Analytical and bioanalytical assay challenges to support comparability studies for biosimilar drug development

Abstract

BioanalysisVol. 5, No. 5 EditorialFree AccessAnalytical and bioanalytical assay challenges to support comparability studies for biosimilar drug developmentXiao-Yan Cai, Ashleigh Wake & Dominique GoutyXiao-Yan Cai* Author for correspondenceDepartment of Biologics Bioanalytical at Merck, 1011 Morris Avenue Building U13–3 Union, NJ 07083, USA. Search for more papers by this authorEmail the corresponding author at xiao-yan.cai@merck.com, Ashleigh WakeIntertek Pharmaceutical, Hexagon Tower Services PO Box 42, Crumpsall Vale off Delauney’s Road, Blackley, Manchester M9 8ZS, UKSearch for more papers by this author & Dominique GoutyIntertek Pharmaceutical Services, 3985 Sorrento Valley Blvd. Suite C, San Diego, CA 92121, USASearch for more papers by this authorPublished Online:20 Feb 2013https://doi.org/10.4155/bio.13.1AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinkedInRedditEmail Keywords: analyticalbioanalyticalbiologicsbiopharmaceuticalsbiosimilarscomparability studiesBiopharmaceutical products (biologics) are active drug substances produced by living cells or derived from a living organism (bacteria, yeast, animal or human cell lines). Biosimilars, or follow-on biologics, are the subsequent versions of originator biopharmaceutical products following expiry of its patent and exclusivity [1]. Biosimilars are also referred to as subsequent entry biologics in Canada [2]. While the market for biosimilars is growing, few have been approved. Reports show that the world biosimilar market is expected to reach annual growth rates in excess of 50% between 2010 and 2015 [3]. This increase is, in some part, driven by the Asian market (one-third of the market) and also due to the strong global push for more affordable healthcare. In the USA, to improve access, Congress passed the biologics Price Competition and Innovation Act of 2009, authorizing the US FDA to oversee an ‘abbreviated pathway’ for approval of biologics that are ‘biosimilar’ to already-approved products [101].Biosimilars present challenges compared with the conventional generic drugs (i.e., chemical or small-molecule drugs whose patent has expired). Unlike small-molecule drugs, biologics exhibit a high level of complexity. The complex 3D structure of biologic products is largely determined by the production process (choice of the cell type, production, fermentation, purification, formulation, storage and packaging). Consequently, seemingly minor variations in these processes can induce much larger variability in macromolecular structure (and thus potency) of biologic drugs than would be seen for conventional drugs. Small changes in these processes can significantly and critically affect, for example, impurity levels or the extent of aggregation and post-translational modification, which can lead to serious safety implications such as loss of efficacy, undesirable immunogenic responses (immunogenicity) and other adverse events.So, demonstrating that a biosimilar is ‘similar’ to its originator is not trivial. One of the most frequently asked questions is ‘how similar is similar?’ The European Medicines Agency as well as the FDA have recognized that a biosimilar might perform differently than the original branded version of the product [4], and in response have published a large number of regulatory guidance documents [102,103]. It must be demonstrated that any differences observed during the physiochemical characterization of the biosimilar candidate do not result in meaningful biological or clinical differences in the performance of the candidate to ensure safety and efficacy.Even though very few biosimilars have been approved on the market, analytical studies show a large heterogeneity of biosimilars (e.g., chemical and molecular structure, and efficacy) produced in different countries. For example, the recombinant human erythropoietin, a glycoprotein composed of 165 amino acids used for the treatment of anemia associated with chronic kidney disease and cancer therapy, exhibited different levels of variability in structure, composition, concentration and activity in products marketed in different countries [5–7]. In addition, those analytical studies failed to demonstrate comparability of the biosimilar to the originator (i.e., each biosimilar product differed in composition and none consistently met the specifications). Clinical studies were also unable to prove equivalent safety and efficacy of the biosimilar products to the recombinant human erythropoietin originator.Therefore, in order to conduct meaningful preclinical and clinical comparability studies, it is critical to establish analytical and bioanalytical equivalency between biosimilars and originators.Analytical challenges in demonstrating biosimilarityAssessment and comparison of physiochemical and structural features of a biologic in order to demonstrate biosimilarity presents many unique challenges. As directed in recent European Medicines Agency draft guidelines, “extensive state-of-the art characterization studies need to be applied to the biosimilar and reference medicinal product (originator) in parallel, to demonstrate with a high level of assurance that the quality of the biosimilar is comparable to the reference medicinal product”[8].Similar draft guidelines issued by the FDA in 2012 describe that studies are therefore designed to establish criteria that define, “a product’s identity, quantity, purity, potency and consistency” and to compare these between the originator and biosimilar [103].ICH guidelines, specifically ICH Q5E [9] and Q6B [10] give more defined guidance on those physiochemical and structural features that could be considered pertinent in the assessment of comparability as presented below: ▪ Amino acid sequence;▪ Amino acid composition;▪ Terminal amino acid sequence;▪ Peptide map;▪ Sulfhydryl groups and disulfide bridges;▪ Carbohydrate structure;▪ Molecular weight;▪ Isoform pattern;▪ Extinction coefficient;▪ Electrophoretic pattern;▪ Liquid chromatographic patterns;▪ Spectroscopic patterns.However, it remains the responsibility of the biosimilar producers to evaluate the scope and relevance of any characterization studies to conduct, to ensure that the chosen package is suitable not only for defining comparability, but also for detecting minor differences in all aspects pertinent to the evaluation of quality, should they exist. In addition to physiochemical and structural elucidation, the evaluation should also include assessment and quantification of both product- and process-related impurities.One of the fundamental challenges in designing experiments to establish physiochemical and structural comparability of the biosimilar is that some degree of heterogeneity in its physiochemical nature is inevitable, and equivalent differences are likely to be inherent in the originator itself. While historic information on the physiochemical properties of an originator material, if freely available, can be used, it is a fundamental and a regulatory requirement that all biosimilarity studies include the concurrent analysis of multiple aged batches of originator material. This can be the first challenge in sourcing the appropriate batches to provide a representative sample group. It is only on determination of the variability within the originator product that a target quality profile can be defined, and significance placed on variability observed between originator and biosimilar.The originator material will likely only be available in the form of the final product (low concentration and highly formulated) and differences in biosimilar and originator formulation are permitted [8]. Analytical techniques used to assess physiochemical properties, such as MS, are highly influenced by concentration and sample matrix. Isolation of the active material(s) from the originator formulation(s) via extraction is therefore required, which could potentially induce a change in physiochemical or structural properties of the material and, hence, influence comparability.Characterization, therefore, relies on the application of a vast array of analytical techniques (e.g., chromatography, MS, electrophoresis and spectroscopy) to generate the requisite level of structural information. Latest advances in analytical instrumentation have enabled comprehensive characterization, but have also introduced additional challenges in comparability measurement for comparing with historic data and expectation of result. While these issues extend the complexity of the process to assess comparability, the need to demonstrate the similarity (or highlight any difference) in physiochemical and structural features remains fundamental for biosimilar registration.In addition to comparing the physiochemical and structural features of the drug substance, consideration must also be given to assessing and comparing levels of product- or process-related impurities, including extractables and leachables. The latter category being of particular relevance given the permitted differences in container/closure systems; the potential impact of which on the safety and efficacy should be appropriately justified [8].Even when ‘comparable variability’ is accepted, assessment of the consequences of the differences on product efficacy and safety, through appropriate preclinical and clinical studies, must be conducted.Bioanalytical challenges in demonstrating biosimilarityDemonstration of comparability is not based solely on physiochemical characterization. Similarity must also be demonstrated through preclinical and clinical comparability studies.Therefore, it is critical to establish both PK and immunogenicity assays in such a way that they can quantify and/or detect both biosimilar and originator analytes ‘equivalently’ in biological matrices. There are substantial regulatory guidance documents from both the European Medicines Agency and the FDA on biosimilar drug development [102,103], as well as regulatory guidance and extensive publications on PK and immunogenicity immunoassay validation for biologics in general [11–14]. Only very few publications, however, attempt to address the specific challenges in developing and validating bioanalytical assays, that is, PK, antidrug antibodies (ADAs) and neutralizing ADA assays, used to support preclinical and clinical comparability studies for biosimilar drug development [15,16].▪ PK assayThe consensus within the industry for developing PK assays for biosimilar programs is that one assay should be applied to quantify both biosimilar and originator analytes in biological matrices [15,17]. One of the most challenging aspects of developing such assays is to demonstrate ‘equivalency’ between the biosimilar compound and the originator using the assay platform of choice. Cai et al. recommended the use of one standard curve (either biosimilar or originator) during validation to quantify both sets of QCs in, at least, accuracy and precision tests, and also, preferably, in the selectivity testing [15]. Establishing assay acceptance criteria to demonstrate ‘equivalency’ is not trivial. The potential quantification bias between biosimilar and originator compounds must be minimized. For example, even if both sets of QCs meet the general accuracy criteria of within 20% relative error (RE), if the biosimilar QC shows -19% RE, whereas originator shows +19% RE, the difference between the two is much larger than optimal. The evaluation of ‘equivalency’ should occur during the assay development stage. Statistical evaluations may be necessary to assess how ‘equivalent’ the two compounds are in the testing matrices.▪ Immunogenicity assayIn contrast with the industry consensus for the biosimilar PK assays, the opinions on biosimilar immunogenicity assays are divided into ‘one-assay’ (one set of labeled drug reagent is used to detect both biosimilar and originator ADAs) versus ‘two-assays’ (each set of labeled drug reagent is used to detect its respective ADA) [16,17]. Since immunogenicity assays are not quantitative assays, attempting to demonstrate ‘equivalency’ using qualitative assays presents additional challenges. When the ‘two-assays’ strategy is deployed, assay characteristics such as assay cut point and confirmatory cut point could be different for each assay. This could make the interpretation of data from future studies very challenging. A concern with using the ‘one-assay’ approach is that the one set of labeled drug reagent (e.g., labeled biosimilar drug) may not be able to fully detect the other ADA (in this case, the originator ADA). This approach is, however, the most conservative since it allows for optimum detection of biosimilar ADAs. If the biosimilar arm of the comparability study shows equal or less immunogenicity than the originator arm, the regulatory requirement for the biosimilar drug to be equal, or less, immunogenic than the originator would be met. The biggest advantage of using the ‘one-assay’ approach is that it does not have the ‘between-assay’ variability introduced by the ‘two-assay’ approach [16].Assessing ‘equivalency’ between biosimilar and originator ADA-positive controls for assay sensitivity and drug tolerance presents another challenge since these positive controls are often polyclonal antibodies generated by hyperimmunizing animals, which can be different. Furthermore, these assays are qualitative assays and, therefore, more variable (especially at assay detection limit, i.e., LOD). Sensitivity within two- to three-fold of each other is generally considered ‘equivalent’ for these nonquantitative assays [16].ConclusionTo achieve regulatory approval of biosimilar drugs, ‘biosimilarity’ must be demonstrated between the physiochemical properties of biosimilar and originator batches. In addition, to ensure safety and efficacy of a biosimilar in comparison with its originator drug, preclinical and clinical comparability studies must be conducted according to the regulatory guidance from both the European Medicines Agency and the FDA. Consequently, developing and validating analytical and bioanalytical methods to support these requirements is essential. Moreover, when addressing the usual industry analytical and bioanalytical assay acceptance criteria, specific considerations must also be taken into account when assessing ‘equivalency’ between biosimilar and originator compounds in these assays. This will allow for meaningful interpretation of comparability study data for biosimilar drug development, not only to ensure safety and efficacy, but also to allow for drug substitution and exchangeability.Financial & competing interests disclosureThe authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.References1 Nick C. 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This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.PDF download