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

Chemotherapy-induced acute kidney injury: epidemiology, pathophysiology, and therapeutic approaches

Despite significant advancements in oncology, conventional chemotherapy remains the primary treatment for diverse malignancies. Acute kidney injury (AKI) stands out as one of the most prevalent and severe adverse effects associated with these cytotoxic agents. While platinum compounds are well-known for their nephrotoxic potential, other drugs including antimetabolites, alkylating agents, and antitumor antibiotics are also associated. The onset of AKI poses substantial risks, including heightened morbidity and mortality rates, prolonged hospital stays, treatment interruptions, and the need for renal replacement therapy, all of which impede optimal patient care. Various proactive measures, such as aggressive hydration and diuresis, have been identified as potential strategies to mitigate AKI; however, preventing its occurrence during chemotherapy remains challenging. Additionally, several factors, including intravascular volume depletion, sepsis, exposure to other nephrotoxic agents, tumor lysis syndrome, and direct damage from cancer's pathophysiology, frequently contribute to or exacerbate kidney injury. This article aims to comprehensively review the epidemiology, mechanisms of injury, diagnosis, treatment options, and prevention strategies for AKI induced by conventional chemotherapy.

WR1065 conjugated to thiol-PEG polymers as novel anticancer prodrugs: broad spectrum efficacy, synergism, and drug resistance reversal

The lack of anticancer agents that overcome innate/acquired drug resistance is the single biggest barrier to achieving a durable complete response to cancer therapy. To address this issue, a new drug family was developed for intracellular delivery of the bioactive aminothiol WR1065 by conjugating it to discrete thiol-PEG polymers: 4-star-PEG-S-S-WR1065 (4SP65) delivers four WR1065s/molecule and m-PEG6-S-S-WR1065 (1LP65) delivers one. Infrequently, WR1065 has exhibited anticancer effects when delivered via the FDA-approved cytoprotectant amifostine, which provides one WR1065/molecule extracellularly. The relative anticancer effectiveness of 4SP65, 1LP65, and amifostine was evaluated in a panel of 15 human cancer cell lines derived from seven tissues. Additional experiments assessed the capacity of 4SP65 co-treatments to potentiate the anticancer effectiveness and overcome drug resistance to cisplatin, a chemotherapeutic, or gefitinib, a tyrosine kinase inhibitor (TKI) targeting oncogenic EGFR mutations. The CyQUANT®-NF proliferation assay was used to assess cell viability after 48-h drug treatments, with the National Cancer Institute COMPARE methodology employed to characterize dose-response metrics. In normal human epithelial cells, 4SP65 or 1LP65 enhanced or inhibited cell growth but was not cytotoxic. In cancer cell lines, 4SP65 and 1LP65 induced dose-dependent cytostasis and cytolysis achieving 99% cell death at drug concentrations of 11.2 ± 1.2 µM and 126 ± 15.8 µM, respectively. Amifostine had limited cytostatic effects in 11/14 cancer cell lines and no cytolytic effects. Binary pairs of 4SP65 plus cisplatin or gefitinib increased the efficacy of each partner drug and surmounted resistance to cytolysis by cisplatin and gefitinib in relevant cancer cell lines. 4SP65 and 1LP65 were significantly more effective against TP53-mutant than TP53-wild-type cell lines, consistent with WR1065-mediated reactivation of mutant p53. Thus, 4SP65 and 1LP65 represent a unique prodrug family for innovative applications as broad-spectrum anticancer agents that target p53 and synergize with a chemotherapeutic and an EGFR-TKI to prevent or overcome drug resistance.

The Progress in Reconstruction of Mandibular Defect Caused by Osteoradionecrosis

Osteoradionecrosis (ORN) is described as a disease with exposed, nonviable bone that fails to heal spontaneously or by means of conservative treatment after radiotherapy in at least 3 months. Though traditional theories in the early stage including hypoxic-hypocellular-hypovascular and fibro-atrophic in addition to new findings such as ferroptosis were put forward to explain the mechanisms of the osteoradionecrosis, the etiology of ORN is still unclear. With the high rate of occurrence in the head and neck area, especially in the mandible, this disease can disrupt the shape and function of the irradiated area, leading to a clinical presentation ranging from stable small areas of asymptomatic exposed bone to severe progressive necrosis. In severe cases, patients may experience pain, xerostomia, dysphagia, facial fistulas, and even a jaw defect. Consequently, sequence therapy and sometimes extensive surgery and reconstructions are needed to manage these sequelae. Treatment options may include pain medication, antibiotics, the removal of sequesters, hyperbaric oxygen therapy, segmental resection of the mandible, and free flap reconstruction. Microanastomosed free-flaps are considered to be promising choice for ORN reconstruction in recent researches, and new methods including three-dimensional (3-D) printing, pentoxifylline, and amifostine are used nowadays in trying increase the success rates and improve quality of the reconstruction. This review summarizes the main research progress in osteoradionecrosis and reconstruction treatment of osteoradionecrosis with mandibular defect.

Salivary Gland Dysfunction Secondary to Cancer Treatment

The number of cancer survivors are increasing and so are the oral toxicities from cancer therapy. Most patients receiving treatment for cancer develop some form of oral adverse events including, but not limited to, mucositis, opportunistic infections, dry mouth, and/or osteonecrosis of the jaw. One of the most common complications from head and neck cancer radiation therapy is salivary gland dysfunction (SGD). SGD is an umbrella term that includes the subjective sensation of dry mouth (xerostomia) and hyposalivation (objective reduction of the salivary flow rate). Dry mouth in cancer patients may lead to functional defects (e.g., eating, speaking, and swallowing), increase the risk of dental caries and oral candidiasis, and can have a negative effect on the nutritional and psychological status of the patients. The aim of this mini review was to summarize the current criteria for diagnosis and management of SGD associated with cancer treatment.

The role of amifostine in preventing radiotherapy induced testicular tissue damage in rats

The germinal epithelium of the adult testis is susceptible to radiation induced damage. Amifostine is a drug used to prevent the side effects of radiotherapy (RT) and chemotherapy. We investigated the protective role of amifostine against RT induced damage to rat testis using the TUNEL assay. We used adult male rats divided equally into four groups: untreated control group; amifostine group, 200 mg/kg amifostine/day for 3 days; RT-saline group, 2 Gy/day local irradiation of testes for 3 days; RT-amifostine group, 2 Gy/day local irradiation of testes for 3 days plus 200 mg/kg amifostine 30 min before each irradiation. Four weeks after treatment, rats were sacrificed for histological examination and apoptosis was assessed using the TUNEL method. The TUNEL staining density was obtained by evaluating separate seminiferous tubules selected randomly from each section using the stereological fractionator method. Apoptosis in the seminiferous tubules in the control group and amifostine groups were evaluated as spontaneous. Frequent apoptosis was observed in the RT-saline group; a statistically significant difference was observed between the RT treated and untreated groups. Administration of amifostine 30 min before RT protected the testicular germ cells against apoptosis.

Changes in Glutathione Content in Liver Diseases: An Update

Glutathione (GSH), a tripeptide particularly concentrated in the liver, is the most important thiol reducing agent involved in the modulation of redox processes. It has also been demonstrated that GSH cannot be considered only as a mere free radical scavenger but that it takes part in the network governing the choice between survival, necrosis and apoptosis as well as in altering the function of signal transduction and transcription factor molecules. The purpose of the present review is to provide an overview on the molecular biology of the GSH system; therefore, GSH synthesis, metabolism and regulation will be reviewed. The multiple GSH functions will be described, as well as the importance of GSH compartmentalization into distinct subcellular pools and inter-organ transfer. Furthermore, we will highlight the close relationship existing between GSH content and the pathogenesis of liver disease, such as non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD), chronic cholestatic injury, ischemia/reperfusion damage, hepatitis C virus (HCV), hepatitis B virus (HBV) and hepatocellular carcinoma. Finally, the potential therapeutic benefits of GSH and GSH-related medications, will be described for each liver disorder taken into account.

Use of Amifostine for Cytoprotection during Radiation Therapy: A Review

BACKGROUND

Radiation therapy is a cornerstone of the therapeutic modalities used in modern oncology. However, it is sometimes limited in its ability to achieve optimal tumor control by radiation-induced normal tissue toxicity. In delivering radiation therapy, a balance must be achieved between maximizing the dose to the tumor and minimizing any injury to the normal tissues. Amifostine was the first Food and Drug Administration (FDA)-approved clinical radiation protector intended to reduce the impact of radiation on normal tissue, lessening its toxicity and potentially allowing for increased tumor dose/control. Despite being FDA-approved almost 20 years ago, Amifostine has yet to achieve widespread clinical use.

SUMMARY

A thorough review of Amifostine's development, mechanism of action, and current clinical status were conducted. A brief history of Amifostine is given, from its development at Walter Reid Institute of Research to its approval for clinical use. The mechanism of action of Amifostine is explored. The results of a complete literature review of all prospective randomized trials to date involving the use of Amifostine in radiation therapy are presented. The results are arranged by treatment site and salient findings discussed. Side effects and complications to consider in using Amifostine are reviewed. Key Messages: Amifostine has been explored as a radiation protectant in most radiation treatment sites. Studies have demonstrated efficacy of Amifostine in all treatment sites reviewed, but results are heterogeneous. The heterogeneity of studies looking at Amifostine as a clinical radiation protectant has precluded a definitive answer on its efficacy. Complicating its clinical use is its toxicity and delivery requirements. Amifostine has largely fallen out of use with the advent of intensity modulated radiation therapy (IMRT). However, side effects with IMRT remain a challenge and concern. The use of Amifostine in the IMRT era has been poorly explored and is worthy of future study.

Examination of the effect of ovarian radiation injury induced by hysterosalpingography on ovarian proliferating cell nuclear antigen and the radioprotective effect of amifostine: an experimental study

Aim

The aim of this study was to examine the effect of amifostine on cellular injury in the ovarian tissue induced by hysterosalpingography (HSG).

Methods

In total, forty 4-month old female Wistar Albino rats were assigned into 8 groups. Each group contained 5 rats. Group 1 (G1): rats were decapitated without any procedure. Group 2 (G2): rats were decapitated after 3 hours of total body irradiation. Group 3 (G3): rats were decapitated 3 hours after HSG procedure. Group 4 (G4): rats were decapitated 3 hours after HSG procedure performed 30 min after receiving amifostine 200 mg/kg intraperitoneally. Group 5 (G5): rats were decapitated after 1 month without any procedure. Group 6 (G6): rats were decapitated after 1 month of total body irradiation. Group 7 (G7): rats were decapitated 1 month after HSG procedure. Group 8 (G8): rats were decapitated 1 month after HSG procedure performed 30 min after receiving amifostine 200 mg/kg intraperitoneally. After rats were decapitated under general anesthesia in all groups, blood samples were obtained and bilateral ovaries were removed. One of the ovaries was placed in 10% formaldehyde solution for histological germinal epithelial degeneration, apoptosis and proliferating cell nuclear antigen scoring. The other ovary and blood sera were stored at −80°C. TNF-α, total antioxidant status, total oxidant status, and malondialdehyde levels were studied in tissue samples and anti-mullerian hormone levels in blood samples.

Results

At the end of the first month, there was significant ovarian germinal epithelium degeneration. Proliferating cell nuclear antigen immunoreactivity was significantly reduced in all other groups when compared with G1 and G5.

Conclusion

In conclusion, amifostine could significantly reduce the ovarian cellular injury induced by HSG.

Californium-252 neutron brachytherapy combined with external pelvic radiotherapy plus concurrent chemotherapy for cervical cancer: a retrospective clinical study

Background

Cervical cancer is the sixth most common cancer in Chinese women. A standard treatment modality for cervical cancer is the combination of surgery, chemotherapy, external-beam radiotherapy and intracavitary brachytherapy. The aim of this study was to retrospectively assess the long-term treatment outcomes of patients with cervical cancer who were treated with californium-252 neutron brachytherapy combined with external-beam radiotherapy plus concurrent chemotherapy.

Methods

We retrospectively analyzed the medical records of 150 patients with primary stages IB-IVB cervical cancer who received neutron brachytherapy combined with external-beam radiotherapy concurrently with cisplatin chemotherapy. All patients were followed up. Using an actuarial analysis, patient outcomes and treatment-related adverse effects were evaluated and compared.

Results

The median overall survival (OS) was 33.2 months. The 3-year progression-free survival rates for patients with stages I–II, III, and IV diseases were 81.0% (68/84), 65.0% (39/60), and 0% (0/6), respectively; the 3-year OS rates were 90.5% (76/84), 85.0% (51/60), and 16.7% (1/6), respectively. Vaginal bleeding was controlled within the median time of 4.0 days. One month after treatment, 97.3% of patients achieved short-term local control. The local recurrence rates for patients with stages I–II, III, and IV disease were 4.8% (4/84), 11.7% (7/60), and 33.3% (2/6), respectively, and the occurrence rates of distant metastasis were 16.7% (14/84), 25.0% (15/60), and 100.0% (6/6), respectively. Cancer stage, tumor size, and lymph node metastasis were identified as prognostic risk factors, but only lymph node metastasis was found to be an independent prognostic factor. The most common adverse effects during treatment were grades 1 and 2 irradiation-related proctitis and radiocystitis.

Conclusion

For patients with cervical cancer, neutron brachytherapy combined with external-beam radiotherapy plus concurrent chemotherapy produces a rapid response and greatly improves local control and long-term survival rates with tolerable adverse effects.

Successes and Failures of Combined Modalities in Upper Gastrointestinal Malignancies: New Directions

Upper gastrointestinal malignancies generally have moderate to poor cure rates, even in the earliest stages, thereby implying that both local and systemic treatments have room for improvement. Therapeutic options are broadening, however, with the development of new immunotherapies and targeted agents, which can have synergistic effects with radiotherapy. Here we discuss the current state of combined modality therapy for upper gastrointestinal malignancies, specifically recent successes and setbacks in trials of radiation therapy with targeted therapies, vaccines, immunotherapies, and chemotherapies.

A phase I clinical and pharmacology study using amifostine as a radioprotector in dose-escalated whole liver radiation therapy

PURPOSE

Diffuse intrahepatic tumors are difficult to control. Whole-liver radiotherapy has been limited by toxicity, most notably radiation-induced liver disease. Amifostine is a prodrug free-radical scavenger that selectively protects normal tissues and, in a preclinical model of intrahepatic cancer, systemic amifostine reduced normal liver radiation damage without compromising tumor effect. We hypothesized that amifostine would permit escalation of whole-liver radiation dose to potentially control microscopic disease. We also aimed to characterize the pharmacokinetics of amifostine and its active metabolite WR-1065 to optimize timing of radiotherapy.

METHODS AND MATERIALS

We conducted a radiation dose-escalation trial for patients with diffuse, intrahepatic cancer treated with whole-liver radiation and intravenous amifostine. Radiation dose was assigned using the time-to-event continual reassessment method. A companion pharmacokinetic study was performed.

RESULTS

Twenty-three patients were treated, with a maximum dose of 40 Gy. Using a logistical regression model, compared with our previously treated patients, amifostine increased liver tolerance by 3.3 ± 1.1 Gy (p = 0.007) (approximately 10%) with similar response rates. Peak concentrations of WR-1065 were 25 μM with an elimination half-life of 1.5 h; these levels are consistent with radioprotective effects of amifostine in patients.

CONCLUSION

These findings demonstrate for the first time that amifostine is a normal liver radioprotector. They further suggest that it may be useful to combine amifostine with fractionated or stereotactic body radiation therapy for patients with focal intrahepatic cancer.

Effects of amifostine in combination with cyclophosphamide on female reproductive system

This study investigated the cytoprotective effects of amifostine against the adverse effects of cyclophosphamide relying on ovarian cell death markers and the fertilization rate of the surviving follicles as a late outcome of the study. Combined pretreatment of amifostine with cyclophosphamide enabled partial recovery of antiapoptotic messenger RNA (mRNA) expression levels while a decrease in expression of BAX and Casp3 were identified. The pretreatment of amifostine to cyclophosphamide significantly reduced the proportion of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive primary and preantral follicles (P < .001 and P < .05, respectively). These findings were comparable with the results obtained from protein expression of cleaved caspase 3. The fertilization rate showed a significant capability of amifostine to improve fertilization potency of oocytes exposed to cyclophosphamide (P < .01). In conclusion, administration of amifostine prior to cyclophosphamide might serve as a promising protocol to improve female fertility.

The anti-tumor effect of resveratrol alone or in combination with immunotherapy in a neuroblastoma model

We investigated the anti-tumor effect of peritumoral resveratrol in combination with immunotherapy in vivo in neuroblastoma-bearing mice. Subcutaneous NXS2 tumors were induced in A/J mice. On day 10, some mice received 15 mcg of intravenous immunocytokine for 5 days, mice received 20 mg of peritumoral resveratrol twice a week (starting on day 12) for a total of 5 injections, and a separate group received a combination of both regimens. Tumor progression and survival were assessed every 3-4 days. Blood and primary tumor tissue samples were collected on day 20 for Complete Blood Count and CD45 immunohistochemistry and histology, respectively. The primary tumor regressed in all mice receiving peritumoral resveratrol. Most of these mice receiving peritumoral resveratrol alone developed metastatic tumors and recurrence of the primary tumor after cessation of therapy. When resveratrol and immunocytokine regimens were combined, 61% of the mice receiving this combination therapy resolved their primary tumors and survived without developing metastatic tumors, compared to 15 and 13% receiving resveratrol or immunocytokine alone, respectively. None of the therapeutic regimes prevented lymphocyte infiltration or affected the complete blood count. Greater necrosis was observed microscopically in tumors from mice receiving the combination therapy. These results demonstrate that the combination therapy of peritumoral resveratrol plus intravenous immunocytokine provides better anti-tumor effects in this model than either therapy alone.

Zebrafish as a model system to screen radiation modifiers

Zebrafish (Danio rerio) is a bona fide vertebrate model system for understanding human diseases. It allows the transparent visualization of the effects of ionizing radiation and the convenient testing of potential radioprotectors with morpholino-modified oligonucleotides (MO) knockdown. Furthermore, various reverse and forward genetic methods are feasible to decipher novel genetic modifiers of radioprotection. Examined in the review are the radioprotective effects of the proposed radiomodifiers Nanoparticle DF-1 (C-Sixty, Inc., Houston, TX) and Amifostine (WR-2721, Ethyol), the DNA repair proteins Ku80 and ATM, as well as the transplanted hematopoietic stem cells in irradiated zebrafish. The presence of any of these sufficiently rescued the radiation-induced damages in zebrafish, while its absence resulted in mutagenic phenotypes as well as an elevation of time- and dose-dependent radiation-induced apoptosis. Radiosensitizers Flavopiridol and AG1478, both of which block progression into the radioresistant S phase of the cell cycle, have also been examined in zebrafish. Zebrafish has indeed become a favorite model system to test for radiation modifiers that can potentially be used for radiotherapeutic purposes in humans.

Radiotherapy and wound healing

Radiotherapy is an invaluable weapon when treating cancer. However, the deleterious effects of radiation, both immediate and long-term, may have a significant effect on local tissues. Problematic wound healing in radiation-damaged tissue constitutes a major problem that is frequently overlooked during the management of patients who require radiotherapy, or have had radiotherapy in the past. Poor wound healing may lead to chronic ulceration, pain, secondary infection and psychological distress and compromise the outcome of general or reconstructive surgery. We discuss the pathophysiology of poor wound healing following radiotherapy, specific problems for radiation-damaged tissue and potential treatments to improve wound healing of irradiated tissues.

In vivo Study to Evaluate the Protective Effects of Amifostine on Radiation-Induced Damage of Testis Tissue

OBJECTIVE

To investigate the early protective effects of amifostine against radiation-induced damage on rat testis tissue.

METHODS

Eighty adult male Wistar rats were randomized to 4 groups: Saline solution was given to group A for control, 200 mg/kg amifostine (WR-2721) to group B, a single fraction of 6 Gy local irradiation to testes in group C and 200 mg/kg amifostine 15-30 min before 6 Gy testicular irradiation to group D. Animals were sacrificed 3 weeks after treatment and their testes were removed for macroscopic, microscopic and ultrastructural histopathological examination.

RESULTS

The weights, widths and lengths of testes in the last 3 groups had decreased significantly when compared with the control group, but the decrease in widths after irradiation was found to be significantly less only in the amifostine plus radiation group. There was a significant reduction of testis weights in relation to the individual body weights in the irradiated testes compared with the other groups (p < 0.005), while there was no significant change of testis weight/total body weight ratio in amifostine plus irradiation group. Spermatogonium A and primary spermatocyte counts were also less in the treatment groups, and primary spermatocyte numbers were significantly higher in amifostine plus radiation group when compared with radiation alone group (p < 0.005). Pretreatment with amifostine reduced the decrease of primary spermatocyte counts by a factor of 1.28. Electron microscopic analysis did not show any cytotoxic effect of amifostine alone, and furthermore, ultrastructural findings were normal with the addition of amifostine prior to irradiation, though there was damage in the radiation exposure group.

CONCLUSION

Amifostine when given alone by itself appears to cause adverse alterations in testis tissue; however, it has a radioprotective effect on spermiogenetic cells when used prior to radiation.

The protective effect of amifostine on radiation-induced acute pulmonary toxicity: Detection by 99mTc-DTPA transalveolar clearances

PURPOSE

The purpose of this study was to determine by using (99m)Tc-diethylenetriaminepentaacetic acid (DTPA) lung scintigraphy whether amifostine given before irradiation protects alveolocapillary integrity in a rabbit model.

METHODS AND MATERIALS

Twenty white New Zealand rabbits were randomly divided into 4 groups: (1) control (CONT), (2) amifostine alone (AMF), (3) radiation (RAD), and (4) radiation plus amifostine (RAD+AMF). The AMF and RAD+AMF groups received amifostine. The RAD and RAD+AMF groups were irradiated to the right hemithorax with a single dose of 20 Gy using a (60)Co treatment unit. Amifostine (200 mg/kg) was given i.p. 30 min before irradiation. The (99m)Tc-DTPA radioaerosol study was performed 14 day after irradiation.

RESULTS

The mean clearance rate of (99m)Tc-DTPA in control subjects was 140 +/- 21 min. The highest t((1/2)) value was noted in the RAD group (603 +/- 105 min, p = 0.001). There were no significant differences between the (99m)Tc-DTPA lung clearance rates of the CONT, RAD+AMF (238 +/- 24 min), and AMF groups (227 +/- 54 min). The mean penetration index values of CONT, RAD, AMF, and RAD+AMF are 63% +/- 1.6%, 63% +/- 2.5%, 60% +/- 2.9%, and 63% +/- 2%, respectively.

CONCLUSIONS

We concluded that amifostine treatment before the lung irradiation protects the lung alveolocapillary integrity. This study confirms the protective effect of amifostine in an acute phase of radiation lung injury.

Organ preservation in patients with squamous cancers of the head and neck

Treatment strategies that have the potential to improve functional organ preservation in patients who have head and neck cancer are emerging. Clinical research in this field, however, has been limited by the lack of standardized, objective criteria of organ function post treatment and by lack of prospective assessment of organ function in treatment trials [56]. Advances in surgical techniques, radiation techniques, radiation protectants, and combined-modality therapies are promising, but well-planned and executed clinical trials are necessary to determine how best to apply these techniques to patient care.

Hematopoietic Protection by Dexamethasone or Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) in Patients Treated With Carboplatin and Ifosfamide

Based on preclinical studies, the authors undertook a pilot study to determine the hematologic and biologic effects of pretreatment with dexamethasone (Dex) or granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients receiving carboplatin and ifosfamide. Patients (n = 28) with metastatic solid tumors were randomized to receive pretreatment with Dex or GM-CSF or no pretreatment prior to courses 1 or 2 of carboplatin and ifosfamide. No alteration in dose of chemotherapy was allowed between course 1 and 2. Alterations of hematologic and nonhematologic toxicity and selected biologic parameters were compared between courses 1 and 2. Patients without any pretreatment demonstrated worsening hematologic toxicity in course 2 compared to course 1. In contrast, Dex pretreatment reduced hematopoietic toxicity and improved the absolute granulocyte count (AGC) and platelet count recovery times. For example, course 1 versus course 2 (with Dex pretreatment): AGC nadir (mm3) 153 versus 549 (p = 0.07), days AGC <500/mm3 7.8 versus 4.0 (p = 0.10), days to AGC recovery >1,500/mm3, 26 versus 22 (p = 0.034). Overall comparison between all five cohorts by analyses of variance demonstrated that intervention with Dex improved multiple hematopoietic toxicities, including AGC nadir (p = 0.015), and recovery times to AGC >1,500/mm3 (p = 0.07) and platelet count to >100,000/mm3 (p = 0.05). GM-CSF pretreatment did not worsen hematopoietic parameters after course 2 compared to course 1. Expected biologic effects of Dex and GM-CSF treatment were observed. Patients demonstrated an overall response rate of 32%, 1 complete response, and 8 partial responses. In patients with cancer, pretreatment with Dex or GM-CSF may significantly decrease the hematopoietic toxicity of chemotherapeutic agents.

Chemical radioprotection: a critical review of amifostine as a cytoprotector in radiotherapy

The use of chemical radioprotectors represents an obvious strategy to improve the therapeutic index in radiotherapy. Amofostine (WR-2721) has recently been approved for use in head and neck cancer to protect against radiation-induced xerostomia. Currently, the question has arisen whether amifostine could be used for radioprotection in broader terms. Amifostine may have the potential to enable intensified treatment by ameliorating mucosal reactions that are often a limiting factor in accelerated fractionation or concomitant chemoradiation. However, it has as yet not been clarified whether sufficient amifostine to reduce mucositis can be administered before each radiation fraction without causing unacceptable toxicity. Also, the optimal dosage and schedule of amifostine in chemoradiation combinations have not yet been established. The major concern related to radioprotectiors is the potential hazard of collateral tumor protection. A number of clinical studies have concluded that amifostine does not reduce antitumor efficacy. However, not even the largest study conducted, with over 300 patients, has sufficient statistical power to detect a clinically significant reduction in tumor control rate. To put this issue ultimately to a rest, a clinical trial with a sufficient accrual to definitely rule out a tumor protective effect of amifostine needs to be conducted. Substances reducing radiation-induced toxicity by modulating the biological response to radiation injury may represent an alternative concept in radioprotection. However, such agents are still at a developmental stage.

Enhancement of fotemustine (Muphoran) cytotoxicity by amifostine in malignant melanoma cell lines

Fotemustine (Muphoran, S10036), a nitrosourea derivative active in the treatment of malignant melanoma and primary brain tumors, was evaluated in combination with the free radicals cytoprotective agent amifostine (Ethyol, WR-2721) and its alkaline phosphatase (AP)-generated active metabolite WR-1065 in four human melanoma (RPMI-7950, SK-MEL2, SK-MEL5 and WM-115) and lung fibroblast (MRC-5) cell lines. No difference in AP activity was found among the melanoma cell lines, but AP was found to be significantly higher in MRC-5. For combination experiments, cell lines were first exposed to amifostine or WR-1065 for 15 min and then exposed to fotemustine for two cell doubling times. Non-cytotoxic amifostine and WR-1065 concentrations used (0.2 and 0.6 and 0.1 and 0.3 mmol/l, respectively) were deduced from clinically achieved plasma values. Interactions were analyzed from the variations in IC(50) of fotemustine induced by pre-exposure of the cells to amifostine or WR-1065. In all melanoma cell lines, amifostine enhanced the cytotoxic activity of fotemustine as a significant decrease in IC(50) was observed. No significant difference was found between synergistic effects achieved with amifostine and WR-1065 given at half concentrations. No differential effect was found in the MRC-5 cell line as compared with the melanoma cell lines. Expression variation of O(6)-methylguanine methyltransferase was not found to be implicated in the interaction. The present results demonstrating that amifostine or its main active metabolite do not impair the cytotoxicity of fotemustine justify an extensive clinical evaluation of this combination in metastatic melanoma.

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.

Has the outlook improved for amifostine as a clinical radioprotector?

Amifostine has recently been approved for clinical radiotherapy as a protector against irradiation-induced xerostomia. It is our aim to review the outlook for using amifostine as a general clinical radioprotector. Protection against X-rays is mainly obtained by the scavenging of free radicals. The degree of protection is therefore highly dependent on oxygen tension, with protection factors ranging from 1 to 3. Maximal protection is observed at physiological levels of oxygenation. A great variability in protection has also been observed between different normal tissues. Some tissue, like brain, is not protected while salivary glands and bone marrow may exhibit a three-fold increase in radiation tolerance. Amifostine is dephosphorylized to its active metabolite by a process involving alkaline phosphatase. Due to lower levels of alkaline phosphatase in tumor vessels, amifostine is marketed as a selective protector of normal tissue and not tumors. However, the preclinical investigations concerning the selectivity of amifostine are controversial and the clinical studies are sparse and do not have the power to evaluate the influence of amifostine on the therapeutic index.

CONCLUSION

based on the present knowledge amifostine should only be used in experimental protocols and not in routine practice.

High-performance liquid chromatographic assay using electrochemical detection for the combined measurement of amifostine, WR 1065 and the disulfides in plasma

A high-performance liquid chromatographic (HPLC) method was developed for the combined analysis of the chemoprotective agent, amifostine, its active metabolite, WR 1065, and the (symmetrical and mixed) disulfides of WR 1065 in plasma. These three compounds were quantified by measuring WR 1065 after three different sample pretreatment procedures. During these procedures, amifostine and the disulfides were quantitatively converted into WR 1065, by incubating the sample either at a low pH or in the presence of dithiothreitol, respectively. The resulting amounts of WR 1065 were determined by HPLC with electrochemical detection (Au electrode, + 1.00 V). The lower limit of quantitation of WR 1065 was 0.15 microM. The within-day and between-day precision were < or =4.4 and < or =8.2% for WR 1065, < or =4.9 and < or =13.1% for amifostine and < or =8.5 and < or =5.5% for the disulfides, respectively. The within-day and between-day accuracy ranged from 97.2 to 109.8% and from 97.6 to 101.5% for WR 1065, from 88.3 to 110.7% and from 99.4 to 101.5% for amifostine and from 99.2 to 110.2% and from 103.3 to 104.9% for the disulfides, respectively. This method is superior to other described methods due to its simple and relatively rapid analysis of all three compounds in one system. Furthermore, it is at least as sensitive as earlier reported methods for one of the compounds and the application of the gold electrode requires only minor maintenance. Therefore, this method is very suitable for pharmacokinetic studies of amifostine and its metabolites. As an example, the plasma concentrations of amifostine, WR 1065 and the disulfides are shown in a patient after receiving an i.v. dose of 740 mg/m2 amifostine.