A Novel, Robust, and Isocratic HPLC‐UV Method for the Comprehensive Determination of Enantiomeric Impurity (R‐Isomer) in Niraparib Drug Substance

Niraparib is a potent, orally bioavailable inhibitor of poly (ADP-ribose) polymerase (PARP) enzymes, specifically targeting PARP-1 and PARP-2 to induce selective cytotoxicity in malignancies by disrupting DNA repair mechanisms. Given that the S-niraparib exhibits significantly higher pharmacological activity than the R-isomer, the development of a precise analytical technique to ensure enantiomeric purity is a critical requirement for pharmaceutical quality control. This study details the development and validation of a stability-indicating chiral high-performance liquid chromatography (HPLC) method for the quantitative assessment of enantiomeric purity content. Separation was successfully achieved using a Chiralpak AS-H 250 × 4.6 mm, 5 μm column under isocratic conditions with a mobile phase consisting of n-hexane, ethanol, methanol, and diethylamine in a 750:100:150:1.0 (v/v/v/v) ratio. The system was operated at a flow rate of 0.7 mL/min and a controlled column temperature of 40°C, with detection monitored via a UV/visible detector at 240 nm. The method was rigorously validated in accordance with ICH Q2(R2) guidelines, demonstrating specificity, accuracy, and precision. A resolution factor of greater than 2.0 was maintained between niraparib and its isomer. Analytical sensitivity was established through the determination of the limit of detection (LOD) and limit of quantitation (LOQ) using signal-to-noise ratios of 3 and 10, respectively, with a 1 mg/mL sample concentration and a 10 μL injection volume. Calibration curves proved linear over the studied range, confirming the method's reliability. The results indicate that this stability-indicating approach is highly effective for routine in-process quality control, batch release testing, and long-term stability monitoring of niraparib drug substances.