Quality by Design‐Based Development and Validation of a Stability‐Indicating RP‐HPLC Method for Quantitative Estimation of Enzalutamide in Eutectic Mixtures

ABSTRACT Metastatic castration‐resistant prostate cancer presents a significant clinical challenge, with Enzalutamide—an androgen receptor inhibitor—serving as a standard therapeutic agent. Despite its efficacy, poor aqueous solubility (Biopharmaceutics classification system Class II) limits its bioavailability, necessitating advanced formulation strategies. This study reports a robust and validated Reverse Phase High Performance Liquid Chromatography (RP‐HPLC) method for quantifying enzalutamide in bulk and eutectic formulations. A Quality by Design framework employing a Box–Behnken design was used to optimize chromatographic parameters: 60% acetonitrile, 1 mL/min flow rate, 30°C column temperature, and 234 nm detection wavelength. The method exhibited strong linearity (2–12 µg/mL, r 2 = 0.9985) with a limit of detection and limit of quantification of 0.464 and 1.40 µg/mL, respectively. Validation per International Council for Harmonisation Q2 (R1/R2) confirmed accuracy, precision, robustness, and system suitability. Forced degradation studies verified its stability‐indicating capability. Eutectic mixtures with succinic acid, caffeine, and ferulic acid were prepared via liquid‐assisted grinding and characterized using powder x‐ray diffraction, confirming crystalline eutectic formation. Recovery ranged from 96.7% to 99.8%, supporting the method's applicability in routine analysis and formulation development. Greenness evaluation using various tools confirmed the method's low environmental impact and high operational feasibility. This validated RP‐HPLC method enables reliable quantification of enzalutamide, supporting the development of novel bioavailability‐enhancing formulations for effective prostate cancer management.