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Regulatory Guidance on BioAvailability and

BioEquivalence Studies

FDA and EMA Guidances

Outline

• Overview of BA and BE studies• Methodology– PK studies– In-vitro studies

• BE Comparisons• Additional considerations• General PK study design

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Bioavailability Studies

• To determine the rate and process by which the active ingredient in drug is absorbed and moves to site of action– Develop a systemic exposure profile by measuring drug/metabolite

concentration over time– Usually part of INDs (investigational new drug) and NDAs– Assess performance of formulations used with regards to safety and efficacy – Serves as a benchmark for subsequent BE studies– Provide info on distribution, elimination, dose proportionality, linearity, influence

of enzymes and transporters

Bioequivalence Studies• To establish the absence of a significant difference in the rate and process to

which the active ingredient in drug equivalents becomes available at the site of drug action– Compare systemic exposure profile of a test drug product vs. reference drug

product (RLD)– Active drug ingredient or active moiety in test product must exhibit same rate and

extent of absorption as RLD– Serves to document product quality– More formal comparison with pre-specified criteria and limits– If test product levels are too high compared to reference, concern is around safety

of test product– If test product levels are too low compared to reference, concern is with

therapeutic efficacy of test product– If variability of test product rises, the concern is both safety and efficacy

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Bioequivalence Studies• Proper mapping of dose-response or concentration-response curves are

important particularly when the test drug product has levels that are higher or lower than the RLD– Studies with doses above the recommended therapeutic doses aim to

demonstrate that the increase in plasma levels are not accompanied by additional risk

– Studies with doses below the recommended therapeutic doses aim to demonstrate that the reduced levels of the test product compared to the RLD are associated with adequate efficacy

• Usually included in NDA, ANDA (generics), or post-approval submissions– BE studies are a critical component of ANDA submissions for demonstrating

the BE between a pharmaceutically equivalent generic drug product and the corresponding RLD

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Methodology• Methods to establish BA/BE (in order of

preference):– PK– PD– Clinical– In vitro

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– Most commonly rely on PK measures such as AUC and Cmax– Typically cross-over design

• Non-replicate recommended for immediate-release and modified-release dosage forms

• Replicate = at least one treatment is repeated in the same subject• Non-replicate = no treatment is repeated in the same subject

– Advantages of replicate studies• Allow comparisons of within subject variances for test and reference• Provide more info about intrinsic factors underlying formulation performance• Reduce the number of subjects in BE study

– Under fasting conditions because fasting is considered most sensitive to detect formulation differences

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PK Studies

PK Studies (continued)• Study population

– Similar proportions of each sex in study– Include as many subjects >60 years in age for elderly studies– Statistical analysis of subgroups not recommended– Restrictions on enrollment need be based on safety considerations– Healthy subjects, but may be appropriate to enroll patients depending on

drug/dose– (EMA) Healthy volunteers is adequate and results can be extrapolated to

populations for which product is approved in (elderly, children, etc)– Preferably with BMI of 18.5-30kg/m2

– Treatment groups should be comparable in all known variables (e.g. age, weight, sex, race, smoking status, etc). In other words, as homogenous as possible across treatment groups

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PK Studies (continued)• Single Dose studies are recommended

– They are more sensitive in assessing release of drug substance from drug product into systemic circulation

• AUC and Cmax are most common measures of BA/BE– Early exposure: partial AUC at Tmax– Peak exposure: Cmax– Total exposure: AUClast, AUCinf, AUCtau (MD)

• Assume that variability arise mainly from formulation factors• Pilot studies are commonly conducted before a full BE study to validate

analytical methods, assess variability, determine timepoints of measurement, etc.

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In-Vitro Studies• Dissolution test is used as a tool to identify formulation factors that are

influencing and may have a crucial effect on the BA of the drug• Used to assess batch-to-batch quality• To establish an in vitro-in vivo correlation• Can be used to waive a BE study

– Such as highly soluble, rapidly dissolving orally administered products

• Specific info is required to be included in report including– pH solubility profile– Dissolution profiles at different agitation speeds– Dissolution profiles in at least 3 different dissolution media (varying pH)

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BE Comparisons• Recommended approach

– A criterion to allow comparison– A confidence interval for the criterion– A BE limit

• Log-transformation recommended• Use of an average BE criterion to compare BA measures• In vivo study is recommended for all solid oral forms• Waiver for in vivo can be granted given

– The drug is in the same dosage form, but different strength– The strength is proportionally similar to the strength of product which an in

vivo study has already been conducted (typically the highest strength)– The new strength meets an appropriate in vitro dissolution test – Oral solutions, elixirs, syrups, etc.

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BE Comparisons• Proportionally similar is defined as

– All active/inactive ingredients are in exactly the same proportion between different strengths

– If not exactly proportional btw strengths, the ratios of inactive ingredients to total weight of dosage form are within limits defined by SUPAC-IR and SUPAC-MR guidances

– For high potency drugs where the amount of active drug substance is relatively low• the total weight of the dosage form remains nearly the same for all strengths

(within +/-10% of total weight of strength on which biostudy was performed)• the same inactive ingredients, and/or the changes in inactive ingredients are within

limits defined by SUPAC-IR and SUPAC-MR

SUPAC-IR = Immediate Release Solid Oral Dosage Forms: Scale-Up and Post-Approval Changes (MR= Modified Release)

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BE Comparisons• Suspensions

– Both in vivo and in vitro studies are recommended

• Immediate-release products: Capsules and tablets– A single-dose, fasting study is recommended– In vivo BE studies and in vitro dissolution profiles on all strengths – Specific guidance on preapproval and postapproval waivers of in vivo BE

studies

• Modified-release products (delayed or extended release)– Delayed-release: coatings are intended to delay release of medication

• In vitro dissolution tests should show they are stable under acidic conditions and drug is released only in a neutral medium

– Extended release: allow for reduction in dosing frequency – Submit as NDA for first modified-release drug product following approved

immediate-release product

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BE Comparisons• (EMA) Strengths to evaluate depends on linearity of PK of active substance• PK is considered to be linear if difference in dose-adjusted mean AUCs is no

more than 25% between different strengths• If linearity is demonstrated, it may be sufficient to establish BE with only one

strength• For drugs with linear PK, selection of a lower strength than the highest is also

acceptable to perform BE study. – e.g. if highest strength cannot be administered to healthy volunteers for safety

reasons

• For drugs with non-linear PK – If more than proportional increase in AUC with increasing dose, BE study should be

conducted at the highest strength– If less than proportional increase in AUC with increasing dose, BE study should be

conducted at the highest and lowest strengths

• When BE assessment at more than 2 strengths is needed, it is acceptable to conduct 2 BE studies at the highest and lowest strengths

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Additional Considerations• Food effect studies

– A single-dose, two-period, two-treatment, two-sequence crossover study is recommended

• Measurement of moieties– For BA studies: Both parent drug and its major metabolites be measured

• Measurement takes into account both concentration and activity

– For BE studies: Measurement of only parent drug is generally needed because concentration-time profile of parent drug is more sensitive to changes in formulation than a metabolite

• Long half-life drugs– For BE study: A non-replicate, single-dose, crossover study can be

conducted, provided an adequate washout period is used– If crossover is problematic, a parallel design can be used– Sample collection time be adequate to ensure completion of passage and

absorption of drug (~2-3 days)

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Additional Considerations• Long half-life drug

– Cmax and truncated AUC can be used to characterize peak and total drug exposure• For drugs with low intrasubject variability AUC @ 72hrs can be used • For drugs with high intrasubject variability Need to be cautious with AUC truncation

• First point Cmax– Insufficient early sampling times may lead to inaccurate measurement of true

Cmax if the first point is the highest point in a concentration-time curve– Pilot study may help avoid problem

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General PK Study Design• Under fasting conditions, unless food-effect study• (EMA) For products with specific formulation characteristics, BE study

should be performed under both fed and fasted states– Either 2 separate two-way crossover, or a four-way crossover study

• Highest marketed strength be administered as a single unit• Adequate washout period (>5 half lives) • Drug content of test product cannot differ from reference product by

more than 5%• (EMA) At least 12 or more subjects in BE study• Collection of blood samples is recommended – serum or plasma in most

cases• (EMA) Urine is acceptable where it is not possible to reliably measure

plasma concentration-time profile– should be collected over at least 3 times the half-life

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General PK Study Design• Sampling frequency and schedule

– 12-18 samples, including pre-dose, per subject per dose is recommended– Sampling should continue for at least 3 or more half lives of drug– At least 3-4 samples be obtained during terminal log-linear phase to obtain

accurate estimate of elimination rate constant (λz) from linear regression– Actual clock time when samples are drawn as well as elapsed time related to

drug administration be recorded– (EMA) Sampling schedule should be long enough to ensure that AUC0-t covers

at least 80% of AUCinf

• (EMA) The bioanalytical method for analyzing PK samples should have a LLOQ of 1/20 of Cmax or lower

• Analysis of samples should be conducted without info on treatment

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General PK Study Design• PK info recommended for submission

– Plasma concentrations and timepoints– Subject, period, sequence, treatment– AUC0-t, AUCinf, Cmax, Tmax, λz, t1/2, (EMA) Residual Area

– Intersubject, intrasubject, and/or total variability– (steady-state studies) Cmin, Cav, degree of fluctuation, swing – Partial AUC, if appropriate– (EMA) For urine, Ae(0-t) and Rmax, if applicable, should be collected

– Non-compartmental methods should be used for determination of PK parameters

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General PK Study Design• Statistical info to be provided for AUC0-t, AUCinf, Cmax

– Geometric mean– Arithmetic mean– Ratio of means– Confidence intervals

• Log transformation be applied • Rounding off of confidence interval values are not recommended.

– To pass 90% CI limit of 80 to 125, value should be at least 80.00 and not more than 125.00

• (EMA) For products with narrow therapeutic index, acceptance interval for AUC should be tightened to 90-111%

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General PK Study Design• (EMA) For highly variable drug products (HVDP), the acceptance criteria

for Cmax can be widened to a maximum of 69.84-143.19%– For CI to be widened, must demonstrate that the within subject variability for Cmax of

the reference compound is >30%– Does not apply to AUC where acceptance range should remain at 80-125%

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General PK Study Design• (EMA) Two-Stage Design Two-Stage approach is acceptable for demonstrating BE

– An initial group of subjects is treated and data analyzed– If BE is not demonstrated, an additional group is recruited and the results from

both groups are combined in a final analysis

• Overall type I error must be preserved• Stopping criteria needs to be clearly defined prior to study• Plan to use two-stage approach must be pre-specified in protocol along

with adjusted alphas to be used for each analysis• A term for stage should be included in the ANOVA model

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General PK Study Design• GLM or linear mixed effects model is recommended

– Model should include factors such as sequence, subjects nested in sequences, period, and treatment

• (EMA) Fixed effect ANOVA model only should be used• Formulation comparisons are primarily based on paired t test

– Only patients who have data from both Test and Reference period will be included

• If there is no missing data – the two models are equivalent• If there is missing data – there can be differences

– Less data points will be included in the method recommended by EMA

• Internally, mixed effects model is recommended as a default approach. it was found that the mixed effects model will have more power

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References• Guidance for Industry Bioavailability and Bioequivalence Studies for Orally Administered Drug Products –

General Considerations. US Department of Health and Human Services, Food and Drug Administration Center for Drug Evaluation and Research (CDER), March 2003. http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/ucm070124.pdf

• Guideline on the Investigation of bioequivalence. European Medicines Agency. Committee for MEDICINAL Products for Human Use. January 2010. http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2010/01/WC500070039.pdf

• Statistical Approaches to Establishing Bioequivalence. US Department of Health and Human Services, Food and Drug Administration Center for Drug Evaluation and Research (CDER), January 2001.

http://www.fda.gov/downloads/Drugs/Guidances/ucm070244.pdf

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