Optimizing Industrial\nSolid-Phase Peptide Synthesis:\nIntegration of Raman Spectroscopy as Process Analytical Technology

Peptide therapeutics have exploded\nin popularity in recent years,\nmotivating the need for advanced manufacturing methods which can be\napplied across the solid-phase peptide synthesis (SPPS) process. The\nFood and Drug Administration’s Process Analytical Technology\n(PAT) initiative offers a platform to implement advanced methods to\nimprove the efficiency and understanding of pharmaceutical manufacturing\nprocesses and shows great promise in application toward industrial\nSPPS. In this work, Raman spectroscopy was used as the main PAT tool\nto implement methods for on-line and real-time monitoring of the entire\nSPPS process, from Fmoc removal, to coupling, and through the extensive\nsolvent-washing steps. Raman spectroscopy is a rapid, specific, and\nnondestructive technique that can provide rich real-time information\nfor SPPS processes and can be used to improve efficiency in solvent\nuse and save process time. Specifically, this work reports on the\ndevelopment of PAT methods for monitoring of amino acid coupling during\nthe coupling stage and residual piperidine concentration during the\npost-deprotection washing stage of SPPS, to help reduce solvent use\nand better understand the coupling reaction and its time frame. We\nshow a significant reduction in solvent use is possible by employing\nRaman spectroscopy along with a partial least squares model to predict\nthe piperidine concentration in real time during continuous wash.\nIn addition, Raman spectroscopy offers a greater understanding of\ncoupling reaction kinetics during SPPS, which could lead to significant\nimprovements in total SPPS process time.