Uncovering the Critical Need for Particle Testing in Developability Assessment for mAb Drug Candidates

December 5, 2023

In the always-evolving landscape of the pharmaceutical industry, the task of identifying and evaluating potential risks associated with drug discovery candidates remains a constant challenge. This process has been further complicated by biological therapeutics, particularly monoclonal antibodies (mAbs).

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The early assessment for drug-like properties (DLP) has become increasingly important, as it can reduce time and cost by providing a comprehensive understanding of potential issues that may affect a final product’s stability.1

mAbs have made a significant impact in the therapeutic landscape with their successful development for a range of indications, including oncology, autoimmune disorders and infectious diseases. Thanks to dedicated R&D efforts, we now understand that certain molecular properties of mAbs can lead to poor physical stability, such as low solubility and high viscosity. Moreover, poor chemical stability has been widely documented. These risks may make some mAbs unsuitable for standard manufacturing processes, requiring additional formulation development and thus increasing cost and timeline. 1

Given the impact of intrinsic molecular properties on Chemistry, Manufacturing, and Controls (CMC) development, it is not surprising that protein engineering solutions are being actively explored to mitigate these risks and stabilize known degradation pathways. However, most drug developers perform developability assessments by screening for DLPs, which then become part of their final candidate selection criteria. Consequently, DLP assessment, which involves studying the structural, physical, chemical, and biological properties of protein molecules, remains an area of active research. 1

As a potential model to readily adapt for DLP assessments of other complex proteins, researchers conducted a study in which four IgG1 mAbs with sequence variations in the variable domain region were screened as potential drug candidates. Selected from a larger pool based on prior evaluations, all four mAb candidates were directed against the same therapeutic target. 1

The study utilized a comprehensive, tiered approach using a series of analytical tools to assess molecular characteristics, conformational stability, colloidal stability, and short-term storage stability. While most DLPs for the four candidates were deemed acceptable, mAb-2 exhibited adverse colloidal properties, indicating the need for additional product development effort. Further investigation of mAb-2 in an expanded pH range revealed a propensity for phase separation, signifying an increased development risk. 1

Importance of Subvisible Particle Assessment

Due to limited sample availability, an assessment of subvisible particulates could not be performed, and an accurate assessment of phase separation and visible particles was not feasible at the evaluated concentration. Despite these constraints, no adverse trends of aggregation and submicron particles were observed. 1

However, the lack of accurate assessment of subvisible and visible particle counts, particularly for mAb-2, was identified as a potential testing gap. 1 The team of researchers also concluded that with new technologies such as Halo Labs’ Backgrounded Membrane Imaging (BMI), a quantitative assessment of sub-visible particle counts with small sample volumes is now feasible and recommended for comprehensive physical stability assessment. 1

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BMI brings clarity to formulation risks that were previously hard to see, breaking through traditional limits quickly and accurately. With the ability to test 96 samples in less than two hours, it’s a valuable tool for drug development.


The case study results demonstrate that the DLP assessment approach works well for traditional mAbs, supporting its use for early comprehensive screening, particularly for colloidal stability. This adaptable approach may prove particularly useful in developing increasingly complex antibody constructs. In addition, this study also showed that the critical need for subvisible particle assessment can be answered in the innovative technologies being developed, including Halo Labs’ Backgrounded Membrane Imaging exclusively on Aura® systems.