Robustness evaluation of weak anion exchange chromatography method for the purity analysis of therapeutic oligonucleotides

•Method optimization for separation of oligonucleotide impurities in a QC environment.•High-organic mobile phase ensures maximal resolution in weak anion exchange chromatography.•Method robustness was assessed for five factors following a risk assessment.•The study emphasizes the importance of method optimization and robustness assessment in the quality control of therapeutic oligonucleotides. Therapeutic oligonucleotides are becoming an important class of therapeutics. Their manufacturing processes can result in the formation of impurities, particularly truncated species. To ensure the quality and safety of the product, it is crucial to evaluate the presence of these species. Liquid chromatography analysis enables such purity determination. In this context, a recently described weak anion exchange chromatography method was optimized to allow the effective separation of different impurities. The optimization addressed the complexity and instability of the mobile phases, which contained salts and organic compounds. Adjustments were made to the mobile phase composition and gradient to meet the requirements of QC laboratories. Additionally, to ensure the method's reliability, a robustness study was conducted based on a risk assessment. Five factors were considered potential risks and were assessed experimentally on different chromatographic outputs. This led to the definition of a robust space, ensuring the method's reliability for the purity determination of oligonucleotides.