Statistical evaluation of the scaled criterion for drug interchangeability

ABSTRACT

As more and more generic drug products become available in the marketplace, it is a concern whether these generic drug products can be used interchangeably in terms of their quality, safety, and efficacy. The United States Food and Drug Administration (FDA) indicates that an approved generic drug product can serve as a substitute for the innovative drug product. The FDA, however, does not indicate that approved generic drug products can be used interchangeably even if they are bioequivalent to the same innovative drug product. In the past decade, several criteria for assessing interchangeability were proposed in regulatory guidances and/or literature. Chow, Xu, and Endrenyi proposed a scaled criterion for drug interchangeability (SCDI), which takes both intra-subject variability and subject-by-drug variability into consideration. In this paper, the performance of this criterion is statistically evaluated by deriving the upper confidence limit of the test statistic and extrapolating expression of the power to facilitate sample size calculation. The performance of SCDI is also compared with that of the criterion for assessment of individual bioequivalence (IBE) for addressing drug switchability recommended by the FDA, which also takes into account the subject-by-drug variability, under various parameter specifications.     

Assessing bioequivalence and drug interchangeability

ABSTRACT

As indicated by the US Food and Drug Administration (FDA), approved generic drug products can be used as substitutes for their respective innovative drug products. The FDA, however, does not indicate that two generic copies of the same innovative drug can be used interchangeably, even though they have been shown to be bioequivalent to the same innovative drug product. As more and more generic drug products become available in the market place, it is a concern whether these approved generic drug products have the same quality and safety/efficacy and hence can be used interchangeably. To address the issue of drug interchangeability, several criteria such as individual bioequivalence criterion, a criterion based on the variability due to subject-by-drug interaction, and a scaled criterion for drug interchangeability (SCDI) have been proposed in the literature. In this article, the performances of these criteria, including a newly proposed reversed average bioequivalence criterion, are studied under a 2x4 replicated crossover design in terms of the percentage of passing at the best and worst possible scenarios of similarity. The goal of this paper is to investigate the interchangeability in terms of switchability between a generic (test) drug product and an originator (reference) drug product.     

Some thoughts on drug interchangeability

Abstract

Current regulation for generic approval is based on the assessment of average bioequivalence. As indicated by the United States Food and Drug Administration (FDA), an approved generic drug can be used as a substitute for the innovative drug. FDA does not indicate that two generic copies of the same innovative drug can be used interchangeably even though they are bioequivalent to the same brand-name drug. In practice, bioequivalence between generic copies of an innovative drug is not required. However, as more generic drug products become available, it is a concern whether the approved generic drug products have the same quality and therapeutic effect as the brand-name drug product and whether they can be used safely and interchangeably. In this article, several criteria including a newly proposed criterion for assessing drug interchangeability are studied. In addition, comments on possible study designs and power calculation for sample size under a specific design are also discussed.     

Are biosimilars patentable?

Introduction: This paper explores whether, and under what circumstances, a biosimilar approved in the United States under the Biologics Price Competition and Innovation Act (hereafter ‘BPCIA’) can be patented. The possibility that a biosimilar product could have meaningful patent protection arises from specific requirements for biosimilarity under the BPCIA, which account for the fact that manufacturing processes of biologics are inherently imprecise. The requirements for biosimilar approval may provide sufficient leeway to a biosimilar applicant to patent structural or formulation differences that provide non-clinical but business-relevant advantages over the reference molecule, such as improved shelf-life or ease of manufacture, without compromising clinical biosimilarity.

Areas covered: Examination of the BPCIA and related Acts, Food and Drug Administration (FDA) guidance papers, case law, patent database searching, and relevant scholarly articles.

Expert opinion: Legislative and regulatory requirements for the approval of a biosimilar under the BPCIA are focused on clinical results and allow a degree of leeway for differences to exist between a biosimilar’s structure and non-clinical components and those of the biosimilar’s reference molecule. This leeway can be exploited to provide the biosimilar with potentially patentable business-relevant advantages over its reference product while maintaining clinical biosimilarity to the reference product.     

Comparability and biosimilarity: considerations for the healthcare provider

BACKGROUND: Healthcare providers use recombinant biologics such as monoclonal antibodies to treat a variety of serious illnesses. Manufacturing of approved biotechnology products is complex, and the quality of the resulting biologic is dependent on careful control of process inputs and operating conditions. Biosimilars, which are similar but not identical to innovator biologics, are entering regulatory evaluation, approval, and marketing in regions with biosimilar approval pathways. SCOPE AND FINDINGS: This article describes the evaluation and potential impact of manufacturing process changes and biosimilar product development, and explores the similarities and distinctions between the two. Regulatory agencies generally require a comparability exercise following a manufacturing process change. This comparability is focused primarily on analytical characterization of the approved product before and after the manufacturing process change, with non-clinical and clinical confirmation required when determined necessary. When developing a biosimilar, the manufacturer does not have access to key information including the innovator manufacturer's cell line, cell culture conditions, purification procedures, and fill and finish processes. Further, the biosimilar manufacturer does not have access to information about the innovator manufacturer's product development history, including knowledge about the quality attributes of lots used in non-clinical and clinical development. We define the biosimilar manufacturer's lack of information as the knowledge gap. As a result, a biosimilarity exercise to compare a biosimilar to an approved innovator biologic requires a rigorous evaluation to ensure the safety and efficacy of the biosimilar. CONCLUSION: Given the knowledge gap under which biosimilars are developed, data to establish biosimilarity should go beyond a simple comparability exercise.     

Comparative subcutaneous repeated toxicity study of enoxaparin products in rats

Enoxaparin is a low-molecular-weight heparin widely used for the prevention and treatment of thromboembolism. With the development of several enoxaparin biosimilars, real medical concerns about their safety and efficacy have been raised. This repeated dose toxicity study consists of preclinical toxicological evaluation of a biosimilar biological version of enoxaparin, the drug product “Enoxa”, compared to the enoxaparin reference drug product, “Lovenox”. Eighty white Wistar rats were treated with “Enoxa” versus the reference product, using subcutaneous therapeutic and toxic doses, varying from 3.5 to 100 mg/kg/day. Dose levels were adjusted and ultimately fixed at 3.5 and 20 mg/kg/day as therapeutic and toxic doses, respectively. A sodium chloride solution (0.9%) was used as the control, and the comparative study was conducted over periods of 14 and 28 days. Comparable effects were observed with few adverse effects at the administration dose of 20 mg/kg/day, for both enoxaparin biosimilar and reference products. Interestingly, mortality started only at high doses of 40 mg/kg/day and reached 25% at 100 mg/kg/day for both products. These results, as part of the recommended biosimilarity monitoring, demonstrated comparable toxicity profiles of “Enoxa” and “Lovenox” products in rats. Continuing investigation of biosimilarity on humans to confirm safety and efficacy is suggested.     

Clinical trials for authorized biosimilars in the European Union: a systematic review

AimIn 2006, Omnitrope (by Sandoz) was the first approved biosimilar in Europe. To date, 21 biosimilars for seven different biologics are on the market. The present study compared the clinical trials undertaken to obtain market authorization.MethodsWe summarized the findings of a comprehensive review of all clinical trials up to market authorization of approved biosimilars, using the European public assessment reports (EPARs) published by the European Medicines Agency (EMA). The features compared were, among others, the number of patients enrolled, the number of trials, the types of trial design, choice of endpoints and equivalence margins for pharmacokinetic (PK)/pharmacodynamic (PD) and phase III trials.ResultsThe variability between the clinical development strategies is high. Some differences are explainable by the characteristics of the product; if, for example, the PD marker can be assumed to predict the clinical outcome, no efficacy trials might be necessary. However, even for products with the same reference product, the sample size, endpoints and statistical models are not always the same.ConclusionsThere seems to be flexibility for sponsors regarding the decision as to how best to prove biosimilarity.     

A Tolerance Interval Approach to Assessing the Biosimilarity of Follow-On Biologics

With many important biologic products due to lose patent protection in the next few years, the development of follow-on biologics has received much attention from both sponsors and regulatory authorities. Biologics are often produced in living systems. The living systems used to produce biologics are highly complex and could be sensitive to very minor changes in the manufacturing process. According to the guideline published by the European Medicines Agency, biosimilar products are similar, not identical, to the innovator products they seek to copy. Therefore, in developing a biosimilar, it is important to assess the similarity between it and the innovator product. In this article, we consider a two-arm, parallel design with a reference biological product and a biosimilar. Then, we construct a biosimilarity index for assessing the degree of similarity based on the tolerance limits. The acceptance criterion is proposed to judge whether the biosimilar is similar to the reference product. We also address the determination of the number of subjects to ensure that the occurring probability of biosimilarity criterion is maintained at a desired level, say 80% or 90%. Supplementary materials for this article are available online.     

Analytical Similarity Assessment in Biosimilar Studies

For assessment of biosimilarity, the US Food and Drug Administration (FDA) recommends a stepwise approach for obtaining the totality-of-the-evidence for demonstrating biosimilarity between a proposed biosimilar product and an innovative (reference) biological product. The stepwise approach starts with analytical studies for functional and structural characterization at various stages of manufacturing process of the proposed biosimilar product. Analytical similarity assessment involves identification of critical quality attributes (CQAs) that are relevant to clinical outcomes. FDA proposes first classifying the identified CQAs into three tiers according to their criticality or risking ranking relevant to clinical outcomes and then performing equivalence test (for CQAs in Tier 1), quality range approach (for CQAs in Tier 2), and raw data or graphical presentation (for CQAs in Tier 3) for obtaining totality-of-the-evidence for demonstrating biosimilarity between the proposed biosimilar product with the reference product. In practice, some debatable issues are evitably raised due to this complicated process of analytical similarity assessment. In this article, these debatable are described and discussed.     

EU pharmacovigilance regulatory requirements of anticancer biosimilar monoclonal antibodies

An increasing number of innovative oncology monoclonal antibodies (mAbs) have been introduced into the global market, and biosimilar versions have now also been approved in Europe. Being complex to develop and difficult to manufacture, the biosimilar is a drug similar but not identical in physicochemical characteristics, efficacy, and safety to an original biological drug already approved in the European Union, for which marketing exclusivity rights have expired. Generally, the safety monitoring of biosimilars follows the same requirements that apply to all biologicals, even if specific pharmacovigilance measures exist and some of them are still being debated. The manufacturing process, immunogenicity, traceability, and extrapolation of indication are keywords which may impact on the achievement of additional knowledge about the safety of a biosimilar mAb. In this article, we aim to discuss elements that play a central role in the pharmacovigilance legislation of biosimilar mAbs.     

仿制药一致性评价工作的进展与展望

目的 研究分析当前仿制药质量和疗效一致性评价的现状及存在问题,提出推进仿制药一致性评价的建议。方法 梳理并分析我国基本药物化学药品目录中口服固体制剂的品种情况、持有文号的生产企业情况、参比制剂公布情况及实施仿制药一致性评价中的问题。结果 低价药、独家品种开展一致性评价比例偏低,未来可及性风险不容忽视。结论 生产企业要落实评价主体责任,以提高质量作为企业发展要务;相关管理部门应加快出台激励政策,助推企业开展仿制药一致性评价。     

Adjustment for unbalanced sample size for analytical biosimilar equivalence assessment

ABSTRACT

Large sample size imbalance is not uncommon in the biosimilar development. At the beginning of a product development, sample sizes of a biosimilar and a reference product may be limited. Thus, a sample size calculation may not be feasible. During the development stage, more batches of reference products may be added at a later stage to have a more reliable estimate of the reference variability. On the other hand, we also need a sufficient number of biosimilar batches in order to have a better understanding of the product. Those challenges lead to a potential sample size imbalance. In this paper, we show that large sample size imbalance may increase the power of the equivalence test in an unfavorable way, giving higher power for less similar products when the sample size of biosimilar is much smaller than that of the reference product. Thus, it is necessary to make some sample size imbalance adjustments to motivate sufficient sample size for biosimilar as well. This paper discusses two adjustment methods for the equivalence test in analytical biosimilarity studies. Please keep in mind that sufficient sample sizes for both biosimilar and reference products (if feasible) are desired during the planning stage.     

Product selection, bioequivalence, and therapeutic equivalence: the generic drug market

Pharmacists are continually faced with drug product selection decisions. When is a generic drug product equivalent to the innovator product and, thus, a suitable candidate for generic substitution? The FDA policy has been that only drug products that are therapeutic equivalents are candidates for product selection decisions. This paper outlines the regulatory and scientific framework for the FDA's policies and requirements for generic drug products. The history and current status of the Drug Efficacy Study Implementation (DESI) project is described. Originally begun in 1966 as a review of about 3,400 drug products, the review in mid-1983 is more than 90% complete, but its impact has already affected more than 7,000 marketed drug products. The therapeutic equivalence policy and the manner in which decisions on therapeutic equivalence are communicated are reviewed. Regulatory policies for the approval of generic drug products are reviewed and specific litigation challenging the rights of generic drug manufacturers to produce generic "look-alikes" and challenging the FDA's policy that a generic drug product is a new drug requiring an approved New Drug Application for marketing is discussed. The conclusion reached is that the evaluation of regulatory requirements and science is leading to a point where all generic drug products will be known to be safe, effective and therapeutically equivalent, and pharmacists can be optimistic about the quality of products in the generic drug market.     

刍议美国生物类似药行动计划

生物类似药是指在质量、安全性和有效性方面与已获准上市的参比制剂具有相似性的治疗性生物制品。结合美国、欧盟、日本和世界卫生组织对生物类似药研发及监管思路,重点介绍了2018年度美国食品药品监督管理局发布的《生物类似药行动计划——简介和概述：创新与竞争间的平衡》,以期对我国生物类似药监管政策的制定提供借鉴。     

Systematic Verification of Bioanalytical Similarity Between a Biosimilar and a Reference Biotherapeutic: Committee Recommendations for the Development and Validation of a Single Ligand-Binding Assay to Support Pharmacokinetic Assessments

For biosimilar drug development, it is critical to demonstrate similar physiochemical characteristics, efficacy, and safety of the biosimilar product compared to the reference product. Therefore, pharmacokinetic (PK) and immunogenicity (antidrug antibody, ADA) assays that allow for the demonstration of biosimilarity are critical. Under the auspices of the American Association of Pharmaceutical Scientists (AAPS) Ligand-Binding Assay Bioanalytical Focus Group (LBABFG), a Biosimilars Action Program Committee (APC) was formed in 2011. The goals of this Biosimilars APC were to provide a forum for in-depth discussions on issues surrounding the development and validation of PK and immunogenicity assays in support of biosimilar drug development and to make recommendations thereof. The Biosimilars APC’s recommendations for the development and validation of ligand-binding assays (LBAs) to support the PK assessments for biosimilar drug development are presented here. Analytical recommendations for the development and validation of LBAs to support immunogenicity assessments will be the subject of a separate white paper.

Electronic supplementary material

The online version of this article (doi:10.1208/s12248-014-9669-5) contains supplementary material, which is available to authorized users.KEY WORDS: bioanalytical method validation, biological product, biosimilar, ligand-binding assay, pharmacokinetic     

Sample size requirement in analytical studies for similarity assessment

ABSTRACT

For the assessment of biosimilar products, the FDA recommends a stepwise approach for obtaining the totality-of-the-evidence for assessing biosimilarity between a proposed biosimilar product and its corresponding innovative biologic product. The stepwise approach starts with analytical studies for assessing similarity in critical quality attributes (CQAs), which are relevant to clinical outcomes at various stages of the manufacturing process. For CQAs that are the most relevant to clinical outcomes, the FDA requires an equivalence test be performed for similarity assessment based on an equivalence acceptance criterion (EAC) that is obtained using a single test value of some selected reference lots. In practice, we often have extremely imbalanced numbers of reference and test lots available for the establishment of EAC. In this case, to assist the sponsors, the FDA proposed an idea for determining the number of reference lots and the number of test lots required in order not to have imbalanced sample sizes when establishing EAC for the equivalence test based on extensive simulation studies. Along this line, this article not only provides statistical justification of Dong, Tsong, and Weng’s proposal, but also proposes an alternative method for sample size requirement for the Tier 1 equivalence test.     

Safety concerns of biosimilar hormone products

Background: Currently, biotherapeutic medicines are the most effective options for the treatment of many severe and chronic diseases. For faster market entry of biotherapeutic products and their cost reduction, the principles of “biosimilarity” have been developed. Development and licensing of biosimilars is allowed only after the end of patent exclusivity of the original preparation period.

Purpose: Characteristics of the main safety parameters of biosimilar hormone preparations licensed by EMA.

Methods: This paper analyzes the results demonstrating the similarities and differences between biosimilar and reference hormone products indicated in the EPAR (public assessment report) for the examination of materials presented for the licensing of biosimilar products.

Results: During the development of biosimilar hormone medicines, differences in the glycosylation profile between biosimilar and reference preparations are revealed. As biotherapeutical preparations are produced by cells, the differences in glycosylation profile between biosimilar and referent preparation are predictable. While carrying out clinical studies, a high similarity of biosimilar and reference product effectiveness is shown, but some differences between them in the safety profile are revealed.

Conclusions: The study of biosimilar product safety has shown the necessity of further improvement in safety and standard approaches for the assessment of the immunogenicity of biosimilar products.     

On hybrid parallel–crossover designs for assessing drug interchangeability of biosimilar products

ABSTRACT

In recent years, a specific hybrid parallel–crossover design that consists of two sequences of treatments, namely R–R–R–R and R–T–R–T, where T and R is a proposed biosimilar product and an innovative biological product, respectively, have been proposed and received much attention for assessing drug interchangeability between T and R, where R could be either a US-licensed product or an EU-reference product. In practice, there are three types of hybrid parallel–crossover designs that are commonly employed in assessing drug interchangeability of biosimilar products. These three types of parallel–crossover hybrid designs include (1) a parallel + 2 × 2 crossover design, (2) a parallel + 2 × 3 crossover design, and (3) a parallel + 2 × 4 crossover design. This article provides a comprehensive review of these study designs including a complete N-of-1 randomized trial design. A specific hybrid parallel–crossover design, that is, (RRRR, RTRT) for addressing drug interchangeability in terms of switching and the relative risk between with/without alternation is discussed.