Volume 8 ; Issue 2 ; in Month : July-Dec (2025) Article No : 174
Kuturu D, Usalingam AK, et al.

Abstract

Ribociclib (RIBO) and Letrozole (LETRO) are chemotherapeutic agents commonly used in combination therapy. In this study, a novel and robust bioanalytical LC–MS/MS method was developed for the simultaneous quantification of both drugs in human plasma. The LC–MS/MS system was operated in positive ionization mode using the following source parameters: collision gas 20, cone gas 20, desolvation gas 700, and source temperature 150°C. Chromatographic separation was achieved using Mobile Phase A, consisting of a mixture of 0.1% formic acid (pH adjusted to 3.5 with triethylamine) and methanol (80:20, v/v), and Mobile Phase B, consisting of 5% acetonitrile. The gradient program was initiated at 95% A and 5% B at 0.8 min, shifted to 5% A and 95% B at 2.2 min, and subsequently returned to 95% A and 5% B at 2.4 min, which was maintained until 3.5 min. An additional gradient step was incorporated to effectively eliminate carry-over. The developed method was fully validated within the relevant linearity ranges that encompassed the anticipated plasma concentrations of both analytes, with correlation coefficients ranging from 0.9999 to 0.9939. Interday precision (%CV) for RIBO ranged from 3.53% to 5.44%, while LETRO showed values between 6.12% and 13.12%. Intraday precision ranged from 3.58% to 8.77% for RIBO and 2.49% to 14.14% for LETRO. These results comply with the EMA and ICH guidelines for bioanalytical method validation, confirming the reliability and reproducibility of the method.

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