1. Bioequivalence trials: design, evaluation, regulatory requirements
Laszlo Tothfalusi Ph.D.

2. BIOEQUIVALENCE
“Two medicinal products containing the same active substance are considered bioequivalent if they are pharmaceutically equivalent or pharmaceutical alternatives and their bioavailabilities (rate and extent of absorption) after administration in the same molar dose lie within acceptable predefined limits. These limits are set to ensure comparable in vivo performance, i.e. similarity in terms of safety and efficacy.”
GUIDELINE ON THE INVESTIGATION OF BIOEQUIVALENCE, EMA (LONDON), 2010.

3. Different approach for establishing equivalence
Studies
Different approach for
establishing equivalence
PD studies
clinical
studies
in vitro
methods
PK studies

4. Clinical studies- endpoint
Comparative
clinical studies
in case PK or PD studies can not be performed
However:
- requires large number of subjects
- methodology establishing equivalence has not yet evolved extensively as for PK BE trials
- insensitive

5. Clinical study

6. In case of local action/ no systemic absorption
PD studies- marker
Comparative
PD studies
In case of local action/
no systemic absorption
Not recommended when:
- active ingredient is absorbed into the systemic circulation
- pharmacokinetic study can be conducted

7. PD studies Comparative PD studies PD measures more variable than PK
response relevant efficacy/safety
placebo effect
method: validated

8. PD based bioequivalence: -skin blanching response to corticosteroids

9. In vitro BCS based biowaiver
Based on in-vitro in-vivo correlation(IVIVC) study

10. PK Bioequivalence study is needed for
Oral Immediate Release products
Critical use medicines
Narrow therapeutic range drug products
Documented BA or BE problems related to API
Scientific evidence suggesting polymorphs of API, excipients, and/or process affecting BA
Non-oral, non-parenteral products designed to act systemically
Oral Modified Release products
Fixed-combination products with systemic absorption where at least one of the API requires an in vivo study

11. But BIOEQUIVALENCE TESTING--- is not only for Generics !
BE tests are not only required
for the registration of generic
drugs but are also carried out
during the development of
new drugs: e.g. during
scale-up and for post-approval
changes.
The same paradigm is also used for:
FDC (Fixed-dose combination),
Food effect
DDI studies !

12. Guidance documents…

13. STUDY DESIGN - standard design: randomized, two-period,
two-sequence, single dose cross-over
design
- alternative designs: parallel design
(substances with very long half-lives) and
replicate designs (in case of highly
variable drugs or drug products)

14. TWO-GROUP PARALLEL DESIGN
RANDOMIZATION
group 1
TEST
subjects
group 2
REFERENCE

15. Two-Group Parallel Design
Advantages
Clinical part shorter than a crossover.
Straigthforward statistical analysis.
No washout period - drugs with long half life.
Potentially toxic drugs or effect and/or AEs unacceptable in healthy subjects.
Studies in patients
Disadvantages
More volunteers are needed than for crossover design
Tight inclusion-/exclusion criteria to reduce between-subject variability.
Phenotyping mandatory for drugs showing polymorphism.

16. 2 x 2 CROSS-OVER DESIGN R T T R RANDOMIZATION period 1 period 2
WASHOUT T
sequence 1
subjects
sequence 2 T R

17. Standard 2x2 design Advantages
Globally applied standard protocol for bioequivalence, drug-drug interaction, food effect studies.
Straigthforward statistical analysis.
Disadvantages
Frequently not suitable for studies in patients
Not optimal for drugs with long half life
Not optimal for highly variable drugs / drug products
replicate designs with reference-scaling

18. REPLICATE DESIGN 4-period, 2-sequence, 2-formulation design
RANDOMIZATION
I II III IV
sequence 1 T R T R
subjects
sequence 2 R T R T
wash-out

19. Replicate designs Two-sequence four-period Two-sequence three-period
TRTR | RTRT
Two-sequence three-period
TRT | RTR
and many others…
(FDA: TRR | RTR | RRT, aka ‘partial replicate’)
The statistical model is complicated and depends on the actual design!

20. Add-On / Two-Stage Designs
Sometimes properly designed studies fail due to ‘true’ bioinequivalence,
pure chance (producer’s risk),
poor study conduct (increasing variability),
false (mainly over- optimistic) assumptions about the CV and/or T/R- ratio – leading to a too small sample size (insufficient power).

21. From H Schütz, BEBAC AT

22. After repeated administration (fasting)
One bioequivalemce study frequently not enough : modified release products
Single dose, fasting
Single dose, fed
After repeated administration (fasting)

23. Power vs. Treatment Difference for Bioequivalence

24. Biowaiver request for different strenghts:
The following general requirements must be met where a waiver for additional strength(s) is claimed:
the pharmaceutical products are manufactured by the same manufacturing process,
the qualitative composition of the different strengths is the same,
the composition of the strengths are quantitatively proportional, i.e. the ratio between the amount of each excipient to the amount of active substance(s) is the same for all strengths (for immediate release products, coating components, capsule shell, colour agents and flavours are not required to follow this rule),
If there is some deviation from quantitatively proportional composition, condition c is still considered fulfilled if condition i) and ii) or i) and iii) below apply to the strength used in the bioequivalence study and the strength(s) for which a waiver is considered
the amount of the active substance(s) is less than 5 % of the tablet core weight, the weight of the capsule content
the amounts of the different core excipients or capsule content are the same for the concerned strengths and only the amount of active substance is changed
the amount of a filler is changed to account for the change in amount of active substance. The amounts of other core excipients or capsule content should be the same for the concerned strengths
appropriate in vitro dissolution data should confirm the adequacy of waiving additional in vivo bioequivalence testing (see section 4.2).

25. EMA Guideline on the Investigation of Bioequivalence, 2010
SAMPLING TIMES
“The sampling schedule should include frequent sampling around the predicted tmax to provide a reliable estimate of peak exposure. In particular, the sampling schedule should be planned to avoid Cmax being the first point of the concentration- time curve.” o
“The sampling schedule should also cover the plasma
concentration time curve long enough to provide a
reliable estimate of the extent of exposure which is
achieved if AUC0-t covers at least 80% of AUC0-.
At least 3 to 4 samples are during the terminal log-
linear phase in order to reliably estimate the terminal
rate constant, which is needed for a reliable estimate
of AUC0-.”
Sampling times: 0, 0.5, 1, 2, 4, 6, 8 and 12 hours.

26. EMA Guideline on the Investigation of Bioequivalence, 2010
PRIMARY PARAMETERS:
- AUC0-t or AUC0-72h: extent of absorption
- Cmax: extent and rate of absorption
- Tmax: rate of absorption

27. Bioequivalence criteria: 90% CONFIDENCE INTERVAL
a 90% confidence interval has to be calculated around the ratio of geometric means obtained for AUC (and Cmax) following administration of test and reference preparation
this ratio of geometric means is called the point estimate

28.  90% CONFIDENCE INTERVAL 90% CI  1.04 (0.91 – 1.20) 1.04
point estimate
Evaluation
The test/reference ratio is calculated.
The 90 % confidence interval (CI) around the ratio is calculated.
The width of the CI depends on the variability observed in
the study.
The location of the CI depends on the observed test/reference-ratio.  
0.80
1.04
1.25
Bioequivalence is accepted if CI in th 0.8 – 1.25 range or

29. HVDPs (EMA)
EU GL on BE (2010)
Average Bioequivalence (AB) with Expanding Limits (EL)  “ABEL”
Based on WR (the intra-subject standard deviation of the reference formulation) calculate the scaled acceptance range based on the regulatory constant k (s = );

30. Any questions ?