Pharmacokinetics of WR-2721

Protective effects of 2-aminoethylthiosulfuric acid and structurally analogous organosulfur compounds against ionizing radiation

High efficacy and minimal toxicity radioprotectors are desirable options for the hazards posed by nuclear medical and energy technologies and the dangers presented by nuclear weapons in an unstable global situation. Although cysteamine is an effective radioprotector, it has considerable toxicity. In this study, the protective effects of the less toxic organosulfur compounds 2-aminoethylthiosulfate (AETS), thiotaurine (TTAU), and hypotaurine (HTAU) against X-ray damage in mice were compared with that of cysteamine. Intraperitoneal injection of either AETS or cysteamine (2.2 mmol/kg body weight) 30 min before X-ray irradiation (7.0 Gy) provided 100% survival for 30 days, limited the decrease in erythrocytes and neutrophils over 9 days, and reduced damage to bone marrow and spleen over 9 days. Neither TTAU nor HTAU provided any protection. In mice, 30 min after AETS administration, non-protein thiol content increased in the spleen, indicating cysteamine generation by AETS hydrolysis, the active protective species of AETS. All examined compounds scavenged ^•OH under diffusion control in aqueous solution, which is inconsistent with the difference in the protective effects among the compounds. The results indicate that AETS protects animals from ionizing radiation by several mechanisms, including scavenging ^•OH as cysteamine.

DMA, a Small Molecule, Increases Median Survival and Reduces Radiation-Induced Xerostomia via the Activation of the ERK1/2 Pathway in Oral Squamous Cell Carcinoma

Survival, recurrence, and xerostomia are considerable problems in the treatment of oral squamous carcinoma patients. In this study, we investigated the role of DMA (5-(4-methylpiperazin-1-yl)-2-[2′-(3,4-dimethoxyphenyl)5″benzimidazoyl]benzimidazole) as a salivary gland cytoprotectant in a patient-derived xenograft mouse model. A significant increase in saliva secretion was observed in the DMA-treated xenograft compared to radiation alone. Repeated doses of DMA with a high dose of radiation showed a synergistic effect on mice survival and reduced tumor growth. The mean survival rate of tumor-bearing mice was significantly enhanced. The increased number of Ki-67-stained cells in the spleen, intestine, and lungs compared to the tumor suggests DMA ablates the tumor but protects other organs. The expression of aquaporin-5 was restored in tumor-bearing mice injected with DMA before irradiation. The reduced expression of αvβ3 integrin and CD44 in DMA alone and DMA with radiation-treated mice suggests a reduced migration of cells and stemness of cancer cells. DMA along with radiation treatment results in the activation of the Ras/Raf/MEK/ERK pathway in the tumor, leading to apoptosis through caspase upregulation. In conclusion, DMA has strong potential for use as an adjuvant in radiotherapy in OSCC patients.

Medical Countermeasures for Radiation Exposure and Related Injuries: Characterization of Medicines, FDA-Approval Status and Inclusion into the Strategic National Stockpile

World events over the past decade have highlighted the threat of nuclear terrorism as well as an urgent need to develop radiation countermeasures for acute radiation exposures and subsequent bodily injuries. An increased probability of radiological or nuclear incidents due to detonation of nuclear weapons by terrorists, sabotage of nuclear facilities, dispersal and exposure to radioactive materials, and accidents provides the basis for such enhanced radiation exposure risks for civilian populations. Although the search for suitable radiation countermeasures for radiation-associated injuries was initiated more than half a century ago, no safe and effective radiation countermeasure for the most severe of these injuries, namely acute radiation syndrome (ARS), has been approved by the United States Food and Drug Administration (FDA). The dearth of FDA-approved radiation countermeasures has prompted intensified research for a new generation of radiation countermeasures. In this communication, the authors have listed and reviewed the status of radiation countermeasures that are currently available for use, or those that might be used for exceptional nuclear/radiological contingencies, plus a limited few medicines that show early promise but still remain experimental in nature and unauthorized for human use by the FDA.

Effects of amifostine on endometriosis, comparison with N-acetyl cysteine, and leuprolide as a new treatment alternative: a randomized controlled trial

PURPOSE

To assess the effects of amifostine, N-acetyl cysteine (NAC), and leuprolide as a scavenger in a rat endometriosis model.

METHODS

This is a prospective randomized animal study. Setting The Animal Laboratory of Medical University. Animals 40 rats were used for transplantation of an autologous fragment of endometrial tissue onto the inner surface of the abdominal wall. After allowing 3 weeks for growth, laparotomies were performed to check the implants. Then animals were randomized into four groups: Group I amifostine (200 mg/day loading dose after 20 mg/kg/day, p.o.); Group II NAC (200 mg/day, p.o.); Group III leuprolide acetate 1 mg/kg single dose, sc; and Group IV (controls) no medication. Three weeks later, implants were evaluated morphologically. Serum and peritoneal TNF-alpha levels were evaluated. The transmission electron microscopic examination of the peritoneal samples and ovaries was also performed.

RESULTS

Leuprolide acetate, amifostine and NAC caused significant decreases in the mean implant areas and significant decreases in serum and peritoneal TNF-alpha levels. On comparing all groups, these reductions were higher in Group II. According to the transmission electron microscopic findings, leuprolide seems to be protecting normal structure of peritoneum best when compared to the other groups.

CONCLUSIONS

Amifostine, NAC and leuprolide caused regression of endometriosis in this experimental rat model by a yet unsettled mechanism.

Amifostine for salivary glands in high-dose radioactive iodine treated differentiated thyroid cancer

BACKGROUND

Radioactive iodine treatment for differentiated thyroid cancer possibly results in xerostomia. Amifostine has been used to prevent the effects of irradiation to salivary glands. To date, the effects of amifostine on salivary glands in radioactive iodine treated differentiated thyroid cancer remain uncertain.

OBJECTIVES

To assess the effects of amifostine on salivary glands in high-dose radioactive iodine treated differentiated thyroid cancer.

SEARCH STRATEGY

Studies were obtained from computerized searches of MEDLINE, EMBASE, The Cochrane Library and paper collections of conferences held in Chinese.

SELECTION CRITERIA

Randomised controlled clinical trials and quasi-randomised controlled clinical trials comparing the effects of amifostine on salivary glands after radioactive iodine treatment for differentiated thyroid cancer with placebo and a duration of follow up of at least three months.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed risk of bias and extracted data.

MAIN RESULTS

Two trials with 130 patients (67 and 63 patients randomised to intervention versus control) were included. Both studies had a low risk of bias. Amifostine versus placebo showed no statistically significant differences in the incidence of xerostomia (130 patients, two studies), the decrease of scintigraphically measured uptake of technetium-99m by salivary or submandibular glands at twelve months (80 patients, one study), and the reduction of blood pressure (130 patients, two studies). Two patients in one study collapsed after initiation of amifostine therapy and had to be treated by withdrawing the infusion and volume substitution. Both patients recovered without sequelae. Meta-analysis was not performed on the function of salivary glands measured by technetium-99m scintigraphy at three months after high dose radioactive iodine treatment due to the highly inconsistent findings across studies (I(2) statistic 99%). None of the included trials investigated death from any cause, morbidity, health-related quality of life or costs.

AUTHORS' CONCLUSIONS

Results from two randomised controlled clinical trials suggest that the amifostine has no significant radioprotective effects on salivary glands in high-dose radioactive iodine treated differentiated thyroid cancer patients. Moreover, no health-related quality of life and other patient-oriented outcomes were evaluated in the two included trials. Randomised controlled clinical trials with low risk of bias investigating patient-oriented outcomes are needed to guide treatment choice.

Amifostine protective effect on cisplatin-treated rat testis

Cisplatin is a potent drug used in clinical oncology but causes spermatogenesis damage. Amifostine is a drug used against toxicity caused by ionizing irradiation and chemotherapeutic drugs. Since cisplatin provokes fertility and induces germ cell apoptosis and necrosis, we proposed to evaluate the amifostine cytoprotective action on testes of cisplatin-treated rats. Thirty-day-old prepubertal Wistar rats received a single cisplatin dose of 5 mg/kg and were killed after 3, 6, and 12 hr. The hematoxylin-eosin stained testicular sections were submitted to histological, morphometric, and stereological analysis. The terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick end-labeling (TUNEL) method was used to label apoptotic cells. TUNEL-positive and TUNEL-negative germ cells with abnormal nuclear morphology (ANM) were scored. Significant alterations of greater part of the parameters occurred in the cisplatin-treated group (CE) compared to the group that received amifostine before the cisplatin-treatment (ACE); however, testicular weight and volume did not vary between these groups. Tubular diameter was reduced in CE in comparison to ACE rats, while interstitial tissue and lymphatic space volume and volume density were significantly higher in CE rats; interstitial testicular edema probably occurred in cisplatin-treated rats. CE rats showed important histological alterations, which were more accentuated than in ACE rats. The numerical densities of apoptotic germ cells and TUNEL-negative cells with ANM were lower in ACE than in CE rats. In conclusion, the amifostine previously administered to prepubertal rats reduced the testicular damage caused by cisplatin. We conclude that amifostine partially protected the rat seminiferous epithelium against cisplatin toxicity.

Amifostine protection against mitomycin-induced chromosomal breakage in fanconi anaemia lymphocytes

Fanconi anaemia (FA) is a rare genetic chromosomal instability syndrome caused by impairment of DNA repair and reactive oxygen species (ROS) imbalance. This disease is also related to bone marrow failure and cancer. Treatment of these complications with radiation and alkylating agents may enhance chromosomal breakage. We have evaluated the effect of amifostine (AMF) on basal and mitomycin C (MMC)-induced chromosomal breakage in FA blood cells using the micronucleus assay. The basal micronuclei count was higher among FA patients than healthy subjects. Pre-treatment with AMF significantly inhibited micronucleation induced by MMC in healthy subjects (23.4 ± 4.0 – MMC vs 12.3 ± 2.9 – AMF → MMC) MN/1000CB, p < 0.01, one way ANOVA) as well as in FA patients (80.0 ± 5.8 – MMC vs 40.1 ± 5.8 – AMF → MMC) MN/1000CB, p < 0.01, ANOVA). Release of ROS by peripheral blood mononuclear cells treated with AMF → MMC and measured by chemoluminometry showed that AMF-protection was statistically higher among FA patients than in healthy individuals. Based on these results we suggest that AMF prevents chromosomal breakage induced by MMC, probably by its antioxidant effect.

Polysaccharides isolated from Ganoderma lucidum occurring in Southern parts of India, protects radiation induced damages both in vitro and in vivo

The in vivo and in vitro radioprotective property of the polysaccharides isolated from Ganoderma lucidum were determined by survival studies, induction of micronucleus in reticulocytes of mice, strand breaks in plasmid pBR322 DNA and inhibition of lipid peroxidation (TBARS assay). Polysaccharides were administered as a single dose after whole body exposure to 10Gy (60)Co γ-radiation to Swiss albino mice. At a dose of 500μg/kg body wt, the polysaccharides were most effective in protecting animals from radiation induced loss of lethality. Administration of 500μg/kg body wt to animal exposed to 10Gy gamma radiation resulted in more than 60% survival on the 30th day compared to the dose of 300mg/kg/body wt administration of amifostine, a clinically used radioprotective drug. The induction of micronuclei was reduced by the administration of polysaccharides. The decrease in micronuclei induction was dose dependent. Thus following 4Gy exposure the micronuclei in polychromatic erythrocytes (MNCE) was reduced from 28.16±3.049 to 16.0243±2.074 and 6.30±2.422 by polysaccharides at doses of 250μg/kg body wt and 500μg/kg body wt, respectively, and to 10.4±2.581 by amifostine at a dose of 300mg/kg body wt. The results indicate the significant protective effect of Ganoderma polysaccharides against radiation induced damages. The findings thus suggest the potential use of Ganoderma polysaccharides as novel radioprotective agent.

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.

Radiation-induced craniofacial bone growth inhibition: efficacy of cytoprotection following a fractionated dose regimen

BACKGROUND

Severe craniofacial growth disturbances are noted in 66 to 100 percent of children with head and neck cancers who received radiotherapy during their growing years. The authors have previously demonstrated the prevention of radiation-induced craniofacial bone growth inhibition following single-dose orthovoltage radiation to the orbitozygomatic complex in an infant rabbit model through the administration of the cytoprotective agent amifostine (WR-2721) before radiation treatment. The purpose of this study was to investigate the efficacy of cytoprotection using a fractionated dose regimen that better approximates the clinical application of radiation therapy.

METHODS

Thirty 7-week-old male New Zealand rabbits were randomized into three groups (n = 10), each receiving six fractions of orthovoltage radiation to the right orbitozygomatic complex: group C, sham irradiation control; group F35, total dose of 35 Gy; and group F35A, total dose of 35 Gy with administration of amifostine 200 mg/kg intravenously 20 minutes before each fraction. Bone growth was evaluated up to skeletal maturity (age 21 weeks) with serial radiographs and computed tomography scans for cephalometric analysis, bone volume, and bone density measurements.

RESULTS

Fractionated radiation resulted in significant (p < 0.05) bone growth inhibition compared with sham radiation in 16 of 21 cephalometric parameters measured and significantly (p < 0.05) reduced bone volume of the rabbit orbitozygomatic complex. Pretreatment with amifostine before each radiation fraction prevented growth deformities in four cephalometric parameters and significantly (p < 0.05) attenuated these effects in another seven parameters compared with radiated animals. Bone volumes were also significantly (p < 0.05) improved in F35A animals compared with F35 animals.

CONCLUSIONS

This study establishes that fractionation of orthovoltage radiation does not prevent the development of growth disturbances of the rabbit craniofacial skeleton and also demonstrates that preirradiation administration of amifostine is highly effective in the prevention and attenuation of radiation-induced craniofacial bone growth inhibition.

Impact on cytoprotective efficacy of intermediate interval between amifostine administration and radiotherapy: a retrospective analysis

PURPOSE

To evaluate the cytoprotective impact of the interval between amifostine administration and radiotherapy (RT).

METHODS AND MATERIALS

In a nonrandomized study, we reviewed the records of 177 patients with tumors localized in the pelvis (prostate, bladder, or gynecologic cancer), upper abdomen (pancreas, stomach, kidney), thorax (lung and breast cancer), head and neck (nasopharynx), soft tissue (sarcomas), and central nervous system. The patient records were stratified according to whether the patients had undergone RT either 25-40 min (Group 1, 96 subjects) or 10-15 min (Group 2, 81 subjects) after i.v. amifostine administration. The mean toxicity score was the mean value of recorded acute radiation toxicity. The mean interruption time was the mean value of the recorded interruption time due to radiation toxicity.

RESULTS

A significantly reduced severity of symptoms related to oral (p = 0.023), esophageal (p = 0.05) and rectal (p = 0.015) mucosa was noted in Group 2. A statistically significant reduction in the mean toxicity score (p <0.001) and mean interruption time (p = 0.001) was observed in Group 2 vs. Group 1. In terms of the incidence of radiation-induced dermatitis and alopecia, multivariate logistic analysis revealed only the total dose (p = 0.018) and the amifostine-RT interval (p = 0.002) as independent factors.

CONCLUSION

A significantly better cytoprotective effect of amifostine against radiation-induced mucositis, dermatitis, and alopecia was noted if RT was administered no later than 15 min after i.v. amifostine infusion. The results presented here need additional investigation with randomized prospective trials.

A randomized trial of amifostine as a cytoprotectant for patients receiving myeloablative therapy for allogeneic hematopoietic stem cell transplantation

We initiated a randomized study of amifostine (the organic thiophosphate formerly known as WR-2721) given to patients during myeloablative conditioning therapy for allogeneic bone marrow transplantation. Amifostine was given at a dose of 1000 mg/day of conditioning and was well tolerated if attention was given to serum calcium levels, blood pressure and antiemetics. Since August 1998, 60 patients (30 on each arm) have completed the study. There was no significant difference in the days to neutrophil or platelet engraftment in either arm of the study. Significantly, the duration of grade I-IV mucositis was decreased in the group that received amifostine (P=0.02). Also grade III or IV infections (P=0.008), duration of antibiotic therapy (P=0.03) and duration of fever (P=0.04) were significantly reduced with amifostine. However, there were no differences in the incidence of grade III or IV mucositis, liver toxicity or renal toxicity. There were also no differences in early mortality, relapse and long-term survival. We conclude that amifostine, while reducing the duration of mucositis and infections (possibly through some preservation of gut mucosal integrity), has a modest effect in allogeneic bone marrow transplants given the multiplicity of factors influencing organ toxicity and survival in this setting.

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.

p53 protein regulates the effects of amifostine on apoptosis, cell cycle progression, and cytoprotection

To determine the role of p53 protein on the cellular effects of amifostine, we used molecularly engineered HCT116 colon cancer cells in which the p53 gene was inactivated by targeted homologous recombination or p53 protein was degraded by high-level expression of papillomavirus E6 protein. Amifostine induced a G1 arrest and protected against paclitaxel toxicity in p53-proficient but not in p53-deficient cells. In the absence of p53 protein, amifostine enhanced the cytotoxicity of paclitaxel. In addition, treatment of HCT116 cells with amifostine alone resulted in apoptotic cell death. Compared with p53-deficient cells, p53-proficient cells exhibited low-level resistance to amifostine-induced apoptosis. Amifostine induced the expression of p53 protein in p53-proficient cells and the expression of p21 protein in both p53-proficient and -deficient cells. These findings indicate that amifostine-induced G1 arrest and cytoprotection are mediated via a pathway that is dependent on p53 protein and that amifostine-induced expression of p21 protein is not sufficient to sustain a G1 arrest or to mediate cytoprotection. In addition, these findings identify p53 protein as a mechanism of resistance to amifostine-induced apoptosis.British

New liquid chromatographic assay with electrochemical detection for the measurement of amifostine and WR1065

A high-performance liquid chromatographic method (HPLC) was developed for the analysis of the radio- and chemo-protectant, amifostine and its active metabolite-WR1065 in deproteinized human whole blood and plasma. The two compounds were quantified by measuring WR1065 after two different sample pretreatment procedures. During these procedures, amifostine was quantitatively converted into WR1065, by incubating the sample at 37 degrees C for 4 h at pH<1.0. The resulting amounts of WR1065 were determined by HPLC with coulometric detection (analytical cell: E(1)=200 mV and E(2)=600 mV; guard cell: E(G)=650 mV). The WR1065 standard curve ranged from 0.37 to 50.37 microM. The lower limit of quantitation of WR1065 was 0.25 microM. The within- and between-day precisions were < or = 4.3% and < or = 6.0% for amifostine, < or = 4.4% and < or = 3.8% for WR1065, respectively. The within- and between-day accuracy ranged from 95.4 to 97.7% and 95.4 to 97.8% for amifostine, and from 97.1 to 101.7% and 97.2 to 99.7% for WR1065, respectively. This method minimizes WR1065 loss during sample preparation, and allows for rapid analysis of both compounds on one system. Furthermore, the application of a coulometric electrode is more efficient and requires less maintenance than previously published methods for the two compounds.

Flow cytometric detection of apoptotic bone marrow cells with fractional DNA content after application of WR-2721, cyclophosphamide, cisplatin, and exposure of mice to gamma rays

Little is known about the mechanisms of apoptosis triggered in normal cells of the haemopoietic system by the aminothiol WR-2721 (Amifostine), chemotherapeutic drugs, and ionizing radiation; thus, the present study was undertaken to evaluate the effects of WR-2721, cyclophosphamide (CP), cisplatin (CDDP), and 60Co gamma rays on induction of apoptotic DNA degradation in bone marrow cells. Adult male Swiss mice were treated with WR-2721 (400 mg/kg b.wt.), CP (200 mg/kg b.wt.), and CDDP (10 mg/kg b.wt.), and exposed to 6 Gy 60Co gamma rays. Alterations in the number of apoptotic cells with fractional DNA content and also the cell cycle position of the non-apoptotic cells were determined in the bone marrow at 7 and 24 hours after treatment of mice with these agents, using flow cytometric assay of the controlled extraction of low-MW DNA from apoptotic cells. The chemotherapeutic drugs CP and CDDP and 60Co gamma rays triggered apoptosis and affected the cell cycle position of the non-apoptotic cells in the mouse bone marrow. The pretreatment of mice with WR-2721 resulted in the modulatory action of the aminothiol on induction of apoptotic cell death and changes in the cell cycle distribution of the non-apoptotic cells caused by the DNA-damaging agents. The patterns of changes in the frequency of apoptotic cells and the cell cycle position of the non-apoptotic cells, observed in the bone marrow, were dependent on the agent(s) applied and the time interval after application of the drug(s) and exposure of mice to gamma rays. Understanding of the mechanisms responsible for triggering of apoptotic cell death and disturbing of the cell cycle by the DNA-damaging agents, and modulation of the apoptotic and cell cycle pathways by the aminothiol WR-2721, can lead to more effective therapy and chemo- and radio-protection of normal cells.

Prophylactic use of amifostine to prevent radiochemotherapy-induced mucositis and xerostomia in head-and-neck cancer

PURPOSE

To determine the prophylactic properties of amifostine against acute and late toxicities from radiochemotherapy in patients with head-and-neck cancer.

METHODS AND MATERIALS

Fifty patients were randomized to receive conventional radiotherapy (RT) (2-Gy fractions, 5 days weekly, to a total of 60-74 Gy, depending on the tumor localization and TNM classification) and carboplatin (90 mg/m(2) infusion once per week before RT). Amifostine (300 mg/m(2)) was administered in the study group only 15-30 min before RT for 6-7.5 weeks. The primary study end point was the grading of acute and late nonhematologic toxicities (mucositis, dysphagia, xerostomia) induced by radiochemotherapy. Secondary end points included treatment duration, hematologic toxicity, and clinical outcome.

RESULTS

The treatment duration was significantly shorter in the amifostine-treated group (p = 0.013), because treatment interruptions were more frequent in the control group. Acute toxicities (mucositis and dysphagia) were less severe in the amifostine-treated group. By Week 3, all in the control group experienced Grade 2 mucositis compared with only 9% in the amifostine-treated group (p <0.0001). By Week 5, 52.2% of the patients in the control group experienced Grade 4 mucositis compared with 4.5% in the amifostine-treated group (p = 0.0006). Similar results were obtained for dysphagia. At 3 months of follow-up, only 27% of patients in the study group experienced Grade 2 xerostomia compared with 73.9% in the control group (p = 0.0001). Eighteen months after cessation of therapy, the proportion of patients with Grade 2 xerostomia was 4.5% vs. 30.4% for each respective treatment group (p = 0.047). Cytoprotection with amifostine did not affect treatment outcome, with 90.9% complete responses in the amifostine-treated group compared with 78.3% in the control group (p = 0.414).

CONCLUSION

Amifostine was effective in reducing mucositis and dysphagia resulting from radiochemotherapy in patients with head-and-neck cancer. Furthermore, amifostine reduced the severity of late xerostomia, a side effect of RT with long-lasting consequences. Amifostine treatment did not affect the clinical outcome.

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.

Randomized phase III trial of radiation treatment +/- amifostine in patients with advanced-stage lung cancer

PURPOSE

This multicenter trial investigated whether daily pretreatment with amifostine (A) could reduce the incidence of acute and late lung toxicity and esophagitis without affecting antitumor efficacy of radiation in advanced lung cancer.

PATIENTS AND METHODS

Radiotherapy (XRT) patients (n = 146) received a daily fraction of 2 Gy/5 days/week to a total of 55-60 Gy +/- amifostine 340 mg/m(2) administered daily 15 min before irradiation. Acute and late toxicities were graded from 0 to 4 according to the Radiation Therapy Oncology Group/European Organization for the Research and Treatment of Cancer system.

RESULTS

Ninety-seven patients were evaluated 2 months post-XRT for the incidence of pneumonitis; 43% (23/53) of patients in the XRT arm and 9% (4/44) in the A + XRT arm experienced > or = Grade 2 pneumonitis (p < 0.001) [corrected]. Forty-nine percent (26/53) of patients in the XRT arm and 16% (7/44) in the A+XRT arm demonstrated changes representative of > or = Grade 2 lung damage (p < 0.001). At 6 months, fibrosis was present in 53% (19/36) receiving XRT vs. 28% (9/32) receiving A+XRT (p < 0.05). Incidence of esophagitis > or = Grade 2 during Week 4 was 42% (31/73) in the XRT arm vs. 4% (3/73) in the A+XRT arm (p < 0.001). Among 97 patients evaluable for response 2 months after XRT, complete or partial response was present in 76% (40/53) of patients in the XRT arm and 75% (33/44) in the A+XRT arm (p = 1.0).

CONCLUSION

Amifostine reduces the incidence of pneumonitis, lung fibrosis, and esophagitis in radiotherapy patients with lung cancer without compromising antitumor efficacy.

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).

Preclinical and clinical aspects on the use of amifostine as chemoprotector in neuroblastoma patients

BACKGROUND

In several studies in adults, amifostine (WR-2721) and its active metabolite WR-1065 have shown protection against myelo- and nephrotoxicity of chemotherapeutic agents without compromising cytotoxic efficacy to the tumor.

PROCEDURE

In the present study, the effect of amifostine and WR-1065 on neuroblastoma tumor growth and its protective potential for hematotoxicity were investigated. Neither amifostine nor WR-1065 reduced the cytotoxic effect of six drugs commonly used for this tumor when tested on neuroblastoma cells in vitro.

RESULTS

In mice carrying human xeno-transplanted neuroblastoma, tumor growth and antitumor activity of chemotherapy were unaffected by amifostine. In addition, hematotoxicity of alkylators was relieved in some cases. In patients with neuroblastoma, amifostine only slightly reduced bone marrow toxicity and was highly emetogenic.

CONCLUSIONS

Therefore, amifostine warrants further investigation before its widespread clinical use in the treatment of children with neuroblastoma.

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.

Stage-specific inhibition of deoxyribonucleic acid synthesis and induction of apoptosis by antracyclines in cultured rat spermatogenic cells

A rapid in vitro method has been developed to detect early effects of cytostatic drugs on rat spermatogenesis. The induction of programmed cell death (apoptosis) and changes in DNA synthesis induced by doxorubicin and idarubicin were measured in specific stages of the cycle of seminiferous epithelium including mitotic (stage V) and meiotic (stage VIII-IX) S-phase cells. The model was used to investigate the protective effect of an organic thiophosphate, amifostine, against the toxicity of antracyclines. Premitotic DNA synthesis was found to be more sensitive than premeiotic DNA synthesis to antracyclines. Idarubicin was more toxic than doxorubicin to germ cells in inducing apoptosis and suppressing DNA synthesis. Amifostine had no protective effect against doxorubicin- or idarubicin-induced inhibition of DNA synthesis. In contrast, a significant stimulation of DNA synthesis in premitotic cells by amifostine was found, suggesting that this compound may have a stimulative effect on spermatogenic stem cells. These data show that stage-specific dissection of the seminiferous tubules and their in vitro exposure to predetermined doses of drugs may give us a unique possibility to detect drug action and protection against the cytotoxicity of antineoplastic agents at the cellular level of the spermatogenic cycle.

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.

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.

Radioprotective effects of the thiols GSH and WR-2721 against X-ray-induction of micronuclei in erythroblasts

The frequency of micronucleated polychromatic erythrocytes (MNPCEs) was assessed in the bone marrow and peripheral blood of adult male Swiss mice treated with reduced glutathione (GSH) and S-2-/3-aminopropylamino/ethyl phosphorothioic acid (WR-2721), at a dose of 400 mg/kg body weight, and exposed to 6 Gy X-rays. GSH or WR-2721 was applied alone, or 60 and 30 min, respectively, prior to X-ray-exposure. The number of MNPCEs was determined at 24 h after the thiol treatment and X-irradiation. The radioprotection and toxicity caused in the mouse erythroblasts by GSH and WR-2721, as indicated by the number of MNPCEs were dependent on the thiol applied. The stronger radioprotective effect is obtained following WR-2721 administration than after GSH application. WR-2721 showed greater toxicity than GSH. The combination of GSH and WR-2721 given before X-ray-exposure resulted in the most radioprotective effect as compared to the respective single-drug treatment of mice. Application of the both thiols, without subsequent X-irradiation appeared to be the most toxic, compared with administration of WR-2721 or GSH alone. The effective radioprotection by the combined action of GSH and WR-2721 against genomic instability induced in the mouse erythroblasts by X-rays was shown.

Subcutaneous administration of amifostine during fractionated radiotherapy: a randomized phase II study

PURPOSE

Amifostine (WR-2721) is an important cytoprotective agent. Although intravenous administration is the standard route, pharmacokinetic studies have shown acceptable plasma levels of the active metabolite of amifostine (WR-1605) after subcutaneous administration. The subcutaneous route, due to its simplicity, presents multiple advantages over the intravenous route when amifostine is used during fractionated radiotherapy.

PATIENTS AND METHODS

Sixty patients with thoracic, 40 with head and neck, and 40 with pelvic tumors who were undergoing radical radiotherapy were enrolled onto a randomized phase II trial to assess the feasibility, tolerance, and cytoprotective efficacy of amifostine administered subcutaneously. A flat dose of amifostine 500 mg, diluted in 2.5 mL of normal saline, was injected subcutaneously 20 minutes before each radiotherapy fraction.

RESULTS

The subcutaneous amifostine regimen was well tolerated by 85% of patients. In approximately 5% of patients, amifostine therapy was interrupted due to cumulative asthenia, and in 10%, due to a fever/rash reaction. Hypotension was never noted, whereas nausea was frequent. A significant reduction of pharyngeal, esophageal, and rectal mucositis was noted in the amifostine arm (P <.04). The delays in radiotherapy because of grade 3 mucositis were significantly longer in the group of patients treated with radiotherapy alone (P <.04). Amifostine significantly reduced the incidence of acute perineal skin and bladder toxicity (P <.0006).

CONCLUSION

Subcutaneous administration of amifostine is well tolerated, effectively reduces radiotherapy's early toxicity, and prevents delays in radiotherapy. The subcutaneous route is much simpler and saves time compared with the intravenous route of administration and can be safely and effectively applied in the daily, busy radiotherapy practice.

Randomized study of a short course of weekly cisplatin with or without amifostine in advanced head and neck cancer. EORTC Head and Neck Cooperative Group

BACKGROUND

Cisplatin is one of the most active cytotoxic agents available for the treatment of patients with head and neck cancer. In a previous phase II study with weekly administration of cisplatin, a response rate of 51% was achieved. However, only in a minority of the patients the planned high dose intensity of 80 mg/m2/week could be reached because of toxicity, mainly thrombocytopenia and ototoxicity. Amifostine is a cytoprotective drug that can diminish the toxicity of alkylating agents and platinum compounds. Therefore the effect of amifostine on toxicity and activity of weekly cisplatin was investigated in a randomized study.

PATIENTS AND METHODS

Patients with locally advanced, recurrent or metastatic head and neck cancer were eligible. Patients were randomized to weekly cisplatin 70 mg/m2 for six cycles preceded by amifostine 740 mg/m2, or cisplatin only. Cisplatin was administered in hypertonic saline (3% NaCl) as a one-hour infusion; amifostine was administered as a 15-minute infusion directly before the administration of cisplatin.

RESULTS

Seventy-four patients were entered in the study. The median number of cisplatin administrations was 6 (range 2-6), equal in both arms. In both treatment arms the median dose intensity of cisplatin achieved was the planned 70 mg/m2/week. In the cisplatin only arm 6 out of 206 cycles were complicated by thrombocytopenia grade 3 or 4 versus 1 of 184 cycles in the amifostine arm (P = 0.035). Hypomagnesaemia grade 2 + 3 was significantly less observed in the amifostine arm (P = 0.04). Neurotoxicity analyzed by serial vibration perception thresholds (VPT) showed a diminished incidence of subclinical neurotoxicity in the amifostine arm (P = 0.03). No protective effect on renal and ototoxicity could be shown. Hypotension was the main side effect of amifostine but only of relevance in one patient. The antitumor activity of cisplatin was preserved as 63% of the evaluable patients in the amifostine arm responded compared to 50% of the evaluable patients in the cisplatin alone arm.

CONCLUSION

Our study indicated that in combination with weekly administered cisplatin amifostine reduced the risk of thrombocytopenia, hypomagnesemia as well as subclinical neurotoxicity, but did not result in a higher dose intensity of cisplatin. Addition of amifostine did not compromise the antitumor effect of cisplatin.

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.

Pharmacokinetics of amifostine and its metabolites in patients

The pharmacokinetics of the cytoprotective agent amifostine (EthyolR; WR 2721) and its main metabolites (WR 1065 and the disulphides) were studied in patients participating in two phase I trials concerning carboplatin or cisplatin in combination with amifostine. Patients were treated with a single dose or three doses of amifostine (740 or 910 mg/m2). The single or first dose was given as a 15 min i.v. infusion just before administration of the chemotherapeutic agent. The additional two infusions were administered 2 and 4 h thereafter. Amifostine was rapidly cleared from the plasma, due to, at least in part, the fast conversion into WR 1065. A biphasic decrease with a final half-life of 0.8 h was observed. The active metabolite WR 1065 was cleared from the plasma with a final half-life of 7.3 +/- 3.6 h. The short initial half-life of WR 1065 can be explained by its fast uptake in tissues and the formation of disulphides. The disulphides were cleared with a final half-life of 8.4-13.4 h and were detectable for at least 24 h after treatment. They may serve as an exchangeable pool of WR 1065. The amifostine peak values at the end of each 15 min infusion did not accumulate in the multiple dosing schedule. For WR 1065 a trend towards an increase in the peak levels was observed [C1,max: 47.5 +/- 11.9 microM, C2,max: 79.0 +/- 13.2 microM, C3,max: 84.8 +/- 15.1 microM, (n = 6)], whereas a trend towards a small decrease was observed for the peak levels of the disulphides [C1,max: 184.2 +/- 12.6 microM, C2,max: 175.0 +/- 23.7 microM, C3,max: 166.0 +/- 17.2 microM, (n = 6)]. This latter finding might suggest a saturation of the disulphide formation or a change in the uptake or elimination of WR 1065, which would result in higher WR 1065 levels in plasma and tissues, after multiple doses of amifostine.

Influence of single and multiple doses of amifostine on the efficacy and the pharmacokinetics of carboplatin in mice

We have previously reported that amifostine potentiates the anti-tumour activity of carboplatin in mice. The present study was carried out in well-established human ovarian cancer xenografts OVCAR-3, A2780 and FMa grown subcutaneously in the nude mouse. It was found that a single dose of amifostine resulted in a higher increase in the anti-tumour activity of carboplatin than three doses of amifostine. A single dose of amifostine increased the AUC (area under the curve) values of total platinum in plasma ultrafiltrate (30.1 vs 18.2 microM x h), liver (307.7 vs 236.4 nmol g(-1) x h), kidney (500.8 vs 368.3 nmol g(-1) x h) and OVCAR-3 tumour tissue (184.0 vs 146.8 nmol g(-1) x h). Despite this increase in total platinum, a decrease in platinum (Pt)-DNA adduct levels was observed in liver, kidney and bone marrow, which was significant in liver. In tumour tissue an insignificant increase in Pt-DNA adduct levels, specifically the Pt-GG adduct, was observed after treatment with a single dose of amifostine, which may explain the increase in anti-tumour activity. The increase in the AUC of total platinum was probably caused by a reduction in body temperature, which was most severe after three doses of amifostine. The extreme hypothermia may be the reason that three doses of amifostine resulted in less potentiation of the efficacy of carboplatin.

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.

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

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

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.

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.

HPLC and 31P NMR characterization of the reaction between antitumor platinum agents and the phosphorothioate chemoprotective agent S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721)

In prior studies, we examined the effects of the radioprotective and chemoprotective agent WR-2721 [S-2-(3-aminopropylamino)ethylphosphorothioic acid] on the in vivo biotransformation of the cisplatin [cis-diamminedichloroplatinum(II)] analog ormaplatin [(d,I)trans-1,2-diaminocyclohexanetetrachloroplatinum(IV), Pt(dach)Cl4, (formerly called tetraplatin)]. Those data suggested that a direct interaction between WR-2721 and ormaplatin and/or the corresponding Pt(II) drug, Pt(dach)Cl2, may be occurring in vivo. This would be in contrast to the generally accepted hypothesis that WR-2721 is a prodrug that must first be converted by alkaline phosphatase to a free thiol compound, WR-1065, before any appreciable reactivity would be evident. However, the major biotransformation product observed in the peritoneal fluid, plasma, and all tissues was Pt(dach)(WR-1065). We report here on further investigations into the in vitro reactivity of Pt(dach) compounds with WR-2721 and WR-1065. Separation of reaction products resulting from incubation of Pt(dach)(malonato) with either WR-2721 or WR-1065 under physiological conditions gave profiles that were indistinguishable by reverse phase HPLC and cation exchange HPLC at two different pHs. 31P NMR characterization of the dephosphorylation of WR-2721 revealed essentially no loss of inorganic phosphate for up to 24 hr when incubated in unbuffered water at 30 degrees. In contrast, when incubated with a 1:1 molar ratio of cisplatin under the same conditions, the WR-2721 signal was decreased markedly in the first 5 min, and had disappeared almost completely by 1 hr. The signal corresponding to inorganic phosphate increased in parallel to the decrease in the WR-2721 signal. No intermediate formation of a complex containing both platinum and phosphate could be detected at any time. These data suggest that the reaction between WR-2721 and platinum complexes results in rapid dephosphorylation of WR-2721, and, consequently, that the reaction products formed with either WR-2721 or WR-1065 and Pt(II) complexes are identical.

Induction of micronucleated erythrocytes by MEA, AET, WR-2721 and X-rays

The induction of micronucleated polychromatic erythrocytes (MNPCEs) was assessed in the bone marrow of adult male Swiss mice treated with MEA (cysteamine HCl), AET (2-aminoethylisothiouronium Br.HBr), or WR-2721 (S-2-(3-aminopropylamino)ethyl phosphorothioic acid), at a dose of 200 mg/kg body weight, and/or exposed to 6 Gy X-rays. MEA, AET, or WR-2721 was given alone or 15 min prior to X-ray exposure, and the frequency of MNPCEs was determined 24 h after the aminothiol treatment and X-irradiation of mice. A genotoxic effect was shown for MEA, AET, WR-2721, and X-rays, as well as a protective effect of the aminothiols against X-ray-induced genotoxicity in the mouse erythropoietic system. The aminothiol drugs given alone, without subsequent X-irradiation, elevated the frequency of MNPCEs, and WR-2721 appeared to be less toxic than AET and MEA. After exposure of mice to X-rays, the number of MNPCEs was distinctly increased. MEA, AET, or WR-2721 administration prior to X-irradiation resulted in a reduction of the X-ray-induced elevation of the frequency of micronuclei, but a stronger radioprotective effect was obtained following WR-2721 and AET treatment than after MEA application. So, the genotoxic and radioprotective effect of the aminothiols was dependent on the compound applied.

Determination of the anticancer drug metabolite WR1065 using pre-column derivatization and diode laser induced fluorescence detection

A liquid chromatographic (LC) procedure using alumina as stationary phase in both the pre- and the analytical column, is reported for the determination of WR1065, the active metabolite of the amino- and thiol-containing anticancer drug WR2721. After pre-column derivatization of the thiol group, the analyte is determined by LC with diode laser induced fluorescence detection in the near-infrared. Selective removal of excess label is achieved by means of column switching; it allows the detection of 5 x 10(-9) M WR1065 in water and 10-fold diluted, deproteinated plasma samples. The detection limit is determined by the derivatization reaction and not by the fluorescence detection of the labelled analyte. Endogeneous thiols do not interfere.

Suppressing effect of WR-2721 on micronuclei induced by cyclophosphamide in mice

The effect of WR-2721 against cyclophosphamide-induced clastogenicity was studied using the in vivo micronucleus assay. The frequency of micronuclei in polychromatic erythrocytes in the peripheral blood of mice treated with WR-2721 and cyclophosphamide (CP), each of the compounds at a dose of 200 mg/kg body weight, was evaluated during the 15-day period. The suppressing effect of WR-2721, given 30 min prior to cyclophosphamide administration, on micronuclei induced by the alkylating agent was demonstrated. The number of micronuclei was increased on day 1 after CP application and declined thereafter with the frequency of micronucleated polychromatic erythrocytes remaining lower in WR-2721 pre-treated mice. The modulatory effect of WR-2721 on the clastogenic activity of cyclophosphamide in the erythropoietic system by the mouse micronucleus test was shown.

Reaction of 4-hydroxynonenal with some thiol-containing radioprotective agents or their active metabolites

The rate of reaction of several radioprotective agents or their active metabolites with 4-hydroxynonenal (4HNE) was studied and compared to the rate of reaction with cysteine (Cys) and glutathione (GSH). The agents studied were: mercapto ethylamine (MEA); 2(3-aminopropyl) aminoethanethiol (WR1065); S-2-aminoethylisothiouronium bromide-hydrobromide (AET); 1,4-dithiothreitol (DTT); 1,4-dithioerythritol (DTE); N-2(2-mercaptopropionyl)-glycine (MPG); penicillamine hydrochloride (PA); N-acetylcysteine (NAC); 2-3 dimercapto-1 propane sulfonic acid (DMPS); 2,3-dimercaptopropanol (BAL), and meso 2,3 dimercapto succinic acid (DMS). All of them reacted with 4HNE. MEA and WR1065 were the most reactive thiols, and PA and DMS were the least reactive thiols. All the others reacted at rates comparable to or higher than that of cysteine or GSH. The potential role of this type of interactions in the protective action of these drugs against deleterious effects of radiation or carbon tetrachloride is analyzed.

Inhibition of the clastogenic effect of cyclophosphamide by WR-2721 in the bone marrow of mice

The frequency of micronucleated polychromatic erythrocytes in the bone marrow of Swiss mice treated with WR-2721, at a dose of 200 mg/kg or 400 mg/kg body weight, 15 or 30 min prior to cyclophosphamide (CP) administration, at a dose of 200 mg/kg body weight, was determined 24 h after CP treatment. In mice injected with CP, the number of micronuclei in polychromatic erythrocytes was significantly increased in comparison with the controls, and in mice treated with WR-2721 and CP, the frequency of micronucleated polychromatic erythrocytes was distinctly decreased in comparison to those given CP alone. The protective effect of WR-2721 against cyclophosphamide-induced clastogenicity was shown. The effect was dependent on the dose of the thiol agent given, and it was more expressed when WR-2721 was applied at the higher dose, 400 mg/kg body weight. However, the protection by the aminothiol appeared not to depend on the time intervals between WR-2721 and CP administration to the mouse organism.

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).

WR2721 as a modulator of cisplatin- and carboplatin-induced side effects in comparison with other chemoprotective agents: a molecular approach

Cisplatin is an active cytostatic that became successful in the treatment of several types of solid tumours after its nephrotoxic potential was controlled by hydration and diuresis. Thiol compounds were tested to reduce further cisplatin-induced nephrotoxicity. Thiosulphate is rapidly excreted by the kidneys and protects against cisplatin-induced nephrotoxicity by inactivating reactive platinum species in the kidney. Due to inactivation of cisplatin in the circulation, thiosulphate also interferes with its antitumour activity. Therefore, it is mainly used in two-route schedules, whereby cisplatin is delivered locally to the tumour (i.p. or i.a.) while systemic (i.v.) thiosulphate protects the kidneys. Diethyldithiocarbamate was shown to protect against cisplatin-induced nephrotoxicity in several animal models by reversing cellular damage. However, in the clinic it has been less successful, partly due to its central nervous system toxicity. The endogenous thiol compounds glutathione and metallothionein have been shown to reduce cisplatin-induced toxicity both in animal models and in clinical trials. However, the results are rather preliminary and a reduction in therapeutic efficacy may be expected, for both glutathione and metallothionein have been reported to be involved in platinum resistance. The thioether methionine has been shown to reduce cisplatin-induced nephrotoxicity in animal models but it has not yet been tested in the clinic. Cisplatin-induced acute emesis can be sufficiently controlled with a new class of 5-hydroxytryptamine-3 (5HT3)-receptor blockers, but delayed emesis remains a problem. High-dose cisplatin regimens with protection of the kidneys induces ototoxicity, peripheral neuropathy and myelotoxicity, which become dose-limiting. Neurotoxicity was partly reversed by the neurogenerative agent ORG2766, but this agent does not reduce other cisplatin-induced toxicities. Therefore, an agent capable of protecting multiple non-tumour tissues is needed. Carboplatin is a second-generation analogue of cisplatin with less nephro-, neuro- and ototoxicity. Carboplatin is at least as active as cisplatin at its maximum tolerated dose, which is defined by its myelotoxicity. Protection from carboplatin-induced myelotoxicity may be controlled by autologous bone marrow transplantation and/or hematopoietic growth factor infusions. High-dose carboplatin schedules may cause nephrotoxicity, neurotoxicity and ototoxicity. Again, the protection of multiple non-tumour tissues is needed. WR2721 appears to be such a modulating agent capable of protecting multiple non-tumour tissues. It was shown to be preferentially metabolized and taken up as the thiol metabolite WR1065 by non-tumour tissues as compared with (hypoxic) solid tumours. It was shown to protect mice from cisplatin-induced nephrotoxicity and from cisplatin- and carboplatin-induced myelotoxicity without interfering with the antitumour activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Phase I study of WR-2721 and carboplatin

Because WR-2721 reduces the toxicity of cisplatin and carboplatin in preclinical systems, we have treated 35 patients in a phase I study of WR-2721 and carboplatin. As the plasma half-life of WR-2721 is short relative to that of carboplatin, WR-2721 was administered in two divided doses. This schedule produced acceptable toxicity in 24 patients treated with carboplatin 400 mg/m2 and escalating doses of WR-2721. In the subsequent 11 patients, WR-2721 was fixed at 740 mg/m2/dose and the dose of carboplatin was escalated. With WR-2721, grade 3-4 thrombopenia (platelets < 50 x 10(9)/l) was produced in 4/5 patients treated with carboplatin 625 mg/m2 and in 1/6 patients treated with carboplatin 500 mg/m2. Carboplatin pharmacokinetic parameters in 4 patients were similar to those reported for carboplatin alone. These results suggest that WR-2721 might increase the maximum tolerated dose of carboplatin from 400 to 500 mg/m2.