Establishing bioequivalence for inhaled drugs; weighing the evidence

INTRODUCTION: During drug development and product life-cycle management, it may be necessary to establish bioequivalence between two pharmaceutical products. Methodologies to determine bioequivalence are well established for oral, systemically acting formulations. However, for inhaled drugs, there is currently no universally adopted methodology, and regulatory guidance in this area has been subject to debate. AREAS COVERED: This paper covers the current status of regulatory guidance on establishing the bioequivalence of topically acting, orally inhaled drugs, the value and limitations of in vitro and in vivo bioequivalence testing, and the practical issues associated with various approaches. The reader will gain an understanding of the issues pertaining to bioequivalence testing of orally inhaled drugs, and the current status of regulatory approaches to establishing bioequivalence in different regions. EXPERT OPINION: Establishing bioequivalence of inhaled drug products involves a multistep process; however, methodologies for each step have yet to be fully validated. Our lack of understanding about the relationship between in vitro, in vivo and clinical data suggests that in most cases, unless there is a high degree of pharmaceutical equivalence between the test and reference products, consideration of a combination of preclinical and clinical data may be preferable to abridged approaches relying on in vitro data alone.     

International Guidelines for Bioequivalence of Locally Acting Orally Inhaled Drug Products: Similarities and Differences

International regulatory agencies have developed recommendations and guidances for bioequivalence approaches of orally inhaled drug products (OIDPs) for local action. The objective of this article is to discuss the similarities and differences among these approaches used by international regulatory authorities when applications of generic and/or subsequent entry locally acting OIDPs are evaluated. We focused on four jurisdictions that currently have published related guidances for generic and/or subsequent entry OIDPs. They are Therapeutic Goods Administration (TGA) in Australia, Health Canada (HC) in Canada, European Medicines Association (EMA) of European Union (EU), and the Food and Drug Administration (FDA) in the United States of America (USA). The comparisons of these bioequivalence (BE) recommendations are based on selection of reference products, formulation and inhaler device comparisons, and in vitro tests and in vivo studies, including pharmacokinetic (PK), pharmacodynamics (PD), and clinical studies. For the in vivo studies, the study design, choices of dose, subject inclusion/ exclusion criteria, study period, study endpoint, and equivalence criteria are elaborated in details. The bioequivalence on multiple-strength products and waiver options are also discussed.

Electronic supplementary material

The online version of this article (doi:10.1208/s12248-015-9733-9) contains supplementary material, which is available to authorized users.KEY WORDS: bioequivalence, exhaled nitric oxide, generic, guidelines, orally inhaled drugs     

吸入制剂体外群体生物等效性的研究进展

为了保证吸入制剂原研药和仿制药体内体外生物等效性,美国食品药品监督管理局（FDA）颁布的指导原则中明确要求对吸入制剂体外非临床研究数据采用群体生物等效性统计分析方法。综述了FDA对吸入制剂体外群体生物等效性研究方面的建议,统计方法原理,相关参数的计算及等效性判断标准并阐述了国外文献的研究实例,旨在为我国吸入制剂仿制药的体外等效性统计方法学研究提供合理可靠的依据。     

Considerations in establishing bioequivalence of inhaled compounds

Introduction: Generic inhalers are often perceived as inferior to their branded counterparts; however, they are safe and effective if they can meet the regulatory requirements. The approach to assess bioequivalence (BE) in oral dosage form products is not sufficient to address the complexities of inhalational products (e.g., patient-device interface); hence, more considerations are needed and caution should be applied in determining BE of inhaled compounds.

Areas covered: This review outlines the evaluation process for generic inhalers, explores the regulatory approaches in BE assessment, and highlights the considerations and challenges in the current in vitro and in vivo approaches (lung deposition, pharmacokinetic, pharmacodynamic/clinical studies, and patient-device interface) for establishing BE of inhaled compounds.

Expert opinion: The ultimate goals in this field are to establish uniformity in the regulatory approaches to speed the drug submission process in different regions, clear physicians’ misconception of generic inhalers, and have meaningful clinical endpoints such as improvement in patient quality of life when compared to placebo and brand name drugs. As inhalational drugs become more common for other indications such as antibiotics, the technologies developed for inhaled compounds in the treatment of chronic pulmonary diseases may be extrapolated to these other agents.     

In Vitro Testing for Orally Inhaled Products: Developments in Science-Based Regulatory Approaches

This article is part of a series of reports from the “Orlando Inhalation Conference-Approaches in International Regulation” which was held in March 2014, and coorganized by the University of Florida and the International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS). The goal of the conference was to foster the exchange of ideas and knowledge across the global scientific and regulatory community in order to identify and help move towards strategies for internationally harmonized, science-based regulatory approaches for the development and marketing approval of inhalation medicines, including innovator and second entry products. This article provides an integrated perspective of case studies and discussion related to in vitro testing of orally inhaled products, including in vitro-in vivo correlations and requirements for in vitro data and statistical analysis that support quality or bioequivalence for regulatory applications.KEY WORDS: aerosol, bioequivalence, deposition, dissolution, in vitro-in vivo correlation, inhaler, regulatory, statistics and data analysis     

Regulatory framework on bioequivalence criteria for locally acting gastrointestinal drugs: the case for oral modified release mesalamine formulations

Introduction: Bioequivalence testing for locally acting gastrointestinal drugs is a challenging issue for both regulatory authorities and pharmaceutical industries. The international regulatory framework has been characterized by the lack of specific bioequivalence tests that has generated a negative impact on the market competition and drug use in clinical practice.

Areas covered: This review article provides an overview of the European Union and United States regulatory frameworks on bioequivalence criteria for locally acting gastrointestinal drugs, also discussing the most prominent scientific issues and advances that has been made in this field. A focus on oral modified release mesalamine formulations will be also provided, with practical examples of the regulatory pathways followed by pharmaceutical companies to determine bioequivalence.

Expert commentary: The development of a scientific rationale to demonstrate bioequivalence in this field has been complex and often associated with uncertainties related to scientific and regulatory aspects. Only in recent years, thanks to advanced knowledge in this field, the criteria for bioequivalence assessment are undergoing substantial changes. This new scenario will likely result in a significant impact on pharmaceutical companies, promoting more competition through a clearer regulatory approach, conceived for streamlining the demonstration of therapeutic equivalence for locally acting gastrointestinal drugs.     

Equivalence-by-Design: Targeting <Emphasis Type="BoldItalic">In Vivo</Emphasis> Drug Delivery Profile

In the United States (U.S.), drug products are considered therapeutically equivalent if they meet regulatory criteria of pharmaceutical equivalence and bioequivalence. These requirements can be traced back to 1977 when the U.S. Food and Drug Administration (FDA) published the regulations on bioavailability and bioequivalence. Over the years, to keep up with the advancement in science and technology, the FDA has been constantly updating the regulatory approaches to assessing and ensuring equivalence. In view of the recent growth in novel pharmaceutical dosage forms and delivery systems, this paper examines the current framework for documentation of therapeutic equivalence and explores the opportunities of further advancing equivalence methods for complex drug products. It is proposed that equivalence may be established by matching the in vivo drug delivery profile (iDDP) between drug products in comparison. This can be achieved by characterizing the iDDP of the reference formulation with application of an equivalence-by-design approach for pharmaceutical development. Critical variables can be identified to serve as in vitro markers or biomarkers for mapping the desired drug delivery profile in vivo. A multidisciplinary approach may be necessary to develop these markers for characterization of iDDPs. The opinions expressed in this article do not necessarily represent the views or policies of the U.S. Food and Drug Administration     

Current Scientific and Regulatory Approaches for Development of Orally Inhaled and Nasal Drug Products: Overview of the IPAC-RS/University of Florida Orlando Inhalation Conference

This article summarizes discussions at the March 2014 conference organized by the University of Florida (UF) and International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS), entitled “Orlando Inhalation Conference: Approaches in International Regulation.” The special focus of the conference was on global scientific and regulatory issues associated with the testing and demonstration of equivalence for the registration of orally inhaled drug products (OIDPs) in the United States, Europe, Brazil, China, and India. The scope included all types of OIDPs throughout their lifecycle, e.g., innovator/brand-name products, generics, modifications due to lifecycle management, device changes, etc. Details were presented for the U.S. “weight of evidence approach” for registration of generic products (which includes demonstration of in vitro and in vivo equivalence, as well as quantitative and qualitative sameness, and device similarity). The European “stepwise” approach was elucidated, and the thinking of regulatory agencies in the major emerging markets was clarified. The conference also highlighted a number of areas that would benefit from further research and discussion, especially around patient/device interface and human factor studies, statistical methods and criteria for demonstrating equivalence, the relative roles of in vivo and in vitro tests, and appropriate designs and metrics for in vivo studies of inhaled drugs.KEY WORDS: bioequivalence, emerging markets, generics, MDIs and DPIs, regulatory science     

The role of predictive biopharmaceutical modeling and simulation in drug development and regulatory evaluation

Advances in predicting in vivo performance of drug products has the potential to change how drug products are developed and reviewed. Modeling and simulation methods are now more commonly used in drug product development and regulatory drug review. These applications include, but are not limited to: the development of biorelevant specifications, the determination of bioequivalence metrics for modified release products with rapid therapeutic onset, the design of in vitro-in vivo correlations in a mechanistic framework, and prediction of food effect. As new regulatory concepts such as quality by design require better application of biopharmaceutical modeling in drug product development, regulatory challenges in bioequivalence demonstration of complex drug products also present exciting opportunities for creative modeling and simulation approaches. A collaborative effort among academia, government and industry in modeling and simulation will result in improved safe and effective new/generic drugs to the American public.     

Regulatory Considerations for Approval of Generic Inhalation Drug Products in the US,EU, Brazil,China, and India

This article describes regulatory approaches for approval of “generic” orally inhaled drug products (OIDPs) in the United States, European Union, Brazil, China and India. While registration of a generic OIDP in any given market may require some documentation of the formulation and device similarity to the “original” product as well as comparative testing of in vitro characteristics and in vivo performance, the specific documentation approaches, tests and acceptance criteria vary by the country. This divergence is due to several factors, including unique cultural, historical, legal and economic circumstances of each region; the diverse healthcare and regulatory systems; the different definitions of key terms such as “generic” and “reference” drug; the acknowledged absence of in vitro in vivo correlations for OIDPs; and the scientific and statistical issues related to OIDP testing (such as how best to account for the batch-to-batch variability of the Reference product, whether to use average bioequivalence or population bioequivalence in the statistical analysis of results, whether to use healthy volunteers or patients for pharmacokinetic studies, and which pharmacodynamic or clinical end-points should be used). As a result of this discrepancy, there are ample opportunities for the regulatory and scientific communities around the world to collaborate in developing more consistent, better aligned, science-based approaches. Moving in that direction will require both further research and further open discussion of the pros and cons of various approaches.     

Current Bioavailability and Bioequivalence Requirements and Regulations

Abstract

The 1977 Bioavailability/Bioequivalence Regulations formalized the position and thinking of the Food and Drug Administration with regard to bioavailability of drug products marketed in the United States. The regulations defined the terminology involved, set forth criteria for waiver of in vivo bioavailability studies and listed the drugs that would require bioavailability/bioequivalence studies. The regulations also delineated the general approaches for determining bioavailability, laid down guidelines for conducting in vivo bioavailability studies for conventional dosage forms, combination drug products, and controlled release drug products; set forth criteria and evidence to establish a bioequivalence requirement and described the types of bioequivalence requirements. Over the last few years, a number of presentations have been made by the officials of the Agency to describe and explain the regulations at various forums. I am sure that most of you are quite familiar with the various aspects of these regulations.     

Influence of Tablet Dissolution on Furosemide Bioavailability: A Bioequivalence Study

In order to evaluate the in vitro dissolution and in vivo bioavailability relationship for furosemide, a bioequivalence study was carried out. Furosemide (40 mg) was administered orally to 12 normal volunteers in a 6 × 6 crossover design using six products (five tablets and one solution) obtained from three pharmaceutical companies. Plasma and urine concentrations of furosemide were quantitated by high-performance liquid chromatography (HPLC). Plasma furosemide profiles were analyzed by non-compartmental methods. Compared to the oral solution, all of the formulations exhibited lower peak furosemide concentrations, longer mean residence times, and, in some cases, diminished bioavailability (range, 66–96%). Similar results were obtained when the reference product (a rapidly dissolving tablet) was used as the standard. All of the products failed the 75/75 rule when compared to either reference standard, apparently because of large intersubject variability. The total amount of furosemide excreted in urine could be associated with the percentage drug dissolved (in vitro) at 30 min. The pH 5.6 dissolution medium (compared to pH 4.6) appears to be an appropriate test medium for assuring batch uniformity and bioequivalence of furosemide products.     

Survey of International Regulatory Bioequivalence Recommendations for Approval of Generic Topical Dermatological Drug Products

The objective of this article is to discuss the similarities and differences in accepted bioequivalence (BE) approaches for generic topical dermatological drug products between international regulatory authorities and organizations. These drug products are locally applied and not intended for systemic absorption. Therefore, the BE approaches which serve as surrogates to establish safety and efficacy for topical dosage forms tend to differ from the traditional solid oral dosage forms. We focused on 15 different international jurisdictions and organizations that currently participate in the International Generic Drug Regulators Pilot Project. These are Australia, Brazil, Canada, China, Chinese Taipei, the European Medicines Association (EMA), Japan, Mexico, New Zealand, Singapore (a member of the Association of Southeast Asian Nations), South Africa, South Korea, Switzerland, the USA and the World Health Organization (WHO). Upon evaluation, we observed that currently only Canada, the EMA, Japan, and the USA have specific guidance documents for topical drug products. Across all jurisdictions and organizations, the three approaches consistently required are (1) BE studies with clinical endpoints for most topical drug products; (2) in vivo pharmacodynamic studies, in particular the vasoconstrictor assay for topical corticosteroids; and (3) waivers from BE study requirements for topical solutions. Japan, South Africa, the USA, and the WHO are also making strides to accept other BE approaches such as in vivo pharmacokinetic studies for BE assessment, in vivo dermatopharmacokinetic studies and/or BE studies with in vitro endpoints.KEY Words: bioequivalence, bioequivalence studies with clinical endpoints, biowaivers, dermatopharmacokinetics, topical dermatological drug products, vasoconstrictor assay     

美国FDA鼻用制剂相关个药指导原则汇总分析

目的 通过梳理美国食品药品监督管理局（Food and Drug Administration,FDA）发布的鼻用制剂相关个药指导原则,总结FDA对鼻用制剂仿制药的研究要求,为国内鼻用制剂仿制药开发和评价提供参考。方法 在FDA官网发布的个药指导原则中筛选出鼻用制剂相关指导原则,进行汇总分析。结果 目前FDA现行43个鼻用制剂相关个药指导原则,推荐的生物等效性方法包括体外生物等效性研究、药动学研究、比较临床终点研究方法等,因不同品种而有所区别。部分个药指导原则已收录先进的体外检测技术如形态定向拉曼光谱用于代替体内临床试验。本文对不同种类生物等效性试验的试验设计、主要研究终点和等效性标准方面进行了代表性描述。结论 本文对FDA发布的鼻用制剂相关个药指导原则进行了汇总分析,为国内鼻用制剂仿制药开发和评价提供参考。     

速释口服固体制剂人体生物等效性试验豁免药学研究的要求

随着科学认知的不断深入,为缩短药品的批准上市时间,不同药品监管机构相继出台了人体生物等效性豁免的相关法规及技术文件,旨在通过体外研究来替代体内试验。总结和比较国内外相关指导原则对速释口服固体剂型的仿制药药学研究的要求,重点关注存在的差异之处,探讨背后的科学原因,并在最终经国际人用药品注册技术协调委员会协调一致的过程中得到思考和启示,以期增加仿制药被豁免体内试验的成功率、进而降低仿制药的开发成本,但同时亦能保证其质量和疗效与参比制剂一致,真正实现其临床可替代性。     

A Systematic Analysis of the Sensitivity of Plasma Pharmacokinetics to Detect Differences in the Pulmonary Performance of Inhaled Fluticasone Propionate Products Using a Model-Based Simulation Approach

The role of plasma pharmacokinetics (PK) for assessing bioequivalence at the target site, the lung, for orally inhaled drugs remains unclear. A validated semi-mechanistic model, considering the presence of mucociliary clearance in central lung regions, was expanded for quantifying the sensitivity of PK studies in detecting differences in the pulmonary performance (total lung deposition, central-to-peripheral lung deposition ratio, and pulmonary dissolution characteristics) between test (T) and reference (R) inhaled fluticasone propionate (FP) products. PK bioequivalence trials for inhaled FP were simulated based on this PK model for a varying number of subjects and T products. The statistical power to conclude bioequivalence when T and R products are identical was demonstrated to be 90% for approximately 50 subjects. Furthermore, the simulations demonstrated that PK metrics (area under the concentration time curve (AUC) and C_max) are capable of detecting differences between T and R formulations of inhaled FP products when the products differ by more than 20%, 30%, and 25% for total lung deposition, central-to-peripheral lung deposition ratio, and pulmonary dissolution characteristics, respectively. These results were derived using a rather conservative risk assessment approach with an error rate of <10%. The simulations thus indicated that PK studies might be a viable alternative to clinical studies comparing pulmonary efficacy biomarkers for slowly dissolving inhaled drugs. PK trials for pulmonary efficacy equivalence testing should be complemented by in vitro studies to avoid false positive bioequivalence assessments that are theoretically possible for some specific scenarios. Moreover, a user-friendly web application for simulating such PK equivalence trials with inhaled FP is provided.

Electronic supplementary material

The online version of this article (doi:10.1208/s12248-015-9768-y) contains supplementary material, which is available to authorized users.Key words: bioequivalence, inhaled corticosteroids, pharmacokinetics, pharmacometrics, trial simulation     

Dissolution Testing as a Prognostic Tool for Oral Drug Absorption: Immediate Release Dosage Forms

Dissolution tests are used for many purposes in the pharmaceutical industry: in the development of new products, for quality control and, to assist with the determination of bioequivalence. Recent regulatory developments such as the Biopharmaceutics Classification Scheme have highlighted the importance of dissolution in the regulation of post-approval changes and introduced the possibility of substituting dissolution tests for clinical studies in some cases. Therefore, there is a need to develop dissolution tests that better predict the in vivo performance of drug products. This could be achieved if the conditions in the gastrointestinal tract were successfully reconstructed in vitro. The aims of this article are, first, to clarify under which circumstances dissolution testing can be prognostic for in vivo performance, and second, to present physiological data relevant to the design of dissolution tests, particularly with respect to the composition, volume, flow rates and mixing patterns of the fluids in the gastrointestinal tract. Finally, brief comments are made in regard to the composition of in vitro dissolution media as well as the hydrodynamics and duration of the test.     

Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Metformin Hydrochloride

Data are examined regarding possible waiver of in vivo bioequivalence testing (i.e. biowaiver) for approval of metformin hydrochloride (metformin) immediate-release solid oral dosage forms. Data include metformin's Biopharmaceutics Classification System (BCS) properties, including potential excipient interactions. Metformin is a prototypical transporter-mediated drug and is highly soluble, but only 50% of an orally administered dose is absorbed from the gut. Therefore, metformin is a BCS Class III substance. A BCS-based approval approach for major changes to marketed products and new generics is admissible if test and reference dosage forms have the identical active pharmaceutical ingredient and if in vitro dissolution from both are very rapid (i.e. at least 85% within 15 min at pH 1.2, 4.5, and 6.8). Recent International Council for Harmonisation BCS guidance indicates all excipients for Class III biowaivers are recommended to be qualitatively the same and quantitatively similar (except for preservatives, flavor agents, colorant, or capsule shell or film coating excipients). However, despite metformin being a prototypical transporter-mediated drug, there is no evidence that commonly used excipients impact metformin absorption, such that this restriction on excipients for BCS III drugs merits regulatory relief. Commonly used excipients in usual amounts are not likely to impact metformin absorption.     

Performance Properties of the Population Bioequivalence Approach for In Vitro Delivered Dose for Orally Inhaled Respiratory Products

Regulatory agencies, industry, and academia have acknowledged that in vitro assessments serve a role in establishing bioequivalence for second-entry drug product approvals as well as innovator post-approval drug product changes. For orally inhaled respiratory products (OIPs), the issues of correctly analyzing in vitro data and interpreting the results within the broader context of therapeutic equivalence have garnered significant attention. One of the recommended statistical tests for in vitro data is the population bioequivalence method (PBE). The current literature for assessing the PBE statistical approach for in vitro data assumes a log normal distribution. This paper focuses on an assessment of that assumption for in vitro delivered dose. Concepts in development of a statistical model are presented. The PBE criterion and hypotheses are written for the case when data follows a normal distribution, rather than log normal. Results of a simulation study are reported, characterizing the performance of the PBE approach when data are expected to be normally distributed, rather than log normal. In these cases, decisions using the PBE approach are not consistent for the same absolute mean difference that the test product is from the reference product. A conclusion of inequivalency will occur more often if the test product dose is lower than the reference product for the same deviation from target. These features suggest that more research is needed for statistical equivalency approaches for in vitro data.     

Assessment of the possibility of using comparative <Emphasis Type="Italic">in vitro</Emphasis> dissolution kinetics (biowaiver) instead of <Emphasis Type="Italic">in vivo</Emphasis> bioequivalence evaluation for establishing the interchanbeability of generic drugs

One way of establishing the interchangeability of generic drugs is based on an in vitro study of the dissolution kinetics (biowaiver). The most common approaches for assessing the ability to use the biowaiver procedure instead of the traditional bioequivalence evaluation for generics are reviewed.