ANALYTICAL QUALITY BY DESIGN (AQBD) APPROACH FOR RP-HPLC METHOD DEVELOPMENT AND VALIDATION OF TOFACITINIB: A SYSTEMATIC OPTIMIZATION STRATEGY

Abstract

Background: Analytical Quality by Design (AQbD) is a systematic, science-based methodology for building robust analytical techniques through identification and management of essential method parameters. A reliable RP-HPLC method is needed for routine quality control and pharmaceutical analysis of tofacitinib, a Janus kinase (JAK) inhibitor used in the treatment of rheumatoid arthritis. Aim: To develop, improve and validate RP-HPLC technique based on AQbD for quantitative measurement of tofacitinib utilizing Design Expert® software and response surface methodology as per ICH requirements. Method: The effect of three important technique parameters (acetonitrile concentration, flow rate and column oven temperature) was studied using a Box-Behnken experimental design with 14 trials. Retention duration, peak asymmetry and theoretical plate count were the analytical responses evaluated. The improved chromatographic conditions were verified according to ICH criteria for system applicability, specificity, linearity, accuracy, precision, robustness, solution stability, limit of detection (LOD) and limit of quantitation (LOQ). Results and Discussion: The linear regression model was statistically significant (F = 7.35, p = 0.0069) with a non significant lack-of-fit (p = 0.9407), supporting the applicability of the AQbD model.  The desirability value of the optimized method was 1.000. The chromatographic peak was crisp with a retention period of around 3.43 min, an asymmetry of 1.14 and theoretical plate count of roughly 9417. The method displayed good linearity over the concentration range 5–15 µg/mL with LOD and LOQ values of 0.22 and 0.67 µg/mL, respectively. Accuracy was obtained with a total recovery of 99.81%. Precision and robustness were within ICH acceptance criteria. Adequate stability was confirmed through solution stability studies, showing a maximum peak area variation of just 0.85% after 24 h. The results indicated that AQbD was able to optimize the analytical method and improve its robustness and reliability. Conclusion: An AQbD based simple, rapid, accurate and precise RP-HPLC technique has been developed and validated for the quantification of tofacitinib. The method showed good selectivity, precision, accuracy, robustness and stability and it is applicable for routine quality control, pharmaceutical analysis and pharmacokinetic studies.