Development of a Control Strategy for a Final Intermediate to Enable Impurities Control

This manuscript describes the development of a control strategy for impurities in the final intermediate step of the asunaprevir drug substance utilizing the concepts outlined in the International Conference on Harmonisation guidelines (ICH Q8 (R2), Q9, Q10, and Q11). Detailed mechanistic understanding enabled the construction of a kinetic model that was used in conjunction with a process risk assessment and well-defined quality attributes to guide the development of the reaction design space. Implementation of continuous monitoring of the reaction facilitated the expansion of the design space and provided suitable parameter ranges to enable a robust process for commercial manufacturing.