Pharmacokinetic Analysis of BE Data - BEBAC • Consultancy ...

Wikimedia Commons • 2005 Snowdog • Creative Commons Attribution-ShareAlike3.0 UnportedPharmacokinetic Analysis of BE Data1• 68PharmacokineticAnalysis of BE DataHelmut SchützBEBACBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 2013

Pharmacokinetic Analysis of BE DataTo bear in Remembrance...Whenever a theory appears to youas the only possible one, take this asa sign that you have neither under-stood the theory nor the problemwhich it was intended to solve.Even though it’s applied sciencewe’re dealin’ with, it still is – science!Karl R. PopperLeslie Z. BenetBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 20132• 68

Pharmacokinetic Analysis of BE DataNCA vs. PK Modeling•Pharmacokinetic models•Useful for understanding the drug/formulation• Study design of BA/BE, e.g.,washout, accumulation / saturation to steady state•Drawbacks• Almost impossible to validate (fine-tuning of sideconditions, weighting schemes, software, …)• Still a mixture of art and science• Impossible to recalculate any given dataset using differentsoftware – sometimes even different versions of the samesoftware!• Not acceptable for evaluation of BE studies!Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 20133• 68

Pharmacokinetic Analysis of BE DataPK Modeling: AUC•Based on integration of a PK model;e.g., extravascular dose, one-compartment, nolag-timef ⋅ D kC t e eV k − ka() (k)eltkat= −AUC0−∞ael∞f ⋅ D k ⎛a1 1 ⎞ f ⋅D f ⋅D= ∫ C () t dt = ⎜ − ⎟= =V k0a−kel ⎝kel ka ⎠ V ⋅kelCLBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 20134• 68

Pharmacokinetic Analysis of BE DataNCA: Single Dose•Noncompartmental methods do not rely on aPK (=compartmental) model•Also known as SHAM (Shape, Height, Area,Moments)•Metrics (plasma, single dose)• Extent of absorption (EU…), total exposure (US):AUC (Area Under the Curve)• Rate of absorption (EU…), peak exposure (US): C max• t max (EU…)• Early exposure (US, CAN): pAUC tmax ; AUC truncated atpopulation’s (CAN: subject’s) t max of the reference• Others: C min , Fluctuation, MRT, Occupancy time, t lag ,…Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 20135• 68

Pharmacokinetic Analysis of BE DataNCA: AUC•Since compartmental models not acceptablein BE, numeric approximation required•Linear trapezoidal rule¹•Lin-log trapezoidal rule¹ , ²•Lin-up/log-down trapezoidal rule•Cubic splines•Lagrange-polynomials•Simpson’s rule¹ Russian GL; only these two acceptable?² WHO GL; only acceptable method?Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 20136• 68

Pharmacokinetic Analysis of BE DataNCA: AUC•Linear trapezoidal rule•Linear interpolation between data points•Sections represented as trapezoids•Sides a, b = neighbouring concentrations•Time interval ha+b•Area of trapezoid A = h2•Totali= n− 1 i= n−1Ci+ Ci+11AUC0− ≈ ∑ tn+ 1−t ≈ ∑ C + C+ 1⋅ t+ 1−t2 2( ) ( ) ( )t i i i i i ii= 1 i=1Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 20137• 68

Pharmacokinetic Analysis of BE DataNCA: AUClinear trapezoidal rule0 2 4 6 8 10 121001008080concentration604060402020000 2 4 6 8 10 12time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 20138• 68

Pharmacokinetic Analysis of BE DataNCA: AUClinear trapezoidal rule:arithmetic means of concentrations0 2 4 6 8 10 121001008080concentration604060402020000 2 4 6 8 10 12time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 20139• 68

Pharmacokinetic Analysis of BE DataNCA: AUC•Log-linear trapezoidal rule•Assumes exponential elimination•Log-linear interpolation between data points•Only valid for iv administration; sections inabsorption phase underestimated if applied to ev•If C = 0 or subsequent concentrations are equal,section calculated by linear trapezoidal•Totali= n−1Ci+1− CiAUC0− t≈ ∑ ( t1 )ni+− tiCi=1 i+1lnCiBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201310 • 68

Pharmacokinetic Analysis of BE DataNCA: AUC•Lin-up/log-down trapezoidal rule•Hybrid of linear and log-linear•Sections with increasing or equal concentrations(C i+1 ≥ C i ) calculated by linear trapezoidal rule•Sections with decreasing concentrations(C i+1 < C i ) calculated by log-linear trapezoidal rule•Avoids bias in both absorption and distribution/elimination phases•Suitable for iv and ev•Suitable for multiphasic profilesBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201311 • 68

Pharmacokinetic Analysis of BE DataNCA: AUClin-up/log-down trapezoidal rule0 2 4 6 8 10 121001008080concentration604060402020000 2 4 6 8 10 12time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201312 • 68

Pharmacokinetic Analysis of BE DataNCA: AUClin-up/log-down trapezoidal rule:arithmetic ~geometric means of concentrations0 2 4 6 8 10 121001008080concentration604060402020000 2 4 6 8 10 12time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201313 • 68

Pharmacokinetic Analysis of BE DataExample 1ModelAUC R 697.8AUC T 662.9T/R 95.00%linear trapezoidalT/R 94.85%concentration100806040AUCi (R) 707.6, AUCi (T) 670.9, T/R 94.8%, bias -0.20%0 4 8 12 16 20 24100ReferenceTest8060402020000 4 8 12 16 20 24time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201314 • 68

Pharmacokinetic Analysis of BE DataExample 1ModelAUC R 697.8AUC T 662.9T/R 95.00%lin-up/log-downT/R 94.89%concentration100806040AUCi (R) 693.7, AUCi (T) 658.0, T/R 94.9%, bias -0.16%0 4 8 12 16 20 24100ReferenceTest8060402020000 4 8 12 16 20 24time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201315 • 68

Pharmacokinetic Analysis of BE DataExample 2ModelAUC R 697.8AUC T 662.9T/R 95.00%linear trapezoidal12 h (R) missingT/R 92.53%concentration100806040AUCi (R) 725.1, AUCi (T) 670.9, T/R 92.5%, bias -2.60%0 4 8 12 16 20 24100ReferenceTest8060402020000 4 8 12 16 20 24time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201316 • 68

Pharmacokinetic Analysis of BE DataExample 2ModelAUC R 697.8AUC T 662.9T/R 95.00%lin-up/log-down12 h (R) missingT/R 94.89%concentration100806040AUCi (R) 693.7, AUCi (T) 658.0, T/R 94.9%, bias -0.15%0 4 8 12 16 20 24100ReferenceTest8060402020000 4 8 12 16 20 24time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201317 • 68

Pharmacokinetic Analysis of BE DataSpaghetti & other pastalinearlinear trapezoidal100Weired?Does thesemi-log plotreflect the calculationof AUC?concentration8060402000 4 8 12 16 20 24Overestimates AUCin the distribution/elimination phase…time (h)semilogarithmicsemilogarithmic1001005050concentration20105concentration2010522110 4 8 12 16 20 240 4 8 12 16 20 24time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 2013time (h)18 • 68

Pharmacokinetic Analysis of BE DataSpaghetti & other pastalinearlinearlin-up/log-down100100Does thelinear plotreflect the calculationof AUC?concentration8060402000 4 8 12 16 20 24concentration8060402000 4 8 12 16 20 24time (h)timesemilogarithmicconcentration1005020105Maybe we shouldchange the way wedraw spaghettiplots…210 4 8 12 16 20 24time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201319 • 68

Pharmacokinetic Analysis of BE DataRecommendations•Don’t exclude a subject if only – a few – datapoints are missing (loss of power)•Only if linear rule is required for any reason:data imputation•Linear within increasing/equal values (C i+1 ≥ C i–1 )ˆ ti − ti−1Ci = Ci− 1+ ( Ci+ 1−Ci−1)ti+ 1−ti−1•Log-linear within decreasing values (C i+1 < C i–1 )Cˆi= et −tln C C C( )i i−1i−1+ln i− 1 i+1ti+ 1−ti−1Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201320 • 68

Pharmacokinetic Analysis of BE DataRecommendations•Don’t exclude a subject … (cont’d)•Although I had never problems with this procedurein 500+ BE studies (stated in the protocol, accordingto SOP, and by validated software) dataimputation may be unfamiliar to assessors•Lin-up/log-down trapezoidal not affected by missingvalues and unbiased estimates are obtainedBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201321 • 68

Pharmacokinetic Analysis of BE DataNCA: AUC Extrapolation•AUC 0–∞•Unweighted log-linear regression of ≥3 data pointsin the elimination phase•Extrapolation from AUC 0–t (regardless the method)CAUC = AUC + Cˆ∞ t or better AUCtˆt= AUC +∞λˆtλzzBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201322 • 68

Pharmacokinetic Analysis of BE DataNCA: AUC Extrapolation•Single dose only!•Method of estimation of λ z stated in protocol!• One-compartment model: ‘TTT’–method *(Two times t max to t z )• Maximum adjusted R² (Phoenix/WinNonlin, Kinetica)22 (1 − R ) ⋅( n−1)WinNonlin ≤5.3:Radj= 1−n − 2• Multi-compartment models: starting point = last inflection• Minimum AIC: AIC = n ⋅[ ln(2 ⋅ π ) + 1]+ n ⋅ ln( RSS n) + 2 ⋅ p• Visual inspection of fit mandatory!C max includedPhoenix/WNL ≥6.0: C max excluded* Scheerans C, Derendorf H, and C KloftProposal for a Standardised Identification of the Mono-Exponential Terminal Phase for OrallyAdministered DrugsBiopharm Drug Dispos 29, 145–57 (2008)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201323 • 68

Pharmacokinetic Analysis of BE DataNCA: AUC Extrapolation•AUC 0–∞•EMA (and all countires except US and Russia):No primary PK metric; but demonstrates that AUC 0–tis a reliable estimate of extent of absorption(i.e., extrapolated area ≤ 20% of AUC 0–∞ )• FDA: Primary PK metric (additionally to AUC 0–t )• What if extrapolated AUC 0–t > 20% of AUC 0–∞ in somesubjects?• EMA: Subjects should not be excluded, but requiresdiscussion if observed in > 20% of cases• Russia: Use AUC 0–∞ instead of AUC 0–t as primarymetric of the studyBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201324 • 68

Pharmacokinetic Analysis of BE DataNCA: AUC Extrapolation100plasma profile (linear scale)80concentration60402000 4 8 12 16 20 24timeBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201325 • 68

Pharmacokinetic Analysis of BE DataNCA: AUC Extrapolation100plasma profile (semilogarithmic scale)concentration10C tCˆt10 4 8 12 16 20 24timeBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201326 • 68

Pharmacokinetic Analysis of BE DataNCA: otheroPK Metrics•Single dose•C max and t max directly from profile•Metrics describing the shape of the profile• Early exposure (US, CAN): AUC tmax = pAUC truncated atpopulation (CAN: subject’s) t max of the reference• Biphasic MR formulations: pAUCs truncated at a prespecifiedcut-off time point• FDA: Product specific guidances (methylphenidate,zolpidem)• EMA: All productsQuestions & Answers: positions on specific questions addressed to the pharmacokineticsworking partyEMA/618604/2008 Rev. 4 (16 February 2012)http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500002963.pdfBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201327 • 68

Pharmacokinetic Analysis of BE DataNCA: otheroPK Metrics•Single dose•Metrics describing the shape of the profile• C max /AUC• t 75% (Plateau time: interval where C(t) ≥ 75% of C max )*• HVD (Half value duration: time interval where C(t) ≥ 50%of C max )• Occupancy time, t ≥ MIC (time interval where C(t) is abovesome limiting concentration)* Russia: mandatory for sustained release formulationsBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201328 • 68

Pharmacokinetic Analysis of BE DataNCA: Urine•Noncompartmental methods (cont’d)•Extent of absorption (EU…), total exposure (US):Ae t (cumulative amount excreted); rarelyextrapolated to t = ∞•Rate of absorption, peak exposure (US):∆Ae max , t∆Ae max•EMA: C max , t max from plasma!Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201329 • 68

Pharmacokinetic Analysis of BE DataNCA (Methods)•Multiple dose•Calculation of AUC τ (dosage interval τ );AUC ss,24h if more than o.a.d. and chronopharmacologicalvariation)•No extrapolation!•C ss,max and C ss,min directly from profile•Peak-Trough-Fluctuation: (C ss,max –C ss,min )/C ss,av ,where C ss,av = AUC τ /τ•Swing: (C ss,max –C ss,min )/C ss,minBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201330 • 68

Pharmacokinetic Analysis of BE Data•Multiple doseNCA (Methods)•Assessment whether steady state is reached (ina linear PK system: AUC τ = AUC ∞ )• No recommendations in GLs (except EU/US Veterinary)• Not required according to comments to EMA’s BE-GL• MANOVA-model (sometimes in CAN, rarely used)• t-test of last two pre-dose concentrations• Hotelling’s T²• Linear regression of last three pre-dose concentrations,individually for each subject/treatment• Only the last method allows the exclusion of subjects beingnot in stead state. Other methods give only a yes|no result!Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201331 • 68

Pharmacokinetic Analysis of BE DataNCA (Methods)200plasma profile (linear scale)concentration1501005000 24 48 72 96 120 144timeC avslope: +0.0459395% CI: [-0.35266 | +0.44452]steady state demonstratedBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201332 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)•C min•Defined by EMA as the concentration (C trough )at the end of the dosing interval τ•Not implemented in PK software: C min globalminimum concentration. Requires adaption.•More variable than C max (if little accumulation closeto LLOQ)•EMA requires pre-dose sampling at ≤–5 min andsampling at τ ±10 min•Common in o.a.d. MD studies last sampleat 23:55 in period 1 and at 24:00 in period 2…Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201333 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)•Missing last samples may lead to ‘Apples-and-Oranges’ statistics (biased treatment effect)•If a reliable estimate of λ z is possible (≥3 datapoints), we can use an estimate• ± shift of C z according to λ z *ˆˆ z( z)= C e −λτ−t(1)Css,minz• or independent from measured C z( Cˆ0− ˆ λz⋅ ( t0+τ))Cˆ = e (2)ss,min* Gabrielsson J and D WeinerPharmacokinetic & Pharmacodynamic Data Analysis: Concepts and ApplicationsSwedish Pharmaceutical Press, Stockholm, p163 (4 th ed. 2006)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201334 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)•Missing values I•Procedure for imputation must be stated in theprotocol; recommended:• in the absorption phase (t < t max ) by linear Interpolation ofadjacent values• in the distribution/elimination phase (t ≥ t max ) by log/linearInterpolation of adjacent values• imputed value must not be used in estimating λ z !•Don’t rely on softwares’ defaults!• Phoenix/WinNonlin interpolates linear – unless thelin-up/log-down trapezoidal method is used• Kinetica interpolates lin/log within descending valuesBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201335 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)10080ReferenceTestLLOQ = 10concentration60402000 12 24 36 48 60 72timeBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201336 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)•Missing values II•Last value of T missing(e.g., vial broken)• AUC tlast (48) T = 2407AUC tlast (72) R = 2984T/R = 80.67% biased!• Using AUC to t where C≥LLOQfor both formulations (48)AUC 48 T = 2534AUC 48 R = 2407T/R = 95% ‣ Not available in software‣ Regulatory acceptance?time00.250.500.751.001.523469121624364872Referenceconc AUC 0-tBLQ 028.57 448.57 1362.50 2772.15 4483.26 8388.14 12690.14 21588.70 30484.07 47777.11 71970.71 94063.00 120850.00 166035.36 217225.00 253412.50 2984Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 2013concBLQTestAUC 0-t027.14 346.14 1359.38 2668.55 4279.10 7983.73 11985.63 20484.26 28979.86 45373.25 68367.18 89359.85 114747.50 157733.59 206323.75 2407Missing NA37 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)10080ReferenceTestLLOQ = 10concentration6040C 72 set to 02000 12 24 36 48 60 72timeBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201338 • 68

Pharmacokinetic Analysis of BE Data•Missing values IINCA (Problems)•Last value of T missing(e.g., vial broken)• Setting the first concentrationin the profile where C

Pharmacokinetic Analysis of BE DataNCA (Problems)10080ReferenceTestLLOQ = 10concentration6040C 72 estimated from C 24 –C 482000 12 24 36 48 60 72timeBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201340 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)•Missing values II•Last value of T missing(e.g., vial broken)• Estimating the missing valuefrom elimination phase.AUC 72* T = 2835AUC 72 R = 2984T/R = 95% ‣ Not available in software‣ Regulatory acceptance ±time00.250.500.751.001.523469121624364872ReferenceconcBLQAUC 0-t028.57 448.57 1362.50 2772.15 4483.26 8388.14 12690.14 21588.70 30484.07 47777.11 71970.71 94063.00 120850.00 166035.36 217225.00 253412.50 2984concBLQTestAUC 0-t027.14 346.14 1359.38 2668.55 4279.10 7983.73 11985.63 20484.26 28979.86 45373.25 68367.18 89359.85 114747.50 157733.59 206323.75 2407*11.88 *2835Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201341 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)•Missing values II•Values below the lowerlimit of quantitation (LLOQ)• Example as before,but LLOQ = 12.5 (instead 10)AUC 72 : T = ?, R = 2984T/R = ?AUC 48 : T = 2407, R = 2534T/R = 95% AUC all : T = 2692, R = 2984T/R = 90.22% biased!AUC 72* : T = ?, R = 2984T/R = ?time24364872time24364872time24364872Referenceconc50.00AUC 0-t166035.36 217225.00 253412.50 2984Referenceconc50.00AUC 0-t166035.36 217225.00 253412.50 2984Referenceconc50.00AUC 0-t166035.36 217225.00 253412.50 2984conc47.50TestAUC 0-t157733.59 206323.75 2407BLQ NATestconc47.50AUC 0-t157733.59 206323.75 2407= *0 2692Testconc47.50AUC 0-t157733.59 206323.75 2407*11.88 NABioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201342 • 68

Pharmacokinetic Analysis of BE DataNCA (Problems)What would you do?10080ReferenceTestLLOQ = 12.510080ReferenceTestLLOQ = 12.5concentration6040concentration6040200BQL0 12 24 36 48 60 72timeconcentration10020800604020ReferenceTestLLOQ = 12.50 12 24 36 48 60 72time00 12 24 36 48 60 72timeBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201343 • 68

Pharmacokinetic Analysis of BE DataSampling at Cmax•With any [sic] given sampling scheme the‘true’ C max is missed•It is extremely unlikely that we sample exactly at thetrue C max for any given subject•High inter- and/or intra-subject variability(single point metric)•Variability higher than AUC’s•In many studies the win/loose metric!•Try to decrease variability• Increase sample size (more subjects)• Increase sampling within each subject (maybe better)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201344 • 68

Pharmacokinetic Analysis of BE DataSampling at Cmax•Theoretical values (from PK simulation)C max : 41.9/53.5 (81.2%), t max : 6.11/4.02 (∆ 2.09)•# samples [2–12h]• n = 4‣ C max 78.3%‣ t max ∆ 4• n = 5‣ C max 78.3%‣ t max ∆ 4• n = 6‣ C max 79.8%‣ t max ∆ 1• n = 7‣ C max 81.2%‣ t max ∆ 255453525R theoreticalT theoreticalR sampledT sampled0 3 6 9 12Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201345 • 68

Pharmacokinetic Analysis of BE DataSampling at Cmax•Quote from the literature:C max was observed within two to five hoursafter oral administration…•Elimination is drug specific,•but what about absorption?•Formulation specific!•Dependent on the sampling schedule (in a strictsense study-specific)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201346 • 68

Pharmacokinetic Analysis of BE DataSampling at Cmax50402–5 hrsarithmetic meangeometric meanmedian30k a = [0.182 | 0.260]201000 4 8 12 16 20 24Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201347 • 68

Pharmacokinetic Analysis of BE DataSampling at Cmax50402–5 hrsarithmetic meangeometric meanmedian30k a = 0.182t lag = [0 | 2.5]201000 4 8 12 16 20 24Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201348 • 68

Pharmacokinetic Analysis of BE DataAnother Problem•EMA GL on BE (2010)•Section 4.1.8 Reasons for exclusion 1)• A subject with lack of any measurable concentrations oronly very low plasma concentrations for referencemedicinal product. A subject is considered to have verylow plasma concentrations if its AUC is less than 5% ofreference medicinal product geometric mean AUC (whichshould be calculated without inclusion of data from theoutlying subject). The exclusion of data […] will only beaccepted in exceptional cases and may question thevalidity of the trial.Remark: Only possible after unblinding!Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201349 • 68

Pharmacokinetic Analysis of BE DataAnother Problem•EMA GL on BE (2010)•Section 4.1.8 Resons for exclusion 1) cont’d• The above can, for immediate release formulations, be theresult of subject non-compliance […] and should as far aspossible be avoided by mouth check of subjects afterintake of study medication to ensure the subjects haveswallowed the study medication […]. The samples fromsubjects excluded from the statistical analysis should stillbe assayed and the results listed.Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201350 • 68

Pharmacokinetic Analysis of BE DataAnother Problem•Gastro-resistant (enteric coated) preparations•Gastric emptying of single unit dosage forms nondisintegratingin the stomach is prolonged andhighly erratic. The consequences of this effect onthe enteric coating of delayed release formulationsare largely unpredictable.• Sampling period should be designed such that measurableconcentrations are obtained, taking into consideration notonly the half-life of the drug but the possible occurrence ofthis effect as well. This should reduce the risk of obtainingincomplete concentration-time profiles due to delay to themost possible extent. These effects are highly dependenton individual behaviour.Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201351 • 68

Pharmacokinetic Analysis of BE DataAnother Problem•Gastro-resistant (enteric coated) preparations• Therefore, but only under the conditions that samplingtimes are designed to identify very delayed absorption andthat the incidence of this outlier behaviour is observed witha comparable frequency in both, test and reference products,these incomplete profiles can be excluded fromstatistical analysis provided that it has been considered inthe study protocol.EMEA, CHMP (EWP-PK)Questions & Answers: positions on specific questions addressed to the pharmacokinetics workingpartyEMA/618604/2008 Rev. 4 (16 February 2012)http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500002963.pdfWhat is ‘comparable’? For a study in 24 subjects, we get asignificant difference for 5/0 (Fisher’s exact test: p 0.0496).Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201352 • 68

Pharmacokinetic Analysis of BE Datat – a lag ‘nasty’ PK Metric•Only relevant for delayed release (gastricresistant) formulations•Highly variable – mainly not due to the formulationbut the intrinsic variability in gastricemptying•Less variability for multiparticulate formulationsthan for monolithic ones, but still problematic•Sampling schedule difficult to design•Assessment (descriptive vs. nonparametric)?Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201353 • 68

Pharmacokinetic Analysis of BE Datat – a lag ‘nasty’ PK Metric•Little is published about calculation; fivemethods assessed *•Commercial software (Phoenix/WinNonlin,Kinetica) treat t lag as the time point prior to thefirst measurable (non-zero) concentration•Other methods require programming skills;some of them might be judged by assessorsalready borderline PK models (?!)* Csizmadia F and L EndrenyiModel-Independent Estimation of Lag Times with First-Order Absorption and DispositionJ Pharmaceut Sci 87(5), 608–12 (1998)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201354 • 68

Pharmacokinetic Analysis of BE Datat – a lag ‘nasty’ PK Metric•Is t lag really clinically relevant – even forformulations where rapid onset of effects is ofimportance?•If two formulations follow identical pharmacokineticsexcept t lag , this difference is reflectedin t max as well (both in SD and MD)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201355 • 68

Pharmacokinetic Analysis of BE Datat vs. lag tmax•Single dose•DR, flip flop PK; V 10, D 100, F 100%,k 0.09902 h -1t lag 1 h (R), 4 h (T)t max 11.1 h (R),14.1 h (T)C max 3.68 (R&T)C τ2.335 (R),2.733 (T)AUC 0–τ 67.0 (R)59.4 (T)AUC 0–∞ 101.0 (R&T)concentrationBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201343210τ0 24 48 72RtimeTττ56 • 68

Pharmacokinetic Analysis of BE Datat vs. lag tmax•Simulation of steady state (τ 24 h; 6 d ≈ 20×t ½ )•Formulations differ in t lag only!concentration6543210Tlag (R)Tlag (T)120 124 128 132 136 140 144timeRTτ• t lag is discriminatory:T 4R 1T – R +3• Might be difficultto measure;frequent samplingrequired• Nonparametricstatistics (EMA!)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201357 • 68

Pharmacokinetic Analysis of BE Datat vs. lag tmax•Simulation of steady state (τ 24 h; 6 d ≈ 20×t ½ )•Formulations differ in t lag only! Surrogate possible?concentration6543210Tmax (R)Tmax (T)120 124 128 132 136 140 144timeRTτ• t max is discriminatoryas well:T 14.1R 11.1T – R +3• Maybe better;frequent samplingin the areaof C max common• Nonparametricstatistics (EMA!)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201358 • 68

Pharmacokinetic Analysis of BE DataCase Study (PPI 1)•Attempt to deal with high variabilityPowered to 90%according to CVfrom previousstudies; 140 (!)subjects and to80% for expecteddropout rate.Sampling every30 min up to14 hours(7,785 total)t max 15 h, C max 3.5×LLOQ150050025050255First time C max0 4 8 12 16 20 24t lag 6htime (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 2013t ½ 12 h59 • 68

Pharmacokinetic Analysis of BE DataCase Study (PPI 2)•Submission in China60005000ReferenceAUC t 87.60, 95.53%C max 75.39, 91.84%t max +0.500, +1.333significantly delayed(CI does not contain zero)•Company’s defendingargument:highly variableGI-transit manifestedin t lag•Let’s see…concentration (µg/mL)concentration (µg/mL)4000300020001000060005000400030002000100000 3 6 9 12 15nominal time (h)Test0 3 6 9 12 15nominal time (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201360 • 68

Pharmacokinetic Analysis of BE DataCase Study (PPI 2)0 2 4•Analysis0.50.4t lag ±0.000, +0.667not different (but borderline)0.30.2ReferenceReferenceTestReferenceTest0.15454Frequency00.1Tlag (h)32Tlag (h)320.2Test110.3000.40.50 2 4Tlag (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 2013Tlag (h)61 • 68

Pharmacokinetic Analysis of BE DataCase Study (PPI 2)0 2 4•Analysis0.8t max –t lag +0.167, +0.667significantly delayed(0 not within CI)ReferenceTestReferenceTest0.60.40.2ReferenceTmax – Tlag (h)4321Tmax – Tlag (h)4321Frequency0.20.40Test000.60.80 2 4Tmax – Tlag (h)Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201362 • 68

Pharmacokinetic Analysis of BE DataCase Study (PPI 2)•Assessment•Although there was no significantdifference in t lag ,the ‘corrected’ t max –t lagwas significantly delayed•Variability of the testformulation was higher•It seems that the company’sassumption doesnot hold – formulationsdiffer•Clinical relevance?Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 2013concentration (µg/mL)concentration (µg/mL)60005000400030002000100006000500040003000200010000Reference0 3 6 9 12 15shifted time (h)Test0 3 6 9 12shifted time (h)63 • 6815

Pharmacokinetic Analysis of BE DataHalf lives•Drug specific, but…•The apparent elimination represents the slowestrate constant (controlled release, topicals,transdermals) – not necessarily elimination!•Avoid the term ‘terminal elimination’ –might not be true•Important in designing studies• To meet AUC t ≥ 80% AUC ∞ criterion• To plan sufficiently long wash-out (avoid carry–over)• To plan saturation phase for steady stateBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201364 • 68

Pharmacokinetic Analysis of BE DataHalf lives•Dealing with literature data•What if only mean ±SD is given?• Assuming normal distribution:µ ± σ covers 68.27% of values (15.87% of values areexpected to lie outside of µ ± σ)• Example: 8.5 ± 2.4 hours, 36 subjects.0.1587 × 36 = 5.71 or in at least five subjects we mayexpect a half life of > 10.9 hours.• Plan for 95% coverage (z 0.95 = 1.96): p 0.95 = µ ± z 0.95 × σ8.5 ± 1.96 × 2.4 = [3.80, 13.2] hours.We may expect a half life of >13.2 hours in ~one subject(0.05/2 × 36 = 0.90).Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201365 • 68

Pharmacokinetic Analysis of BE DataHalf lives755010010µ 1.96σµ − 1.96σµ µ − σµµ µ + σµ + 1.96σµ σµ + 1.96σ10 12 24 36 482500 12 24 36 48Bioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201366 • 68

Pharmacokinetic Analysis of BE DataThank You!PharmacokineticAnalysis of BE DataOpen Questions?Helmut SchützBEBACConsultancy Services forBioequivalence and Bioavailability Studies1070 Vienna, Austriahelmut.schuetz@bebac.atBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201367 • 68

Pharmacokinetic Analysis of BE DataTo bear in Remembrance...The fundamental cause of trouble in the world today isthat the stupid are cocksurewhile the intelligent are full of doubt.Bertrand RussellIt is a good morning exercise for a research scientistto discard a pet hypothesis every day beforebreakfast.It keeps him young.Konrad LorenzIf you shut your door to all errorstruth will be shut out.Rabindranath TagoreBioequivalence Assessment of Oral Dosage Forms: Basic Concepts and Practical ApplicationsLeuven, 5–6 June, 201368 • 68