Multicolumn Countercurrent Solvent Gradient Purification (MCSGP) is a continuous chromatography technique used to maximize purification yields compared to traditional batch purification methods. Here we apply MCSGP for the reversed phase purification of a N-acetylgalactosamine (GalNAc)-cluster-conjugated DNA-LNA gapmer oligonucleotide therapeutic using a twin-column chromatography system. Based on a batch process as a starting point, MCSGP was designed, optimized and compared with the batch process regarding process performance and scale-up requirements. Product yields increased from 52.7% using batch chromatography to 91.5% using MCSGP, with purity, productivity, and buffer consumption otherwise comparable. In a manufacturing scenario, use of MCSGP would allow the downscaling of oligonucleotide synthesis by 42.5%, which would result in a significant cost reduction and increased throughput. Moreover, the equipment, chemicals and methodology used in MCSGP are analogous to a standard reversed phase purification allowing for a "like for like" transition to the upgraded MCSGP process.

Oligonucleotides (ONs) are breaking through in the biopharmaceutical industry as a promising class of biotherapeutics. The main success of these molecules is due to their peculiar way of acting in the cellular process, regulating the gene expression and hence influencing the protein synthesis at a pretranslational level. Although the Food and Drug Administration (FDA) already approved a few ON‐based therapeutics, their production cost strongly limits large‐scale manufacturing: a situation that can be alleviated through process intensification. In this study, we address this problem by developing an efficient and continuous chromatographic purification process for ONs. In particular, we considered the chromatographic purification of an ON crude prepared by chemical synthesis using anion exchange resins. We demonstrate that in this system the competitive adsorption of the various species on the same sites of the resin leads to the displacement of the more weakly adsorbing species by the more strongly adsorbing ones. This phenomenon affects the behavior of the chromatographic units and it has been investigated in detail. Then, we developed a continuous countercurrent solvent gradient purification (MCSGP) process, which can significantly improve the productivity and buffer consumption compared to a classical single‐column, batch chromatographic process.

N-Rich is a twin-column continuous chromatography technology well suited for small-scale isolation and the enrichment of product related impurities. For the first time, N-Rich was used for impurity isolation from a double-stranded RNA (dsRNA) therapeutic synthetic oligonucleotide (ON), produced by solid-phase synthesis. By employing the N-Rich process, where the desired impurities are recycled and selectively enriched, and interfering substances are depleted, it was possible to obtain substantial amounts of high purity marginal impurities with a reproducible, automatized, and productive method. The productivity-purity tradeoff inherent to traditional impurity isolation methods, i.e., analytical chromatography, was effectively alleviated. Using N-Rich, satisfactory purity values and mass recoveries of several low-concentrated impurities could be obtained simultaneously. A performance comparison demonstrated an up to 15-fold increase for purity values and up to 20-fold mass impurity isolation and concentration with the N-Rich technology in comparison to conventional isolation procedures, drastically reducing processing times, manual handling, and waste production.

N-Rich is a twin-column chromatography process that enriches target compounds relative to other components in a mixture, thereby facilitating their isolation and characterization. This study demonstrates the performance of N-Rich for isolation of Angiotensin II peptide impurities compared with standard analytical and preparative chromatography approaches. Peptides have diverse chemical properties and are produced using a wide range of methods, resulting in products with complex impurity profiles. The characterization of impurities for clinical development is essential but obtaining high purity samples in sufficient quantities is often a difficult task when using standard chromatographic techniques. In contrast, by using cyclic continuous chromatography with UV-based process control, N-Rich enables automatic on-column accumulation of target impurities while other compounds in the mixture are depleted. This has multiple advantages compared to standard techniques. Firstly, at the end of the cyclic accumulation phase the highly enriched target is eluted in one step with high purity and concentration. This means fewer fractions for analysis are generated and up-concentration steps are reduced. Secondly, the purification of target impurities using semi-preparative scale chromatography becomes viable, even if initial resolution is poor compared to analytical HPLC. This allows for very significant increases in productivity for purification of difficult to isolate impurities. This study demonstrates two N-Rich strategies: Example 1: Purification of µg quantities of multiple Angiotensin II impurities with a >9-fold increase in productivity compared to analytical HPLC. Example 2: Specific isolation of 1 mg of a critical impurity at 88% purity. 79-fold increase in productivity and a 69-fold reduction in solvent consumption compared to analytical HPLC.