Validation of a Method for Quantifying Elexacaftor, Elexacaftor-M23, Tezacaftor, Tezacaftor-M1, and Ivacaftor by HPLC-PDA.

INTRODUCTION/OBJECTIVE: Cystic fibrosis is a genetic disease primarily treated with pharmacological modulators of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, such as Elexacaftor, Tezacaftor, and Ivacaftor. This study developed and validated a method using Ultra-Fast Liquid Chromatography with Photodiode Array Detection (UFLC/PAD) to simultaneously quantify these three drugs and two of their main pharmacologically active metabolites (Ele-M23, Tez-M1) in plasma. METHODS: A Shimadzu UFLC/PAD system was used with a Shim-pack VP-ODS column and an isocratic mobile phase (water:acetonitrile, 35:65). Itraconazole served as the internal standard for plasma calibration curves (0.1-10 μg/ml). Samples were processed by protein precipitation with methanol followed by centrifugation. Linearity, limit of quantification (LQ), precision, and accuracy were validated. RESULTS: The limit of quantification for each calibration curve was 0.1 μg/ml. Intra-day precision (coefficient of variation [CV%]) ranged from 3.8% to 7.2%, and inter-day precision from 8.6% to 16.3%, meeting standard acceptance criteria. Retention times were 2.83 min for Ele-M23, 3.2 min for Elexacaftor, 5.6 min for Tezacaftor, 7.9 min for Tez-M1, 12.8 min for Ivacaftor, and 16.6 min for Itraconazole. DISCUSSION/CONCLUSION: The method is fast, reproducible, and suitable for the simultaneous quantification of CFTR modulators and their main metabolites in plasma. It is applicable in clinical laboratories for the therapeutic monitoring and optimization of cystic fibrosis pharmacotherapy.