In the push to de-risk biologics manufacturing, downstream purification steps are increasingly under the microscope. Now, new research led by Jonathan Bones, PhD, principal investigator in the characterization and comparability group at the National Institute for Bioprocessing Research in Dublin, and his colleagues provided compelling evidence that ultrafiltration and diafiltration (UF/DF) deliver robust clearance of process-related leachables—while also offering a predictive framework to better understand that performance.
Although UF/DF has long been assumed to reduce small-molecule contaminants, systematic data have been scarce. To address this gap, the team evaluated 28 representative organic compounds spiked into three distinct protein systems. Using liquid chromatography–high resolution mass spectrometry, they tracked how effectively these compounds were removed during UF/DF operations.
The results were striking. Twenty-four of the compounds demonstrated greater than 98% clearance across all three protein processes. Notably, variations in protein characteristics and process parameters had minimal impact on removal efficiency. Instead, clearance behavior was remarkably consistent, as reflected in similar sieving coefficients across the systems.
The intrinsic physicochemical properties of the leachables impacted clearance. Among these, lipophilicity—expressed as the octanol-water partition coefficient (Log P)—emerged as the dominant factor. Compounds with Log P values below four exhibited near-ideal clearance, while even highly hydrophobic molecules (Log P above seven) still achieved removal rates exceeding 93%. Molecular weight, polarizability, and solvent-accessible surface area also contributed to clearance outcomes.
Beyond empirical findings, the study advances the field with predictive modeling. By applying orthogonal partial least squares (OPLS) regression, the researchers developed tools capable of estimating sieving coefficients based on compound properties. These models could prove invaluable for anticipating leachable behavior without exhaustive experimental testing.
The implications are significant. As regulatory scrutiny around extractables and leachables intensifies, demonstrating effective clearance becomes central to product safety. This work not only confirms that UF/DF is a powerful mitigation step but also equips developers with quantitative tools to support risk assessments.
In an industry where unseen contaminants can pose outsized risks, the ability to both measure and predict their removal marks a meaningful step forward.
