This guidance describes the Agency’s current thinking on factors to consider when demonstrating that a proposed therapeutic protein product (hereinafter proposed product or proposed biosimilar product) is highly similar to a reference product licensed under section 351(a) of the Public Health Service Act (PHS Act) for the purpose of submitting a marketing application under section 351(k) of the PHS Act. Specifically, this guidance is intended to provide recommendations to sponsors on the scientific and technical information for the chemistry, manufacturing, and controls (CMC) section of a marketing application for a proposed product submitted under section 351(k) of the PHS Act.
The Biologics Price Competition and Innovation Act of 2009 (BPCI Act) amends the PHS Act and other statutes to create an abbreviated licensure pathway in section 351(k) of the PHS Act for biological products shown to be biosimilar to or interchangeable with an FDA-licensed biological reference product (see sections 7001 through 7003 of the Patient Protection and Affordable Care Act (Affordable Care Act) (Public Law 111-148). The BPCI Act also amended the definition of biological products to include “protein (except any chemically synthesized polypeptide).” A 351(k) application for a proposed biosimilar product must include information demonstrating biosimilarity, based on data derived from, among other things, “analytical studies that demonstrate that the biological product is highly similar to the reference product notwithstanding minor differences in clinically inactive components.”
Although the 351(k) pathway applies generally to biological products, this guidance focuses on therapeutic protein products and provides an overview of analytical factors to consider in demonstrating biosimilarity between a proposed product and the reference product.
本指南是为了指导申请人对拟申请的治疗性蛋白制品（后文称“拟申请产品”）根据《公共健康服务法（PHS法案）》351（K）部分要求提交上市许可申请时，如何证明其与参比制剂的生物相似性。《生物制品价格竞争和创新法案2009》（BPCI Act）修订了PHS法案和其他相关规定，为拟申请生物制品在PHS Act 351（K）要求下证明与已获批参比制剂的生物相似性或可替代性提供了一个简化申请路径（详见《患者保护和可支付医疗法案》7001-7003部分）。虽然351（K）路径普遍适用于生物制品，本指南重点关注治疗性蛋白制品，并概括了这些制品在生物相似性论证过程中的注意事项。本指南中描述的科学原则也可用于其他类型的生物类似药。
This guidance is one in a series of guidances that FDA is developing to implement the BPCI Act. These guidances address a broad range of issues, including:
• Quality Considerations in Demonstrating Biosimilarity of a Therapeutic Protein Product to a Reference Product
• Scientific Considerations in Demonstrating Biosimilarity to a Reference Product
• Biosimilars: Questions and Answers Regarding Implementation of the Biologics Price Competition and Innovation Act of 2009
• Formal Meetings Between the FDA and Biosimilar Biological Product Sponsors or Applicants
• Clinical Pharmacology Data to Support a Demonstration of Biosimilarity to a Reference Product本指南是FDA为了实施BPCI Act所发布的指南之一，这些指南涉及多方面的问题，主要包括：
In general, FDA’s guidance documents do not establish legally enforceable responsibilities. Instead, guidances describe the Agency’s current thinking on a topic and should be viewed only as recommendations, unless specific regulatory or statutory requirements are cited. The use of the word should in Agency guidances means that something is suggested or recommended, but not required.
This guidance gives an overview of FDA’s approach to determining biosimilarity and discusses important scientific considerations in demonstrating biosimilarity, including:
• A stepwise approach to demonstrating biosimilarity, which can include a comparison of the proposed product and the reference product with respect to structure, function, animal toxicity, human pharmacokinetics (PK) and pharmacodynamics (PD), clinical immunogenicity, and clinical safety and effectiveness
• The totality-of-the-evidence approach that FDA will use to review applications for biosimilar products, consistent with a longstanding Agency approach to evaluation of scientific evidence
• General scientific principles in conducting comparative structural analyses, functional assays, animal testing, human PK and PD studies, clinical immunogenicity assessments, and comparative clinical studies (including clinical study design issues).
Additional topics discussed include the following:
• Considerations of the complexities of therapeutic protein products when designing a biosimilar development program, including manufacturing process considerations
• Use of data derived from studies comparing a proposed product with a non-U.S.- licensed comparator product
• Postmarketing safety monitoring considerations
This guidance applies to applications submitted under section 351(k) of the PHS Act. However, some scientific principles described in this guidance may be informative for the development of certain biological products under section 505(b)(2) of the FD&C Act.Section 505(b)(2) of the FD&C Act and section 351(k) of the PHS Act are two separate statutory schemes. This guidance is not intended to describe any relationship between the standards for approval under these schemes.
本指南适用于依据PHS Act351（K）提交的申请。但是，本指南中的一些科学原则也适用FD&C Act 505(b)(2)中某些生物制品的开发。FD&C Act505(b)(2)与PHS Act 351(K)是相互独立的阶段，本指南不对两者审批标准的关系进行说明。
The BPCI Act was enacted as part of the Affordable Care Act on March 23, 2010. The BPCI Act creates an abbreviated licensure pathway for biological products demonstrated to be biosimilar to or interchangeable with a reference product. Section 351(k) of the PHS Act (42 U.S.C. 262(k)), added by the BPCI Act, sets forth the requirements for an application for a proposed biosimilar product and an application or a supplement for a proposed interchangeable product. Section 351(i) of the PHS Act defines biosimilarity to mean “that the biological product is highly similar to the reference product notwithstanding minor differences in clinically inactive components” and that “there are no clinically meaningful differences between the biological product and the reference product in terms of the safety, purity, and potency of the product.”The BPCI Act also amended the definition of biological product to include “protein (except any chemically synthesized polypeptide).”
BPCI Act是2010年3月23日颁布的《可支付医疗法案》的一部分。BPCI Act为那些已证明与参比制剂具有生物相似性或可替代性的生物制品提供了简化申请路径。PHS Act中351(K)(42u.s.c.262(K)部分补充了BPCI Act对生物类似药申请的相关规定。PHS Act的351(i)定义“生物相似性”为：“一种生物制品和参比制剂高度相似，尽管非活性成分存在微小差异”，且“两者在安全性、纯度和产品效价（有效性）上不存在临床意义上的差异”。此外，BPCI Act还修定了生物制品的定义，包括蛋白制品，但不包括化学合成多肽。
Under section 351(k) of the PHS Act, a proposed biological product that is demonstrated to be biosimilar to a reference product can rely on certain existing scientific knowledge about the safety, purity, and potency of the reference product to support licensure. FDA will license a proposed biological product submitted under section 351(k) of the PHS Act if FDA “determines that the information submitted in the application is sufficient to show that the biological product is biosimilar to the reference product” and the 351(k) applicant (or other appropriate person) consents to an inspection of the facility that is the subject of the application (i.e., a facility in which the proposed biological product is manufactured, processed, packed, or held).
An application submitted under section 351(k) of the PHS Act must contain, among other things, information demonstrating that “the biological product is biosimilar to a reference product” based upon data derived from:
• Analytical studies that demonstrate that the biological product is highly similar to the reference product notwithstanding minor differences in clinically inactive components;
• Animal studies (including the assessment of toxicity); and
• A clinical study or studies (including the assessment of immunogenicity and pharmacokinetics or pharmacodynamics) that are sufficient to demonstrate safety, purity, and potency in one or more appropriate conditions of use for which the reference product is licensed and intended to be used and for which licensure is sought for the biological product.
The Agency has the discretion to determine that an element described above is unnecessary in a 351(k) application. FDA advises sponsors intending to develop biosimilar products to meet with FDA to present their product development plans and establish a schedule of milestones that will serve as landmarks for future discussions with the Agency. FDA anticipates that early discussions with FDA about product development plans and about approaches to providing adequate scientific justifications will facilitate biosimilar development.
A sponsor should consider the complexities of protein products and related scientific issues when designing a development program to support a demonstration of biosimilarity.
A．Nature of Protein Products and Relates Scientific Considerations
Unlike small molecule drugs, whose structure can usually be completely defined and entirely reproduced, proteins are typically more complex and are unlikely to be shown to be structurally identical to a reference product. Many potential differences in protein structure can arise. Because even minor structural differences (including certain changes in glycosylation patterns) can significantly affect a protein’s safety and/or effectiveness, it is important to evaluate these differences.
In general, proteins can differ in at least three ways:
(1) primary amino acid sequence;
(2) modification to amino acids, such as sugar moieties (glycosylation) or other side chains; and
(3) higher order structure (protein folding and protein-protein interactions).
Modifications to amino acids may lead to heterogeneity and can be difficult to control. Protein modifications and higher order structure can be affected by formulation and environmental conditions, including light, temperature, moisture, packaging materials, container closure systems, and delivery device materials. Additionally, process- as well as product-related impurities may increase the likelihood and/or the severity of an immune response to a protein product, and certain excipients may limit the ability to characterize the protein product.
Advances in analytical sciences enable some protein products to be extensively characterized with respect to their physicochemical and biological properties, such as higher order structures and functional characteristics. These analytical methodologies have increasingly improved the ability to identify and characterize not only the drug substance of a protein product but also excipients and product- and process-related impurities.
Despite such significant improvements in analytical techniques, however, current analytical methodology may not be able to detect all relevant structural and functional differences between two protein products. In addition, there may be incomplete understanding of the relationship between a product’s structural attributes and its clinical performance. Thus, as set forth in the PHS Act, data derived from analytical studies, animal studies, and a clinical study or studies are required to demonstrate biosimilarity unless FDA determines an element unnecessary.
B．Manufactring Process Considerations 生产工艺的考虑
Different manufacturing processes may alter a protein product in a way that could affect the safety or effectiveness of the product. For example, differences in biological systems used to manufacture a protein product may cause different posttranslational modifications, which in turn may affect the safety and/or effectiveness of the product. Thus, when the manufacturing process for a marketed protein product is changed, the application holder must assess the effects of the change and demonstrate—through appropriate analytical testing, functional assays, and/or in some cases animal and/or clinical studies—that the change does not have an adverse effect on the identity, strength, quality, purity, or potency of the product as they relate to the safety or effectiveness of the product. The International Conference on Harmonisation (ICH) guidance for industry Q5E Comparability of Biotechnological/Biological Products Subject to Changes in Their Manufacturing Process (ICH Q5E) describes scientific principles in the comparability assessment for manufacturing changes.
Demonstrating that a proposed product is biosimilar to a reference product typically will be more complex than assessing the comparability of a product before and after manufacturing changes made by the same manufacturer. This is because a manufacturer that modifies its own manufacturing process has extensive knowledge and information about the product and the existing process, including established controls and acceptance parameters. By contrast, the manufacturer of a proposed product is likely to have a different manufacturing process (e.g., different cell line, raw materials, equipment, processes, process controls, and acceptance criteria) from that of the reference product and no direct knowledge of the manufacturing process for the reference product. Therefore, even though some of the scientific principles described in ICH Q5E may also apply in the demonstration of biosimilarity, in general, FDA anticipates that more data and information will be needed to establish biosimilarity than would be needed to establish that a manufacturer’s post-manufacturing change product is comparable to the pre-manufacturing change product.
To obtain licensure of a proposed product under section 351(k) of the PHS Act, a sponsor must demonstrate that the proposed product is biosimilar to a single reference product that previously has been licensed by FDA. In general, a sponsor needs to provide information to demonstrate biosimilarity based on data directly comparing the proposed product with the reference product. As a scientific matter, analytical studies and at least one clinical PK study and, if appropriate, at least one PD study, intended to support a demonstration of biosimilarity for purposes of section 351(k) of the PHS Act must include an adequate comparison of the proposed biosimilar product directly with the U.S.-licensed reference product unless it can be scientifically justified that such a study is not needed. However, a sponsor may seek to use data derived from animal or clinical studies comparing a proposed product with a non-U.S.-licensed comparator product to address, in part, the requirements under section 351(k)(2)(A) of the PHS Act. In such a case, the sponsor should provide adequate data or information to scientifically justify the relevance of these comparative data to an assessment of biosimilarity and establish an acceptable bridge to the U.S.- licensed reference product.17 Sponsors are encouraged to discuss with FDA during the development program their plans to provide an adequate scientific justification and bridge to the U.S.-licensed reference product. A final decision about the adequacy of such justification and bridge will be made by FDA during review of the 351(k) application.
为获得PHS Act351(k)项下的生物制品许可证，申请人必须证实生物类似药和一个已经获得FDA 批准的产品的生物相似性。通常情况下，申请人需要提供两者生物相似性的直接对比数据。包括通过分析研究、至少一个临床药代动力学研究和药效学研究等充分的对比研究，除非通过科学论证某一项研究可免。然而，某些情况下，申请人可以通过与非美国批准的参比制剂的动物或临床研究对比来论证PHS Act 351(k)(2)(A)的部分要求。这种情况下，申请人必须提供足够的数据信息来论证这些可比性数据与生物相似性评价的相关性，并且和美国获批产品建立适当桥接。FDA鼓励申请者在项目开发的过程中主动沟通讨论，最终，FDA将在351(K)申请审评时会对信息是否充足做出决定。
FDA recommends that sponsors use a stepwise approach to develop the evidence needed to demonstrate biosimilarity. FDA intends to consider the totality of the evidence provided by a sponsor when the Agency evaluates the sponsor’s demonstration of biosimilarity, consistent with a longstanding Agency approach to evaluating scientific evidence.
FDA 建议申请人采用阶梯式方法来收集证据论证生物相似性。FDA 将整体衡量申请者证明生物相似性的所有证据，这和一直以来用以评价科学证据的方法一致。
A.Using a Stepwise Approach to Demonstrate Biosimilarity 阶梯式方法论证生物相似性
The purpose of a biosimilar development program is to support a demonstration of biosimilarity between a proposed product and a reference product, including an assessment of the effects of any observed differences between the products, but not to independently establish the safety and effectiveness of the proposed product. FDA recommends that sponsors use a stepwise approach to developing the data and information needed to support a demonstration of biosimilarity. At each step, the sponsor should evaluate the extent to which there is residual uncertainty about the biosimilarity of the proposed product and identify next steps to try to address that uncertainty. Where possible, studies conducted should be designed to maximize their contribution to demonstrating biosimilarity. For example, a clinical immunogenicity study may also provide other useful information about the safety profile of the proposed product.
The stepwise approach should start with extensive structural and functional characterization of both the proposed product and the reference product, which serves as the foundation of a biosimilar development program (sections VII.A and VII.B). The more comprehensive and robust the comparative structural and functional characterization—the extent to which these studies are able to identify (qualitatively or quantitatively) differences in relevant product attributes between the proposed product and the reference product (including the drug substance, excipients, and impurities)—the more useful such characterization will be in determining what additional studies may be needed. For example, rigorous structural and functional comparisons that show minimal or no difference between the proposed product and the reference product will strengthen the scientific justification for a selective and targeted approach to animal and/or clinical testing to support a demonstration of biosimilarity. It may be useful to further quantify the similarity or differences between the two products using a meaningful fingerprint-like analyses algorithm that covers a large number of additional product attributes and their combinations with high sensitivity using orthogonal methods. Such a strategy may further reduce the possibility of undetected structural differences between the products and lead to a more selective and targeted approach to animal and/or clinical testing. A sufficient understanding of the mechanism of action (MOA) of the drug substance and clinical relevance of any observed structural differences, clinical knowledge of the reference product and its class that indicates low overall safety risks, and the availability of a relevant PD measure(s) may provide further scientific justification for a selective and targeted approach to animal and/or clinical studies.
这种阶梯式方法应基于对类似药和参比制剂全面的结构和功能表征信息，这也是相似性研究的基础( VII.A 和VII.B)。这些结构和功能特性的比较越全面彻底，包括药物成分、辅料和杂质是定量或定性比较研究，对确定下一步具体研究越有利。例如，如果有严格的结构和功能比较表明类似药和参比制剂没有或者仅有很小的差异，越能说明为什么采用一个选择性和目标性的动物或临床试验来证明相似性。也可以利用指纹图谱分析方法（利用正交法能覆盖到大部分产品性质及之间的关系），进一步对这相似性或差异进行定量分析。这种方法能进一步降低检测不到产品间差异存在的可能性，从而使下一步动物或临床试验的选择更有目的性。为了证明选择该试验的合理性，还要对活性成分作用机制、结构差异导致的临床反应、参比制剂的临床信息及其产品类别表明的低风险性、动物或临床相关PD研究方法及数据等进行全面的了解。
The sponsor should then consider the role of animal data in assessing toxicity and, in some cases, in providing additional support for demonstrating biosimilarity and in contributing to the immunogenicity assessment (section VII.C). The sponsor should then conduct comparative human PK and PD studies (if there is a relevant PD measure(s)) (section VII.D.1) and compare the clinical immunogenicity of the two products in an appropriate study population (section VII.D.2). If there is residual uncertainty about biosimilarity after conducting structural analyses, functional assays, animal testing, human PK and PD studies, and the clinical immunogenicity assessment, the sponsor should then consider what additional clinical data may be needed to adequately address that uncertainty (section VII.D.3). FDA encourages sponsors to consult extensively with the Agency after completion of comparative structural and functional analyses (before finalizing the clinical program) and throughout development as needed.
申请人要考虑动物试验数据在毒理学研究和某些情况下证明生物相似性的和免疫原性研究当中的重要性（详见VII.C部分），然后在合适的试验人群中进行类似药和参比制剂的人体PK/PD的可比性研究(VII.D.1部分)和临床免疫性的比较研究( VII.D.2部分)。若在结构分析、功能测定、动物试验、人体PK/PD试验后还不能完全确定其生物相似性，则需提供更充分的临床安全数据(VII.D.3部分)。FDA 建议，结构和功能比较分析完成之后（临床试验完成前）或研究过程如有需要，申请者应当和审批机构进行广泛的沟通讨论。
FDA recognizes that some of the aforementioned investigations could be performed in parallel; however, the Agency recommends that sponsors use a stepwise approach to better address residual uncertainty about biosimilarity that might remain at each step and incorporate FDA’s advice provided after FDA review of data and information collected at certain milestones.
B.Using a Totality-of-the-Evidence Approach to Assess a Demonstration of Biosimilarity 采用证据整体法评价生物相似性论证过程
In evaluating a sponsor’s demonstration of biosimilarity, FDA will consider the totality of the data and information submitted in the application, including structural and functional characterization, nonclinical evaluation, human PK and PD data, clinical immunogenicity data, and comparative clinical study(ies) data. FDA intends to use a risk-based approach to evaluate all available data and information submitted in support of the biosimilarity of the proposed product.
Thus, a sponsor may be able to demonstrate biosimilarity even though there are formulation or minor structural differences, provided that the sponsor provides sufficient data and information demonstrating that the differences are not clinically meaningful and the proposed product otherwise meets the statutory criteria for biosimilarity. For example, differences in certain posttranslational modifications or differences in certain excipients (e.g., human serum albumin) might not preclude a finding of biosimilarity if data and information provided by the sponsor show that the proposed product is highly similar to the reference product notwithstanding minor differences in clinically inactive components and that there are no clinically meaningful differences between the products in terms of safety, purity, and potency. Clinically meaningful differences could include a difference in the expected range of safety, purity, or potency of the proposed product and the reference product. By contrast, slight differences in rates of occurrence of certain adverse events between the two products ordinarily would not be considered clinically meaningful differences.
This section discusses scientific considerations in the stepwise approach to developing data and information needed to support a demonstration of biosimilarity. To demonstrate biosimilarity, a sponsor must provide sufficient data and information to show that the proposed product and the reference product are highly similar notwithstanding minor differences in clinically inactive components and that there are no clinically meaningful differences between the two products in terms of safety, purity, and potency. The type and amount of analyses and testing that will be sufficient to demonstrate biosimilarity will be determined on a product-specific basis.
The PHS Act requires that a 351(k) application include information demonstrating biosimilarity based on data derived from, among other things, analytical studies that demonstrate that the biological product is highly similar to the reference product notwithstanding minor differences in clinically inactive components, unless FDA determines that an element is unnecessary in a 351(k) application. FDA expects that first, a sponsor will extensively characterize the proposed product and the reference product with state-of-the-art technology, because extensive characterization of both products serves as the foundation for a demonstration of biosimilarity. It is expected that the expression construct for a proposed product will encode the same primary amino acid sequence as its reference product. However, minor modifications such as N- or Cterminal truncations that are not expected to change the product performance may be justified and should be explained by the sponsor. Additionally, sponsors should consider all relevant characteristics of the protein product (e.g., the primary, secondary, tertiary, and quaternary structure; posttranslational modifications; and biological activities) to demonstrate that the proposed product is highly similar to the reference product notwithstanding minor differences in clinically inactive components. The more comprehensive and robust the comparative structural and functional characterization is, the stronger the scientific justification for a selective and targeted approach to animal and/or clinical testing.
除非FDA认为不需要，PHS Act要求 351(k) 申请提交的证明生物相似性性的信息，除了其他必需事项外，还应包括能够证明即使临床非活性成分存在微小差异，类似药和参比制剂仍然高度相似的分析试验研究。首先，FDA 希望申请者采用最先进的技术对类似药和参比制剂进行广泛研究，因为这些研究结果是论证生物相似性的基础。通常情况下，FDA 希望类似药和参比制剂的氨基酸序列表达构造相同，但是，像N-或C-端断裂等不会影响安全有效性的微小差异，申请者只要给出科学合理性的解释即可。另外，申请人还必须考虑到蛋白制品所有相关性质（包括一、二、三、四级结构、翻译后修饰、生物活性），以证明即使在临床非活性成分存在微小差异的情况下，其与参比制剂仍具有高度生物相似性。对结构功能比较得越全面，动物和/或临床试验的选择和针对性越科学合理。
Sponsors should use appropriate analytical methodologies with adequate sensitivity and specificity for structural characterization of the proteins. Generally, such tests include the following comparisons of the proposed product and the reference product:
• Primary structures, such as amino acid sequence
• Higher order structures, including secondary, tertiary, and quaternary structure (including aggregation)
• Enzymatic posttranslational modifications, such as glycosylation and phosphorylation
• Other potential variations, such as protein deamidation and oxidation
• Intentional chemical modifications, such as PEGylation sites and characteristics
Sponsors should conduct extensive structural characterization of both the proposed product and the reference product in multiple representative lots to understand the lot-to-lot variability of both products in the manufacturing processes. Lots used for the analyses should support the biosimilarity of both the clinical material used in the clinical study(ies) intended to support a demonstration of biosimilarity, and the to-be-marketed proposed product, to the reference product. Characterization of lots manufactured during process development for the proposed product may also be useful. Sponsors should justify the selection of the representative lots, including the number of lots.
In addition, FDA recommends that sponsors analyze the finished dosage form of multiple lots of the proposed product and the reference product, assessing excipients and any formulation effect on purity, product- and process-related impurities, and stability. Differences in formulation between the proposed product and the reference product are among the factors that may affect the extent and nature of subsequent animal or clinical testing. A sponsor considering manufacturing changes after completing the initial analytical similarity assessment or after completing clinical testing intended to support a 351(k) application should perform an additional analytical similarity assessment with lots manufactured by the new process and the reference product and establish comparability of the proposed product manufactured by the old and new manufacturing processes. The nature and extent of the changes may determine the extent of the analytical similarity and comparability studies and any necessary additional studies.
If the reference product or the proposed product cannot be adequately characterized with stateof-the-art technology, the application for the proposed product may not be appropriate for submission under section 351(k) of the PHS Act; and the sponsor should consult FDA for guidance on the appropriate submission pathway.
如果利用最先进的技术仍不能全面描述类似药和参比制剂的特征，则PHS Act351(k) 可能不适用于该产品的申请，申请人应咨询FDA，请FDA指导PHS Act 351(k)是否适用于这种蛋白产品的申请。
The pharmacologic activity of protein products should be evaluated by in vitro and/or in vivo functional assays. In vitro assays may include, but are not limited to, biological assays, binding assays, and enzyme kinetics. In vivo assays may include the use of animal models of disease (e.g., models that exhibit a disease state or symptom) to evaluate functional effects on pharmacodynamic markers or efficacy measures. A functional evaluation comparing a proposed product to the reference product using these types of assays is also an important part of the foundation that supports a demonstration of biosimilarity and may be used to scientifically justify a selective and targeted approach to animal and/or clinical testing.
Sponsors can use functional assays to provide additional evidence that the biologic activity and potency of the proposed product are highly similar to those of the reference product and/or to support a conclusion that there are no clinically meaningful differences between the proposed product and the reference product. Such assays also may be used to provide additional evidence that the MOA of the two products is the same to the extent the MOA of the reference product is known. Functional assays can be used to provide additional data to support results from structural analyses, investigate the consequences of observed structural differences, and explore structure-activity relationships. These assays are expected to be comparative so they can provide evidence of similarity or reveal differences in the performance of the proposed product compared to the reference product, especially differences resulting from variations in structure that cannot be detected using current analytical methods. FDA also recommends that sponsors discuss limitations of the assays they used when interpreting results in their submissions to FDA. Such discussions would be useful for the evaluation of analytical data and may guide whether additional analytical testing would be necessary to support a demonstration of biosimilarity.
Functional assays can also provide information that complements the animal and clinical data in assessing the potential clinical effects of minor differences in structure between the proposed product and the reference product. For example, cell-based bioactivity assays may be used to detect the potential for inducing cytokine release syndrome in vivo. The available information about these assays, including sensitivity, specificity, and extent of validation, can affect the amount and type of additional animal or clinical data that may be needed to establish biosimilarity. As is the case for the structural evaluation, sponsors should justify the selection of the representative lots, including the number of lots.
The PHS Act also requires that a 351(k) application include information demonstrating biosimilarity based on data derived from animal studies (including the assessment of toxicity), unless FDA determines that such studies are not necessary in a 351(k) application. Results from animal studies may be used to support the safety evaluation of the proposed product and more generally to support the demonstration of biosimilarity between the proposed product and the reference product.
1.Animal Toxicity Studies动物毒理学研究
As a scientific matter, animal toxicity data are considered useful when, based on the results of extensive structural and functional characterization, uncertainties remain about the safety of the proposed product that need to be addressed before initiation of clinical studies in humans (assuming results from animal studies can meaningfully address the remaining uncertainties).
The scope and extent of any animal toxicity studies will depend on information about the reference product, information about the proposed product, and the extent of known similarities or differences between the two. As described further in section IX, FDA encourages sponsors to initiate early discussions with the Agency with regard to their biosimilar development plans, including identifying appropriate scientific justifications for not conducting an animal toxicity study or for the scope and extent of such a study.
If comparative structural and functional data using the proposed product provide strong support for analytical similarity to a reference product, then limited animal toxicity data may be sufficient to support initial clinical use of the proposed product. Such a study may be non-sacrificial and include endpoints that measure in-life parameters, PD, and PK (with an assessment of immunogenicity).
If the structural and functional data are limited in scope or there are concerns about the proposed product quality, a general toxicology study may be needed that includes full animal pathology, histopathology, PD, PK, and immunogenicity assessments. When animal toxicology studies are conducted, it will be useful to perform a comparative study with the proposed product and the reference product (i.e., comparative bridging toxicology studies). The selection of dose, regimen, duration, and test species for these studies should provide a meaningful toxicological comparison between the two products. It is important to understand the limitations of such animal studies (e.g., small sample size, intra-species variations) when interpreting results comparing the proposed product and the reference product. For a detailed discussion on the design of animal toxicology studies relevant to biological products, see the ICH guidance for industry S6(R1) Preclinical Safety Evaluation of Biotechnology-Derived Pharmaceuticals (ICH S6(R1)).
Safety data derived from animal toxicity studies generally are not expected if clinical data (e.g., from studies or marketing experience outside the United States) using the proposed product are available (with the same proposed route of administration and formulation) that provide sufficient evidence for its safe use, unless animal toxicity studies are otherwise needed to address a specific product quality concern.
Animal toxicity studies are generally not useful if there is no animal species that can provide pharmacologically relevant data for the product (i.e., no species in which the biologic activity of the product mimics the human response). For a detailed discussion about demonstrating species relevance, see the criteria described in ICH S6(R1). However, there may be some instances when animal data from a pharmacologically nonresponsive species (including rodents) may be useful to support clinical studies with a proposed product that has not been previously tested in human subjects, for example, comparative PK and systemic tolerability studies. If animal toxicity studies are not warranted based on an acceptable scientific justification, additional comparative in vitro testing (using human cells or tissues when appropriate) is encouraged. Data derived using human cells can provide important comparative information between the proposed product and the reference product regarding potential clinical effects (section VII.B), particularly in situations where there are no animal species available for safety testing.
In general, nonclinical safety pharmacology, reproductive and developmental toxicity, and carcinogenicity studies are not warranted when the proposed product and the reference product have been demonstrated to be highly similar through extensive structural and functional characterization and animal toxicity studies (if such studies were conducted).
2. Inclusion of Animal PK and PD Measures动物PK/PD研究
Under certain circumstances, a single-dose study in animals comparing the proposed product and the reference product using PK and PD measures may contribute to the totality of evidence that supports a demonstration of biosimilarity. Specifically, sponsors can use results from animal studies to support the degree of similarity based on the PK and PD profiles of the proposed product and the reference product. PK and PD measures also can be incorporated into a single animal toxicity study, where appropriate. Animal PK and PD assessment will not negate the need for human PK and PD studies.
3. Interpreting Animal Immunogenicity Results动物免疫学研究
Animal immunogenicity assessments are conducted to assist in the interpretation of the animal study results and generally do not predict potential immune responses to protein products in humans. However, when differences in manufacturing (e.g., impurities or excipients) between the proposed product and the reference product may result in differences in immunogenicity, measurement of anti-therapeutic protein antibody responses in animals may provide useful information. Additionally, differences observed in animal immunogenicity assessments may reflect potential structural or functional differences between the two products not captured by other analytical methods.