Quality by design of solid‐phase peptide/protein coupling reaction via mechanistic reaction kinetics modeling approach

Abstract The peptide coupling reaction is one of the most critical steps in the solid phase synthesis of therapeutic peptides/proteins. Improper reaction conditions can result in several common impurities such as single amino acid deletions, additions, N‐terminus modifications, and D‐isomers, all while potentially impacting the active pharmaceutical ingredient critical quality attributes. In this work, we developed a first‐principle mechanistic reaction kinetics model for the solid‐phase peptide/protein coupling reaction based on well‐established reaction mechanisms and experimental data from literature. Utilizing the reaction kinetics model, we present a systematic, quality by design approach for the coupling reaction control strategy. Critical process parameters are identified via univariate analysis and the design space is designated via multivariate risk assessment. The presented approach provides a novel solution for designing solid‐phase peptide/protein synthesis control strategies and identifying normal operating ranges for each process parameter, as well as the associated design space.