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Unresectable pancreatic cancer is almost universally lethal because chemotherapy and radiation cannot completely stop the growth of the cancer. The major problem with using radiation to approximate surgery in unresectable disease is that the radiation dose required to ablate pancreatic cancer exceeds the tolerance of the nearby duodenum. WR-2721, also known as amifostine, is a well-known radioprotector, but has significant clinical toxicities when given systemically. WR-2721 is a prodrug and is converted to its active metabolite, WR-1065, by alkaline phosphatases in normal tissues. The small intestine is highly enriched in these activating enzymes, and thus we reasoned that oral administration of WR-2721 just before radiation would result in localized production of the radioprotective WR-1065 in the small intestine, providing protective benefits without the significant systemic side effects. Here, we show that oral WR-2721 is as effective as intraperitoneal WR-2721 in promoting survival of intestinal crypt clonogens after morbid irradiation. Furthermore, oral WR-2721 confers full radioprotection and survival after lethal upper abdominal irradiation of 12.5 Gy × 5 fractions (total of 62.5 Gy, EQD2 = 140.6 Gy). This radioprotection enables ablative radiation therapy in a mouse model of pancreatic cancer and nearly triples the median survival compared to controls. We find that the efficacy of oral WR-2721 stems from its selective accumulation in the intestine, but not in tumors or other normal tissues, as determined by in vivo mass spectrometry analysis. Thus, we demonstrate that oral WR-2721 is a well-tolerated, and quantitatively selective, radioprotector of the intestinal tract that is capable of enabling clinically relevant ablative doses of radiation to the upper abdomen without unacceptable gastrointestinal toxicity.

Background/Aims: We have undertaken this study to investigate the feasibility of topical application of the radioprotective compound WR-2721 to the buccal mucosa. Methods: Saliva samples were collected from 5 volunteers and were reconstituted in 3 amifostine solutions. Measurements of amifostine and WR-1065 contents were performed at 6 different time points. Young-adult guinea pigs were topically administered amifostine 50 and 100 mg to each buccal mucosa. At 0, 15 and 30 min after application, the blood samples obtained from the heart and the buccal tissues were prepared for the analysis of amifostine and WR-1065. Results: There was no significant difference between the 3 concentrations of amifostine in saliva in vitro at any of the 6 study time points (p > 0.05). No WR-1065 was detected in saliva. In the guinea pigs from groups A and B, there were significant differences in concentrations of amifostine and WR-1065 in the tissues between the 0-min and 15-min subgroups and between the 0-min and 30-min subgroups (p < 0.05). The concentrations of amifostine and WR-1065 from the 15-min and 30-min subgroups did not differ statistically (p > 0.05). Conclusions: It is feasible to administer topical amifostine (WR-2721) to mucosa to prevent radiation-induced oral mucositis, and systemic absorption is negligible. Relatively high concentrations of amifostine in human saliva in vitro were maintained, although some inconsistent changes are observed.

Thirteen years after its discovery, there is still controversy over the chemical identity of endothelium-derived relaxing factor (EDRF). Although pharmacological and chemical evidence indicates that EDRF is nitric oxide, other candidates, including S-nitrosocysteine, dinitrosyl-iron-cysteine complex, nitroxyl and hydroxylamine, have been proposed to account for the vasorelaxant properties of EDRF. Such diverse compounds should differ in their stability and in reactivity with oxyhaemoglobin and with redox-active nucleophiles such as thiols. Here we use a bioassay to compare the pharmacodynamic profiles of these and other compounds with those of nitric oxide and EDRF. We find that some S-nitrosothiols, dinitrosyl-iron-cysteine complex, sodium nitroxyl and hydroxylamine can be eliminated as candidates as they are more stable than EDRF and less susceptible to inhibition by oxyhaemoglobin. Co-infusion of cysteine revealed major differences between the remaining candidates because it reduced the effect of authentic nitric oxide and EDRF on the bioassay tissues but enhanced the survival of S-nitrosocysteine and S-nitrosocysteamine. Our results further support the evidence that EDRF, the pharmacological entity described by Furchgott and Zawadzki, is nitric oxide.

Amifostine (Ethyol ® ) is a cytoprotective drug approved for the reduction of xerostomia in head and neck cancer when administered to patients receiving postoperative radiation therapy. Although amifostine is approved for intravenous infusion, the off-label subcutaneous route of administration has become more prevalent. Although human patient data indicate higher plasma bioavailability of the active metabolite (WR-1065) following intravenous compared to subcutaneous administration, there are no corresponding data showing human tissue levels of WR-1065 following either route of administration due to the difficulty in obtaining human specimens. In our study we compared plasma and tissue pharmacokinetics of WR-1065 in primates following both routes of administration. Monkeys received amifostine at a dose of 260 mg/m 2 either intravenously or subcutaneously. Plasma samples were analyzed for total WR-1065 by reverse-phase high-pressure liquid chromatography (HPLC) and fluorescence detection up to 4 h after amifostine administration. Tissues were analyzed for free WR-1065 by reverse-phase HPLC and electrochemical detection 30 and 60 min after administration. Following intravenous administration, plasma WR-1065 levels peaked rapidly and showed a bi-exponential decline, while following subcutaneous administration WR-1065 levels rose slowly and declined exponentially. The relative plasma bioavailability of WR-1065 given subcutaneously was lower at 30 and 60 min. Interestingly, after 30 min, tissues showed equal or slightly greater concentrations of WR-1065 following subcutaneous administration. Levels following 60 min were comparable following both routes. The plasma bioavailability studies performed in primates confirm human plasma data. Expanding the study to evaluate primate tissue levels of WR-1065 revealed that despite lower plasma bioavailability following subcutaneous administration, tissue levels of the active metabolite were surprisingly greater than or equal to those measured in animals that received the drug intravenously. These studies strengthen the argument for subcutaneous administration of amifostine in radiation oncology.

Binding of thiols of varying charge (Z) in nuclei prepared in suspension was determined to assess the extent to which histones, Mg2+, spermine and chromatin structure influence counter-ion condensation of cationic thiols and co-ion depletion of anionic thiols at DNA. The nuclei were prepared in suspension buffer, washed and incubated in buffer containing thiol and graded amounts of Mg2+ and spermine. The nuclei were separated from the incubation medium by centrifugation through silicone oil, and the thiols were determined in the nuclear pellet and in the incubation buffer by labeling with monobromobimane and HPLC. Measurements of the water content of nuclei indicated that chromatin was fully condensed in buffer containing 5 mM MgCl2 and 115 mM KCl. Under these conditions nuclei incubated in 1 mM substrate had concentrations of 0.80 ± 0.21 mM glutathione (Z = -1), 1.05 ± 0.12 mM 2-mercaptoethanol (Z = 0), 0.95 ± 0.15 mM cysteine (Z = 0), 0.75 ± 0.29 mM cysteamine (Z = +1), 2.5 ± 0.3 mM WR-1065 (Z = +2), 3.4 ± 0.5 mM WR-35980 (Z = +3) and 12 ± 2 mM WR-33278 (disulfide of WR-1065, Z = +4), respectively. Spermine up to 1 mM in the presence of 5 mM Mg2+ had little effect upon the binding of these thiols and disulfide, but did suppress the binding of 0.1 mM WR-33278, the results indicating that WR-33278 and spermine compete for the same sites with comparable affinity. From the results observed and the assumption that deviations from the bulk solution concentration (1 mM) result from counter-ion condensation within 3 nm of DNA, we estimate that WR-1065 (Z = +2), WR-35980 (Z = +3) and WR-33278 (Z = +4) were concentrated near DNA 6-, 8- and 20-fold, respectively, in the presence of histones, 5 mM Mg2+ and 1.0 mM spermine.

Radioprotection by WR-2721, S-2-(3-aminopropylamino)ethyl phosphorothioate, is thought to involve its corresponding thiol (WR-1065) or symmetrical disulfide (WR-33278). It has been suggested that these metabolites concentrate close to the DNA target molecule; to test this hypothesis we have measured their in vitro binding to DNA. The binding of WR-33278 (0.05-0.4 mM) to calf thymus DNA (6 mM, with respect to DNA phosphate) was determined at 50, 100, and 150 mM KCl in 1 mM Tris, pH 7, by equilibrium dialysis. The binding of WR-1065 (0.5-8 mM) was determined at 25, 50, and 100 mM KCl, under similar conditions, but with 2 mM EDTA and 3 mM dithiothreitol (DTT) added to the dialysis buffer to prevent thiol oxidation. Drug levels were quantitated by HPLC after fluorescent labeling with monobromobimane; disulfide samples were reduced with DTT prior to analysis. Dissociation constants ($K_{d}=[\\text{Free Drug}]\\ [{\\rm DNA}\\ \\text{site}]/[\\text{bound drug}]$) under these conditions were found to vary with ionic strength, being in the range of 0.02 ± 0.01 to 0.18 ± 0.06 mM for WR-33278 and 0.43 ± 0.24 to 3.5 ± 1.5 mM for WR-1065. WR-2721, glutathione, cysteine, and DTT showed no detectable binding to DNA in 25 mM KCl. However, cysteamine and cystamine did bind to DNA, with unbound drug to bound drug ratios of 8 ± 2 and 0.6 ± 0.1, respectively, at total drug concentrations of 1 mM. Cystamine and WR-1065 bound to DNA with comparable affinity under similar conditions. These results indicate that binding of WR-33278 and WR-1065 by DNA phosphate are probably significant in the mechanism of radioprotection by WR-2721.

Purpose The most important problem with acetaminophen is its hepatotoxicity. N-acetylcysteine (NAC) is used to treat the hepatotoxicity of acetaminophen. Due to the structural similarities of this compound with amifostine, we decided to test the effect of this substance and its metabolite, WR-1065, on the hepatotoxicity of acetaminophen. Methods The single-dose method contained 1. Control; 2. Acetaminophen (1 g/kg, gavage); 3–5. Acetaminophen + amifostine (100, 200, 400 mg/kg, i.p.); 6–8. Acetaminophen + WR-1065 (50, 100, 200 mg/kg, i.p.); and 9. Acetaminophen + NAC (100, 200 mg/kg, i.p.). The multiple-dose method included the same groups: amifostine (50, 100, 200 mg/kg), WR-1065 (25, 50, 100 mg/kg), and NAC (100 mg/kg). Then, animals were sacrificed, and blood samples were collected for measuring ALT, AST, ALP, and T-Bil, liver tissue for histopathological examination, MDA, and GSH amounts. Results Acetaminophen increased the levels of MDA, T-Bil, ALT, AST, and ALP, decreased GSH levels, and augmented necrosis, neutrophils, lymphocytes, and macrophages in the port space in single-dose and multiple-dose studies. Amifostine and WR-1065 significantly reduced the levels of MDA, T-Bil, ALT, AST, ALP, increased GSH content, and ameliorated histopathological alterations in a single-dose and multiple-dose method compared to the acetaminophen group. Moreover, NAC caused a significant decrease in the levels of MDA, T-Bil, ALT, AST, and ALP, and reduced GSH amounts in single-dose and multiple-dose studies. Conclusion Amifostine and WR-1065 as antioxidant and hepatoprotective compounds are effective in reducing acetaminophen-induced hepatotoxicity with a similar effect to NAC and can be administered as an adjunct in the treatment of acetaminophen overdose.

PurposeAmifostine (AMF), a radioprotectant, is FDA-approved for intravenous administration in cancer patients receiving radiation therapy (XRT). Unfortunately, it remains clinically underutilized due to adverse side effects. The purpose of this study is to define the pharmacokinetic profile of an oral AMF formulation potentially capable of reducing side effects and increasing clinical feasibility.MethodsCalvarial osteoblasts were radiated under three conditions: no drug, AMF, and WR-1065 (active metabolite). Osteogenic potential of cells was measured using alkaline phosphatase staining. Next, rats were given AMF intravenously or directly into the jejunum, and pharmacokinetic profiles were evaluated. Finally, rats were given AMF orally or subcutaneously, and blood samples were analyzed for pharmacokinetics.ResultsWR-1065 preserved osteogenic potential of calvarial osteoblasts after XRT to a greater degree than AMF. Direct jejunal AMF administration incurred a systemic bioavailability of 61.5%. Subcutaneously administrated AMF yielded higher systemic levels, a more rapid peak exposure (0.438 vs. 0.875 h), and greater total systemic exposure of WR-1065 (116,756 vs. 16,874 ng*hr/ml) compared to orally administered AMF.ConclusionsOrally administered AMF achieves a similar systemic bioavailability and decreased peak plasma level of WR-1065 compared to intravenously administered AMF, suggesting oral AMF formulations maintain radioprotective efficacy without causing onerous side effects, and are clinically feasible.

The search for effective neuroprotective agents for the treatment of neurotrauma has always been of great interest to researchers around the world. Extracellular heat shock protein 70 (eHsp70) is considered a promising agent to study, as it has been demonstrated to exert a significant neuroprotective activity against various neurodegenerative diseases. We showed that eHsp70 can penetrate neurons and glial cells when added to the incubation medium, and can accumulate in the nuclei of neurons and satellite glial cells after axotomy. eHsp70 reduces apoptosis and necrosis of the glial cells, but not the neurons. At the same time, co-localization of eHsp70 with p53 protein, one of the key regulators of apoptosis, was noted. eHsp70 reduces the level of the p53 protein apoptosis promoter both in glial cells and in the nuclei and cytoplasm of neurons, which indicates its neuroprotective effect. The ability of eHsp70 to reverse the proapoptotic effect of the p53 activator WR1065 may indicate its ability to regulate p53 activity or its proteosome-dependent degradation.