Overall Review on Development and Validation of RP-HPLC Method for Relugolix in Bulk and Marketed Formulations

Overview

This digest summarizes the development and validation of a reversed-phase high-performance liquid chromatography (RP-HPLC) method for quantification of relugolix in bulk drug substance and a marketed tablet formulation. The method employed an Inertsil ODS-2 C18 stationary phase with acetonitrile and 0.1% orthophosphoric acid buffer (60:40 v/v) as the mobile phase, PDA detection at 293 nm, and a 1.0 mL/min flow rate. Method objectives included achieving rapid analysis with adequate resolution, demonstrating linearity, sensitivity, accuracy, precision, specificity, robustness, and suitability for routine quality-control assays of finished dosage forms.

Methods and approach

Chromatographic conditions: Inertsil ODS-2 C18 column (4.6 × 150 mm, 5 µm); mobile phase acetonitrile:0.1% orthophosphoric acid buffer (60:40 v/v); flow rate 1.0 mL/min; detection at 293 nm using a photodiode array detector. System suitability parameters and retention time were optimized to obtain a single sharp, symmetric peak for relugolix with minimal run time. Validation followed typical analytical validation domains: linearity over 20–100 µg/mL, determination of limit of detection (LOD) and limit of quantitation (LOQ), intra- and inter-day precision, accuracy via recovery studies, specificity against formulation excipients, and robustness through deliberate variation of chromatographic parameters. Assay performance was assessed on a marketed tablet formulation.

Key Findings

The method produced a symmetric relugolix peak at approximately 2.0 minutes, indicating high chromatographic efficiency and reduced analysis time. Linearity across 20–100 µg/mL exhibited an R2 of 0.999. Sensitivity metrics were LOD = 0.05 µg/mL and LOQ = 0.17 µg/mL. Accuracy was demonstrated by recovery values within 98–102%. Precision evaluations returned %RSD values below 2% for repeatability and intermediate precision. Specificity testing showed no interference from common excipients in the tablet matrix. Robustness testing indicated method resilience to small variations in chromatographic conditions. The assay of the marketed formulation recovered 99.12% of the labeled content.

Implications

The validated RP-HPLC method provides a rapid, sensitive, and precise analytical procedure suitable for routine quality-control quantification of relugolix in bulk and tablet dosage forms. The short retention time combined with demonstrated specificity and robustness supports high-throughput analyses in manufacturing and stability testing environments. Given the method's low LOD/LOQ and tight accuracy and precision metrics, it is appropriate for assay determinations and could be incorporated into standard analytical control strategies for relugolix-containing products.