Localized Delivery of Amifostine Enhances Salivary Gland Radioprotection.

Radiotherapy for head and neck cancers commonly causes damage to salivary gland tissue, resulting in xerostomia (dry mouth) and numerous adverse medical and quality-of-life issues. Amifostine is the only Food and Drug Administration-approved radioprotective drug used clinically to prevent xerostomia. However, systemic administration of amifostine is limited by severe side effects, including rapid decrease in blood pressure (hypotension), nausea, and a narrow therapeutic window. In this study, we demonstrate that retroductal delivery of amifostine and its active metabolite, WR-1065, to murine submandibular glands prior to a single radiation dose of 15 Gy maintained gland function and significantly increased acinar cell survival. Furthermore, in vivo stimulated saliva secretion was maintained in retrograde-treated groups at levels significantly higher than irradiated-only and systemically treated groups. In contrast to intravenous injections, retroductal delivery of WR-1065 or amifostine significantly attenuated hypotension. We conclude that localized delivery to salivary glands markedly improves radioprotection at the cellular level, as well as mitigates the adverse side effects associated with systemic administration. These results support the further development of a localized delivery system that would be compatible with the fractionated dose regimen used clinically.

Novel Formulation Strategy to Improve the Feasibility of Amifostine Administration.

PURPOSE: Amifostine (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. METHODS: Calvarial 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. RESULTS: WR-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. CONCLUSIONS: Orally 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.

Effects of WR1065 on 6-hydroxydopamine-induced motor imbalance: Possible involvement of oxidative stress and inflammatory cytokines.

Over production of reactive oxygen species (ROS) is postulated to be the main contributor in degeneration of nigrostriatal dopaminergic neurons. In this study we investigated the effects of WR1065, a free radical scavenger, on motor imbalance, oxidative stress parameters and inflammatory cytokines in CSF and brain of hemi-parkinsonian rats. Lesion of dopaminergic neurons was done by unilateral infusion of 6-hydroxydopamine into the central region of the substentia nigra pars compacta (SNc) to induce hemi-parkinsonism and motor imbalance in rats. WR1065 (20, 40 and 80µg/2µl/rat) was administered three days before 6-OHDA administration. After three weeks behavioral study was performed and then brain and CSF samples were collected to assess tumor necrosis factor (TNFα), interlukin (IL-1ß), reduced glutathione (GSH), and malondialdehyde (MDA). WR1065 pre-treatment in rats before receiving 6-OHDA, improved significantly motor impairment and caused reduction of MDA and inflammatory cytokines TNFα and IL-1ß levels, while GSH level significantly increased when compared with lesioned rats. Our study indicated that WR1065 could improve 6-OHDA-induced motor imbalance. Furthermore, it decreased lipid peroxidation and inflammatory cytokines and restored the level of GSH up to normal range. We suggest that WR1065 can be proposed as a potential neuroprotective agent in motor impairments of PD. However to prove this hypothesis more clinical trial studies should be done.

Radioprotection in mice following oral administration of WR-1065/PLGA nanoparticles.

PURPOSE: N-(2-mercaptoethyl)1,3-diaminopropane (WR-1065), is the active metabolite of amifostine, a broad spectrum cytoprotective agent used in conjunction with both chemo- and radiotherapy of certain cancers. This report describes for the first time an oral formulation of WR-1065 and follows on from our earlier report of a similar oral formulation of amifostine. MATERIALS AND METHODS: The nanoparticles of WR-1065 were prepared by spray drying technique using poly lactide-co-glycolide (PLGA) as the polymer matrix. Radioprotection was determined by measuring reductions in radiation-induced: (i) 30-day survival; (ii) bone marrow suppression; and (iii) intestinal injury following 9 Gray (Gy) whole body gamma irradiation in mice. All treatments were given 1 hour pre-irradiation and WR-1065 was tested at the dose of 500 mg/kg. RESULTS: The WR-1065/PLGA nanoparticles were smooth and spherical with the average diameter of 206 nm and contained 21.7% (w/w) WR-1065. While irradiation markedly reduced 30-day survival in non-treated control mice, and caused significant bone marrow suppression and intestinal injury in surviving mice, oral administration of WR-1065/PLGA nanoparticles resulted in significant radioprotection as evidenced by a marked reduction in all three of the above mentioned parameters of radiation injury. CONCLUSIONS: These findings clearly demonstrate the feasibility of developing an effective oral formulation of WR-1065 as a radioprotective agent.

Manganese superoxide dismutase (SOD2)-mediated delayed radioprotection induced by the free thiol form of amifostine and tumor necrosis factor alpha.

RKO36 cells, a subclone of RKO colorectal carcinoma cells that have been stably transfected with the pCMV-EGFP2Xho vector, were grown to confluence and then exposed to either the radioprotector WR-1065, i.e. the active thiol form of amifostine, for 30 min at doses of 40 microM and 4 mM or the cytokine tumor necrosis factor alpha (TNFalpha, TNFA) for 30 min at a concentration of 10 ng/ml and then washed. Total protein was isolated as a function of time up to 32 h after these treatments. Both doses of WR-1065 as well as the concentration of TNFalpha used were effective in elevating intracellular levels of the antioxidant protein SOD2 (also known as MnSOD) at least 15-fold over background levels as determined by Western blot analysis, while measured SOD2 activity was elevated between 5.5- and 6.9-fold. SOD2 reached a maximal level 24 h and 20 h after WR-1065 and TNFalpha treatments, respectively. The antioxidant proteins catalase and glutathione peroxidase (GPX) were also monitored over the 32-h period. In contrast to the robust changes observed in intracellular levels of SOD2 as a function of time after exposure of cells to WR-1065, catalase levels were elevated only 2.6-fold over background as determined by Western blot analysis, while GPX activity was unaffected by WR-1065 exposure. GPX protein levels were extremely low in cells, and analysis of GPX activity using a spectrophotometric method based on the consumption of reduced NADPH also revealed no measurable change as a function of WR-1065 or TNFalpha exposure. RKO36 cells either were irradiated with X rays in the presence of either 40 microM or 4 mM WR-1065 or 10 ng/ml TNFalpha or were irradiated 24 or 20 h later, respectively, when SOD2 protein levels were most elevated. The concentrations and exposure conditions used for WR-1065 and TNFalpha were not cytotoxic and had no effect on plating efficiencies or cell survival compared to untreated controls. No protection or sensitization was observed for cells irradiated in the presence of 40 microM WR-1065 or TNFalpha. Survival was elevated 1.90-fold for cells irradiated in the presence of 4 mM WR-1065. When RKO36 cells were irradiated with 2 Gy 24 h after 40 microM or 4 mM WR-1065 and 20 h after TNFalpha treatments when SOD2 levels were the most increased, survival was elevated 1.42-, 1.48- and 1.36-fold, respectively. This increased survival represents a SOD2-mediated delayed radioprotective effect. SOD2 appears to be an important antioxidant gene whose inducible expression is an important element in adaptive cellular responses in general, and the delayed radioprotective effect in particular. It can be induced by a range of agents including cytoprotective nonprotein thiols such as WR-1065 and pleiotropic cytokines such as TNFalpha.

Amifostine (ETHYOL) protects rats from mucositis resulting from fractionated or hyperfractionated radiation exposure.

PURPOSE: The cytoprotective drug amifostine (Ethyol) protects rats from oral mucositis resulting from a single dose of gamma-irradiation. We expanded earlier studies to determine whether multiple doses of amifostine protect against fractionated or hyperfractionated radiation and whether the active metabolite of amifostine (WR-1065) accumulates in tissues upon repeated administration. METHODS AND MATERIALS: Rats received amifostine daily for 5 days in conjunction with a 1-week fractionated radiation schedule and were evaluated for oral mucositis. Rats also received amifostine before the am or pm exposure or b.i.d. in conjunction with hyperfractionated radiation. To determine the pharmacokinetics of WR-1065 after repeated dosing, amifostine was given 5 days a week for 1 or 3 weeks, and rat tissue and plasma were collected at intervals during and after treatment and analyzed for WR-1065. RESULTS: Amifostine protected rats from mucositis resulting from fractionated or hyperfractionated radiation. When the number of days of amifostine administration was reduced, protection was diminished. A dose of 100 mg/kg given in the morning or 2 doses at 50 mg/kg provided the best protection against hyperfractionated radiation. WR-1065 did not accumulate in tissues or tumor upon repeated administration. CONCLUSIONS: Amifostine prevented radiation-induced mucositis in a rat model; protection was dose and schedule dependent.

Blood thiols following amifostine and mesna infusions, a pediatric oncology group study.

The Pediatric Oncology Group study for metastatic Ewing's sarcoma used amifostine and mesna with the alkylating agents. To determine the fate of combined drug thiols, we measured thiol levels in plasma, red blood cells (RBC), and peripheral blood mononuclear cells (PBMC) of four patients. We also conducted analogous measurements on two patients who received mesna alone and a volunteer's blood following in vitro treatment. Thiols were labeled with monobromobimane, separated on high-pressure liquid chromatography, and detected by fluorescence. Incubation of a volunteer's blood with mesna, WR-1065, or both revealed that cellular uptake of total reducible drug was approximately 10% of plasma level for mesna but approximately 60% for WR-1065. Cellular drugs were mainly the thiol form, whereas half of the plasma drugs were disulfides. Combined incubation with both thiols did not change the extent or form of uptake. WR-1065 and mesna prevented glutathione depletion by 4-hydroperoxycyclophosphamide. Results from patients were similar. WR-1065 and mesna appeared in the cells by the end of the drug infusions, although WR-1065 uptake was more efficient than mesna. The concentration-time profiles of mesna in RBC paralleled those in plasma. Amifostine administration during mesna infusion caused transient increase in mesna levels. Both agents increased blood cysteine and decreased total reducible cysteine. Mesna alone and mesna plus amifostine prevented cellular glutathione depletion. In conclusion, mesna is imported by RBC and PBMC, but less efficiently than WR-1065. When present at equal levels, these thiols do not influence each other's uptake. Adequate dosing of either drug is necessary for protecting the cells from toxic effects of alkylating agents.

Selective radioprotection of hepatocytes by systemic and portal vein infusions of amifostine in a rat liver tumor model.

PURPOSE: The tolerance of the liver to radiation is too low to permit an effective dose to be delivered to patients who have diffuse intrahepatic cancer. In this study we evaluated whether systemic or portal venous administration of the aminothiol compound, amifostine, could protect the normal liver from the effects of ionizing radiation without compromising tumor cell kill in a rat liver tumor model. METHODS AND MATERIALS: Rats implanted with liver tumors were infused with 200 mg/kg amifostine over 15 min via the femoral or portal vein. The livers were irradiated with a single 6-Gy fraction 15-20 min after the termination of amifostine infusion. Protection of the liver was assessed by an in vitro hepatocyte micronucleus assay and tumor protection by an in vivo-in vitro clonogenic survival assay. Tissue levels of the active metabolite, free WR-1065, were determined in the tumor and in the normal liver using a specific HPLC assay with electrochemical detection. RESULTS: After a 6-Gy fraction, the frequency of hepatocyte micronuclei after administration of saline, systemic amifostine, and portal venous amifostine was 18.7+/-1%, 6.8+/-1%, and 9.9+/-2%, respectively, corresponding to a radiation equivalent effect of 6 Gy +/- 0.5, 1.8 Gy +/- 0.3, and 2.5 Gy +/- 1.3, respectively. Both amifostine conditions showed considerably less radiation effect than saline-treated controls (p < 0.01); the two amifostine conditions did not differ (p = 0.3). The surviving fraction of tumor cells was not affected by amifostine treatment and was 0.03+/-0.02 and 0.05+/-0.03 for systemic and portal venous delivery and 0.06+/-0.02 for control animals (ANOVA analysis showed no significant difference of the means p = 0.34). Portal venous delivery produced significantly less WR-1065 in the tumor compared to systemic administration (54 microM +/- 36 vs. 343 microM +/- 88, respectively, p = 0.03). CONCLUSIONS: Both systemic and portal venous administration of amifostine effectively protect hepatocytes from ionizing radiation without compromising tumor cell kill in a clinically relevant animal model. These findings suggest that amifostine may be a selective normal tissue radioprotectant in liver cancer and that regional/portal infusions may be preferable to systemic dosing.

Pharmacokinetics and disposition of WR-1065 in the rhesus monkey.

The pharmacokinetics of WR-1065 [S-2-(3-aminopropylamino)ethanethiol] were investigated following iv, intraduodenal, and intraportal administrations in the rhesus monkey. Pharmacokinetic parameters were estimated by compartmental modeling of plasma concentration data from 10-min and 120-min iv infusions. Higher apparent volumes of distribution (Vc and Vss) and higher mean residence time (MRT) were observed at the slower infusion rate but a constant total dose. The values reflect a change in the distribution of WR-1065, possibly due to to saturation of binding in plasma and tissue. However, clearance remained unchanged. For a monkey administered approximately twice the 60 mg/kg dose infused over 120 min, data analysis indicates a disproportional increase in AUC and a substantial decrease in clearance. Low and erratic plasma concentrations of free drug (analytically determined without reductive cleavage) were observed following intraduodenal administration of WR-1065, demonstrating the drug's poor oral bioavailability. Results of intraduodenal administrations of radiolabeled drug indicated than an appreciable amount of the radiolabel in the dose reached the systemic circulation. However, after either intraduodenal or iv administration, only 31% of the AUC (radiolabel) could be accounted for as total (free and disulfide-bound) WR-1065 by specific analysis in separate experiments. Low levels of total cysteamine strongly suggest it to be a minor contributor to the disposition of the drug. Free WR-1065 AUC values following intraportal administration were similar to values obtained after iv administration.(ABSTRACT TRUNCATED AT 250 WORDS)

[Adenosine triphosphoric acid pool in rat tissues after the administration of beta-mercaptoethylamine]. / Fond adenozintrifosfornoi kisloty v tkaniakh krys posle vvedeniia beta-merkaptoétilamina.

Pool of ATP in thymus, spleen and liver tissues of non-irradiated rats underwent distinct tissue-specific alterations just after intraperitoneal administration of hydrotartrate of beta-mercaptoethylamine (cisteamine, MEA) at e radioprotective dose 300 mg/kg. The data obtained suggest that there are marked impairments in turnover of adenylic nucleotides at the period corresponding to manifestation of the MEA radioprotective efficiency.

Protection of the skin of mice against irradiation with cyclotron-accelerated helium ions by 2-mercaptoethylamine.

Mouse skin was exposed to doses of 1 250 to 3 000 rad using a helium ion beam with modal LET of 15 keV per micron. The skin reactions were evaluated for mice treated with a topical application of 10% MEA in a cream base or a placebo 15 minutes before irradiation. A comparison of the skin reactions indicated that the MEA treatment resulted in a DMF of at least 1.2. The implication for radiation therapy was discussed.