Development of a single-unit SMB process for clean production of 2′-fluoro nucleoside phosphoramidites to be used as the key building blocks of antisense oligonucleotide drugs and mRNA-vaccine capping primers

Abstract

Due to the recent increase in incurable diseases and the pandemic of COVID-19, there have been global interests in antisense 2 '-fluoro modified oligonucleotide drugs and mRNA-vaccine capping primers. To ensure stable and economical production of these oligonucleotides and primers, it is essential to establish a reliable process for securing a large amount of their corresponding monomer (2 '-fluoro nucleoside phosphoramidite, abbreviated as "2 ' F-NP" hereafter) at high purity (>99%) from the output of the relevant reaction. Currently, this task has been handled using two-stage separation processes (extraction and chromatography in series) based on batch (noncontinuous) modes, which, however, had the problems of excessive solvent consumption and low yield. For cleaner production of 2 ' F-NP, these problems should be resolved. To address such issue, this study aimed to develop a new single-step process that can recover 2 ' F-NP at once in a continuous mode at high purity. For this purpose, we introduced a simulated-moving-bed (SMB) method into the development phase of the targeted 2 ' FNP recovery process, and further established the appropriate SMB configuration and solvent-gradient strategy to continuously remove all the impurities at once. The SMB mode process determined based on such considerations was then optimized using the intrinsic parameters estimated, the regeneration method explored, and the optimization tool prepared. The relevant SMB experiment was carried out, which confirmed that the developed process in this study was quite effective in continuous-mode recovery of 2 ' F-NP at high purity (99.5%) and high yield (96.5%) without the aid of a further process, thereby enabling a significant reduction in solvent consumption. The results in this paper will thus contribute to the clean and eco-friendly production of 2 ' F-NP, which will also be of benefit to antisense oligonucleotide drug and mRNA-vaccine capping primer production processes.