Structural Identification of Novel Degradation Impurities in Teriflunomide Drug Product Using NMR, IR, Mass Spectrometry, and Quantification by RP‐HPLC

ABSTRACT Teriflunomide, a disease‐modifying agent indicated for the treatment of multiple sclerosis, exhibits susceptibility for degradation under various environmental stress conditions, potentially resulting in the formation of impurities that may affect the drug's efficacy and safety. In the present study, two novel degradation impurities were identified during forced degradation and stability studies. These unknown impurities were subsequently isolated and structurally characterized using nuclear magnetic resonance, infrared spectroscopy, mass spectrometry, and designated as Teriflunomide Impurities 1 and 2. A robust and stability‐indicating reverse phase high‐performance liquid chromatography method was developed and validated for the quantitative determination of process‐related and degradation impurities in teriflunomide solid oral dosage form. Optimal chromatographic separation was achieved using a YMC pack pro C18 column (250 mm × 4.6 mm, 5 µm) with a gradient elution consisting of a buffer and acetonitrile as the mobile phase. The method employed a flow rate of 1.1 mL/min and a detection wavelength of 250 nm. The developed method was validated in accordance with International Council for Harmonisation guidelines. Teriflunomide demonstrated linearity over the concentration range of 0.079 to 1.484 µg/mL, with a limit of detection and limit of quantification of 0.040 and 0.080 µg/mL, respectively. Teriflunomide Impurities 1 and 2 were found to be linear over the range of 0.252–3.783 µg/mL and 0.254–3.812 µg/mL, with a detection limit of 0.060 µg/mL and quantitation limit of 0.250 µg/mL. The method was shown to be simple, precise, accurate, linear, and reproducible, and is suitable for routine analysis of teriflunomide and its degradation products in pharmaceutical formulations.