Quantitation of unbound sunitinib and its metabolite N-desethyl sunitinib (SU12662) in human plasma by equilibrium dialysis and liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study

Abstract

A rapid, selective, and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous determination of unbound sunitinib and its active metabolite N-desethyl sunitinib in plasma. Plasma and post-dialysis buffer samples were extracted using a liquid-liquid extraction procedure with acetonitrile-n-butylchloride (1:4, v/v). Chromatographic separation was achieved on a Waters X-Terra® MS RP(18) column with a mobile phase consisting of acetonitrile and water (60:40, v/v) containing formic acid (0.1%, v/v) using an isocratic run, at a flow-rate of 0.2 mL/min. Analytes were detected by electrospray tandem mass spectrometry in the selective reaction monitoring mode. Linear calibration curves were generated over the ranges 0.1-100 and 0.02-5 ng/mL for sunitinib and 0.2-200 and 0.04-10 ng/mL for N-desethyl sunitinib in plasma and in phosphate-buffered solution, respectively. The values for both within-day and between-day precision and accuracy were well within the generally accepted criteria for analytical methods. The analytical range was sufficient to determine the unbound and total concentrations of both analytes. The method was applied for measurement unbound concentrations in addition to total concentrations of sunitinib and its metabolite in plasma of a cancer patient receiving 50 mg daily dose.

Trial registration: ClinicalTrials.gov NCT00890747.

Copyright © 2012 John Wiley & Sons, Ltd.

Figures

Fig. 1

The mass spectra of daughter scan for (a) sunitinib at m/z 399 → 283.2 (b) N-desethyl sunitinib at m/z 371.2 → 283.2, and (c) sunitinib-d10 m/z 409.1→283.2. Asterisks represent the deuterium atoms in the deutrated internal standard.

Fig. 2

Chromatograms of blank human plasma (a,b,c,) and PBS (d,e,f,) for monitoring of (a,d) sunitinib, (b,e) N-desethyl sunitinib, and (c,f,) internal standard sunitinib-d10.

Fig. 3

Chromatograms of plasma (a,b,c,) and post-dialysis buffer solution (d,e,f,) spiked with (a,d) sunitinib 0.1 ng/mL (LLOQ), (b,e) the N-desethyl sunitinib 0.2 ng/mL (LLOQ), and (c,f) the internal standard sunitinib-d10.

Fig. 4

Representative chromatograms from a select cancer patient 3 hrs after receiving a 50 mg dose of sunitinib of plasma (a,b,c,) and post-dialysis buffer solution (d,e,f,) of (a, d) sunitinib, (b,e) N-desethyl sunitinib, and (c,f) the internal standard sunitinib-d10.

Fig. 5

Plasma concentration–time profile of total (●) and unbound (○) sunitinib and total (▲) and unbound (△) N desethyl sunitinib after an oral dose of 50 mg/day.