Bioequivalence Research Articles

Evaluation of product bioequivalence when subject blood volume necessitates limited sampling strategies.

In a traditional blood level bioequivalence (BE) study, every subject provides drug concentrations at each blood sampling time. However, this approach is not suitable for animals whose blood volume limits or prohibits multiple sample collections. In our previous research, we presented an approach that can be applied to studies using a destructive sampling design where each animal provides only 1 blood sample that is then incorporated into a composite profile. Another situation we sometimes face is that of when the animals can contribute more than one sample but are still limited in the number of blood draws (e.g., 3) such that a complete profile per animal is not feasible. Unlike the destructive sampling situation, we cannot combine all blood samples into a single "composite" profile and ignore the correlation of values obtained from the same subject. To avoid the complexities associated with needing to include a covariance component among experimental units into the statistical model, we propose an approach whereby study subjects are randomly assigned to housing unit (e.g., cage or pen) and then randomly assigned to a sampling schedule within each housing unit. In doing so, housing unit rather than the individual subject serves as the experimental unit. This article provides an assessment of this alternative approach to assess product BE when only a limited number of samples can be obtained per study subject.

Taste-masked formulation of sodium phenylbutyrate (ACER-001) for the treatment of urea cycle disorders

Urea cycle disorders (UCDs) are a group of rare inherited metabolic diseases caused by a deficiency of one of the enzymes or transporters that constitute the urea cycle. Defects in these enzymes lead to acute accumulation (hyperammonemic crises, HAC) or chronically elevated levels (hyperammonemia) of ammonia in the blood and/or various tissues including the brain, which can cause persistent neurological deficits, irreversible brain damage, coma, and death. Ongoing treatment of UCDs include the use of nitrogen-scavenging agents, such as sodium phenylbutyrate (salt of 4-phenylbutyric acid; NaPBA) or glycerol phenylbutyrate (GPB). These treatments provide an alternative pathway for nitrogen disposal through the urinary excretion of phenylacetylglutamine. ACER-001 is a novel formulation of NaPBA with polymer coated pellets in suspension, which is designed to briefly mask the unpleasant bitter taste of NaPBA and is being developed as a treatment option for patients with UCDs. Four Phase 1 studies were conducted to characterize the bioavailability (BA) and/or bioequivalence (BE) of ACER-001 (in healthy volunteers) and taste assessment relative to NaPBA powder (in taste panelists). ACER-001 was shown to be bioequivalent to NaPBA powder under both fed and fasting conditions. Lower systemic exposure of phenylacetate (PAA) and phenylbutyrate (PBA) was observed when ACER-001 was administered with a high-fat meal relative to a fasting state suggesting that the lower doses of PBA administered under fasting conditions may yield similar efficacy with potentially fewer dose dependent adverse effects relative to higher doses with a meal. ACER-001 appeared to be adequately taste-masked, staying below the aversive taste threshold for the first 3min after the formulation was prepared and remaining palatable when taken within 5min.

Health professionals' perceptions on local production and bioequivalence study of generic medicines: A cross-sectional survey of physicians and pharmacy professionals in Addis Ababa, Ethiopia.

Local production of generic medicines in developing countries has a critical role to meet public health needs by ensuring the availability of essential medicines and providing patients' relief from the burden of unaffordable medical bills. Compliance with bioequivalence (BE) requirements increase the quality and competitiveness of generic drugs regardless of the source. In this regard, a regional BE center has been established in Addis Ababa, Ethiopia to serve the needs of Ethiopia and neighbouring countries. The present study aimed to assess the knowledge and perceptions of health professionals working in Addis Ababa regarding local production and BE studies of generic medicines. A cross-sectional survey was employed and physician participants working at public hospitals and pharmacists from various practice settings were selected using convenient sampling technique. Data was collected using self-administered structured questionnaire. Descriptive statistics was used to summarize the data and multinomial logistic regression analyses was used to assess predictors of health professionals' perception towards the source of drugs. Statistically significant association was declared at p-value < 0.05. A total of 416 participants responded and 272 (65.4%) of them were male. Nearly half of the study participants (n = 194) preferred the imported products. Compared to physicians, participants with diploma (AOR = 0.40; 95%CI: 0.18-0.91, p = 0.028) and bachelor degree and above holders (AOR = 0.32; 95%CI: 0.15-0.68, p = 0.003) in pharmacy were more likely to prefer locally produced products. Participants who practiced in pharmaceutical industries (AOR = 0.40, 95%CI: 0.22-0.77, p = 0.006) preferred locally manufactured products as compared to those practicing in the hospital. While a majority (321, 77.2%) believed in the advantages of doing BE studies locally, only 106 (25.5%) recognized that local pharmaceutical manufacturers did not implement BE studies for their generic products and lack of enforcement by the national regulatory body was raised as a reason for not conducting BE studies by most of the participants (67.9%). The present study revealed a modest preference by physicians and pharmacy professionals towards locally produced products. Majority of participants supported the idea of doing BE studies locally. However, manufacturers and regulators should devise ways to increase health professionals' confidence in local products. Strengthening local BE study capacity is also highly recommended.

Confocal Raman Spectroscopy for Assessing Bioequivalence of Topical Formulations.

The evaluation of bioequivalence (BE) for topical dermatological drug products is challenging, and there has been significant interest from regulatory authorities in developing new BE methodologies in recent years. Currently, BE is demonstrated by comparative clinical endpoint studies; these are costly and time-consuming and often lack sensitivity and reproducibility. Previously, we reported excellent correlations between in vivo Confocal Raman Spectroscopy in human subjects and in vitro skin permeation testing (IVPT) with the human epidermis for skin delivery of ibuprofen and a number of excipients. The aim of the present proof-of-concept study was to evaluate CRS as a method to assess BE of topical products. Two commercially available formulations, Nurofen Max Strength 10% Gel and Ibuleve Speed Relief Max Strength 10% Gel, were selected for evaluation. Delivery of ibuprofen (IBU) to the skin was determined in vitro and in vivo by IVPT and CRS, respectively. The formulations examined were found to deliver comparable amounts of IBU across the skin over 24 h in vitro (p > 0.05). Additionally, the formulations resulted in similar skin uptake values measured with CRS in vivo, either at 1 h or 2 h after application (p > 0.05). This is the first study to report the capability of CRS for the demonstration of BE of dermal products. Future studies will focus on the standardisation of the CRS methodology for a robust and reproducible pharmacokinetic (PK)-based evaluation of topical BE.

Pharmacokinetic comparison of sitagliptin and metformin HCl extended-release tablets versus JANUMET® XR in healthy volunteers under fasting and fed conditions.

Background and Objectives: Janumet® XR is the combination of sitagliptin and extended metformin hydrochloride produced by Merck Sharp & Dohme. It is specially designed for diabetes mellitus patients taking both drugs already. Janumet® XR exhibited clinically significant blood glucose lowering efficacy and long-term use safety. However, no generic form of Janumet® XR has been approved in western countries. The relatively high cost made the medication less prescribed. A more affordable form of this drug may benefit an immense diabetes mellitus population. The current study compared the bioequivalence (BE) of sitagliptin 100mg and metformin 1000mg produced by Nanjing Chia-Tai Tianqing Pharmaceutical Company to Janumet® XR in healthy Chinese subjects. Methods: Twenty-eight healthy Chinese subjects were enrolled in Study 1 and 2, respectively. Both studies were conducted with an open, randomized, two-period crossover design using the test (T) or the reference (R) drug. Study 1 is conducted under the fasting state, and Study 2 is under the fed state. Subjects received an oral dose of sitagliptin 100mg and metformin 1000mg, and plasma concentrations of sitagliptin and metformin were determined up to 72h post-dose. Pharmacokinetic (PK) parameters, including maximum serum concentration (Cmax) and area under the concentration-time curve up to the last quantifiable concentration (AUC0-t) of both sitagliptin and metformin, were calculated and compared between the T and R treatments. Results: In the fasting study, the geometric mean ratios of Cmax, AUC0-t, and AUC0-∞ for sitagliptin were 109.42%, 101.93%, and 101.95%, respectively; the corresponding ratios for metformin were 98.69%, 94.12%, and 93.42%, respectively. In the fed study, the geometric mean ratios of Cmax, AUC0-t, and AUC0-∞ for sitagliptin were 98.41%, 100.30%, and 100.24%, respectively; the corresponding ratios for metformin were 97.79%, 99.28%, and 100.69%, respectively. The 90% CIs of Cmax, AUC0-t, and AUC0-∞ in both studies were all within acceptance limits (80.00%-125.00%). Conclusion: The results demonstrated for the first time that sitagliptin 100mg and metformin 1000mg produced by Nanjing Chia-Tai Tianqing Pharmaceutical Company was bioequivalent to the branded Janumet® XR, and both drugs were well tolerated.

Mechanistic modeling of ophthalmic, nasal, injectable, and implant generic drug products: A workshop summary report.

For approval, a proposed generic drug product must demonstrate it is bioequivalent (BE) to the reference listed drug product. For locally acting drug products, conventional BE approaches may not be feasible because measurements in local tissues at the sites of action are often impractical, unethical, or cost-prohibitive. Mechanistic modeling approaches, such as physiologically-based pharmacokinetic (PBPK) modeling, may integrate information from drug product properties and human physiology to predict drug concentrations in these local tissues. This may allow clinical relevance determination of critical drug product attributes for BE assessment during the development of generic drug products. In this regard, the Office of Generic Drugs of the US Food and Drug Administration has recently established scientific research programs to accelerate the development and assessment of generic products by utilizing model-integrated alternative BE approaches. This report summarizes the presentations and panel discussion from a public workshop that provided research updates and information on the current state of the use of PBPK modeling approaches to support generic product development for ophthalmic, injectable, nasal, and implant drug products.

Comparative Bioequivalence of Tablet and Capsule Formulations of Ulotaront and the Effect of Food on the Pharmacokinetics of the Tablet Form in Humans.

Ulotaront (SEP-363856), a dual trace animeassociated receptor 1 (TAAR1) and 5-HT1A receptor agonist, is in phase 3 clinical development for the treatment of schizophrenia. This study evaluated the comparative bioequivalence (BE) between tablet and capsule formulations of ulotaront and the food effect (FE) on pharmacokinetics (PK) of tablet form in healthy adult human subjects. The BE study applied an open-label two-period crossover design in 24 healthy volunteers. Subjects were randomly assigned (1:1) to dosing sequence AB or BA (A, 25 mg ulotaront tablet; B, 25 mg ulotaront capsule). The FE study also used an open-label randomized two-period crossover design in 20 healthy volunteers. Subjects were fasted overnight then randomly assigned (1:1) to dosing sequence AB or BA (A, fasted condition; B, fed condition). Dosing periods were separated by 1 week for both studies. Serial plasma samples from each period were collected and analyzed by LC-MS/MS. PK parameters were calculated using Phoenix WinNonlin® software. For the BE study, geometric mean ulotaront Cmax values were 93.28 and 86.98 ng/mL for tablet and capsule, respectively. Cmax ratio was 107.25% (90% CI 101.84-112.94%). Geometric mean ulotaront area under the plasma concentration-time curve from time 0 to infinity (AUC0-∞) values were 868.8 and 829.3 ng·h/mL for tablet and capsule, respectively. AUC0-∞ ratio was 104.76% (90% CI 100.68109.01%). For the FE study, geometric mean ulotaront Cmax was 157.89 and 157.95 ng/mL under fed and fasted conditions, respectively. Geometric mean ratio of Cmax was 99.96% (90% CI 94.48-105.77%). Geometric mean ulotaront AUC0-∞ was 1584.2 ng·h/mL fed and 1589.2 ng·h/mL fasted. Geometric mean ratio for AUC0-∞ was 99.69% (90% CI 95.02-104.58%). There was a delay in tmax (median difference 1.47 h) in the fed condition. The results showed geometric mean ratios and 90% CIs for both Cmax and AUC0-∞ for ulotaront were well within typical bioequivalence criteria of 80-125% for both the BE and FE studies, thereby confirming the bioequivalence of the two dosage forms and no significant food effect.

Predictive Potential of BCS and Pharmacokinetic Parameters on Study Outcome: Analysis of 198 In Vivo Bioequivalence Studies.

Understanding predictive potential of parameters to perform early bioequivalence (BE) risk assessment is crucial for good planning and risk mitigation during product development. The objective of the present study was to evaluate predictive potential of various biopharmaceutical and pharmacokinetic parameters on the outcome of BE study. Retrospective analysis was performed on 198 Sandoz (Lek Pharmaceuticals d.d., A Sandoz Company, Verovskova 57, 1526 Ljubljana, Slovenia) sponsored BE studies [52 active pharmaceutical ingredients (API)] where characteristics of BE study and APIs were collected for immediate-release products and their predictive potential on the study outcome was assessed using univariate statistical analysis. Biopharmaceutics Classification System (BCS) was confirmed to be highly predictive of BE success. BE studies with poorly soluble APIs were riskier (23% non-BE) than with highly soluble APIs (0.1% non-BE). APIs with either lower bioavailability (BA), presence of first-pass metabolism, and/or being substrate for P-glycoprotein substrate (P-gP) were associated with higher non-BE occurrence. Insilico permeability and time at peak plasma concentrations (Tmax) were shown as potentially relevant features for predicting BE outcome. In addition, our analysis showed significantly higher occurrence of non-BE results for poorly soluble APIs with disposition described by multicompartment model. The conclusions for poorly soluble APIs were the same on a subset of fasting BE studies; for a subset of fed studies there were no significant differences between factors in BE and non-BE groups. Understanding the association of parameters and BE outcome is important for further development of early BE risk assessment tools where focus should be first in finding additional parameters to differentiate BE risk within a group of poorly soluble APIs.

Computational design of clinical trials using a combination of simulation and the genetic algorithm.

Artificial intelligence (AI) has come to be used in various technological fields in recent years. However, there have been no reports of AI-designed clinical trials. In this study, we tried to develop study designs by a genetic algorithm (GA), which is an AI solution for combination optimization problems. Specifically, the computational design approach was applied to optimize the blood sampling schedule for a bioequivalence (BE) study in pediatrics and optimize the allocation of dose groups for a dose-finding study. The GA could reduce the number of blood collection points from 15 (typical standard) to seven points without meaningful impact on the accuracy and precision of the pharmacokinetic estimation for the pediatric BE study. For the dose-finding study, up to 10% reduction of the total number of required subjects from the standard design could be achieved. The GA also created a design that would lead to a drastic reduction of the required number of subjects in the placebo arm while keeping the total number of subjects at a minimum level. These results indicated the potential usefulness of the computational clinical study design approach for innovative drug development.

Bioequivalence Dissolution Test Criteria for Formulation Development of High Solubility-Low Permeability Drugs.

The purpose of the present study was to provide the experimental and theoretical basis of bioequivalence (BE) dissolution test criteria for formulation development of high solubility-low permeability drugs. According to the biowaiver scheme based on the biopharmaceutics classification system (BCS), for BCS class III drugs, a test formulation and a reference formulation are predicted to be BE when 85% of the drug dissolves within 15 min (T85% < 15 min) in the compendial dissolution test. However, previous theoretical simulation studies have suggested that this criterion may possibly be relaxed for use in practical formulation development. In the present study, the dissolution profiles of 14 famotidine formulations for which BE has been clinically confirmed were evaluated by the compendial dissolution test at pH 1.2 and 6.8. The plasma concentration-time profiles of famotidine formulations were simulated using the dissolution data. In addition, virtual simulations were performed to estimate the range of dissolution rates to be bioequivalent. The fastest and slowest dissolution rates among the famotidine formulations were T85% = 10 min and T85% = 60 min at pH 6.8, respectively. The virtual simulation BE study suggested that famotidine formulations can be bioequivalent when T85% < 99 min. In the case of BCS III drugs, the rate-limiting step of oral drug absorption is the membrane permeation process rather than the dissolution process. Therefore, a difference in the dissolution process has less effect on BE. These results contribute to a better understanding of the biowaiver approach and would be of great help in the formulation development of BCS class III drugs.

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.

Drilling down the bioequivalence assessment of topical antifungal products: Microstructure and release

In recent years, the regulatory mechanisms for topical generic product bioequivalence (BE) assessment have been subjected to noteworthy changes, with the FDA issuing product specific guidances, and the EMA adopting a more universal approach with the quality and equivalence of topical products draft guideline. The agencies advise on a modular strategy for BE documentation. Nevertheless, their scope, data analysis and criteria are rather distinct.This study aims to tackle bioequivalence assessment issues of complex topical formulations starting by statistical implications of the EMA/FDA approaches concerning the documentation of qualitative (Q1), quantitative (Q2), microstructure (Q3) and performance requirements (Q4). As a model drug product, a bifonazole 10 mg/g cream formulation was selected. For this specific formulation, the commercially available Reference Product (RP) was compared with two comparator products, also commercially available, referred to as comparator product A (CPA) and comparator product B (CPB). The former displays Q1 sameness and Q2 differences, whilst CPB is categorically considered as Q1/Q2 different. Furthermore, intending to establish a regulatory rationale for the submission of a generic product according to the updated regulatory requirements, the RP was likewise compared with a Test Product (TP). This formulation was designed to display equal Q1/Q2 profile to that of the RP. Validated rheology and in vitro release test (IVRT) methods were used to infer on Q3/Q4 characteristics.During rheology studies, statistically significant RP batch to batch differences were observed. Therefore, in an attempt to surpass this heterogeneity, the initial pool of RP batches was expanded to include RP product batches at different lifecycle stages. Despite this effort, it was not possible to classify the RP/TP, RP/CPA or RP/CPB as rheologically equivalent products. Nevertheless, product performance results, retrieved from IVRT, were able to sustain equivalence between the RP and the formulations exhibiting Q1 sameness (TP and CPA). It should however be mentioned, that for some RP batch combinations, the IVRT results failed to demonstrate equivalence according to the EMA requirements. Enlarging the RP batch pool was then a critical step in further understanding an optimum statistical approach for establishing equivalence in product performance.This study highlights the need to that a ‘one-fits-all approach’ may not be an optimum path way for establishing the regulatory strategy and requirements to support generic product bioequivalence.

Evaluation of Pharmacokinetics and Safety With Bioequivalence of Voriconazole Injection of 2 Formulations in Chinese Healthy Volunteers: Bioequivalence Study.

Voriconazole is a first-line medicine for treating invasive aspergillosis. We aimed to evaluate the bioequivalence (BE) of voriconazole injection in Chinese healthy volunteers (HVs). In this single-center, randomized, single-dose, 2-cycle, fasting-dose BE study, HVs (n=24) were 1:1 divided into 2 groups (test [T]-reference [R] and R-T) and received 6mg/kg of voriconazole intravenously with a 7-day washout. The plasma was collected for up to 72hours at the time point after dosing on day 1/day 8. The plasma concentration of voriconazole was measured by liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were ascertained on the basis of a noncompartmental model. In the BE study, the geometric mean ratios of the maximum concentration, area under the concentration-time curve from time 0 to the last measurable plasma concentration, and area under the concentration-time curve from time 0 to infinity were 101.1%, 105.6%, and 105.5%, respectively, and the 90%CI fell within 80%-125%. Adverse events were observed in 26.1% of subjects in the T formulation stage and 17.4% in the R formulation stage. Under the BE study, voriconazole values from T and R formulations were bioequivalent.

Increasing impact of quantitative methods and modeling in establishment of bioequivalence and characterization of drug delivery.

Increasing impact of quantitative methods and modeling in establishment of bioequivalence and characterization of drug delivery.

Establishing the suitability of model-integrated evidence to demonstrate bioequivalence for long-acting injectable and implantable drug products: Summary of workshop.

On November 30, 2021, the US Food and Drug administration (FDA) and the Center for Research on Complex Generics (CRCG) hosted a virtual public workshop titled "Establishing the Suitability of Model-Integrated Evidence (MIE) to Demonstrate Bioequivalence for Long-Acting Injectable and Implantable (LAI) Drug Products." This workshop brought relevant parties from the industry, academia, and the FDA in the field of modeling and simulation to explore, identify, and recommend best practices on utilizing MIE for bioequivalence (BE) assessment of LAI products. Thisreportsummerizedpresentationsandpaneldiscussionsfor topics including challenges and opportunities in development and assessment of generic LAI products, current status of utilizing MIE, recent research progress of utilizing MIE in generic LAI products, alternative designs for BE studies of LAI products, and model validation/verification strategies associated with different types of MIE approaches.

Regulatory utility of mechanistic modeling to support alternative bioequivalence approaches: A workshop overview.

On September 30 and October 1, 2021, the US Food and Drug Administration (FDA) and the Center for Research on Complex Generics cosponsored a live virtual workshop titled "Regulatory Utility of Mechanistic Modeling to Support Alternative Bioequivalence Approaches." The overall aims of the workshop included (i) engaging the generic drug industry and other involved stakeholders regarding how mechanistic modeling and simulation can support their product development and regulatory submissions; (ii) sharing the current state of mechanistic modeling for bioequivalence (BE) assessment through case studies; (iii) establishing a consensus on best practices for using mechanistic modeling approaches, such as physiologically based pharmacokinetic modeling and computational fluid dynamics modeling, for BE assessment; and (iv) introducing the concept of a Model Master File to improve model sharing between model developers, industry, and the FDA. More than 1500 people registered for the workshop. Based on a postworkshop survey, the majority of participants reported that their fundamental scientific understanding of mechanistic models was enhanced, there was greater consensus on model validation and verification, and regulatory expectations for mechanistic modeling submitted in abbreviated new drug applications were clarified by the workshop.

Regulatory utility of physiologically based pharmacokinetic modeling for assessing food impact in bioequivalence studies: A workshop summary report.

This workshop report summarizes the presentations and panel discussion related to the use of physiologically based pharmacokinetic (PBPK) modeling approaches for food effect assessment, collected from Session 2 of Day 2 of the workshop titled "Regulatory Utility of Mechanistic Modeling to Support Alternative Bioequivalence Approaches." The US Food and Drug Administration in collaboration with the Center for Research on Complex Generics organized this workshop where this particular session titled "Oral PBPK for Evaluating the Impact of Food on BE" presented successful cases of PBPK modeling approaches for food effect assessment. Recently, PBPK modeling has started to gain popularity among academia, industries, and regulatory agencies for its potential utility during bioavailability (BA) and/or bioequivalence (BE) studies of new and generic drug products to assess the impact of food on BA/BE. Considering the promises of PBPK modeling in generic drug development, the aim of this workshop session was to facilitate knowledge sharing among academia, industries, and regulatory agencies to understand the knowledge gap and guide the path forward. This report collects and summarizes the information presented and discussed during this session to disseminate the information into a broader audience for further advancement in this area.

In Vitro-In Vivo Correlations (IVIVC) for Predicting the Clinical Performance of Metronidazole Topical Creams Intended for Local Action.

The safety and efficacy of a generic medicine can be confirmed by demonstrating bioequivalence (BE) between the generic product and its reference listed drug (RLD) by measuring drug concentrations in the blood following administration. However, for topical dermatological products that are not absorbed into the systemic circulation, clinical trials in patients are required. The objective of this investigation was to use an in vitro method to predict in vivo performance by correlating in vitro release testing (IVRT) data with tape stripping (TS) data following the application of metronidazole (MTZ) creams to the skin of healthy human participants. Whereas IVRT is generally used to characterize the release of a drug from topical products across a synthetic membrane into a suitable receptor medium, TS involves the sequential removal of layers of stratum corneum (SC) with an adhesive tape to determine the amount of the drug in the skin. The resulting IVRT and TS data were correlated using the IVRT parameter of the apparent release constant (ARC), which is the slope obtained from the release rate profile, with the TS parameter of the area under the curve (AUC) obtained from a plot of the amount of drug per tape strip vs. the relative SC depth. A rank order relationship for these parameters was established for the reference and test products. A graph of AUC vs. ARC was plotted to establish a Level C in vitro-in vivo correlation (IVIVC). Although the ARC for T1 was slightly lower than that for the reference, the rank order was essentially consistent. A linear relationship was observed between the AUCs and ARCs. The equation derived was used to predict the AUCs for all the tested products based on their respective ARCs. The predicted AUC values based on the observed ARCs were similar to the observed AUCs. The lower and upper limits for the in vitro and in vivo parameters for BE were computed based on regulatory acceptance criteria. In order to predict BE from the IVRT studies, the values of the ARC should be between 30.50 and 47.67 when comparing test and reference cream products containing MTZ.

Using mechanistic models to support development of complex generic drug products: European Medicines Agency perspective.

Model-informed drug development (MIDD) approaches receive wide regulatory acceptance in the European Medicines Agency (EMA) to support new drug development. For generic drugs, the European regulators have not reached a common position on how to use these methods. This commentary expands on the existing EMA regulatory framework for bioequivalence and physiological based pharmacokinetic (PBPK) modeling to propose conditions where mechanistic models could support or potentially waive clinical bioequivalence (BE)/bioavailability (BA) studies.

Pharmacokinetics and Bioequivalence of the Lubiprostone Capsule in Healthy Chinese Subjects.

A pharmacokinetic (PK) study and a bioequivalence (BE) study were conducted to investigate the PK characteristics and safety of lubiprostone in healthy Chinese subjects and to evaluate the BE between the test and the reference drugs. The PK study consisted of a fasting state cohort (a single dose of 24µg of lubiprostone), a 2-period crossover fasting and fed state cohort (a single dose of 48µg of lubiprostone), and a multiple-dose cohort (24µg of lubiprostone twice daily). The BE study was a single-dose, 2-treatment, 4-period, replicated crossover study. The plasma concentration of 15-OH-lubiprostone (M3) was measured by high-performance liquid chromatography-tandem mass spectrometry. The PK parameters were calculated using the noncompartment model with Phoenix WinNonlin. After a single dose of 24ug of lubiprostone, the main PK parameters of M3 were 49.2pg/mL, 74.0h/pg/mL, and 1.1hours for maximum plasma concentration (Cmax ), area under the plasma concentration time curve from time 0 to the last time point, and t1/2 , respectively. The main PK parameters of M3 showed dose-proportional characteristics in the dose range of 24-48µg. Food affects the PK parameters of M3. Compared to the fasting state, time to maximum plasma concentration was delayed, Cmax decreased slightly, while AUC increased significantly under the fed state. The test and reference products had similar PK parameters and were bioequivalent in the fed state.