LC-MS/MS Method for the Quantification of the Leflunomide Metabolite, Teriflunomide, in Human Serum/Plasma

Saliva as Blood Alternative in Therapeutic Monitoring of Teriflunomide-Development and Validation of the Novel Analytical Method

Therapeutic drug monitoring (TDM) is extremely helpful in individualizing dosage regimen of drugs with narrow therapeutic ranges. It may also be beneficial in the case of drugs characterized by serious side effects and marked interpatient pharmacokinetic variability observed with leflunomide and its biologically active metabolite, teriflunomide. One of the most popular matrices used for TDM is blood. A more readily accessible body fluid is saliva, which can be collected in a much safer way comparing to blood. This makes it especially advantageous alternative to blood during life-threatening SARS-CoV-2 pandemic. However, drug’s saliva concentration is not always a good representation of its blood concentration. The aim of this study was to verify whether saliva can be used in TDM of teriflunomide. We also developed and validated the first reliable and robust LC-MS/MS method for quantification of teriflunomide in saliva. Additionally, the effect of salivary flow and swab absorptive material from the collector device on teriflunomide concentration in saliva was evaluated. Good linear correlation was obtained between the concentration of teriflunomide in plasma and resting saliva (p < 0.000016, r = 0.88), and even better between plasma and the stimulated saliva concentrations (p < 0.000001, r = 0.95) confirming the effectiveness of this non-invasive method of teriflunomide’s TDM. The analyzed validation criteria were fulfilled. No significant influence of salivary flow (p = 0.198) or type of swab in the Salivette device on saliva’s teriflunomide concentration was detected. However, to reduce variability the use of stimulated saliva and synthetic swabs is advised.

Quantitative determination of cyanoacetic acid content in teriflunomide drug substance by ion chromatography using conductivity detector

Background

The current study focuses on the development and validation of an analytical method for quantifying cyanoacetic acid (CAA) in teriflunomide drug substance using a high-performance ion chromatography (IC) with cation suppressed conductivity detection (TFM). Water was used as the diluent for preparing the sample solution, which was injected into a standard chromatographic device with 250 mm, 4.0 mm ID, and 5.0 μm particle size Metrosep A Supp 5 Ion exchange column and a suppressed conductivity detector. At a flow rate of 0.6 mL min−1 and a temperature of 40 °C, the mobile phase was delivered in an isocratic mode.

Results

CAA and TFM had retention times of 12.78 and 15.82 min, respectively. CAA has a limit of detection (LOD) of 33 μg/g and a limit of quantification (LOQ) of 101 μg/g, respectively. For LOD and LOQ accuracy, the percentage RSD of CAA is 1.7 and 1.2, respectively. The average CAA recovery percentage was found to be between 98.6 and 100.1%. With a value of 0.9998, the calibration curve yielded an excellent linear correlation coefficient for CAA. According to the ICH guidelines, all verification parameters are within the range, indicating that the system is stable.

Conclusion

The elution time and run time in the currently developed ion chromatography analytical method have been reduced, demonstrating that the method is cost-effective and generally accepted, as well as simple and functional, and can be used in routine quality control tests in the industry.

Evaluation of stability using one versus three tubes for each quality control concentration in matrix-based bioanalysis

Aim: Contract research organizations and pharmaceutical firms have performed stability testing using one of two methods: storing in the freezer a single tube of matrix for each quality control concentration (Method 1), followed by aliquoting and analysis; and storing three tubes for each quality control concentration, followed by analysis (Method 2). This research project was conducted to determine if there were detectable differences between Method 1 and Method 2. Methodology: Five model drugs were selected: teriflunomide (stable compound) and acetyl salicylic acid, simvastatin, tenofovir alafenamide and valganciclovir (stability concerns). Samples were stored at -80°C for 1, 3 and 12 months and then analyzed. Samples were also placed at different locations within the freezer. Results: For the drugs tested, the results suggest that there is no significant difference in the outcome of stability testing, regardless whether Method 1 or Method 2 was followed.