title: Phase I and pharmacokinetic study of the multidrug resistance modulator dexverapamil with EPOCH chemotherapy.
abstract: OBJECTIVE
  Dexverapamil is a competitive inhibitor of the P-glycoprotein (Pgp) efflux pump, a potent mechanism of multidrug resistance (mdr-1) in vitro. We performed a phase I study to determine the maximum-tolerated dose (MTD) and pharmacokinetics of dexverapamil with etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (EPOCH) chemotherapy.
  
  
  METHODS
  Eligible patients had relapsed or refractory lymphoma or sarcoma. Patients initially received EPOCH alone, and those with stable or progressive disease were crossed-over to received dexverapamil on subsequent cycles of EPOCH. Dexverapamil was administered orally for 6 days and escalated over eight dose levels ranging from 240 to 1,200 mg/m2/d. Pharmacokinetics of dexverapamil and its active metabolite, nor-dexverapamil, were obtained in most patients. In seven patients, pharmacokinetics of doxorubicin, doxorubicinol, and etoposide were determined on paired cycles of EPOCH with or without dexverapamil.
  
  
  RESULTS
  Sixty-five patients received 130 cycles of dexverapamil/EPOCH chemotherapy. The MTD of dexverapamil was 150 mg/m2 every 4 hours (900 mg/m2/d), and hypotension was the principal dose-limiting toxicity. The dexverapamil area under the curve (AUC) increased proportionally with dexverapamil dose, but significant interpatient variation occurred. At the MTD, the median plasma average concentrations of dexverapamil and nor-dexverapamil were 1.2 and 1.4 mumol/L, respectively. Dexverapamil did not affect the steady-state concentration (Css) of etoposide, but increased the Css of doxorubicin and doxorubicinol nearly twofold. The absolute neutrophil and platelet nadirs were significantly lower on the dexverapamil cycles compared with cycles of EPOCH alone, but other chemotherapy-related toxicities did not change.
  
  
  CONCLUSIONS
  The phase II recommended dose of dexverapamil with EPOCH is 150 mg/m2 every 4 hours. This dose was well tolerated on an outpatient basis and achieved plasma concentrations of dexverapamil and nor-dexverapamil within the effective range for Pgp inhibition in vitro. Although dexverapamil increased the hematopoietic toxicity of EPOCH, it was mild, readily reversible, and offset by EPOCH dose reductions. Dexverapamil should be considered for further study.
authors.affiliation: Medicine Branch, National Cancer Institute, Bethesda, MD 20892, USA.
authors.forename: W H
authors.initials: WH
authors.lastname: Wilson
authors.forename: C
authors.initials: C
authors.lastname: Jamis-Dow
authors.forename: G
authors.initials: G
authors.lastname: Bryant
authors.forename: F M
authors.initials: FM
authors.lastname: Balis
authors.forename: R W
authors.initials: RW
authors.lastname: Klecker
authors.forename: S E
authors.initials: SE
authors.lastname: Bates
authors.forename: B A
authors.initials: BA
authors.lastname: Chabner
authors.forename: S M
authors.initials: SM
authors.lastname: Steinberg
authors.forename: D R
authors.initials: DR
authors.lastname: Kohler
authors.forename: R E
authors.initials: RE
authors.lastname: Wittes
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000627:therapeutic use*; D018592:Cross-Over Studies; D003520:Cyclophosphamide / Q000008:administration & dosage / Q000009:adverse effects; D004317:Doxorubicin / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D018432:Drug Resistance, Multiple; D005047:Etoposide / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D005260:Female; D006801:Humans; D007022:Hypotension / Q000139:chemically induced; D007958:Leukocyte Count / Q000187:drug effects; D008223:Lymphoma / Q000097:blood / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D009504:Neutrophils; D010976:Platelet Count / Q000187:drug effects; D011241:Prednisone / Q000008:administration & dosage / Q000009:adverse effects; D012509:Sarcoma / Q000097:blood / Q000188:drug therapy; D013237:Stereoisomerism; D014700:Verapamil / Q000008:administration & dosage* / Q000009:adverse effects / Q000031:analogs & derivatives / Q000097:blood / Q000493:pharmacokinetics; D014750:Vincristine / Q000008:administration & dosage / Q000009:adverse effects
chemical_list: D014750:Vincristine; D005047:Etoposide; D004317:Doxorubicin; D003520:Cyclophosphamide; C016904:norverapamil; D014700:Verapamil; D011241:Prednisone