Enrichment and purification of peptide impurities using twin-column continuous chromatography

 N-Rich is a twin-column chromatography process that enriches target compounds relative to other com- ponents 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 an- alytical 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 char- acterization of impurities for clinical development is essential but obtaining high purity samples in suf- ficient 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 resolu- tion 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 produc- tivity and a 69-fold reduction in solvent consumption compared to analytical HPLC.