title: Clinical effects and P-glycoprotein inhibition in patients with acute myeloid leukemia treated with zosuquidar trihydrochloride, daunorubicin and cytarabine.
abstract: OBJECTIVE
  P-glycoprotein (P-gp) is a major cause of multidrug resistance (MDR) in acute myelogenous leukemia (AML) and is thought to contribute to the failure of chemotherapy. Zosuquidar trihydochloride (Z.3HCL) is a potent and selective inhibitor of P-gp which rapidly and effectively inhibits drug efflux.
  
  
  METHODS
  The aim of this study was to evaluate the clinical effects of Z.3HCL and determine its influence on P-gp activity. Sixteen AML patients were entered into a phase 1 dose ranging clinical trial of Z.3HCL, co-administered intravenously with daunorubicin and cytosine arabinoside (ARA-C). Clinical outcomes, toxicity abd adverse events were assessed. P-gp function was analyzed by flow cytometry. In vitro cytotoxicity was studied using the MTT assay.
  
  
  RESULTS
  Eleven patients achieved a complete remission and one a partial remission with a median survival of 559 (range 38-906) days. Non-hematologic grade 3 and 4 toxicities were seen in 4 patients. Z.3HCL infusion was associated with rapid inhibition of Rh123 efflux in CD56+ cells in 16/16 patients and in CD33+ cells from 6/10 patients. The median inhibition was 95% for CD56+ cells and 85.25% for CD33+ cells was significantly elevated in 6/16 patients. The median IC50, using a MTT assay for daunorubicin, decreased significantly between Z.3HCL modulated and unmodulated cells (n=11,153 and 247 ng/mL respectively, p=0.01).
  
  
  CONCLUSIONS
  The modulator Z.3HCL is a specific inhibitor of P-gp efflux and can be given safely to patients with AML in combination with induction doses of conventional cytotoxic drugs.
authors.affiliation: Department of Haematology, Royal Free and University College Medical School, Royal Free Campus, London, UK.
authors.forename: Gareth
authors.initials: G
authors.lastname: Gerrard
authors.forename: Elspeth
authors.initials: E
authors.lastname: Payne
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Baker
authors.forename: Dylan T
authors.initials: DT
authors.lastname: Jones
authors.forename: Michael
authors.initials: M
authors.lastname: Potter
authors.forename: H Grant
authors.initials: HG
authors.lastname: Prentice
authors.forename: Mark
authors.initials: M
authors.lastname: Ethell
authors.forename: Heather
authors.initials: H
authors.lastname: McCullough
authors.forename: Michael
authors.initials: M
authors.lastname: Burgess
authors.forename: Atul B
authors.initials: AB
authors.lastname: Mehta
authors.forename: Kanagasabai
authors.initials: K
authors.lastname: Ganeshaguru
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors*; D015746:Abdominal Pain / Q000139:chemically induced; D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage* / Q000009:adverse effects / Q000633:toxicity; D003561:Cytarabine / Q000008:administration & dosage; D003630:Daunorubicin / Q000008:administration & dosage; D003967:Diarrhea / Q000139:chemically induced; D003986:Dibenzocycloheptenes / Q000008:administration & dosage* / Q000009:adverse effects / Q000633:toxicity; D004351:Drug Resistance; D004354:Drug Screening Assays, Antitumor; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D009325:Nausea / Q000139:chemically induced; D011804:Quinolines / Q000008:administration & dosage* / Q000009:adverse effects / Q000633:toxicity; D012074:Remission Induction
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003986:Dibenzocycloheptenes; D011804:Quinolines; D003561:Cytarabine; C095179:zosuquidar trihydrochloride; D003630:Daunorubicin