The bioequivalence study design recommendations for immediate-release solid oral dosage forms in the international pharmaceutical regulators programme participating regulators and organisations: differences and commonalities.

Bioequivalence (BE) studies are considered the standard for demonstrating that the performance of a generic drug product in the human body is sufficiently similar to that of its comparator product. The objective of this article is to describe the recommendations from participating Bioequivalence Working Group for Generics (BEWGG) members of the International Pharmaceutical Regulators Programme (IPRP) regarding the conduct and acceptance criteria for BE studies of immediate release solid oral dosage forms. A survey was conducted among BEWGG members regarding their BE recommendations and requirements related to study subjects, study design, sample size, single or multiple dose administration, study conditions (fasting or fed), analyte to be measured, selection of product strength, drug content, handling of endogenous substances, BE acceptance criteria, and additional design aspects. All members prefer conducting single dose cross-over designed studies in healthy subjects with a minimum of 12 subjects and utilizing the parent drug data to assess BE. However, differences emerged among the members when the drug's pharmacokinetics and pharmacodynamics become more complex, such that the study design (e.g., fasting versus fed conditions) and BE acceptance criteria (e.g., highly variable drugs, narrow therapeutic index drugs) may be affected. The survey results and discussions were shared with the ICH M13 Expert Working Group (EWG) and played an important role in identifying and analyzing gaps during the harmonization process. The draft ICH M13A guideline developed by the M13 EWG was endorsed by ICH on 20 December 2022, under Step 2.

The Prevalence of Several Treatments in Preventing the Back Conversion of Acyl Glucuronide Metabolites in Abbreviated New Drug Applications.

The bioanalysis of drugs that undergo acyl glucuronidation presents an analytical challenge due to poor stability of acyl glucuronide metabolites in biological matrices. The objective of this study was to investigate the impact of back conversion of acyl glucuronide metabolites on drug concentration measurement in bioequivalence (BE) studies submitted to Abbreviated New Drug Applications (ANDAs). The prevalence of several treatments for preventing the back conversion of acyl glucuronide metabolites and the results of incurred sample reanalysis (ISR) were analyzed. In total, 322 ANDAs for 26 drugs known to generate acyl glucuronide metabolites were surveyed. Many studies have applied multiple preventive treatments during the clinical and bioanalytical phases. More than two-thirds (67.2%) of the studies utilized procedures of lowering the temperature for sample collection during clinical phase. Fewer studies have utilized procedures for lowering the pH of plasma samples (12.3%) or adding enzyme inhibitors (4.4%) in the clinical phase. A small fraction (16.9%) validated the pre-study method in the presence of the acyl glucuronide metabolites. The majority (62.2%) of the studies employed the procedure of lowering the pH during the sample extraction process in the bioanalytical phase. Among the studies that had significantly higher (p-value < 0.01 by sign test) ISR results than the corresponding original concentration values, 41 BE studies did not carry out any preventive treatments during the bioanalysis phase, suggesting that back conversion of acyl glucuronide metabolites to parent drugs may be present in these studies. The awareness of appropriate treatments of study samples for possible back-conversions of acyl glucuronide metabolites is expected to assist generic drug applicants in improving the quality of their future applications.

A Survey of the Criteria Used for the Selection of Alternative Comparator Products by Participating Regulators and Organizations of the International Pharmaceutical Regulators Programme.

The safety and efficacy of a generic product are partly based on demonstrating bioequivalence to the innovator product; however, when the innovator product is no longer available as a comparator product, a survey conducted within the Bioequivalence Working Group for Generics (BEWGG) of the International Pharmaceutical Regulators Programme (IPRP) indicated that the criteria for selecting an alternative comparator product varies. For most members of the BEWGG, an existing marketed generic that was approved based on a comparison with the locally registered innovator product can be used, contingent on criteria that ranges from allowing any generic to be used, to allowing only specific criteria-defined generics to be used. Notwithstanding the acceptability of a generic as an alternative comparator, it is not always the preferred comparator for several jurisdictions. Some jurisdictions require the use of a locally sourced alternative innovator comparator (e.g., the same medicinal ingredient manufactured by a different company) or a foreign innovator comparator. Unlike the other members of the BEWGG, the European Union (EU) has no such options available, rather mechanisms are in place to allow manufacturers to develop a new comparator. The criteria described herein regarding the use of an alternative comparator product can also be applied to scenarios where a specific strength of a series of strengths or an innovative fixed dose combination are discontinued. The results of the survey demonstrate that while criteria for selecting alternative comparator products are not harmonized among the BEWGG participants, the common concern for all jurisdictions is to select a comparator product that meets the safety and efficacy standards of the original innovator product.

A Survey of the Regulatory Requirements for the Waiver of In Vivo Bioequivalence Studies of Generic Products in Certain Dosage Forms by Participating Regulators and Organisations of the International Pharmaceutical Regulators Programme.

The requirements to waive in vivo bioequivalence studies for immediate release solid oral dosage forms based on the Biopharmaceutics Classifications System (BCS) are well known, and biowaivers[1] for other types of oral dosage forms based on pre-defined criteria may also be acceptable. Similarly, biowaivers for dosage forms such as injectable products may also be allowed if certain criteria are met. The current paper summarises the biowaiver requirements for oral solutions and suspensions, soft gelatin capsules and injectable products (intravenous injections, subcutaneous and intramuscular injections, emulsions for injection and micellar solutions for injection) among the participants of the Bioequivalence Working Group for Generics (BEWGG) of the International Pharmaceutical Regulators Programme (IPRP). A review of the requirements indicated that there was a trend towards convergence when the dosage form became less complex; however, the most common approach used by each of the jurisdictions was a case-by-case approach given that most jurisdictions do not have well defined guidelines to support all possible scenarios. Even in the simplest case of intravenous solutions, the acceptability of qualitative changes in excipients differ between the IPRP members.  Notwithstanding the differences, the dissemination of the information is a first step towards regulatory convergence regarding biowaivers for certain dosage forms and should be useful for pharmaceutical companies currently developing generic medicinal products for IPRP jurisdictions.

A Survey of the Regulatory Requirements for the Acceptance of Foreign Comparator Products by Participating Regulators and Organizations of the International Generic Drug Regulators Programme.

The acceptance of foreign comparator products is the most limiting factor for the development and regulatory assessment of generic medicines marketed globally. Bioequivalence studies have to be repeated with the local comparator products of each jurisdiction because it is unknown if the comparators of the different countries are the same product, with the consequent duplication of efforts by regulators and industry alike. The regulatory requirements on the acceptability of foreign comparator products of oral dosage forms differ between countries participating in the Bioequivalence Working Group for Generics of the International Pharmaceutical Regulators Programme. Brazil, Colombia, the European Union member States, Japan, Mexico, South Korea and the United States only accept bioequivalence studies with their local comparator. In contrast, Australia, Canada, New Zealand, Singapore, South Africa, Switzerland and Taiwan accept studies with foreign comparators under certain conditions. Canada limits its use to highly soluble drugs with a wide therapeutic range in immediate release products. Australia requires a comparison of the quantitative composition. In contrast, there are fewer restrictions on the acceptance of foreign comparators in New Zealand, Singapore, South Africa, Switzerland and Taiwan. For the WHO Prequalification of Medicines and for developing generics of the essential medicines the WHO lists comparators from different countries. In conclusion, there is currently no consensus amongst regulators on the acceptability of foreign comparator products.

The Requirements for Additional Strength Biowaivers for Immediate Release Solid Oral Dosage Forms in International Pharmaceutical Regulators Programme Participating Regulators and Organisations: Differences and Commonalities.

In relation to the registration of generic products, waivers of in vivo bioequivalence studies (biowaivers) are considered in three main cases: certain dosage forms for which bioequivalence is self-evident (e.g. intravenous solutions), biowaivers based on the Biopharmaceutics Classification System and biowaivers for additional strengths with respect to the strength for which in vivo bioequivalence has been shown. The objective of this article is to describe the differences and commonalities in biowaivers for additional strengths of immediate release solid oral dosage forms between the participating members of the International Pharmaceutical Regulators Program (IPRP). The requirements are based on five main aspects; the pharmacokinetics of the drug substance, the manufacturing process, the qualitative and quantitative composition of the different strengths, and the comparative dissolution profiles. For the pharmacokinetic aspects, many regulators/agencies have the same requirements. All strengths must be manufactured with the same process, although a few regulators/agencies accept small differences. In relation to the formulation aspects, the data required breaks down into three major approaches based initially on one of those of the EU, the USA or Japan, but there are some differences in these three major approaches with some country specific interpretations. Most regulators/agencies also have the same requirements for the dissolution data, though there are some notable exceptions.

A Survey of the Regulatory Requirements for BCS-Based Biowaivers for Solid Oral Dosage Forms by Participating Regulators and Organisations of the International Generic Drug Regulators Programme.

PURPOSE: The Biopharmaceutics Classification System (BCS) based biowaiver is a scientific model which enables the substitution of in vivo bioequivalence studies with in vitro data as evidence of therapeutic equivalence subject to certain conditions. Despite being based on the same principles, BCS-based biowaivers are interpreted and regulated differently among international regulatory agencies. In this survey, the Bioequivalence Working Group (BEWG) of the International Generic Drug Regulators Programme (IGDRP) compared the criteria for BCS-based biowaivers applied by the participating regulators and organisations. METHODS: Differences and similarities regarding solubility, permeability, dissolution, excipients and fixed-dose combination products, were identified and compared in a detailed survey of each participant's criteria for BCS-based biowaivers. These criteria were determined based upon the participants' respective regulatory guidance documents, policies and practices. RESULTS: This review has, with the exception of two participants who do not accept BCS-based biowaivers, revealed that most IGDRP participants interpret the BCS principles and conditions similarly but notable differences exist in the application of these principles.  Conclusion: Although many similarities exist, this review identifies several opportunities for greater convergence of regulatory requirements amongst the surveyed jurisdictions. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

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.

International guidelines for bioequivalence of systemically available orally administered generic drug products: a survey of similarities and differences.

The objective of this article is to discuss the similarities and differences among bioequivalence approaches used by international regulatory authorities when reviewing applications for marketing new generic drug products which are systemically active and intended for oral administration. We focused on the 13 jurisdictions and organizations participating in the International Generic Drug Regulators Pilot. These are Australia, Brazil, Canada, China, Chinese Taipei, the European Medicines Association, Japan, Mexico, Singapore, South Korea, Switzerland, the USA, and the World Health Organization. We began with a comparison of how the various jurisdictions and organizations define a generic product and its corresponding reference product. We then compared the following bioequivalence approaches: recommended bioequivalence study designs, method of pharmacokinetic calculations and bioequivalence acceptance limits, recommendations for modifying bioequivalence study designs and limits for highly variable drugs and narrow therapeutic index drugs, provisions for waiving bioequivalence study requirements (granting biowaivers), and implementation of the Biopharmaceutics Classification System. We observed that, overall, there are more similarities than differences in bioequivalence approaches among the regulatory authorities surveyed.

Role of metabolites for drugs that undergo nonlinear first-pass effect: impact on bioequivalency assessment using single-dose simulations.

We investigated the effects of dose and intrasubject variability (ISV) on bioequivalence (BE) of a parent drug with a single metabolite formed by nonlinear first-pass. A BE simulation was done using a four-compartment model at doses of 17.5, 35.0, and 70.0 mg. ISV was set at either 10% or 20% for clearance and either 20% or 50% for the absorption rate constant, K(a). The ratio of Katest/Kreference was fixed at 1.00 while fraction available ratios, F(test)/F(reference), were varied from 1.00 to 1.25. Results showed the probability of passing the 90% confidence interval (CI) BE requirement for AUC(I), area-under-the-concentration curve to time infinity, and C(max), concentration maximum, were greater for the metabolite than the parent at all F(test)/F(reference) ratios. For the parent, the probability of meeting BE criteria for AUC(I) and C(max) declined from 100% to 60% at the 70 mg dose as the ISV for K(a) increased from 20% to 50% with an increased F(test)/F(reference) ratio. For the metabolite, the probability of meeting BE criteria was above 80% for all doses and ISV values and F(test)/F(reference) ratios less than 1.15. Results show that the parent, reflected absorption, is more informative for determining BE than the metabolite. Clinical data gave a similar result.

Micellar aggregation and membrane partitioning of bile salts, fatty acids, sodium dodecyl sulfate, and sugar-conjugated fatty acids: correlation with hemolytic potency and implications for drug delivery.

The co-administration of a drug with a penetration enhancer (PE) is one method by which the membrane permeability of a drug can be improved. To facilitate PE design, it is important that the molecular basis of PE toxicity and efficacy be examined, so we investigated the membrane affinity and micellar aggregation of a series of synthetic liposaccharide PEs and correlated these properties with hemolytic potency. The influence of liposaccharide alkyl chain length (nc) on the system was studied, and comparisons were made with conventional PEs such as bile salts, fatty acids, and surfactants. The liposaccharides were each synthesized in eight steps in good overall yield. Their critical micelle concentrations (CMCs) in phosphate-buffered saline ranged from 0.207 to 20.2 mM, and it was found that increasing nc by 2 afforded a 1 order of magnitude decrease in the CMC. Immobilized artificial membrane (IAM) chromatography was used to determine each PE's affinity for biological membranes, and an increase in nc caused a significant increase in the extent of membrane binding. A study of hemolytic activity revealed that liposaccharides with an nc of < or = 12 are the most likely to be biocompatible. The CMC values for all PEs showed a negative correlation with hemolytic potency; however, it was PE monomers, not micelles, that were responsible for the onset of hemolysis. The affinity of all enhancers for the IAM displayed a positive correlation with hemolytic potency, and therefore, IAM chromatography can be used to predict PE hemolytic activity. It was concluded that the biocompatibility of liposaccharides can be modulated by minor alterations in nc.

Prodrugs to enhance central nervous system effects of the TRH-like peptide pGlu-Glu-Pro-NH2.

Potential prodrugs for the TRH-like tripeptide pGlu-Glu-Pro-NH(2) were synthesized either by esterifying the Glu side-chain of the parent peptide in solution with alcohols in the presence of resin-bound dicyclohexylcarbodiimide or by solid-phase peptide chemistry. Affinities of these ester prodrugs to lipid membranes as predictors of the transport across the blood-brain barrier were compared by immobilized artificial membrane chromatography, and prodrug activation was tested in the brain tissue of experimental animals. Esters of pGlu-Glu-Pro-NH(2) with long-chain primary alcohols emerged as potentially useful prodrugs to improve the central nervous system activity of pGlu-Glu-Pro-NH(2) upon systemic administration, as revealed by the enhancement of analeptic activity in mice.

Immobilized artificial membrane chromatography coupled with atmospheric pressure ionization mass spectrometry.

Liquid chromatographic separations on monolayers of cell membrane phospholipids covalently immobilized to silica particles at high molecular density is used for mimicking solute partitioning into biological membranes that generally correlates with membrane transport. This technique called immobilized artificial membrane chromatography usually employs ultraviolet (UV) detection where a single compound is analyzed in a chromatographic run limiting thereby its throughput for drug discovery applications. For coupling with atmospheric pressure ionization mass spectrometry, the phosphate-buffered saline mobile phase was replaced with one that used ammonium acetate as a volatile buffer. While atmospheric pressure chemical ionization accommodated a purely aqueous effluent, interfacing with electrospray ionization required effluent splitting and the addition of an organic modifier (5%, v/v, acetonitrile). Neuropeptide FF antagonists as early-phase drug candidates were used for the comparative evaluation of the methods. Whereas electrospray ionization produced essentially no fragment ions, several compounds involved in our study yielded low-abundance molecular ions with atmospheric pressure chemical ionization. The use of mass spectrometry yielded data that correlated well with those obtained by the method employing UV detection. Both atmospheric pressure ionization methods permitted the simultaneous determination of the k'(IAM), capacity factors and, therefore, an increased-throughput ranking of potential new leads emerged from the drug discovery process based on affinity to artificial membranes.