inducible Factor HIF1α, lactate dehydrogenase LDH5, glucose transporter GLUT2, phosphorylated pyruvate dehydrogenase pPDH and PDH-kinase. This effect was confirmed on normal mouse NCTC hepatocytes, but not on hepatoma cells. A sharp reduction of acetyl-CoA and ATP levels in NCTC cells indicated reduced mitochondrial usage of pyruvate. Transient changes of mitochondrial membrane potential and reactive oxygen species ROS production were evident. Amifostine selectively protects NCTC cells against radiation, whilst HepG2 neoplastic cells are sensitized. The radiation protection was correlates with HIF levels. These findings shed new light on the mechanism of amifostine cytoprotection and encourage clinical research with this agent for the treatment of primary and metastatic liver cancer.

Cisplatin-Induced Ototoxicity: Effects, Mechanisms and Protection Strategies

Cisplatin is a highly effective chemotherapeutic agent that is widely used to treat solid organ malignancies. However, serious side effects have been associated with its use, such as bilateral, progressive, irreversible, dose-dependent neurosensory hearing loss. Current evidence indicates that cisplatin triggers the production of reactive oxygen species in target tissues in the inner ear. A variety of agents that protect against cisplatin-induced ototoxicity have been successfully tested in cell culture and animal models. However, many of them interfere with the therapeutic effect of cisplatin, and therefore are not suitable for systemic administration in clinical practice. Consequently, local administration strategies, namely intratympanic administration, have been developed to achieve otoprotection, without reducing the antitumoral effect of cisplatin. While a considerable amount of pre-clinical information is available, clinical data on treatments to prevent cisplatin ototoxicity are only just beginning to appear. This review summarizes clinical and experimental studies of cisplatin ototoxicity, and focuses on understanding its toxicity mechanisms, clinical repercussions and prevention strategies.

Cisplatin-induced nephrotoxicity and targets of nephroprotection: an update

Cisplatin is a highly effective antitumor agent whose clinical application is limited by the inherent nephrotoxicity. The current measures of nephroprotection used in patients receiving cisplatin are not satisfactory, and studies have focused on the investigation of new possible protective strategies. Many pathways involved in cisplatin nephrotoxicity have been delineated and proposed as targets for nephroprotection, and many new potentially protective agents have been reported. The multiple pathways which lead to renal damage and renal cell death have points of convergence and share some common modulators. The most frequent event among all the described pathways is the oxidative stress that acts as both a trigger and a result. The most exploited pathways, the proposed protective strategies, the achievements obtained so far as well as conflicting data are summarized and discussed in this review, providing a general view of the knowledge accumulated with past and recent research on this subject.

Radiation damage and radioprotectants: new concepts in the era of molecular medicine

Exposure to ionising radiation results in mutagenesis and cell death, and the clinical manifestations depend on the dose and the involved body area. Reducing carcinogenesis in patients treated with radiotherapy, exposed to diagnostic radiation or who are in certain professional groups is mandatory. The prevention or treatment of early and late radiotherapy effects would improve quality of life and increase cancer curability by intensifying therapies. Experimental and clinical data have given rise to new concepts and a large pool of chemical and molecular agents that could be effective in the protection and treatment of radiation damage. To date, amifostine is the only drug recommended as an effective radioprotectant. This review identifies five distinct types of radiation damage (I, cellular depletion; II, reactive gene activation; III, tissue disorganisation; IV, stochastic effects; V, bystander effects) and classifies the radioprotective agents into five relevant categories (A, protectants against all types of radiation effects; B, death pathway modulators; C, blockers of inflammation, chemotaxis and autocrine/paracrine pathways; D, antimutagenic keepers of genomic integrity; E, agents that block bystander effects). The necessity of establishing and funding central committees that guide systematic clinical research into evaluating the novel agents revealed in the era of molecular medicine is stressed.

Limited cytoprotective effects of amifostine in high-dose radioactive iodine 131-treated well-differentiated thyroid cancer patients: analysis of quantitative salivary scan

PURPOSE

The aim of present study was to investigate the cytoprotective effect of amifostine on salivary glands in 131I-treated differentiated thyroid cancer (DTC) patients using serial quantitative analysis of salivary gland scans.

METHODS

Serial quantitative salivary scintigraphies were performed in 80 newly diagnosed DTC patients (9 men, 71 women; mean age, 43.2 years old; range, 21-58 years old). Forty-two patients were assigned randomly to the amifostine treatment group, which received 300 mg/m2 amifostine intravenously before 131I administration.

RESULTS

In both amifostine-treated and nontreated groups statistically significant declines of functional parameters after 131I treatment were revealed by quantitative salivary scintigraphy in DTC patients. Amifostine pretreatment did not prevent the parenchymal damage to major salivary gland function after 131I treatment (F = 1.37, p = 0.2461). However, the dose of 131I had significant effects on salivary gland function after 131I treatment (F = 9.72, p = 0.0002).

CONCLUSION

The present study did not show cytoprotective effects of amifostine for DTC patients treated with 131I.

A pilot study of addition of amifostine to melphalan, carboplatin, etoposide, and cyclophosphamide with autologous hematopoietic stem cell transplantation in pediatric solid tumors-A pediatric blood and marrow transplant consortium study

Limited information is available regarding the use of amifostine in pediatric hematopoietic stem cell transplant (HSCT) patients. Melphalan, carboplatin, etoposide +/- cyclophosphamide is a commonly used preparatory regimen in pediatric solid tumor HSCT. Therefore, we decided to determine the feasibility of the addition of amifostine (750 mg/m b.i.d. x 4 d) to melphalan (200 mg/m), carboplatin (1200 mg/m), and etoposide (800 mg/m) (level 1) and escalating doses of cyclophosphamide (3000 mg/m and 3800 mg/m, levels 2 and 3, respectively) followed by autologous HSCT. Thirty-two patients with a variety of pediatric solid tumors were studied. Seventeen patients were accrued at level 1, 9 at level 2, and 6 at level 3. Major toxicities during the administration of the preparatory regimen were hypocalcemia, emesis, and hypotension. Hypocalcemia required aggressive calcium supplementation during the conditioning phase. No dose limiting toxicities were encountered at level 3. Amifostine at 750 mg/m b.i.d. for 4 days can be administered with a double alkylator regimen consisting of melphalan (200 mg/m), cyclophosphamide (up to 3800 mg/m), carboplatin (1200 mg/m), and etoposide (800 mg/m) with manageable toxicities.

Amifostine increases cure rate of cisplatin on ascites hepatoma 22 via selectively protecting renal thioredoxin reductase

It has been demonstrated via in vitro experiments that the anti-cancer drug cisplatin (CDDP) can inactivate thioredoxin reductase (TrxR), a molecular target for cancer therapy. The present study in mice revealed that CDDP at pharmacological doses inhibited TrxR activity in both ascitic hepatoma 22 (H22) cells and kidney, leading to suppression of H22 cells proliferation along with nephrotoxicity. Amifostine, a clinical used cytoprotective agent, protected against CDDP-induced TrxR inactivation in kidney but not in H22 cells. Such an excellent selective modulation of amifostine on TrxR led us to exploit the potential of amifostine in increasing cure rate of CDDP on cancer. In mice, CDDP at the doses of 5 and 7.5 mg/kg once weekly for 4 weeks could not completely control H22 ascites development and the cure rate was no more than 12.5%; CDDP 9 mg/kg by the same schedule prominently suppressed the ascites development, but finally resulted in 87.5% mortality caused by CDDP toxicity. Thus, these dose-dependent therapeutic results well recapitulated the clinical dilemma of chemotherapy on cancer. However, co-treatment of CDDP (9 mg/kg) and amifostine largely reduced CDDP toxicity, and obtained a cure rate as high as 87.5%. Overall, the present study demonstrates both pharmacological and toxicological effects of CDDP involve TrxR inactivation, and the large enhancement on CDDP cure rate in H22 ascites model by using amifostine is, at least in part, ascribed to its selective modulation on TrxR.

A new intensive induction schedule, including high-dose Idarubicin, high-dose Aracytin and Amifostine, in older AML patients: feasibility and long-term results in 42 patients

OBJECTIVE

We evaluated the feasibility of a new regimen in elderly patients with acute myeloid leukemia (AML). The main end points were overall response rate (ORR) and toxicity; secondary end points were feasibility of peripheral blood stem cells (PBSC) collection, leukemia-free survival, and overall survival (OS).

PATIENTS AND METHODS

We treated 42 fit elderly patients with high-dose (HD) idarubicin plus HD-cytarabine (Ara-C), with amifostine.

RESULTS

We observed one treatment-related death (2%). The main extrahematological toxicity was represented by grade III to IV infections in 64% of patients. Hematological toxicity was acceptable with 15 days (range, 9-29 days) to reach >500 x 10(6)/L absolute neutrophil count and 16 days (range, 3-39 days) to achieve an unsupported platelet count >20,000 x 10(6)/L. Median duration of severe neutropenia was 12 days (range, 1-36) and median number of febrile days and intravenous antibiotics therapy was 6 (range, 0-17) and 17 days (range, 0-34), respectively, Median duration of hospitalization was 31 days (range, 20-61). ORR was 83% (34 of 41); 32 patients received intensive consolidation therapy; 15 patients were able to mobilize a sufficient number of CD34+ cells; and 14 were transplanted.

CONCLUSION

According to the intention to treat criteria all patients were analyzed for outcomes. Five-year OS was 19%, with median follow-up of 38 months. Patients with unfavorable cytogenetic and those with secondary AML had poorer OS; about 40% of patients could mobilize a sufficient amount of PBSC for autologous stem cell transplantation.

Effect of Amifostine on Response Rates in Locally Advanced Non–Small-Cell Lung Cancer Patients Treated on Randomized Controlled Trials: A Meta-Analysis

PURPOSE

Amifostine can reduce the cytotoxic effects of chemotherapy and radiotherapy in patients with locally advanced non-small-cell lung cancer, but concerns remain regarding its possible tumor-protective effects. Studies with sufficient statistical power to address this question are lacking.

METHODS AND MATERIALS

We performed a meta-analysis of all published clinical trials involving locally advanced non-small-cell lung cancer patients treated with radiotherapy with or without chemotherapy, who had been randomized to treatment with amifostine vs. no amifostine or placebo. Random effects estimates of the relative risk of overall, partial, and complete response were obtained.

RESULTS

Seven randomized trials involving 601 patients were identified. Response rate data were available for six studies (552 patients). The pooled relative risk (RR) estimate was 1.07 (95% confidence interval, 0.97-1.18; p = 0.18), 1.21 (95% confidence interval, 0.83-1.78; p = 0.33), and 0.99 (95% confidence interval, 0.78-1.26; p = 0.95) for overall, complete, and partial response, respectively (a RR >1 indicates improvement in response with amifostine compared with the control arm). The results were similar after sensitivity analyses. No evidence was found of treatment effect heterogeneity across the studies.

CONCLUSIONS

Amifostine has no effect on tumor response in patients with locally advanced non-small-cell lung cancer treated with radiotherapy with or without chemotherapy.

Future opportunities in preventing cisplatin induced ototoxicity

Cisplatin is one of the most commonly used cytotoxic agents. Ototoxicity is an important and dose-limiting side-effect of cisplatin therapy. It is believed that cisplatin suppresses the formation of endogenous anti-oxidants that normally prevent the inner ear against reactive oxygen species (ROS). These ROS affect the outer hair cells (OHCs) in the organ of Corti. Results from clinical trials with amifostine, an anti-oxidant with possible otoprotective action during cisplatin therapy, were disappointing. A variety of agents with chemoprotective action against cisplatin-induced ototoxicity were successfully tested in animal models. It is important to translate these promising results from animal models into clinical practice. The possible routes of administration are systemic and transtympanic. An important condition when using such an agent systemically is that the compound may not affect the anti-tumor effect of cisplatin. The critical step at transtympanic administration is the diffusion of the compound through the round window membrane (RWM). This diffusion depends on the characteristics of the medication as on the properties of the RWM. Positive results of an otoprotector in clinical practice may increase the effectiveness of cisplatin therapy and can improve the quality of life for a large group of patients.

Neuroprotection with amifostine in the first-line treatment of advanced ovarian cancer with carboplatin/paclitaxel-based chemotherapy--a double-blind, placebo-controlled, randomized phase II study from the Arbeitsgemeinschaft Gynäkologische Onkologoie (AGO) Ovarian Cancer Study Group

GOALS OF WORK

Neurotoxicity is a common side effect of platinum/taxane-based therapy of ovarian cancer. We performed a double-blind randomized placebo-controlled trial to evaluate the influence of the cytoprotectant amifostine on the neurotoxicity of first-line therapy of ovarian cancer with paclitaxel/carboplatin with or without epirubicin.

PATIENTS AND METHODS

Of 72 patients randomized, 71 were treated with paclitaxel 175 mg/m2 and carboplatin AUC5 with or without epirubicin 60 mg/m2 (q21 x 6) and randomized for i.v. premedication with amifostine 740 mg/m2 or placebo. Assessment included a questionnaire, NCI-CTC, tendon reflex activity (TRA), two-point discrimination (2-PD), measurement of vibration perception threshold (VPT) and vibration disappearance threshold (VDT), and quality of life.

RESULTS

The majority of neurotoxicity criteria showed a significant impairment during therapy in both treatment arms. A significant protective effect of amifostine was observed for 2-PD, TRA, VPT and VDT. Amifostine failed to improve the 'global health status quality of life' score significantly. Toxicities according to NCI-CTC showed improved sensory neuropathy (P = 0.0046) but a worsening in terms of nausea (P = 0.0005) and vomiting (P = 0.0083). No significant differences were observed for single sensory and motor symptoms, except for a better skilfulness in the amifostine group (P = 0.0404).

CONCLUSION

Amifostine improved sensory neuropathy according to NCI-CTC and with regard to objective neurological assessment, but there were almost no differences in self-estimated specific sensory or motor symptoms. Disadvantages with regard to non-neurological toxicities and inconsistent results for quality of life demand further evaluation of neuroprotection with amifostine as well as alternative approaches to prevent platinum-taxane induced neurotoxicity.

Time dependent protection of amifostine from renal and hematopoietic cisplatin induced toxicity

Efficacy of chemotherapy may be maximized and its toxicity can be minimized if drugs would be administered at specified daily times. The present study was aimed to examine if the protection of amifostine against cisplatin toxicity is time dependent. Amifostine is an organic thiophosphate that protects selectively normal tissues, but not tumors, against the cytotoxicity of DNA binding chemotherapeutic agents such as cisplatin. ICR male mice which were entrained to Light:Dark (L:D) 14:10 were injected (intrapritoneal bolus) for 5 consecutive days with either: cisplatin, cisplatin plus amifostine (administered 30 minutes prior to cisplatin). Injections were given at either 08:00, 13:00, 20:00 or 01:00. Five days later, on day 10, each set of mice was sacrificed (at the same hour corresponds to the injection hour), blood count, blood creatinine and blood urea nitrogen (BUN) were assayed. Cisplatin treated mice exhibited nephrotoxicity, as indicated by increased blood urea nitrogen values and by high blood urea nitrogen to creatinine ratios, as well as myelotoxicity that was indicated by low levels of hemoglobin and platelets. Co-administration of amifostine-cisplatin reversed both, the nephrotoxicity of cisplatin, and its myelosuppressive effects. For BUN, hemoglobin and platelets, maximal protections were observed at 08:00, (p <0.05, p <0.01 and p <0.01 respectively). For BUN/Cr ratio (p <0.05), maximal protections was observed at 13:00. These findings show that amifostine exhibits time dependent protection against cisplatin toxicity and thus it is recommended to use the protector when treatments are given during morning hours. The results also further validate the notion that chronochemotherapy is advantageous at least in reducing drug toxicity and thus should be integrated in the design of clinical protocols.

Cytoprotection in Acute Myelogenous Leukemia (AML) therapy

Planning therapy for acute myelogenous leukemia (AML) is difficult because of the heterogeneous nature of the disease and varying patient age at presentation. Cytogenetics and patient age at the time of diagnosis are two major factors determining treatment outcome in AML. Patients with poor-risk cytogenetics have much lower complete remission rates than other groups. In addition, AML in patients greater than 55 to 60 years of age often exhibits a resistant phenotype, more akin to secondary AML or AML arising from myelodysplastic syndromes. This group is also characterized by lower complete remission rates, and often requires the delivery of intensive therapy to a patient population that is the least likely to tolerate it. At the Jefferson Health System (Philadelphia, PA), we wished to develop a regimen that was maximally intensive to treat stubborn disease, but gentle enough to be given to all patients regardless of age. Toward this end, 33 patients received a maximal dose of the cytoprotective agent, amifostine, before each infusion of idarubicin in the "7 + 3" regimen, escalating the dose of idarubicin in a phase I fashion to a maximum dose of 24 mg/m2 . The data indicate that the addition of amifostine to "7 + 3" AML induction therapy enables a substantial escalation of the idarubicin dose through the 21-mg/m2 dose level, without a concomitant increase in side effects, thus providing a regimen that is both intensive and applicable to patients of all ages. Currently, phase II studies are ongoing on a national basis to evaluate the efficacy of this regimen.

Comparative study between the interaction of dephosphorylated amifostine (WR-1065) and amoxicilline with pBR322 in absence and presence of cisplatin by AFM

The effect of the amoxicilline as a possible cisplatin-action protector on pBR322 DNA has been visually studied by atomic force microscopy in comparison with the modifications caused by the controversed cisplatin protector amifostine. Incubation of amoxicilline with the plasmid DNA showed aggregation and compaction of DNA. Cisplatin incubated in the same conditions with DNA produced kinks and super-coiling of the circular form. In the case of previous treatment of DNA with amoxicilline, the characteristic effect of cisplatin is only partially observed. The amoxicilline seemed to control the action of cisplatin on DNA. The initial effect of dephosphorylated amifostine (WR-1065) when this protector was incubated with the plasmid was also the formation of aggregates and the compaction of DNA. However, addition of cisplatin successively after 1 and 2 h showed the characteristic modification caused by cisplatin but only in a decreasing percentage of molecules of DNA. Both molecules, amoxicilline and WR-1065 seem to control the strong direct action of cisplatin on DNA. This effect can justify the role as protecting agent of amifostine on side effects caused by cisplatin and can open new possibilities to other agents like amoxicilline.

Amifostine pretreatment for protection against topotecan-induced hematologic toxicity: results of a multicenter phase III trial in patients with advanced gynecologic malignancies

OBJECTIVE

To determine if amifostine could reduce the hematologic toxicity associated with topotecan.

METHODS

Thirty patients with recurrent/refractory gynecologic malignancies were randomized to receive topotecan (TOPO) (1.5 mg/m(2)/day days 1-5) with or without amifostine (AMI/TOPO) (500 mg/m(2)/day days 1-5) every 3 weeks for six cycles. The primary study endpoints were the incidence of grade 3 and 4 neutropenia.

RESULTS

Fifteen patients were randomized to each arm for a total of 49 TOPO and 53 AMI/TOPO cycles. Patient characteristics and pretreatment ANC were similar between groups. Topotecan 1.5 mg/m(2)/day days 1-5 was initially administered to seven patients. Five developed neutropenic fevers, one an uncomplicated grade 4 neutropenia, and the other an uncomplicated grade 3 neutropenia. There were two treatment-related deaths due to sepsis (one in each treatment arm). The starting dose was thereafter reduced to 1.25 mg/m(2)/day days 1-5 every 21 days. No treatment related deaths occurred after this dose reduction. The incidence of combined grade 3/4 neutropenia was reduced from 67% (33/49 cycles) to 38% (20/53 cycles) with the addition of amifostine (P = 0.003; OR 0.29; 95% CI 0.12-0.71).

CONCLUSIONS

Topotecan at 1.5 mg/m(2)/day days 1-5 in heavily pretreated patients resulted in excessive toxicity not manageable with amifostine. At the reduced topotecan dose (1.25 mg/m(2) x 5 days), pretreatment with amifostine reduced the hematologic toxicity associated with topotecan chemotherapy in women with recurrent/refractory gynecologic malignancies.

The cytoprotective aminothiol WR1065 activates p53 through a non-genotoxic signaling pathway involving c-Jun N-terminal kinase

WR1065 is an aminothiol with selective cytoprotective effects in normal cells compared with cancer cells. In a previous study (North, S., El-Ghissassi, F., Pluquet, O., Verhaegh, G., and Hainaut, P. (2000) Oncogene 19, 1206-1214), we have shown that WR1065 activates wild-type p53 in cultured cells. Here we show that WR1065 induces p53 to accumulate through escape from proteasome-dependent degradation. This accumulation is not prevented by inhibitors of phosphatidylinositol 3-kinases and is not accompanied by phosphorylation of Ser-15, -20, or -37, which are common targets of the kinases activated in response to DNA damage. Furthermore, WR1065 activates the JNK (c-Jun N-terminal kinase), decreases complex formation between p53 and inactive JNK, and phosphorylates p53 at Thr-81, a known site of phosphorylation by JNK. A dominant negative form of JNK (JNK-APF) reduces by 50% the activation of p53 by WR1065. Thus, WR1065 activates p53 through a JNK-dependent signaling pathway. This pathway may prove useful for pharmacological modulation of p53 activity through non-genotoxic mechanisms.

Amifostine in clinical oncology: current use and future applications

Amifostine (Ethyol), an inorganic thiophosphate, is a selective broad-spectrum cytoprotector of normal tissues that provides cytoprotection against ionizing radiation and chemotherapeutic agents, thus preserving the efficacy of radiotherapy and chemotherapy. This review summarizes the preclinical data and clinical experience with amifostine, and provides insight into future clinical directions. Amifostine, an inactive pro-drug, is transformed to an active thiol after dephosphorylation by alkaline phosphatase found in the normal endothelium. The absence of alkaline phosphatase in the tumoral endothelium and stromal components, and the hypovascularity and acidity of the tumor environment, may explain its cytoprotective selectivity. The cytoprotective mechanism of amifostine is complicated, involving free radical scavenging, DNA protection and repair acceleration, and induction of cellular hypoxia. Intravenous administration of amifostine 740-900 mg/m(2) before chemotherapy and 250-350 mg/m(2) before each radiotherapy fraction are widely used regimens. The US Food and Drug Administration has approved the use of amifostine as a cytoprotector for cisplatin chemotherapy and for radiation-induced xerostomia. Ongoing trials are being conducted to determine the efficacy of amifostine in reducing radiation-induced mucositis and other toxicities. Novel schedules and routes of administration are under investigation, and may further simplify the use of amifostine and considerably broaden its applications.

Kinetics of cisplatin binding to cellular DNA and modulations by thiol-blocking agents and thiol drugs

DNA platination by cisplatin (CDDP) was investigated in peripheral blood mononuclear cells and ovarian cancer cells using atomic absorption spectroscopy. Plots showing the amount of platinum (Pt) bound to DNA versus the molar concentration of cisplatin in the incubation medium ([CDDP]) were nonlinear. For [CDDP] < about 5 microM, the amount of Pt bound to DNA increased slowly with added drug. However, for larger [CDDP], the slope of the plot increased significantly. To study the role of thiols in affecting cisplatin binding to DNA, cells were treated with N-ethylmaleimide, which modifies thiol groups, rendering them incapable of binding cisplatin. Analysis using high-pressure liquid chromatography showed that approximately 99% of cellular glutathione was modified by N-ethylmaleimide. A plot of the amount of Pt bound to DNA versus [CDDP] for thiol-blocked cells is linear, with a slope similar to that of unblocked cells at high [CDDP]. Neither S-2-(3 aminopropylamino)ethanethiol (WR-1065) nor mesna, when added at clinically achievable concentrations (i.e., < approximately 300 microM), affected DNA platination. However, DNA platination was totally abolished by millimolar concentrations of the drug thiols (approximately 1.25 mM WR-1065 or approximately 5 mM mesna). Thus, the data show that endogenous thiols intercept cellular cisplatin, but this mechanism is less important at high [CDDP]. Moreover, therapeutic concentrations of drug thiols do not significantly affect DNA platination. A simple model that reproduces the experimental results of the amount of cisplatin binding to DNA as a function of [CDDP], time, and thiol content is proposed. The model takes into account passage of cisplatin and thiols through the cell membrane, binding of cisplatin to cellular thiols, and platination of DNA.

The potential role of amifostine in the treatment of carcinoma of the uterine cervix: a review

Carcinoma of the uterine cervix affects approximately 13,000 women annually in the United States. Radiotherapy is a commonly applied therapy, either as definitive treatment or combined with surgery. Although highly effective, radiotherapy can be associated with significant complications. Amifostine has been shown to be an effective radioprotector in head and neck malignancies. Preliminary evidence suggests a role in cervical cancer.

A randomized phase II study of amifostine used as stem cell protectant in non-hodgkin lymphoma patients receiving cisplatin-based salvage chemotherapy prior to stem cell transplant

Stem cell mobilization may be inadequate in many lymphoma patients in need for autologous stem cell transplant (SCT). In this study, we sought to evaluate a potential role of amifostine as a stem cell chemoprotective agent in lymphoma patients receiving DHAP chemotherapy in preparation for high-dose chemotherapy (HDC) and stem cell transplant (SCT). In the beginning of the DHAP course, patients were randomized 1:1 to receive amifostine at 740 mg/m(2). Stem cells were mobilized with GCSF after the last cycle of DHAP. Stem cell collection started upon ANC recovery over 1000/mm(3). Standard 10 lt. apheresis daily with a goal of a minimum of 2 x 10(6) stem cells/kg were performed. Twenty-one patients have been enrolled; 10 received amifostine pretreatment (age, 20-64) and 11 were randomized to the control arm (age, 18-63). Prior chemotherapy was balanced in the two groups. The median number of DHAP treatments for each group was 2. Amifostine was well tolerated and was associated with higher stem cell collection. Toxicity and time to engraftment were comparable between the two groups. Our preliminary results may suggest a role of amifostine in protecting stem cells during salvage chemotherapy, thus facilitating stem cell collection.

Amifostine: chemotherapeutic and radiotherapeutic protective effects

Amifostine (Ethyoltrade mark, Alza Pharmaceuticals) is an inorganic thiophosphate cytoprotective agent known chemically as ethanethiol, 2-[3- aminopropyl)amino]dihydrogen phosphate. It is a prodrug of free thiol (WR-1065) that may act as a scavenger of free radicals generated in tissues exposed to cytotoxic drugs and binds to reactive metabolites of such drugs. Amifostine was originally developed as a radioprotective agent in a classified nuclear warfare project. Following declassification of the project it was evaluated as a cytoprotective agent against toxicity of the alkylating drugs and cisplatin. Differences in the alkaline phosphatase concentration of normal versus tumour tissues can result in greater conversion of amifostine in normal tissues. Inside the cell, WR-1065 provides an alternative target to DNA and RNA for the reactive molecules of alkylating or platinum agents and acts as a potent scavenger of the oxygen free radicals induced by ionizing radiation and some chemotherapy agents. Preclinical animal studies have demonstrated that the administration of amifostine protects against a variety of chemotherapy-related toxicities including cisplatin-induced nephrotoxicity, cisplatin-induced neurotoxicity, cyclophosphamide- and bleomycin-induced pulmonary toxicity and the cytotoxicities (including cardiotoxicity) induced by doxorubicin and related chemotherapeutic agents. Amifostine has been shown to protect a variety of animal species from lethal doses of radiation. Amifostine gives haematological protection from cyclophosphamide, carboplatin, mitomycin C, fotemustine and radiotherapy; renal and peripheral nerve protection from cisplatin; mucosa, skin and salivary gland protection from radiotherapy. Multiple Phase I studies were carried out with amifostine in combination with chemotherapy for various neoplasms. Appropriate doses of amifostine were found to be 740 - 910 mg/m(2) in single-dose regimens and 340 mg/m(2) in multiple-dose regimens. In radioprotection, doses are generally 200 - 350 mg/m(2). For all these characteristics, amifostine has been recently approved and suggested in ASCO clinical practice guidelines as a radioprotector for head and neck cancer treatment and supportive agent during cisplatin-based chemotherapy, in lymphomas and solid tumours. Moreover, its spectrum of possible applications is enlarging. As data have been provided indicating that amifostine stimulates haematopoiesis, it has been employed with intriguing results in the treatment of myelodysplastic syndromes (MDS).

Bone marrow stem cell protection from chemotherapy by low--molecular-weight compounds

The stem cells of the bone marrow have the capacity for both self-renewal and derivation of all the blood cell lineages. Consequently, toxicity to these cells can result in neutropenia, agranulocytosis, thrombocytopenia, pancytopenia, or aplastic anemia. Many anticancer drugs adversely affect the bone marrow, and neutropenia is a common limiting factor in dose escalation. In this review, we discuss agents that appear to have potential as bone marrow sparing agents. Computerized catalogs of the National Library of Medicine and Medline were searched for reports on low-molecular-weight compounds that detailed effects on the hematopoietic progenitor cells. The most promising agents are the endogenous peptides p-glutamic acid-glutamic acid-aspartic acid-cysteine-lysine and acetyl-serine-aspartic acid-lysine-proline, and the exogenous compounds amifostine and ammonium trichloro[dioxoethylene-O,O']tellurate, but several others are also discussed. These compounds preserve stem cell function in the presence of antineoplastic drugs of diverse pharmacological classes, and they do so by various mechanisms of action. Their present status in clinical practice is also detailed. More needs to be learned about their mechanisms of action and therapeutic potential, but the results are encouraging for some of these compounds and more clinical trials should be expected.

Amifostine

Amifostine (WR-2721) is a cytoprotective agent that protects a broad range of normal tissues from the toxic effects of chemotherapy and radiotherapy without attenuating tumour response. This selective protection is due to the greater conversion and uptake of the active metabolite, WR- 1065, in normal versus neoplastic tissues. In a pivotal phase III trial, 242 patients with advanced ovarian cancer were randomised to receive treatment with cisplatin 100 mg/m2 and cyclophosphamide 1000 mg/m2 every 3 weeks with or without pretreatment with intravenous amifostine 910 mg/m2. Over 6 cycles of therapy, amifostine significantly reduced haematological, renal and neurological toxicities: treatment delays, treatment discontinuation and days in hospital related to these adverse events were also significantly reduced in patients receiving amifostine versus patients receiving chemotherapy alone. In another randomised phase III trial in 303 patients with head and neck cancer undergoing irradiation therapy (total dose 50 to 70Gy), pretreatment with intravenous amifostine 200 mg/m2 significantly reduced the incidence of acute and late grade > or =2 xerostomia. However, mucositis was not significantly reduced in amifostine recipients compared with patients receiving radiotherapy alone, although this has been shown in smaller randomised trials. Amifostine (340 mg/m2) also provided significant protection against pneumonitis and oesophagitis in patients with lung cancer receiving thoracic irradiation in a preliminary report from a phase III trial (n = 144). Other studies have demonstrated protective effects of amifostine in other tumour types and other chemotherapy, radiation and radiochemotherapy regimens; however, evidence is still limited in these indications. No evidence of tumour protection by amifostine has been demonstrated in any clinical trials. Amifostine has also been shown to stimulate haematopoietic stem cells and has been investigated as a therapy for patients with myelodysplastic syndrome in number of small preliminary studies. At the recommended dose and schedule, amifostine is generally well tolerated. Adverse effects are usually reversible and manageable and those most frequently experienced include nausea and vomiting, transient hypotension and somnolence and sneezing.

CONCLUSION

The results of phase III trials have confirmed the safety and efficacy of amifostine as a cytoprotectant to ameliorate cisplatin-induced cumulative renal toxicity, for which it is the only agent proven to be effective, and neutropenia in patients with advanced ovarian cancer, and to reduce xerostomia in patients with head and neck cancer receiving irradiation therapy. Depending on the outcome of numerous ongoing clinical trials, amifostine may eventually find broader clinical applications, both as a cytoprotectant and as a potential therapy in myelodysplastic syndrome.

Amifostine can reduce mucosal damage after high-dose melphalan conditioning for peripheral blood progenitor cellautotransplant: a retrospective study

Amifostine (WR-2721; Ethyol) is a well-known cytoprotector, but a possible role in preventing extrahaematological toxicity after high-dose therapy (HDT) has never been investigated. We compared two historical groups of patients who either received (group A, n = 35) or did not receive (group B, n = 33) amifostine (740 mg/m2) before high-dose (HD) melphalan, followed by autologous infusion of peripheral blood progenitor cells (PBPCs). Amifostine was well tolerated at this dose level. Emesis grade 1-2 was the most important side-effect, but the interruption of infusion was never required. The incidence and median duration of severe mucositis (grade 3-4) was 21% and 0 d (range 0-11 d) in group A and 53% and 7 d (range 0-11 d) in group B. The duration of analgesic therapy was also significantly lower in group A (0 d; range 0-12) than in group B (6 d, range 0-20) (P = 0.0001). Severe diarrhoea (3% vs. 25%; P = 0.01) and emesis (9% vs. 34%; P = 0.01) were also reduced in group A in comparison with group B. No differences were observed between the two groups for haematological recovery. This retrospective study strongly suggests that amifostine can reduce severe mucositis and the use of analgesic drugs in this setting. A randomized study is warranted to confirm these preliminary results.

Pilot trial of cytoprotection with amifostine given with high-dose chemotherapy and autologous peripheral blood stem cell transplantation

In an attempt to limit toxicities associated with dose-intensive therapy used for transplant regimens, we performed a pilot study using amifostine with high-dose busulfan (12 mg/kg), melphalan (100 mg/m2), and thiotepa (500 mg/m2) in 21 patients with a variety of malignancies. After 3 days of oral busulfan, amifostine was given at 910 mg/m2 IV for 10 minutes, preceding the infusion of each of 2 doses of melphalan and thiotepa given for 4 days. Antiemetic premedication for amifostine was given to all patients. The median patient age was 50 years (range: 32-65 years). Twenty-one patients received 82 separate amifostine infusions. One patient discontinued amifostine after the second dose because of severe nausea and emesis, and two infusions were temporarily held secondary to hypotension. Of these 82 cycles, there was a total of 37 episodes of nausea/vomiting, 28 episodes of sneezing, 11 episodes of flushing, and 1 episode of oral paresthesia. Systolic blood pressure and mean arterial pressure decreased by a mean of 8.4 mm Hg and 5.0 mm Hg, respectively. In general, the infusion was well tolerated. Patients were observed until discharge home (N = 15), until initiation of an additional tandem transplant procedure (N = 4), or until death (N = 2). All twenty-one patients experienced nonhematologic toxicities grade II or greater. Grade II toxicities included mucositis (N = 21), gastrointestinal (N = 3), skin (N = 1), and liver (N = 1), and grade III toxicities included liver (N = 1). Mucositis was also scored according to a detailed toxicity assessment. Mucositis did not appear to be improved with amifostine when compared with a control group of patients not receiving amifostine. Renal dysfunction after transplantation was decreased in the amifostine group, whereas there was no significant effect on posttransplant hepatic dysfunction. Although these data demonstrate the feasibility of delivering parenteral amifostine in conjunction with dose-intensive chemotherapy and autologous peripheral blood stem cell transplantation, there was no evidence of a significant reduction in nonmarrow toxicities.

The potential role of amifostine in the treatment of non small cell lung cancer

Amifostine protects healthy tissues but not tumor cells from the damage induced by cytotoxic treatments, particularly ionizing radiations, alkylating and platinating agents. The clinical effectiveness of amifostine has been demonstrated by randomized trials in ovarian and head-and-neck cancer patients treated with chemotherapy with or without radiation therapy. The available pharmacoeconomic data confirm a favorable cost/utility ratio. The majority of non small cell lung cancer (NSCLC) patients receive radio and/or chemotherapy. A role for amifostine in these patients has been hypothesized, and some experiences performed. The aim of this paper is to outline the present role of amifostine in the treatment of NSCLC.

In vitro protection from cisplatin-induced neurotoxicity by amifostine and its metabolite WR1065

Cisplatin-induced neuropathy is a major dose-limiting toxicity. Counteraction by amifostine and its metabolite WR1065 may reduce peripheral neurotoxicity in a number of patients. Using the nerve growth factor (NGF)-dependent neurite outgrowth from the PC12 pheochromocytoma cell line as an in vitro assay for neurotoxicity, the protective effects of amifostine and WR1065 against cisplatin action on neurite formation by PC12 cells were studied. Cisplatin in a concentration of 10 microg/ml significantly decreased the percentage of neurite forming cells from 84% to 40%. Amifostine in doses of 0.4 and 0.8 mM proved to protect significantly against the cisplatin-induced decrease in neurite formation, when co-incubated with cisplatin. Also the metabolite WR1065 protected significantly against cisplatin neurotoxicity in a dose of 0.12 mM. Our results show a significant protection by amifostine and its main metabolite WR1065 against cisplatin-induced neurotoxicity using an in vitro model.

Cisplatin, radiation, and amifostine in carcinoma of the uterine cervix

A pilot, open, comparative study was performed on patients with locally advanced cervical cancer to investigate the efficacy and safety of amifostine. Twenty patients with a histologic diagnosis of squamous cervical cancer were treated with radiotherapy and randomized in two groups. Group A received cisplatin at 20 mg/m2 for five days in two cycles during intracavitary radiotherapy and 100 mg/m2 x 2 cycles during external radiotherapy, and amifostine 825 mg/m2 15 min before the cisplatin infusion. Patients in group B received cisplatin in the same doses without amifostine. All patients had complete responses during a median follow-up of 20 months. Grade three neutropenia was present in two patients in group A and in four of the control group, P = 0.31; grade 2 neurologic toxicity was seen in four patients in group B and in one of the patients in group A, P = 0.15. One patient needed temporary interruption of amifostine due to hypotension. Eight of 10 patients in group A developed hypocalcemia during the treatment with amifostine. Our findings indicate that amifostine was well tolerated. In this series a mild neurologic and hematologic protection was found in patients that received amifostine, although this was not statistically significant. No differences in disease-free survival response and overall survival was seen between the two groups.

Effects of amifostine on cisplatin induced DNA adduct formation and toxicity in malignant glioma and normal tissues in rat

The chemoprotective effect of amifostine (WR2721) was studied in a BDIX rat model with intracerebral BT4C glioma implants. Twenty-one rats were given cisplatin 5 mg/kg i.p., 21 were given amifostine 200 mg/kg i.p. + cisplatin 5 mg/kg i.p. Ten rats served as untreated controls. An immunohistochemical method for analysis of cisplatin-DNA adducts was used to elucidate the adduct formation in tumor, normal brain and kidney. Tumor volume and serum creatinine level were analysed 10 days after treatment. In animals pretreated with amifostine there was a delayed adduct formation rate in the normal brain, and in the kidney cortex the number of tubular cells with extremely high adduct level was reduced. No difference in adduct formation was seen in tumors. Tumor volume was significantly larger following amifostine + cisplatin (66% of controls) compared to cisplatin alone (38% of controls). Weight loss was, however, severe in rats given cisplatin alone. In the tumor growth study only 3 out of 11 rats treated with cisplatin 5 mg/kg alone survived until time of sacrifice at 10 days, whereas all those pretreated with amifostine survived. Mean serum creatinine was 48 micromol/l (controls), 146 micromol/l (cisplatin) and 59 micromol/l (amifostine + cisplatin). A marked reduction of histopathological renal changes was found when amifostine was added. Amifostine thus significantly reduced general and renal toxicity of cisplatin. The tumor growth retardation was stronger when cisplatin was given alone but this is probably related to general toxicity and malnutrition indirectly supported by the fact that amifostine did not significantly reduce cisplatin-DNA adduct formation in tumors. The results of the present study suggest that amifostine may have a role in increasing the therapeutic ratio of cisplatin, also in the treatment of malignant glioma.

Pharmacokinetics of cisplatin with and without amifostine in tumour-bearing nude mice

Amifostine (Ethyol, WR-2721) is in use in the clinic as a protector against platinum-induced toxicities. We have previously reported that amifostine induced a potentiation of the antitumour activity of carboplatin in human ovarian cancer xenografts. An influence of amifostine on the pharmacokinetics of carboplatin, resulting in higher platinum concentrations in plasma and tissues of the tumour-bearing nude mice, was thought to be the cause of enhancement of the antitumour activity. Therefore, the pharmacokinetics of cisplatin were investigated in tumour-bearing nude mice treated with cisplatin alone or in combination with amifostine. A significant increase in the area under the curve (AUC) of the total platinum concentration in mice treated with amifostine was only observed in the kidney (from 355 to 398 nmol h/g), whereas in the other tissues and plasma no significant changes were measured. The selective protection of normal tissues by amifostine was confirmed by a decrease in the AUC of the cisplatin-DNA adduct levels in normal tissues. The decrease was only significant in the liver (282-240 fmol h/microgram DNA), whereas in tumour tissue a slight increase in the AUC of the cisplatin-DNA adducts could be detected (91.3-110.1 fmol h/microgram DNA). The minor influence of amifostine on the pharmacokinetics of cisplatin may be the reason why amifostine did not potentiate the antitumour activity of cisplatin. The influence of amifostine on cisplatin-DNA adduct levels in normal tissues versus tumour tissues is further evidence for the usefulness of this toxicity modulator in cancer patients.

Amifostine protects normal tissues from paclitaxel toxicity while cytotoxicity against tumour cells is maintained

The objectives of this study were to evaluate the protective effects of amifostine against paclitaxel-induced toxicity to normal and malignant human tissues. Haematopoietic progenitor colony assays were used to establish the number of CFU-GEMM and BFU-E colonies after incubation with WR-1065 alone, Amifostine alone, paclitaxel (2.5 or 5 microM) +/- WR-1065 or amifostine. MTT and alkaline elution assays evaluated the in vitro growth inhibitory and DNA damaging effects, respectively, of paclitaxel with or without amifostine against normal human fibroblasts and human non-small cell lung cancer (NSCLC) cells. This combination was also evaluated in vivo using severe combined immune deficient (scid) mouse models of early (non-palpable tumours) and advanced (palpable tumours) human ovarian cancer. Human 2780 ovarian cancer cells were inoculated subcutaneously while paclitaxel and amifostine were administered intraperitoneally. A brief exposure (15 min) to amifostine not only protected human haematopoietic progenitor colonies from paclitaxel toxicity, but stimulated the growth of CFU-GEMM and BFU-E beyond control values. Amifostine protected normal human lung fibroblasts from paclitaxel-induced cytotoxicity and DNA single-strand breaks. However, paclitaxel cytotoxicity and DNA single-strand breaks were actually enhanced by pretreatment with amifostine in the NSCLC model. Importantly, amifostine did not interfere with paclitaxel antitumour activity even with prolonged exposure (24.5 h) of the lung cancer cells to high concentrations (1.2 mM) in vitro or following five repetitive high doses (200 mg/kg) given to scid mice with human ovarian cancer xenografts. Indeed, under certain circumstances, amifostine resulted in sensitisation of tumour cells to paclitaxel. Our results confirm previous reports of the ability of amifostine to protect normal tissues from the toxic effects of chemotherapy drugs and now extend these observations to paclitaxel.

The preclinical basis for broad-spectrum selective cytoprotection of normal tissues from cytotoxic therapies by amifostine (Ethyol)

Administered prior to cytotoxic chemotherapy or radiation, the aminothiol amifostine provides broad-spectrum cytoprotection of various normal tissues without attenuating antitumour response. The basis for the selectivity of action resides in the anabolism of amifostine at the normal tissue site by membrane-bound alkaline phosphatase. Dephosphorylation to the free thiol, WR-1065, is followed by rapid uptake into normal tissues by a carrier mediated, facilitated diffusion process; in contrast, uptake into tumour tissue is slow to negligible. Preclinical studies have shown that pretreatment with amifostine provides protection of normal tissues from the cytotoxic effects of alkylating agents, organoplatinums, anthracyclines, taxanes and radiation. Normal tissues protected include bone marrow, kidney, neural tissues, the heart, intestinal crypt cells and pulmonary tissues. Additionally, the mutagenic and carcinogenic effects of these modalities are also attenuated. With respect to bone marrow, preclinical studies have shown significant protection of progenitor cells that give rise to the red and white cells and platelets. Comparative in vitro and in vivo studies using murine and human tumour xenografts show no decrease of antitumour effects of these same therapies despite the protection of normal organs. The unique preclinical profile of amifostine serves as a model for the clinical development programme for this important new broad-spectrum cytoprotective agent.

Amifostine (Ethyol): pharmacokinetic and pharmacodynamic effects in vivo

Amifostine (Ethyol) administered to cancer patients is rapidly cleared from plasma by a biphasic decay with an alpha half-life (T1/2 alpha) of 0.88 min and a T1/2 beta of 8.8 min. The result is that more than 90% of the drug has disappeared from the plasma compartment 6 min after intravenous (i.v.) administration. Only approximately 1% of the dose appears in the ascites. Animal studies indicate that amifostine is primarily excreted in urine-approximately 6% of the dose is excreted in the urine as amifostine and its metabolites WR-1065 and disulphides-which means that a large percentage of the dose is taken up by the tissues. Maximal tissue concentrations of WR-1065 and the disulphides were obtained between 10 and 30 min after an intraperitoneal injection of amifostine in mice, with the lowest concentrations in tumour tissues. Because WR-1065 gives protection to normal tissues rather than rescue, the pharmacokinetic data indicate that amifostine must be given shortly before administration of the cytostatic drug or radiation from which protection is required. For these reasons, amifostine is given to patients as a 15-min i.v. infusion before cisplatin and carboplatin to protect against their dose-limiting toxicities. In some regimens carboplatin is combined with three doses of amifostine because of the high concentration of the active carboplatin species during the first 4 h after administration. When carboplatin was administered as a 15-min i.v. infusion of 400 mg/m2 and amifostine as a 15-min i.v. infusion of 740 mg/m2 just before and 2 and 4 h after carboplatin, the area under the plasma concentration-time curve for ultrafilterable platinum increased from 253 +/- 45 microM.h (n = 6) for carboplatin alone to 305 +/- 63 microM.h (n = 11) for carboplatin+three doses of amifostine. Experiments in nude mice bearing OVCAR-3 xenografts showed that amifostine, given once before cisplatin or three times in combination with carboplatin, did not affect the antitumour effect of these drugs. When amifostine was only given just before carboplatin, it even stimulated the antitumour effect of carboplatin significantly.

Exploration of platinum-based dose-intensive chemotherapy strategies with amifostine (Ethyol)

The preclinical evaluation of amifostine confirms selective protection of normal tissues against toxicity due to cisplatin therapy while maintaining the antitumour effects. The mechanism of protection relates to the selective uptake of the free thiol, amifostine, into normal tissue compared with tumour tissue, intracellular binding and therefore detoxification of anticancer drugs, as well as through the scavenging of oxygen free radicals. Although vigorous hydration schedules have helped to alleviate nephrotoxicity, ototoxicity and cumulative dose-related peripheral neuropathy, these side effects remain important dose-limiting toxicities related to cisplatin therapy. The preclinical and clinical results to date demonstrate that amifostine can protect against cisplatin toxicities, in particular nephrotoxicity. Recent studies have demonstrated that higher single and cumulative cisplatin doses have an important impact on survival outcome; however, the improvement in survival comes at the cost of increased acute and cumulative haematological, renal and neurological toxicities that can result in serious morbidity. The role of amifostine as a unique supportive measure to reduce these toxicities offers the possibility of improving the quality of life of patients receiving chemotherapy.

Amifostine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential as a radioprotector and cytotoxic chemoprotector

Amifostine (WR-2721) was originally developed as a radioprotective agent. In animals, it protects normal tissues from the damaging effects of irradiation and, as shown in more recent studies, of several cytotoxic agents. Protection of tumours is generally reduced compared with that of normal tissues in animals, suggesting that amifostine may increase the therapeutic window of cytotoxic therapies. Clinical data concerning amifostine suggest that cytotoxic chemotherapy-induced haematological toxicity and cisplatin-induced neurotoxicity, nephrotoxicity and ototoxicity are decreased upon administration of amifostine prior to cytotoxic drugs. Similarly, amifostine reduces damage to normal tissues caused by radiotherapy. Available data show that this protection is achieved without adversely affecting tumour response or patient survival. In 1 large trial, the reduction in cyclophosphamide- and cisplatin-related toxicities manifested as a decrease in the incidence and severity of neutropenia-related fever and sepsis and in the number of patients with ovarian cancer who discontinue therapy before completion of treatment, thus improving the tolerability of this antineoplastic regimen. In addition, the incidences of cisplatin-induced nephro- and neurotoxicity were reduced. Increased doses of cytotoxic therapy have also been administered when amifostine was given prior to therapy, which may increase tumour response. The predominant adverse effect associated with amifostine are hypotension, nausea and vomiting, somnolence and sneezing. Thus, amifostine is likely to be a useful adjuvant to the treatment of patients with malignancy, particularly those receiving cyclophosphamide plus cisplatin. discontinued therapy before completion of treatment, thus improving the tolerability of this antineoplastic regimen. In addition, the incidences of cisplatin-induced.

Audiological findings in a Phase I protocol investigating the effect of WR 2721, high-dose cisplatin and radiation therapy in patients with locally advanced cervical carcinoma

WR 2721 (ethiofos) protects against the toxic effects of the heavy metal compound cisplatin, which is used in the treatment of solid tumours. In a Phase I protocol designed to determine the maximum dose of WR 2721 which could be tolerated when administered in combination with cisplatin and radiation therapy to patients with cervical carcinoma, 11 patients were evaluated by audiologic testing before and after cisplatin WR 2721 administration in an attempt to identify the degree of ototoxicity. Forty-five per cent were noted to have significant hearing threshold changes, predominantly in the high frequencies. There were no significant changes in the speech frequencies in this series. This contrasts with the greater degrees of ototoxicity observed in controls treated in the same way who received cisplatin without WR 2721 protection.

Protection of normal tissues from the cytotoxic effects of chemotherapy and radiation by amifostine (WR-2721): preclinical aspects

Amifostine is a radioprotective agent that prevents radiation- and chemotherapy-induced cellular injury through free-radical scavenging, hydrogen donation, and inhibition of DNA damage. Amifostine is metabolised and accumulated to a much greater extent in normal cells than in tumour cells. As a result, it exerts a protective effect from toxicity on normal tissues induced by chemo- or radiotherapy without reducing the antitumour effects of cancer therapy. Extensive preclinical studies have shown that amifostine protects against radiation damage and against the myelotoxic, nephrotoxic and neurotoxic effects of chemotherapeutic agents such as alkylating agents and platinum compounds. In some cases, the antitumour effects of these agents have been potentiated by amifostine. Amifostine has also been shown to protect against radiation- and chemotherapy-induced mutagenesis and, as a result, carcinogenesis. Use of amifostine allows for safer and more effective administration of radio- and anticancer therapy.

Amifostine: potential for clinically useful cytoprotection

The ability to target malignant cells for cytotoxicity while sparing normal host tissues has proven to be limited. These limitations have resulted in unacceptable toxicity or insufficiently effective therapy. Continuing investigation of new, potentially useful cytotoxic agents must continue. An alternative approach, also worthy of study, is the selective protection of normal tissues. This approach, used in conjunction with available therapeutic agents, may open the therapeutic window and incrementally enhance the effectiveness of cytotoxic therapy. A variety of methods have been used to protect normal tissues selectively. Regional protection can be used for certain organ systems, such as the oral mucosa. Selective protection on a systemic level is more difficult but agents that seem to protect normal but not malignant tissues selectively are being developed. Among these is amifostine, which was originally selected by the U.S. defense department for study as a radioprotectant. Pre-clinical studies have suggested that amifostine is differentially concentrated in normal tissues but not in malignant tissues. Tissue-specific differences in the activity of alkaline phosphatase, which dephosphorylates amifostine to its active metabolite WR-1065, and in pH are thought to be involved in this relative specificity. Clinical studies indicate that amifostine can reduce the myelosuppression produced by cyclosphosphamide, the combination of cyclophosphamide and cisplatin, and, perhaps, carboplatin. The protective effects of amifostine on nonhematopoietic toxicities are being investigated. Future trials will investigate the integration of amifostine with cytokine-based supportive care in order to define the role of this potentially clinically useful cytoprotectant agent.

Effects of the modulating agent WR2721 on myelotoxicity and antitumour activity in carboplatin-treated mice

The selective modulation of carboplatin [diammine(1,1-cyclo-butanedicarboxylato)platinum(II)]-induced myelotoxicity was investigated in mice, using the protective agent WR2721 [S-2-(3-aminopropylamino)ethyl-phosphorothioic acid, ethiofos]. In female BALB/c mice, WR2721 (200 mg/kg intraperitoneally, i.p.) partly prevented the reduction of in vitro proliferation of whole bone marrow cells and non-adherent cells when administered at different time points relative to 90 mg/kg carboplatin (i.p.). Protection was highest when WR2721 was administered 5 min prior to carboplatin. In vitro proliferation of whole bone marrow cells and non-adherent cells in liquid culture increased from 15% of control for carboplatin alone to 45% when WR2721 was administered 5 min prior to carboplatin. However, WR2721 did not significantly prevent the loss in clonogenic capacity of early hematopoietic progenitors in the bone marrow, as determined by a bilayered soft agar colony forming units assay. In nude mice, bearing well-established subcutaneous human ovarian carcinoma xenografts OVCAR-3, WR2721 (200 mg/kg i.p.) 5 min prior to intravenous carboplatin allowed a 1.5-fold increase in the maximum tolerated dose of carboplatin as determined by overall weight loss. WR2721 alone did not affect tumour growth. However, WR2721 had a potentiating effect on the tumour growth inhibition of a standard dose of carboplatin in this model. Minimal tumour volume compared to control (T/C) decreased from 9.4% with carboplatin alone to 2.2% with WR2721 5 min prior to the same dose of carboplatin. Specific growth delay (SGD) increased from 7.4 to 10.3. With the 1.5-fold increased, equitoxic dose of carboplatin in combination with WR2721, the antitumour activity was only slightly further increased (T/C = 1.4%, SGD = 10.5).

Sulphhydryl-modifying reagents alter ototoxin block of muscarinic receptor-linked phosphoinositide turnover in the cochlea

In the 12-day-old rat cochlea, the synthesis of inositol phosphates (IPs) can be activated via M3 cholinoceptors. This stimulation is blocked by ototoxins (mercury, ethacrynate, cisplatin, neomycin), drugs with side effects that lead to damage of hair cells and strial cells. As these toxic effects can be reversed in vivo by thiol molecules, we investigated whether modifications of thiol compounds could be involved in ototoxin-induced inhibition of the IP turnover in the cochlea. For this purpose, we assessed whether the sulphhydryl-modifying reagents N-ethylmaleimide and cadmium modify the carbachol-stimulated formation of IPs in the 12-day-old rat cochlea. Both molecules inhibit the carbachol effect on a dose-dependent way without altering the basal metabolism of IPs. As cadmium may block some calcium channels, the effect of verapamil, another calcium channel antagonist, was tested. Verapamil (1-50 microM) does not alter carbachol-evoked IP formation, suggesting that the inhibitory effect of cadmium is not due to a calcium influx block. Binding experiments with the muscarinic ligand quinuclidinyl benzylate (QNB) showed that the sulphhydryl-modifying reagents do not displace QNB from binding sites. Combining ototoxins and reagents shows that N-ethylmaleimide acts synergistically with all ototoxins but ethacrynate while cadmium does so only with mercury. Both N-ethylmaleimide and cadmium have additive effects with ethacrynate. As a supplement, disulphide bond-modifying agents do not alter the carbachol-enhanced metabolism of IPs. These results suggest that molecules having thiol-modifying properties inhibit the carbachol-induced turnover of IPs without acting at the muscarinic sites.(ABSTRACT TRUNCATED AT 250 WORDS)