title: Evaluation of the combination of nelarabine and fludarabine in leukemias: clinical response, pharmacokinetics, and pharmacodynamics in leukemia cells.
abstract: OBJECTIVE
  A pilot protocol was designed to evaluate the efficacy of fludarabine with nelarabine (the prodrug of arabinosylguanine [ara-G]) in patients with hematologic malignancies. The cellular pharmacokinetics was investigated to seek a relationship between response and accumulation of ara-G triphosphate (ara-GTP) in circulating leukemia cells and to evaluate biochemical modulation of cellular ara-GTP metabolism by fludarabine triphosphate.
  
  
  METHODS
  Nine of the 13 total patients had indolent leukemias, including six whose disease failed prior fludarabine therapy. Two patients had T-acute lymphoblastic leukemia, one had chronic myelogenous leukemia, and one had mycosis fungoides. Nelarabine (1.2 g/m(2)) was infused on days 1, 3, and 5. On days 3 and 5, fludarabine (30 mg/m(2)) was administered 4 hours before the nelarabine infusion. Plasma and cellular pharmacokinetic measurements were conducted during the first 5 days.
  
  
  RESULTS
  Seven patients had a partial or complete response, six of whom had indolent leukemias. The disease in four responders had failed prior fludarabine therapy. The median peak intracellular concentrations of ara-GTP were significantly different (P =.001) in responders (890 micromol/L, n = 6) and nonresponders (30 micromol/L, n = 6). Also, there was a direct relationship between the peak fludarabine triphosphate and ara-GTP in each patient (r = 0.85). The cellular elimination of ara-GTP was slow (median, 35 hours; range, 18 to > 48 hours). The ratio of ara-GTP to its normal counterpart, deoxyguanosine triphosphate, was higher in each patient (median, 42; range, 14 to 1,092) than that of fludarabine triphosphate to its normal counterpart, deoxyadenosine triphosphate (median, 2.2; range, 0.2 to 27).
  
  
  CONCLUSIONS
  Fludarabine plus nelarabine is an effective, well-tolerated regimen against leukemias. Clinical responses suggest the need for further exploration of nelarabine against fludarabine-refractory diseases. Determination of ara-GTP levels in the target tumor population may provide a prognostic test for the activity of nelarabine.
authors: Departments of Experimental Therapeutics, Biostatistics, and Leukemia, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA. vgandhi@mdanderson.org
authors: V
authors: V
authors: Gandhi
authors: W
authors: W
authors: Plunkett
authors: S
authors: S
authors: Weller
authors: M
authors: M
authors: Du
authors: M
authors: M
authors: Ayres
authors: C O
authors: CO
authors: Rodriguez
authors: P
authors: P
authors: Ramakrishna
authors: G L
authors: GL
authors: Rosner
authors: J P
authors: JP
authors: Hodge
authors: S
authors: S
authors: O'Brien
authors: M J
authors: MJ
authors: Keating
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D001087:Arabinonucleosides / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D001088:Arabinonucleotides / Q000032:analysis / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis; D005260:Female; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy*; D015463:Leukemia, Prolymphocytic / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy*; D011379:Prognosis; D016896:Treatment Outcome; D014740:Vidarabine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D001087:Arabinonucleosides; D001088:Arabinonucleotides; D015415:Biomarkers; C104457:nelarabine; C022206:9-beta-D-arabinofuranosylguanosine 5'-triphosphate; D006160:Guanosine Triphosphate; D014740:Vidarabine; C024352:fludarabine