Dried Blood Spot Methodology in Combination With Liquid Chromatography/Tandem Mass Spectrometry Facilitates the Monitoring of Teriflunomide

Abstract

Background: Teriflunomide, a once-daily oral immunomodulator approved for treatment of relapsing-remitting multiple sclerosis, is eliminated slowly from plasma. If necessary to rapidly lower plasma concentrations of teriflunomide, an accelerated elimination procedure using cholestyramine or activated charcoal may be used. The current bioanalytical assay for determination of plasma teriflunomide concentration requires laboratory facilities for blood centrifugation and plasma storage. An alternative method, with potential for greater convenience, is dried blood spot (DBS) methodology. Analytical and clinical validations are required to switch from plasma to DBS (finger-prick sampling) methodology.

Methods: Using blood samples from healthy subjects, an LC-MS/MS assay method for quantification of teriflunomide in DBS over a range of 0.01-10 mcg/mL was developed and validated for specificity, selectivity, accuracy, precision, reproducibility, and stability. Results were compared with those from the current plasma assay for determination of plasma teriflunomide concentration.

Results: Method was specific and selective relative to endogenous compounds, with process efficiency ∼88%, and no matrix effect. Inaccuracy and imprecision for intraday and interday analyses were <15% at all concentrations tested. Quantification of teriflunomide in DBS assay was not affected by blood deposit volume and punch position within spot, and hematocrit level had a limited but acceptable effect on measurement accuracy. Teriflunomide was stable for at least 4 months at room temperature, and for at least 24 hours at 37°C with and without 95% relative humidity, to cover sampling, drying, and shipment conditions in the field. The correlation between DBS and plasma concentrations (R = 0.97), with an average blood to plasma ratio of 0.59, was concentration independent and constant over time.

Conclusions: DBS sampling is a simple and practical method for monitoring teriflunomide concentrations.

FIGURE 1.

Chromatogram of (A) blank DBS, (B) blank DBS spiked with IS, and (C) blank DBS spiked with teriflunomide at the LLOQ (0.01 mcg/mL), and IS.

FIGURE 2.

Influence of HCT on quantification of teriflunomide at low and high QC concentrations: linear regression with 95% mean CIs of bias depending on HCT level. AdjRsq, adjusted R square; L90M, lower 90% confidence limit for the mean; PRED, predicted value for % bias; Rsq, R square; RMSE, root mean square error; U90M, upper 90% confidence limit for the mean.

FIGURE 3.

Incurred sample reproducibility in plasma (yellow dots) and in DBS from finger-prick (red dots).

FIGURE 4.

Passing–Bablok relationship obtained from plotting plasma and DBS teriflunomide concentrations. Each symbol represents 1 subject. All data of the same subject are represented with the same symbol. Passing–Bablok regression: R² = 0.97, slope 0.60 [95% CI 0.58–0.61], intercept −0.04 (95% CI −0.15 to 0.01).

FIGURE 5.

Diagnostic plot comparing ratio of DBS to plasma concentration versus plasma concentration. Each symbol represents 1 subject. All data of the same subject are represented with the same symbol. One ratio of 2.77 has not been shown for plasma concentration value of 0.67 mcg/mL.

FIGURE 6.

DBS to plasma teriflunomide concentration over time. Each symbol represents 1 subject. All data of the same subject are represented with the same symbol. One ratio of 2.77 has not been shown for day 17.