BIOEQUIVALENCE, BIOWAIVERS AND IVIVC

STUDIES

ASRA HAMEED

P h a r m . D ( J U

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a s r a _ h a m e e d 1 @ h o t m a i l .c o m

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BIOEQUIVALENCE“The absence of a significant difference in the rate and

extent to which the active ingredient or active moiety in pharmaceutical equivalents or pharmaceutical alternatives becomes available at the site of drug action when administered at the same molar dose under similar conditions in an appropriately designed study.”

2CDER U.S. Food & Drug Administration

What are Pharmaceutical EquivalentsDrug Products in identical dosage form that containsthe same active ingredients i.e. the same salt or ester are of the same dosage formuse the same route of administrationidentical in strength or concentrationsame amount of active ingredientmeet the same or compendial or other applicable standards They may differ in characteristics such as shape, scoring configuration, release mechanisms, packaging, excipients (including color, flavours, preservatives), expiration time and within certain limits labeling.

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What are Pharmaceutical alternativesDrug product that contain the same therapeutic moiety but as different salts, ester, or complexes. For e.g. Tetracycline hydrochloride or tetracycline phosphate equivalent to 250 mg tetracycline base.

Different dosage form and strength within a product line by a single manufacturer for eg. an extended release and standard immediate release.

Tablet and capsule containing the same active ingredient in the same dosage strength.

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Reasons for Bioequivalence StudyTo prove that Generic Drug Products are bioequivalent to innovators/marketed drug product (Reference Listed Drugs).

Change in formulations i.e. from capsule to tablets.

Change in any process or manufacturing site (In few cases)

To determine the efficacy and safety from the bioequivalence data.

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APPROACHES TO DETERMINE BIOEQUIVALENCE In vivo measurement of active moiety in biological fluid

Plasma Drug Concentration Cmax, Tmax and AUC

Urinary Drug Excretion Ae, Ae/t, t

Acute Pharmacodynamic effect Dose-Response Curve (Skin Blanching-Topical cortico steroids, Force Expiratory

Volume-Inhaled Bronchodilators)Clinical Observations

Well controlled Clinical Trials to establish efficacy and safety In vitro Studies

Comparative Drug Release/Dissolution Studies (f2 test) IVIVC studies In vitro biomarker/in vitro binding studies

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IN-VIVO BIOEQUIVALENCE STUDY DESIGN

CROSS OVER STUDY

SINGLE DOSE, TWO WAY CROSS OVER-

FASTED

SINGLE DOSE, TWO WAY

CROSS OVER-FED

SINGLE DOSE REPLICATE DESIGN

(Highly variable drugs)

MULTIPLE DOSE TWO WAY

CROSS OVER-FASTED

(Less Sensitive, Non Linear

Kinetic)

PARALLEL GROUP STUDY

SINGLE DOSE, PARALLEL, FASTED(Long Elimination Half Life Drugs)

CLINICAL END POINT STUDY

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COM

PON

ENTS

OF

BIO

EQU

IVAL

ENCE

STU

DY

PRO

TOCO

LCLINICAL PHASE

TitlePrincipal

Invesitgator/Project Number

Study Objective and Design

Drug Products, Dosage Regimen, Sample

Collection Schedule

Study Population Subjects, Selection, Inclusion/Exclusion criteria

Ethical Considerations IRB, Informed consent

Clinical Procedures Drug Administration and Sampling

ANALYTICAL PHASE

Analytical Method Validation

Sensitivity, specificity, selectivity accuracy, precision, recovery,

stability etc

Sample AnalysisPK parameters such as Cmax, Tmax, AUC, Rate

constants etc.

Statistical Analysis ANOVA, Two one sided test etc.

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IMPORTANT CONSIDERATION IN BIOEQUIVALENCE STUDYObjectives

Why, Is there any requirement. Benefit-Risk and ethical consideration with regard to testing in humans

Basic Guiding Principle “Do not do unnecessary human research”Nature of Reference Material and the dosage form testedStudy type

Usually Single Dose, Randomized Cross Over (Occasionally Parallel)Volunteers Selection

Healthy based on clinical examination and lab test Male or Female (Usually Male) Age group 18-45 years Same Average weight group within 10% of the ideal body weight No other medication at least 1 weak prior to study Non alcoholic/non smokers Should sign informed consent containing detailed information about the study including risks and right to withdraw at anytime9

Sample size Depends on the variability in the PK parameters At least 12 (Ideally 24)Sample Type Usually Blood, Plasma/serum Urine in some cases if requiredSample Collection schedule Test/Reference Dosage form with 250 ml of water from subjects in an overnight fast condition

First sample immediately before dose administration (Just before zero time).

Fasting conditions till 2-4 hrs of the first dose At least 10 blood Samples (5-10 ml) upto 7th elimination half lives.

Three samples from absorption phase, three from distribution, and four from elimination phase

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Sample Analysis Chromatographic (LC-UV, LC-PDA, LC-MS recommended) Validated method i.e. sensitivity, specificity, accuracy, precision and recovery etc should be done prior to study.

Method should be sensitive enough to analyze the drug in trace levels (usually less than 100 ng/ml is required for analytical methods)

Stability determination of the frozen storage of the study samples

Pharmacokinetic Analysis Non compartmental method Cmax, Tmax, AUC0-t and AUC0-

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Statistical Analysis Analysis of Variance (ANOVA) explaining different sources of errors in the calculated PK parameters such as Sequence effect (Order effect) Subject nested in sequence Period Effect (phase effect) Treatment Effect (Product Effect)

Two one sided t test to test BE Calculation of 90% Confidence Interval for the ratio (or difference) of

the average log-transformed pharmacokinetic parameters for the test and reference products

Log transformed Cmax and Tmax as these parameters are not normally distributed (Log transformed values are normally distributed-log normal distribution)

90% CI for the ratio of the average log transformed AUC and Cmax should fall within the BE limit of 80-125%.

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NEED TO REDUCE OUR RELIANCE ON IN VIVO BE STUDIES – BE THEME FOR 21ST CENTURY

Ethical reasons 21 CFR 320.25(a) “… no unnecessary human research should be done.”

Science continues to provide new methods to identify and eliminate unnecessary in vivo BE studies

Focus on prevention - “building quality into products” - “right first time”

Time and cost of drug development and review

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BIOWAIVERS

Termed as In-vitro Bioequivalence StudiesMeans in vivo bioavailability and/or bioequivalence

studies may be waived offInstead of conducting expensive and time consuming

in vivo studies, an in vitro dissolution test could be adopted as the surrogate basis for the decision as to whether the two pharmaceutical products are equivalent.

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PD studies clinicalstudies

in vitromethods

Different Approach for Establishing Equivalence

Standard: in vivo BE studies

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HISTORICAL BACKGROUND IN THE DEVELOPMENT OF DISSOLUTION AS A PROGNOSTIC TOOL FOR ORAL DRUG ABSORPTION

In 1985, Amidon and co-workers, using a Pseudoequilibrium Model where solubility and dose were taken into account for the estimation of the absorption potential (AP) of a drug.

Quantitative version of the Absorption potential concept was published which enabled the estimation of the fraction of dose absorbed as a function of AP (Macheras and Symillides, 1989).

Microscopic model publish in 1993 based on mass balance considerations can be considered as a landmark in the history of oral drug absorption since it revealed the three fundamental parameters, namely, dissolution, absorption and dose numbers (Oh et al, 1993)

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Amidon et al. in 1995 published a revolutionary paper in Pharmaceutical Research i.e. A theoretical basis for a Biopharmaceutic drug classification—the correlation of in-vitro drug product dissolution and in-vivo bioavailability. Classifying drugs on the basis of BCS

Dressman et al in 1998 established correlations between in vitro dissolution and in vivo absorption using artificial fluids, simulated gastric and intestinal fluids both in fasted and fed conditions. (i.e. BIO-RELEVENT Dissolution mediums).

FDA acknowledges Amidon et al 1995 BCS system with the guidance documents. “FDA, 2000. Guidance for Industry,Waiver of In Vivo Bioavailability and Bioequivalence Studies for Immediate Release Solid Oral Dosage Forms based on a Biopharmaceutics Classification System. FDA/CDER”.

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BIOPHARMACEUTICS CLASSIFICATION

SYSTEM

CLASS I

HIGH SOLUBILITY

HIGH PERMEABILITY

CLASS II

LOW SOLUBILITYHIGH

PERMEABILITY

CLASS III

HIGH SOLUBILITYLOW

PERMEABILITY

CLASS IV

LOW SOLUBILITYLOW

PERMEABILITY

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HIGH SOLUBLEA drug substance is considered HIGHLY SOLUBLE when the highest dose strength is soluble in < 250 ml water over a pH range of 1 to 7.5.

250 ml: derived from typical BE study protocols that prescribe the administration of a drug product to fasting human volunteers with a glass (approximately 250 ml) water

Relevance of pH 1-7.5 i.e. Physiological pH range from stomach (Dissolution) to small intestine –Duodenum to Ileum (Dissolution and Absorption).

Solubility can be determined by pH-solubility profile of test drug at 37oC in aqueous media with a

pH range of 1 to 7.5 Shake-flask or titration method Analysis by validated stability-indicating assay

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HIGH PERMEABLEA drug substance is considered HIGHLY PERMEABLE when the extent of absorption in humans is determined to be > 90% of an administered dose, based on mass-balance or in comparison to an intravenous reference dose.

Permeability can be determined byPharmacokinetic studies in humans: Mass-balance studies Absolute bioavailability studiesIntestinal permeability methods: In vivo intestinal perfusions studies in humans In vivo or in situ intestinal perfusion studies in animals In vitro permeation experiments with excised human or animal intestinal tissue

In vitro permeation experiments across epithelial cell monolayers (Caco2 cell)

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BCS Class I DrugIR solid Oral Dosage FormsStable Drugs in G I TractDrug must not have narrow therapeutic IndexDrug is designed not to be absorbed in the oral cavityFDA approved safe excipients

FDA BCS Class I, Class II (weak acid), Class III (rapidly dissolving)IR solid Oral Dosage FormsExtended Release, Delayed Release (Dose Proportionality Formulations)Drug must not have narrow therapeutic IndexWell established safe and approved excipients

WHO

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DISSOLUTION BASED BIOWAIVERS

BCS GUIDANCE FOR DRUG PRODUCT PERFORMANCEBCS CLASS I-VERY RAPIDLY DISSOLVING

When no less than 85% of the drug dissolves within 15 minutes using

USP Dissolution Apparatus I at 100 rpm or Apparatus II at 50-75 rpm

In a volume of 900 ml or less in each of the following medium 0.1 N HCl or simulated gastric juice pH 4.5 and 6.8 phosphate buffers or simulated intestinal juice

No further profile comparison of Test (T) and Reference (R) product is required

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BCS CLASS I – RAPIDLY DISSOLVING When no less than 85% of the drug dissolves within 30 minutes

using USP Dissolution Apparatus I at 100 rpm or Apparatus II at 50-75

rpm In a volume of 900 ml or less in each of the following medium

0.1 N HCl or simulated gastric juice pH 4.5 and 6.8 phosphate buffers or simulated intestinal juice

Proving similarity of dissolution profiles of T and R e.g., using f2-test A minimum of 12 dosage units of a drug product should be

evaluated to support a biowaiver request Samples should be collected at a sufficient number of intervals to

characterize the dissolution profile of the drug product (e.g., 10, 15, 20, and 30 minutes)

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When comparing the test and reference products, dissolution profiles should be compared using a similarity factor

Two dissolution profiles are considered similar when the value is ≥50.

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BCS CLASS II DRUGSWeakly Acidic DrugsDose: solubility ratio of 250 ml or less at pH 6.8 Multisource product is rapidly dissolving (no less than 85% in pH 6.8 in 30 minutes)

Dissolution profile is similar to that of the comparator product at pH 1.2, 4.5 and 6.8

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BCS CLASS III DRUGSMultisource and comparator product are very rapidly dissolving (no less than 85% in 15 minutes at pH 1.2, 4.5 and 6.8)

Note: FDA has not allowed Dissolution based biowaivers for Class II and Class III (VERY CONSERVATIVE said by WHO)

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BCS

IVIVC

BIOWAIVERS

COMPOSITION PROPORTIONAL

ITY

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BCS (Dissolution based)Class I-Very Rapidly Dissolving, Rapidly DissolvingClass II-Weak Acid, HS in pH 6.8 Class III-Very Rapid Dissolving

IVIVC

Composition Proportionality

BIOWAIVERS

Level A

Level BLevel C

Multiple Level C

• API and Excipient are same qualitatively and quantitatively.

• Same manufacturing process

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IN-VITRO IN-VIVO CORRELATIONS (IVIVC)Correlations between an in-vitro property of dosage form and

a relevant in-vivo responseIn-vitro property is the rate and extent of drug dissolutionIn-vivo response is the amount of drug absorbed or the

plasma concentration time profileBased on developing and optimizing the conditions of in vitro

dissolution testing procedures for a particular formulation that can predict the in vivo performance of that formulation

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LEVEL A• Point to Point

Correlations between in vitro input rate and in vivo out put rate

• Highest level• Most informative• Regulatory

Support

LEVEL B• Using the

Principle of statistical moment theory

• Mean in vitro dissolution Time (MDT) compared to Mean in vivo Dissolution time (MRT)

• Single integrated parameter and no point to point correlations

• No Regulatory Support so no importance

LEVEL C• A single point

correlations between an in vitro dissolution parameter (eg. Time to release 50% of the drug T50 and an in vivo parameter (eg. Cmax and AUC)

• Does not reflect complete in vivo plasma conc time profile

• Not very useful for regulatory support.

• Use for earlier formulation development

MULTIPLE LEVEL C• Extension of

single point Level C

• Relates several in vivo parameter to in vitro parameters related to drug release at several time point of Dissolution profiles

• Useful like Level A

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LEVEL OF CORRELATIONS

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LEVEL A LEVEL B

LEVEL C

IVIVCLevel A

Development of FormulationsSlowIntermediateFast

In Vitro Dissolution Data12 individual dosage form in each

lotAdequate sampling Point0.1MHCl, pH 4.5 and6.8 buffers, Biorelevant mediums <10% CV for the mean dissolution profiles

In Vivo PK DataCross over or Parallel12-36 subjectsReference IR Formulation (Solution/suspension/tablets) or IV also included 35

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In Vitro Dissolution Data

In Vivo PK Data

0 10 20 30 400

20

40

60

80

100In vivo vs. In vitro absorbed

Time (h)

Cp (ng/ml)

DeconvolutionConvolution

DECONVOLUTION

• Two Step Process

In vivo profile transformed to in vitro dissolution profile(Output to Input)

• Wagner Nelson (1 comp)

• Loo Reigelman (2 Comp)

• Numerical Deconvolution

Model Fitting of In vitro/in vivo Dissolution Curves

• Weibull Model

Time Scaling

• Where

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STEP BY STEP DECONVOLUTION

IVIVC

CONVOLUTION

• Single Step Process

In vitro profile transformed to in vivo Time Plasma conc profile(Input to Output)

• Unit Impulse Response

In vivo/In vitro Time plasma conc profile

• Cmax and AUC calculated from both In vitro and In vivo Data.

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IVIVC MODEL PREDICTABILITY (VALIDATION)

For Cmax:

For AUC:

Acceptance criteria: According to FDA guidance

• ≤15% for absolute prediction error (%P.E.) of each formulation.• ≤ 10% for mean absolute prediction error (%P.E.)

BCS CLASSIFICATION AND EXPECTED IVIVC FOR IMMEDIATE RELEASE PRODUCTS

CLASS SOLUBILITY PERMEABILITY IVIVC

I HIGH HIGH POSSIBLE (IF DISSOLUTION IS RATE LIMITING

II LOW HIGH EXPECTED

III HIGH LOW LITTLE OR NO IVIVC

IV LOW LOW LITTLE OR NO IVIVC

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SOFTWARES FOR BE, BIOWAIVERS AND IVIVC STUDIESPhoenix Winnonlin (Certara)Gastro Plus, IVIVC Plus and DDD Plus (Simulation–Plus)IVIVC for RDD Solver (Excel Add in)Equiv Test (Statcon)Kinetica (Thomson)

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IVIVC PACKAGE FROM SIMULATION PLUS

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IVIVC FROM R PACKAGES

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IVIVC TOOLKIT FROM PHOENIX

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RESEARCH SCOPE AND BENEFITSMore than 400 manufacturing units involved in Generic ManufacturingBioequivalence required for many products Areas covered

Pharmacokinetics Pharmacodynamics Chromatographic method development and validation Understanding Statistical Techniques

Dissolution based biowaivers, an alternative for in vivo BE can be performed within the regulatory framework

IVIVC, another alternative in which a surrogate dissolution medium can be developed Areas Covered

Developing New Formulations Optimization Techniques Development and understanding of new and existing dissolution mediums Development and understanding of new and existing mathematical dissolution models

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Proper use of these methods leads toSafeCost effectiveLess Time consumingOptimized

Quality Product

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