Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.1 (alkaline phosphatase)
 47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Amifostine (WR-2721, S-2 [3-aminopropylamino]-ethylphosphorothioic acid; Ethyol, US Bioscience, Inc. West Conshohocken, PA), developed as a radiation protector, has exhibited activity as a chemoprotector. The compound requires activation by dephosphorylation to produce the free thiol, WR-1065. This process is catalyzed by capillary alkaline phosphatase that is close to the desired site of protection. Additionally, the neutral pH of normal tissues, compared with the slightly acidic pH of tumors, favors selective activation. The protective mechanism against radiation damage is produced, and is, most probably, different from that of chemotherapy. The most likely mechanism for radioprotection involves free radical scavenging and hydrogen donation to repair damaged DNA. The hydrogen ion donation by the thiol group is required for both chemoprotection and radioprotection. Chemoprotection is presumed to be mediated by inactivation of the charged carbonium ions of activated alkylating agents through a nucleophilic attack, thereby protecting the nucleic acids from alkylation. Amifostine is able to reduce DNA platination when preincubated or coincubated with cisplatin, but this effect is much weaker when given postincubation. Observations show that maximum protection can only be obtained if amifostine is given before the administration of cytotoxic therapy. Amifostine side effects, as seen in mice, are dose dependent. A dose of 200 mg/kg has been found to be relatively nontoxic, although some hypothermia was observed.
 ...
PMID:Protection of normal tissues from the cytotoxic effects of chemotherapy and radiation by amifostine (Ethyol): preclinical aspects. 797 74

This article reviews the chemistry, measurement, metabolism, and pharmacokinetics of the cytoprotective agent amifostine. Validated analytic methodology to measure parent drug and pharmacologically active metabolites and pharmacokinetic studies are essential to the efficient performance and analysis of clinical studies. Well-validated analytic methods developed in the authors' laboratory were used to characterize this agent. Amifostine [s-2-(3-aminopropylamino)ethyl-phosphorothioate] is the phosphorylated pro-drug form of the active free thiol drug WR-1065 [2-(3-aminopropylamino)ethanethiol]. Observations described here support the hypothesis that amifostine is dephosphorylated rapidly by alkaline phosphatase present on the plasma membranes of the arteriolar endothelium of various normal tissues and on the plasma membranes of the kidneys' proximal tubular epithelium to its active thiol metabolite WR-1065, which in turn immediately enters normal tissues. Other metabolites that have been identified are WR-33278, the symmetrical disulfide of WR-1065; the mixed disulfides WR-1065-cysteine and WR-1065-glutathione; and cysteamine. Amifostine was recently approved by the US Food and Drug Administration for use as a cytoprotector in cancer patients receiving chemotherapy. Current pharmacokinetic studies in cancer patients are focusing on establishing a population model as a basis for developing limited sampling strategies for future investigations of the pharmacokinetic-pharmacodynamic behavior of amifostine.
 ...
PMID:Pharmacokinetic profile of amifostine. 878 62

Originally developed against the effects of ionizing radiations, amifostine is an organic thiophosphate compound shown able to selectively protect normal tissues against cytotoxic agents in cellular and animal models, without protecting tumor tissues. Amifostine is a prodrug which is dephosphorylated into its active metabolite, a free thiol derivative, by membrane alkaline phosphatase of the target issue. This unique metabolism supports its cellular selectivity and its preferential uptake by normal tissues. In phase II clinical trials, a decreased toxicity has been demonstrated in patients given alkylating agents; however, reduction of the response has not been observed. On the basis of these results, a prospective, randomized, phase III study has been conducted in patients with ovarian carcinoma receiving a combination of cisplatinum and cyclophosphamide. A significant decrease in hematologic, renal and neurologic toxicity was observed in the amifostine-treated patients compared with the control group, and response rates did not significantly differ between the two groups. Insufficient or emerging data are only available for other applications, including either in vitro manipulation of hematopoietic grafts or in vivo treatment of non-Hodgkin's lymphoma, head and neck carcinoma, non-small cell lung cancer and radioprotection. No data are yet available in regard to the potential protective effects of amifostine against mutagenicity and cancerogenicity of both chemo- and radiotherapy.
 ...
PMID:[Amifostine: current and future applications in cytoprotection]. 895 58

The mechanism of action, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of amifostine are reviewed. Amifostine is a prodrug converted by alkaline phosphatase to the active sulfhydryl compound WR-1065. WR-1065 protects normal cells by scavenging free radicals, donating hydrogen ions to free radicals, depleting oxygen, and binding to active derivatives of antineoplastic agents. The immediate conversion of amifostine to WR-1065, its small volume of distribution, and the limited amount of drug and metabolite recovered in the urine suggest that amifostine is rapidly dephosphorylated and enters cells as its active metabolite. The selectivity of amifostine for normal tissue is hypothesized to be a results of the decreased vascularity of tumors, decreased activity of alkaline phosphatase in tumor cells, and pH dependence of WR-1065 uptake. In clinical studies, amifostine decreased the frequency of cisplatin-induced nephrotoxicity, ototoxicity, neurotoxicity, and myelosuppression. Amifostine has demonstrated an ability to decrease the hematologic toxicity of cyclophosphamide, carboplatin, mitomycin, and antineoplastic drug combinations. Amifostine has FDA-approved labeling for use in reducing cumulative renal toxicity in patients receiving repeat doses of cisplatin for advanced ovarian cancer and non-small-cell lung cancer. The recommended dose in adults is 910 mg/m2 administered as a 15-minute infusion 30 minutes before the start of chemotherapy. The major adverse effects of amifostine include hypotension and emesis. The benefits of amifostine must be weighted against its potential adverse effects, and the drug's impact on the efficacy of antineoplastics should be further investigated. Amifostine has shown promise in protecting non-malignant cells from the toxic effects of antineoplastics, apparently without compromising toxicity against cancer cells.
 ...
PMID:Amifostine for protection from antineoplastic drug toxicity. 977 47

Amifostine (Ethyol, ALZA Pharmaceuticals, Palo Alto, CA/US Bioscience, West Conshohocken, PA) is a phosphorylated cysteamine derivative that was originally developed by the US Army Walter Reed Institute (Washington, DC) as a radioprotectant. Amifostine, a prodrug, is metabolized by the enzyme alkaline phosphatase to an active sulfhydryl compound (WR-1065) capable of scavenging radiation-generated free radicals and preventing cell damage. The disulfides of WR-1065 are structurally analogous to endogenous polyamines, which can bind to DNA molecules and stabilize them in a compact form less vulnerable to damage by cytotoxic agents. Preclinical and clinical studies show that amifostine is a selective radioprotectant that reduces both early and late radiation-induced toxicities to normal tissues while leaving tumor cells exposed to the cytotoxic effects of radiation. Preclinical data indicate that amifostine could reduce the risk of secondary cancers caused by radiation and certain forms of chemotherapy.
 ...
PMID:Radioprotectants: pharmacology and clinical applications of amifostine. 979 95

Administered before cytotoxic chemotherapy or radiation, the aminothiol, amifostine (Ethyol; Alza Pharmaceuticals, Palo Alto, CA/US Bioscience, West Conshohocken, PA), provides broad-spectrum cytoprotection of various normal tissues without attenuating antitumor 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. In contrast, uptake into tumor tissue is slow to negligible. Pretreatment with amifostine provides protection of normal tissues from the cytotoxic effects of alkylating agents, organoplatinums, anthracyclines, taxanes, and radiation. Additionally, the mutagenic and carcinogenic effects of these modalities are also attenuated. Preclinical studies show significant protection of marrow progenitor cells. Synergistic effects in marrow recovery are noted with the sequential use of amifostine and granulocyte colony-stimulating factor. Protection of kidneys and neural tissues from cisplatin toxicity has been shown, as well as protection of the heart, intestinal crypt cells, and pulmonary tissues from chemotherapy and radiation, and vasculoconnective and musculoconnective tissue in an irradiated field. Comparative in vitro and in vivo studies using murine and human tumor xenografts show no protection of antitumor effects of these same therapies despite the protection of normal organs. The unique preclinical profile of amifostine serves as the basis for the clinical development program for this new broad-spectrum cytoprotective agent.
 ...
PMID:The preclinical basis for broad-spectrum selective cytoprotection of normal tissues from cytotoxic therapies by amifostine. 1034 55

Patients receiving systemic cancer chemotherapy must often have their dose intensity of therapeutic agents reduced, because a broad range of organs are adversely affected. Therefore, research and the development of agents protecting the normal tissues from the toxicity of antineoplastic therapy, without reducing the antitumour efficacy, are very important. Amifostine, a prodrug that forms an activated free thiol, when dephosphorylated by alkaline phosphatase, appears selective in its entry in non-malignant cells, and exerts a protective effect from toxicity induced by chemo- or radiotherapy on normal tissues, through free radical scavenging, hydrogen donation and inhibition of DNA damage. Studies in vitro and experimental models have confirmed the protective properties of amifostine in normal cells. In clinical trials pretreatment with amifostine reduced the frequency of cyclophosphamide induced neutropenia and nephro-, oto- and neurotoxicity of platinum compounds. In some cases the use of amifostine have also potentiated the effects of several drugs, such as alkylating agents and, in recent studies, taxanes. The main potentially dose-limiting adverse effect is hypotension, that is often asymptomatic. Amifostine is thus usefully employed in order to obtain a better quality of life in patients receiving oncologic treatments.
 ...
PMID:Amifostine: A selective cytoprotective agent of normal tissues from chemo-radiotherapy induced toxicity (Review). 1052 12

Amifostine is a protective agent of normal tissue from adverse effects of radiochemotherapy. It is the prodrug that is dephosphorylated by alkaline phosphatase on plasma membrane into the active form named WR-1065. More than 90 per cent of the drug is cleared from plasma in 6 minutes and the peak tissue concentration is 10-30 minutes after intravenous administration. Amifostine has the selective property to protect normal tissue but not cancer cells by mainly scavenging free radicals induced by radiation and chemocytotoxic agents. Both preclinical and clinical studies of this drug provide the significant protection of hematopoietic progentitors from a broad range of cytotoxic agents such as cyclophosphamide, cisplatin, vinblastine, carboplatin, mitomycin-C, fotemustine, doxorubicin, daunorubicin and radiation as well. Moreover, this drug can protect other normal organs or tissues including kidney, salivary gland, liver, heart, lung and small intestine. Amifostine is quite safe, the two major side effects are vomiting and hypotension, and the minor effects are flushing, sneezing, dizziness, chills, metallic taste etc. The drug was approved by the FDA of U.S.A. for use as a cytoprotectant in cyclophosphamide and cisplatin treatment for advanced ovarian cancer and non small cell lung cancer.
 ...
PMID:Amifostine and hematologic effects. 1080 97

Clinical trials indicate that amifostine may confer protection on various normal tissues without attenuating anti-tumor response. When administered prior to chemotherapy or radiotherapy, it may provide a broad spectrum of cytoprotection including against alkylating drugs. The mechanism of protection resides in the metabolism at normal tissue site by membrane-bound alkaline phosphatase. Toxicity of this drug is moderate with hypotension, nausea and vomiting, and hypocalcemia being observed. We report a phase II study using amifostine as a protective drug against high-dose cyclophosphamide (HDCY) (7 g/m2), used to mobilize peripheral blood progenitor cells (PBPC) and to reduce tumor burden. We enrolled 29 patients, 22 (75. 9%) affected by aggressive and 7 (24.1%) by indolent non-Hodgkin's lymphoma (NHL), who were submitted to 58 infusions of amifostine and compared them with a historical group (33 patients) affected by aggressive NHL and treated with VACOP-B followed by HDCY. The most important results in favor of amifostine were the reduction of intensity of cardiac, pulmonary and hepatic toxicity, and a significant reduction of frequency and severity of mucositis (P = 0. 04). None of the 29 patients died in the protected group, while in the historical group 2/33 patients died because of cardiac or pulmonary toxicity and 2 patients stopped therapy due to toxicity. Amifostine did not prevent the aplastic phase following HDCY. PBPC collection and hematological recovery were adequate in both groups. The number of CFU-GM (colony-forming units-granulocyte/macrophage) colonies and mononuclear cells in the apheresis products was significantly higher in the amifostine group (P = 0.02 and 0.01, respectively). Side effects were mild and easily controlled. We conclude that amifostine protection should be useful in HDCY to protect normal tissues, with acceptable side effects.
 ...
PMID:Amifostine (WR-2721), a cytoprotective agent during high-dose cyclophosphamide treatment of non-Hodgkin's lymphomas: a phase II study. 1088 Oct 54

Amifostine (WR-2721) is an aminothiol compound dephosphorylated at the tissue site by alkaline phosphatase to the active metabolite, which is able to inactivate electrophilic substances and scavenge free radicals. Amifostine effects against melphalan-induced DNA strand breaks were studied in normal human white blood cells (WBC) and K562 leukemic cells using the single cell gel electrophoresis (SCGE) or Comet assay, a reported method for measuring DNA damage in individual cells. Prior to treatment (1 h, 37 degrees C) with increasing doses of melphalan, with or without S9, the cells were treated (15 min, 37 degrees C) with a control medium or amifostine (3 mg/ml). Treatment of normal and leukemic cells with melphalan induced a dose-dependent 'comet formation'. Melphalan-induced DNA damage follows a normal distribution in WBC. On the other hand, in K562, a significant proportion of undamaged cells remains even with doses at which mean DNA damage is serious. Pretreatment with WR-2721 protects WBC, but not K562, against the genotoxic effect of melphalan. Amifostine might even strengthen the action of the antiblastic drug against K562 cells. S9 addition appears to enhance melphalan effectiveness. SCGE appears as a suitable primary screening method for in vitro and in vivo studies on drug-DNA interactions and their modulations by endogenous/exogenous factors.
 ...
PMID:Amifostine (WR-2721) selective protection against melphalan genotoxicity. 1099 12


1 2 3 Next >>