Real-Time Process Analytical Technology Assurance for Flow Synthesis of Oligonucleotides

A feasibility study has been conducted using Process Analytical Technology (PAT) monitoring and chemometric modeling techniques to mitigate risks identified for the solid-phase synthesis of a model oligonucleotide compound in a flow reactor manifold. This paper will discuss three of the key risks identified for this automated process that are generally applicable to oligonucleotide manufacturing: (1) connection of an incorrect chemical solution to a designated input port of the synthesizer; (2) incorrect quantitative preparation of a chemical solution; and (3) errors that may come from mechanical or other unknown sources associated with the synthesizer. Mid-infrared and Raman spectroscopy were the key PAT techniques used to monitor the automated synthetic process in real time. Classification, quantitative (partial least-squares), and multivariate statistical process control (MSPC) modeling were then used to analyze the acquired data and detect the occurrence of the aforementioned failure modes. MSPC models were constructed and tested with intentionally induced key process deviations to explore their sensitivity and detection capability. Suggestions are proposed for more stringent validated processes that would be required to implement these techniques in a manufacturing environment.