Investigations on the pharmacokinetics of trofosfamide and its metabolites-first report of 4-hydroxy-trofosfamide kinetics in humans.
Trofosfamide (TRO), like cyclophosphamide (CYCLO) and ifosfamide (IFO), is a prodrug oxazaphosphorine derivative that requires hepatic biotransformation to form the cytotoxically active 4-hydroxy derivative (4-hydroxy-TRO). Individual 4-hydroxyoxazaphosphorines and 4-hydroxy-TRO itself have not been demonstrated in humans up to now. For investigation of the principal pharmacokinetics of TRO and its metabolites, six tumour patients (49-65 years of age, Karnofsky index >70%) with normal liver and renal function were given a single oral dose of 600 mg/m(2) TRO. Plasma was sampled using a bedside technique. Individual 4-hydroxyoxazaphosphorines and TRO together with further metabolites were determined by a specially developed HPLC-UV method and a HPLC-MS method, respectively. With a short apparent half-life (1.2 h) and high apparent clearance (Cl/F 4.0 l/min), TRO was very quickly eliminated from plasma and highly converted to its metabolites, mainly 4-hydroxy-TRO and IFO. In relation to the AUC values of TRO (1.0) the following molar quotients were calculated: 1.59 (4-hydroxy-TRO), 0.40 (4-hydroxy-IFO), 6.90 (IFO) and 0.74 (CYCLO). C(max) values were in the range 10-13 micromol/l for TRO, 4-hydroxy-TRO and IFO and in the range 1.5-4.0 micromol/l for CYCLO, 2- and 3-dechloroethyl-IFO and 4-hydroxy-IFO. Kinetic data indicate that 4-hydroxy-IFO is formed by both hydroxylation of TRO and exocyclic N-dechloroethylation of 4-hydroxy-TRO. 4-hydroxy-CYCLO was not detected above the quantification limit of the method. Only mild haemodepressive side effects were observed after oral administration of 600 mg/m(2) TRO. In relation to known data for IFO, TRO is much more 4-hydroxylated than IFO. The high 4-hydroxy-TRO/TRO ratio found suggests that TRO is a promising tumourstatic agent.
Preiss
Rainer
R
Institute of Clinical Pharmacology, University of Leipzig, Härtelstrasse 16-18, 04107 Leipzig, Germany. rainer.preiss@medizin.uni-leipzig.de
Baumann
Frank
F
Stefanovic
Dragan
D
Niemeyer
Ulf
U
Pönisch
Wolfgang
W
Niederwieser
Dietger
D
D000284:Administration, Oral; D000368:Aged; D018906:Antineoplastic Agents, Alkylating / Q000008:administration & dosage / Q000493:pharmacokinetics*; D019540:Area Under Curve; D003520:Cyclophosphamide / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D007069:Ifosfamide / Q000097:blood; D008232:Lymphoproliferative Disorders / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged
D018906:Antineoplastic Agents, Alkylating; D003520:Cyclophosphamide; C003726:trofosfamide; D007069:Ifosfamide