The aim of this study was to evaluate the enantioselective pharmacokinetics of
cyclophosphamide and its metabolites
4-hydroxycyclophosphamide and
carboxyethylphosphoramide mustard in patients with systemic or
multiple sclerosis. Patients with
systemic sclerosis (n = 10) or
multiple sclerosis (n = 10), genotyped for the allelic variants of
CYP2C9*2 and
CYP2C9*3 and of the
CYP2B6 G516T polymorphism, were treated with 50 mg
cyclophosphamide/kg daily for 4 days. Serial blood samples were collected up to 24 hours after administration of the last
cyclophosphamide dose.
Cyclophosphamide,
4-hydroxycyclophosphamide, and carboxyethylphosphoramide enantiomers were analyzed in plasma samples using liquid chromatography-tandem mass spectrometry coupled to chiral column
Chiralcel OD-R or
Chiralpak AD-RH.
Cytokines IL-2,
IL-4,
IL-6,
IL-8,
IL-10, IL- 12p70,
IL-17, TNF-α, and INT-δ in the plasma samples collected before
cyclophosphamide infusion were analyzed by Milliplex MAP human
cytokine/
chemokine. Pharmacokinetic parameters showed higher plasma concentrations of (S)-(-)-
cyclophosphamide (AUC 215.0 vs 186.2 μg·h/mL for
multiple sclerosis patients and 219.1 vs 179.2 μg·h/mL for
systemic sclerosis patients) and (R)-4-hydroxycyclophosphamide (AUC 5.6 vs 3.7 μg·h/mL for
multiple sclerosis patients and 6.3 vs 5.6 μg·h/mL for
systemic sclerosis patients) when compared to their enantiomers in both groups of patients, whereas the pharmacokinetics of the carboxyethylphosphoramide metabolite was not enantioselective.
Cytokines' plasma concentrations were similar between multiple and
systemic sclerosis groups. The pharmacokinetics of
cyclophosphamide is enantioselective in patients with
systemic sclerosis and
multiple sclerosis, with higher plasma concentrations of the (S)-(-)-
cyclophosphamide enantiomer due to the preferential formation of the (R)-4-hydroxycyclophosphamide metabolite.