Estimation of Ribociclib and Letrozole in Solid Dosage form (Tablet): A Novel Analytical Method

An attempt was made to develop a simple, rapid, and validated method for the simultaneous estimation of ribociclib and letrozole in combination tablet dosage form.

Inhibitors of cyclin D1/CDK4 (Cyclin-dependent kinase 4) [2] and CDK6 (Cyclin-dependent kinase 6) [2] are found in Ribociclib, which is marketed by Novartis under the brand names Kisqali and Kryxana. This drug is used to treat some types of breast cancer. The combination of aromatase inhibitors and fulvestrant Inhibitors of cyclin D1/CDK4 (Cyclin-dependent kinase 4) and CDK6 (Cyclin-dependent kinase 6) are found in Ribociclib, This drug is used to treat some types of breast cancer. The combination of aromatase inhibitors and fulvestrant.

The chromatographic separation was carried out on Waters, symmetry C18 (150 mm×4.6 mm with 3.5 µm), mobile phase used was a mixture of buffer and acetonitrile in the ratio of 80:20, with flow rate of 1ml/min and injection volume of 10 µL for the assay. The detection was done using PDA at 260 nm, with run time of 5 min. The retention time for the drugs ribociclib and letrozole was detected to be 2.648 min and 3.151 min, respectively. The method was validated according to ICH guidelines.

The linearity of letrozole and ribociclib was observed to be in the range of 0.50–7.50 and 40.01–600.15, Correlation coefficient (r2) 0.999 and 0.9983, respectively. Accuracy for ribociclib and letrozole is carried out by repeatable concentrations of 50%, 100%, and 150. Validation factors of robustness and ruggedness were detected to be in limits.

The developed method was simple, rapid, and consistent; it can be used for the simultaneous estimation of ribociclib and letrozole tablet dosage form in routine analysis. The validated method can be used for the routine analysis of both the drugs from bulk and different formulations and will help in therapeutic drug monitoring (TDM) and bioavailability studies.