Development and Validation of a Sensitive Lc–ms Method for the Determination of Four Potential Impurities (Las-I, Las-Ii and Their Regioisomers) in Lasmiditan Drug Substance at PPM Levels

Lasmiditan is a selective 5-HT1F receptor agonist indicated for treatment of acute migraine attack. The impurities such as trace levels of process related impurities in the drug substance need to be controlled at low ppm levels and this is not detectable by conventional HPLC–UV method. A selective liquid chromatography–mass spectrometry (LC–MS) method was developed and validated for the simultaneous determination of four impurities, LAS-I, LAS-II, LAS-I regioisomer and LAS-II regioisomer, in lasmiditan. It was performed on a Hypersil BDS C18 column (250 × 4.6 mm, 5 µm) with a gradient of ammonium acetate buffer and acetonitrile at 1.0 mL/min, and a positive mode electrospray ionisation with multiple-ion monitoring at m/z 335 and 301. Impurities eluted at 11.0 - 16.6 min which was very well resolved from the lasmidatan peak (about 3.1 min). The method was validated according to ICH Q2(R1) for specificity, system suitability, limit of detection (0.02–0.03 ppm), limit of quantitation (0.06–0.1 ppm), precision at the LOQ (%RSD ≤ 4.89), linearity (R² ≥ 0.9970 from the LOQ to 3.0 ppm) and accuracy (recovery 98.0– 103.0% at the LOQ and 96.8–103.2% at 1.8 ppm (120% of the specification limit); %RSD ≤ 2.62). The LOQs range from 15 to 25 times lower than the 1.5 ppm limit, making the method suitable to quantitate the impurities at the Specification limit in the lasmiditan drug substance.