Monoclonal antibodies (mAbs) and related products are one of the fastest-growing classes of therapeutics. More than 200 molecules have already been approved globally, including mAbs, antibody-drug conjugates (ADCs), bispecifics and fusion-proteins. This surge reflects both the clinical impact of biologics and the remarkable expansion in therapeutic modalities. Currently, several hundred candidates are in development across oncology, immunology, neurology, and other fields.
Driving this momentum are breakthroughs in antibody engineering technologies that have paved the way for numerous antibody formats with distinct mechanisms of action and pharmacological properties. Some of the key innovations in mAb engineering encompass Fc engineering to extend half-life or modulate immune effector functions, site‑specific conjugation techniques that power next‑generation ADCs, and innovative mAb architectures such as CrossMab, DuoBody, and Nanobodies®. Collectively, these novelties have introduced a higher degree of structural variability and functional complexity.
Proper characterization is therefore essential to define Critical Quality Attributes (CQAs). Defining these quality attributes guides safe, effective biologic development under Quality by Design principles.
This underscores the need for robust and comprehensive characterization studies to ensure therapeutic success in clinic. But how can clinical-grade reference drugs be leveraged as trusted benchmarks to better characterize therapeutic mAbs and accelerate early development?
Defining CQAs: Leveraging platform knowledge and clinical-grade reference drugs
Critical Quality Attributes (CQAs) encompass the physical, chemical, and biological properties of the molecule, which should be within a particular range to guarantee product consistency and clinical performance. They are central to ensuring the quality, safety, and efficacy of the therapeutic molecule or biosimilar. Establishing CQAs early creates the foundation for process optimization, regulatory alignment, and long-term therapeutic success.
Unlike small molecules, mAb-based biologics require extensive structural and functional characterization, assessingg post-translational modifications (PTMs), purity, specificity, potency, and toxicity in accordance with international regulatory standards, throughout all stages
If CQAs aren’t properly characterised, subtle yet critical quality attributes may be missed, leading to risks including reduced therapeutic potency, increased immunogenicity, unpredictable toxicity, and batch inconsistency.
This can potentially lead to delayed development timelines, costly repeat studies, regulatory non-compliance, and ultimately, compromised patient safety. In a competitive biologics market, this can mean failed programs and loss of commercial opportunity.
For CROs aiming to define CQAs with confidence, leveraging platform knowledge and benchmarking against approved therapeutics within the same molecular class (e.g., IgGs, bispecifics, or ADCs) is key.
By incorporating clinical-grade reference molecules into your workflows, development risk is reduced and the path to regulatory approval is accelerated.
How could integrating approved drug references help your analytical teams streamline characterization and boost project success?
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Establish benchmarks:
Clinical-grade reference molecules provide validated standards against which new candidates can be directly compared for establishing Quality Target Product Profile (QTPP). Scientists use these benchmarks to assess key molecular features like amino acid sequence, glycosylation patterns, charge variants, and aggregation profiles. This comparison ensures that candidate molecules meet proven quality levels associated with clinical safety and efficacy, reducing guesswork and accelerating development decisions.
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Development of analytical methods:
Reference drugs serve as high-quality controls in developing and validating analytical methods. Using well-characterized clinical molecules enables development of precise and sensitive assays to measure CQAs throughout development and manufacturing. This facilitates reliable characterization of critical structural and functional attributes with established clinical relevance, ensuring that analytical data are accurate and reproducible.
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Screen candidates:
During early development, candidate biosimilars or novel molecules are evaluated in head-to-head characterization studies against the reference molecule benchmarks. This comparative approach identifies structural or functional divergences that could impact product quality or clinical performance, informing prioritization and optimization to achieve similarity or desired quality therapeutic profiles.
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Ensure consistency:
By relying on clinical-grade reference materials rather than research-use-only substitutes, variability and uncertainty are minimized. This consistency is crucial for robust product development workflows, regulatory compliance, and ultimately delivering safe and effective biologics that conform closely to established quality expectations.
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Guide formulation development:
Reference molecules help formulation scientists in selecting the most appropriate formulation approach (lyophilization or liquid), excipient/buffer composition, and dosage form. Leveraging known formulation strategies from approved drugs accelerates early-stage development and supports formulation decisions aligned with the molecule’s critical quality profile.
Let’s explore the key dimensions of structural, functional, and purity characterization of mAbs, highlighting how clinical-grade reference drugs can be leveraged to strengthen these assessments and accelerate decision-making.
Structural and physiochemical characterization
Most therapeutic antibodies are derived from IgG1 due to its longer half-life, strong effector function, and structural uniformity (Figure 1).
However, recombinant production in live cells and subsequent exposure to culture media or storage can introduce heterogeneity. Therefore, various physio-chemical assays in accordance to ICH guideline Q6B are utilized to analyse the following mAb attributes.
Primary and higher order structures
Characterizing both the primary and higher-order structures is fundamental to understanding antibody integrity and function. Primary structure analysis confirms the amino acid sequence and molecular mass and detects potential sequence variants.
Peptide mapping of enzyme-digested protein is used to compare lots and identify subtle modifications. Higher-order structure analysis evaluates folding patterns such as α-helices, β-sheets, and random coils, as well as maps the disulfide bonds to assess structural and functional stability.
How can clinical-grade reference drugs help?
Using clinical‑grade reference molecules from approved biotherapeutics can be used as isotype controls and helps establish reliable baselines and validate analytical workflows with greater confidence.
Post-translational modifications (PTMs)
PTMs such as glycosylation, disulfide bond formation, proteolytic cleavage, oxidation, deamidation, and glycation, can arise during production, formulation, or storage and significantly influence stability, efficacy, and immunogenicity.
While some PTMs can be detected during peptide mapping, comprehensive characterization is essential to fully understand their impact on product quality and clinical performance.
How can clinical-grade reference drugs help?
Using clinical‑grade, approved-drug reference molecules as comparators, enable accurate PTM profiling and accelerating comparability studies for both novel biologics and biosimilars.
Aggregation and Process-Induced Heterogeneity
Antibody dimerization and aggregation can impact immunogenicity and alter biological function, while also complicating downstream manufacturing processes. Similarly, certain analytical procedures and downstream processes can introduce heterogeneity in charge, size, and PTMs such as N‑linked glycosylation, all of which may influence stability and effector functions.
How can clinical-grade reference drugs help?
Detecting and characterizing these variations is critical for ensuring product quality and consistency. Reference mAbs from approved therapeutics is an effective way to benchmark regulatory quality standards and support robust method validation.
Functional characterization of monoclonal antibodies
Evaluation of the functional attributes is critical to determine the safety, toxicity and efficacy of mAb products.
Functional characterization—conducted via systematic preclinical in vitro and in vivo studies—should be part of your early drug development, product release, and ongoing lifecycle management processes:
Ligand binding studies
Characterizing the antibody–antigen interaction is a primary quality requirement. Binding affinity, often represented by the equilibrium dissociation constant (KD), is measured under various conditions using in vitro ligand binding assays.
Epitope mapping of Fab further defines critical binding regions, supporting mechanism-of-action (MoA) studies and comparability assessments. Approved biologics targeting the same antigen serve as effective controls for determining binding affinity and epitope specificity.
Cell-based assays
Cell-based assays evaluate how binding events translate into functional outcomes, helping to establish the product’s mechanism of action (MoA) and potency. These assays measure downstream signalling responses, such as growth factor inhibition or apoptosis induction, using quantitative and qualitative bioassays. They also reveal how structural or chemical modifications can influence biological activity.
Regulatory approved mAbs or clinical grade mAbs are well-characterized for their MoAs and serve as valuable positive controls for benchmarking new candidates or biosimilars.
Assessment of effector functions
The MoA, safety, and efficacy of antibodies are closely linked to their interactions with Fc gamma receptors (FcγR). The Fc region influences serum half-life and effector functions, including antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and antibody-dependent cellular phagocytosis (ADCP).
These attributes are evaluated using functional bioassays with cell-based systems and are critical for both innovator and biosimilar development. Many approved biologics such as rituximab, trastuzumab, infliximab, obinutuzumab, and daratumumab, exert their therapeutic effects through effector functions and provide robust controls for comparative studies.
Characterizing purity and managing impurities
Beyond structural and functional characterization, ensuring purity and controlling contaminants are critical components of CQAs that directly impact patient safety, regulatory compliance, and overall product quality.
MAbs often exhibit structural heterogeneity due to modifications such as Cterminal lysine clipping, oxidation, deamidation, fragmentation, isomerization, disulfide mismatches, glycation, and variable glycosylation patterns.
These changes create a complex profile of molecular variants that must be accurately characterized. Analytical assessments typically include evaluation of molecular size and weight, charge variants, isoform distribution, and secondary or tertiary structural integrity.
In addition to product-related variants, controlling process- and product-related impurities such as microbial residues, endotoxins, and pro-inflammatory contaminants is vital. Analytical methods, including cell-based activation assays, enable detection of even trace non-endotoxin impurities, ensuring product safety and regulatory compliance. Clinical-grade reference molecules, derived from approved therapeutics, serve as high-quality benchmarks displaying established purity and extremely low endotoxin levels, providing valuable insight into acceptable impurity limits.
Enabling next-generation antibody development and characterization
As antibody-based drugs evolve into increasingly sophisticated designs and formats, the Precise and reliable characterization grows essential.
Meeting rising expectations demands Meeting rising expectations demands rigorous analysis of molecular, biophysical, biochemical, and immunological properties using well-characterized, reliable, clinical-grade reference products.
These have approved clinical-grade standards with well-characterized properties, ensuring consistency and confidence throughout development.
Specialized providers such as Evidentic make this possible by sourcing EU-licensed, clinical-grade biologics that serve as trusted standards, anchoring innovation to regulatory and clinical benchmarks.
References:
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- Woojeong Kim W, Kui Hyun Kang KH and Jung-Keun Suh JK. Characterization of Biopharmaceuticals Focusing on Antibody Therapeutics. Biopharmaceuticals, IntechOpen, Nov 5, 2018. DOI: 10.5772/intechopen.79107
- Goulet DR, Atkins WM. Considerations for the Design of Antibody-Based Therapeutics. J Pharm Sci. 2020;109(1):74-103. doi:10.1016/j.xphs.2019.05.031
- Natsume A, Niwa R, Satoh M. Improving effector functions of antibodies for cancer treatment: Enhancing ADCC and CDC. Drug Des Devel Ther. 2009;3:7-16. Published 2009 Sep 21.
- Martineau R, Susini S, Marabelle A. Fc Effector Function of Immune Checkpoint Blocking Antibodies in Oncology. Immunol Rev. 2024;328(1):334-349. doi:10.1111/imr.13427
- Guideline on Development, Production, Characterization and Specification for Monoclonal Antibodies and Related Products, Committee for Medicinal Products for Human Use, European Medicines Agency, July 2016. Accessed on 8 August 2025. Available online: https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-development-production-characterisation-specification-monoclonal-antibodies-related_en.pdf
