title: Mechanistic study of BNP7787-mediated cisplatin nephroprotection: modulation of gamma-glutamyl transpeptidase.
abstract: OBJECTIVE
  The mechanisms for cisplatin-induced renal cell injury have been the focus of intense investigation for many years with a view to provide a more effective and convenient form of nephroprotection. BNP7787 (disodium 2,2'-dithio-bis ethane sulfonate; dimesna, Tavocept), is a water-soluble disulfide investigational new drug that is undergoing clinical development for the prevention and mitigation of clinically important chemotherapy-induced toxicities associated with platinum-type chemotherapeutic agents. We hypothesized that part of BNP7787's mechanism of action (MOA) pertaining to the potential prevention of cisplatin-induced nephrotoxicity involves the inhibition of gamma-glutamyl transpeptidase (GGT) activity, mediated by BNP7787-derived mesna-disulfide heteroconjugates that contain a terminal gamma-glutamate moiety [e.g., mesna-glutathione (MSSGlutathione) and mesna-cysteinyl-glutamate (MSSCE)].
  
  
  METHODS
  Inhibition studies were conducted on human and porcine GGT to determine the effect of mesna-disulfide heteroconjugates on the enzyme's activity in vitro. These studies utilized a fluorimetric assay that monitored the hydrolysis of L-gamma-glutamyl-7-amino-4-trifluoromethylcoumarin (GG-AFC) to AFC.
  
  
  RESULTS
  Mesna-disulfide heteroconjugates that contained gamma-glutamyl moieties were potent inhibitors of human and porcine GGT. An in situ-generated mesna-cisplatin conjugate was not a substrate for GGT.
  
  
  CONCLUSIONS
  The GGT xenobiotic metabolism pathway is postulated to be a major toxification pathway for cisplatin nephrotoxicity, and BNP7787 may play a novel and critical therapeutic role in the modulation of GGT activity. We further postulate that there are two general mechanisms for BNP7787-mediated nephroprotection against cisplatin-induced nephrotoxicity involving this pathway. First, the active BNP7787 pharmacophore, mesna, produces an inactive mesna-cisplatin conjugate that is not a substrate for the GGT toxification pathway (GGT xenobiotic metabolism pathway) and, second, BNP7787-derived mesna-disulfide heteroconjugates may serve as selective, potent inhibitors of GGT, possibly resulting in nephroprotection by a novel means.
authors.affiliation: BioNumerik Pharmaceuticals, Inc., 8122 Datapoint Drive, Suite 1250, San Antonio, TX 78229, USA. fred.hausheer@bnpi.com
authors.forename: Frederick H
authors.initials: FH
authors.lastname: Hausheer
authors.forename: Dakshine
authors.initials: D
authors.lastname: Shanmugarajah
authors.forename: Betsy D
authors.initials: BD
authors.lastname: Leverett
authors.forename: Xinghai
authors.initials: X
authors.lastname: Chen
authors.forename: Quili
authors.initials: Q
authors.lastname: Huang
authors.forename: Harry
authors.initials: H
authors.lastname: Kochat
authors.forename: Pavankumar N
authors.initials: PN
authors.lastname: Petluru
authors.forename: Aulma R
authors.initials: AR
authors.lastname: Parker
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity*; D002945:Cisplatin / Q000633:toxicity*; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D015080:Mesna / Q000031:analogs & derivatives* / Q000494:pharmacology; D020011:Protective Agents / Q000494:pharmacology*; D013552:Swine; D005723:gamma-Glutamyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D020011:Protective Agents; C027032:2,2'-dithiodiethanesulfonic acid; D005723:gamma-Glutamyltransferase; D015080:Mesna; D002945:Cisplatin