Continuous Purification of a Conjugated Short Interfering RNA Therapeutic Using Anion Exchange Twin-Column Chromatography (MCSGP)

Multicolumn Countercurrent Solvent Gradient Purification (MCSGP) process technology improves yields and production efficiency in clinical and commercial manufacturing of therapeutic APIs such as peptides and oligonucleotide drugs (ONDs). In this case study, we developed an MCSGP process for the purification of a sugar-conjugated sense strand of a therapeutic siRNA (short interfering RNA) using anion exchange (AIEX) chromatography and state-of-the-art twin-column chromatography equipment. MCSGP is relatively complex and requires specialized process development tools to optimize and implement. We describe a simplified, software-aided MCSGP method development procedure for fast transfer from batch to continuous-mode chromatography. As expected with MCSGP, the yield improved from 80% to 93% compared to single-column chromatography, allowing for proportional downscaling of steps preceding and including oligonucleotide synthesis. This greatly decreases manufacturing costs and reduces waste (e.g., byproducts, solvents, and reagents). In addition to increasing the OND yield, throughput was increased by 87%. Other generic benefits of implementing MCSGP are also outlined; for example, due to automation, process robustness is improved; column dimensions and resin volumes are downscaled; laborious side-fraction rechromatography is eliminated; and fewer “in-process control” samples are generated, reducing the manufacturing support burden. The automation enabled by MCSGP is a significant advancement in the commercial-scale manufacturing of APIs.