Mechanism-informed evaluation of particle formation in high-concentration monoclonal antibodies during fill-finish: Impact of pump materials, surface interactions, and system architecture.

Particle formation during fill-finish operations poses a critical risk to the quality and manufacturability of high-concentration monoclonal antibody drug products. This study systematically evaluates the influence of pump material, clearance tolerance, and flow-path architecture on subvisible and visible particle generation using a model IgG formulation. Controlled simulations compared peristaltic pumping with ceramic and stainless-steel rotary piston pumps under standstill and recirculation conditions, including a configuration incorporating a three-way valve and deliberate metal particulate spiking. Subvisible particle analysis revealed that particulate generation was dominated by surface-mediated mechanisms: stainless-steel components, tighter (5 µm) pump clearances, and increased flow-path complexity produced the highest particle levels, while ceramic RPPs with moderate clearance generated substantially fewer particulates and avoided pump seizure. Visible particles were observed only in the stainless-steel RPP system containing the three-way valve and metal spiking. Orthogonal characterization (FTIR, Raman, SEM-EDX) confirmed that particulates were primarily proteinaceous and frequently contained embedded metallic inclusions, in the deliberate particulate challenge configuration, consistent with heterogeneous nucleation at high-energy interfaces In contrast, DSC, DSF, MM-IR, DLS-derived kD, and wNMR analyses demonstrated unchanged thermal stability, secondary structure, and protein-protein interaction behavior across all conditions, with no measurable changes in bulk stability metrics across conditions. Mechanistically, the standstill-restart design and orthogonal particle characterization support a surface-mediated pathway in which proteins accumulate at high-energy interfaces during static holds and are subsequently detached under flow, with metal inclusions providing heterogeneous nucleation sites, while bulk IgG stability remains unchanged across conditions. The data support process-development strategies that underscore pump material of contact evaluations, avoid overly tight clearances, reduce recirculation, and simplify valve geometry. This mechanistic-informed framework provides practical guidance for designing robust, patient-centric fill-finish processes aligned with quality-by-design principles. While the study uses a single model IgG1, the observed surface-mediated trends align with broader literature on adsorption-induced particle formation at solid-liquid interfaces.