Novartis chromatography study shows downstream purification benefits

Research by Novartis has shown how membrane chromatography could enhance impurity removal in monoclonal antibody (mAb) purification, leading to safer biologics.

As host cell proteins and aggregates can be residual major impurities in biopharmaceutical purification processes, membrane-based chromatography and technologies could address this issue by boosting “productivity, improving flexibility, and delivering higher product quality and purity”, according to Šprager et al.

Their study involved an initial Design of Experiments (DoE) screening, residual esterase monitoring and a downstream processing sequence implementation study. Findings from the latter step indicated that the hybrid purifier used in the study could “effectively couple depth filtration and [anion exchange membrane] polishing steps, simplifying the purification process and increasing productivity”.

As the proposed approach is resource intensive and requires long incubation times to get the necessary readout, the team adapted a high-throughput esterase assay “based on fluorescent substrates of esterified fatty acids to monitor esterase activity”.

Šprager et al. compared impurity removal efficiency of three anion-exchange media types in a flow-through mode during a purification of a mAb product.

The media used were as follows:

• quaternary amine-functionalised agarose resin
• cellulose membrane adsorber
• hybrid purifier composed of two complementary anion-exchange media, a quaternary ammonium functional non-woven and a guanidinium functional polyamide membrane.

The team reported that as well as process step optimisation, “all three chromatographic media were included in the downstream purification train, allowing for a comprehensive evaluation of their impact on process intensification and product quality”.

“Several critical [host cell proteins] that can influence product stability or quality were identified and quantified with LC-MS/MS in [anion-exchange membrane] starting material.” Šprager et al. reported that the extent of aggregate entrapment varies by host cell protein type and may have a “major impact” on their persistence.

Additionally, the membrane-based devices exhibited high impurity removal capacity. For instance, the hybrid purifier showed an ability to lower host cell protein levels “from 8000 ppm down to as low as 10 ppm at competitive loading densities”.

While it is not a conventional anion exchange membrane adsorber, the hybrid purifier could provide an alternative to both traditional depth filtration and a flow-through anion exchanger, Šprager et al. said.

Anion-exchange chromatography alone was insufficient at clearing aggregates, so the researchers performed further orthogonal polishing. As such, they recommended combining several orthogonal host cell protein analytical tools to provide a more informed process development.

The study was published in Journal of Chromatography B.