Overview and Recent Advances in the Purification and Isolation of Therapeutic Oligonucleotides

Therapeutic oligonucleotides are a novel chemical modality with unique characteristics that offer significant therapeutic potential. With the latest surge in development, they are paving the way to the market at a rapid pace. To support that, scalable and economically sustainable oligonucleotide production is required. The upstream part exploits the well-studied phosphoramidite chemistry, known from the 1960s, using automated synthesis on a solid support. On the other hand, the downstream processing, which consists of purification and isolation steps, has stayed in the shadow of the more thoroughly studied synthesis, even though it is often regarded as the bottleneck of therapeutic oligonucleotide production. Therefore, this review aims to highlight the most important traditional purification and isolation approaches for the production of therapeutic oligonucleotides that ensure product quality, yields, scale, and cost-efficiency as well as newly emerging separation technologies that could become relevant in the future.