1. Evaluation of immunogenicity Case presentations CEMDC-PharmaTrain, Module 8. Budapest, Hungary, 12-May-2017
Vid Stanulovic MD, PhD
Clinical pharmacologist,
Clinical Development and Pharmacovigilance Consultant

2. Clinical immunogenicity testing
Strategy for the evaluation of immungenicity is based on regulatory documentation:
- FDA Guidance for Industry (2009): Assay development for Immunogenicity Testing of Therapeutic Proteins. Draft.
- FDA Guidance for Industry (2014): Immunogenicity Assessment for Therapeutic Proteins Products.
- EMA (2015) Guideline on Immunogenicity Assessment of Biotechnology-derived Therapeutic Proteins. EMEA/CHMP/BMWP/14327/2006 Rev. 1

4. Consequences Safety Impact Exposure/Efficacy Impact
Cross reactivity with endogenous proteins
Allergic reactions
Immune complexes-complement activation
Exposure/Efficacy Impact
Neutralizing and/or clearing antibodies
Enhanced drug clearance
Drug accumulation

5. Risk-Based Testing Breadth of immunogenicity (testing) dependent on
Likelihood of an immune response
Likely clinical consequences of an immune response
As the concern around immunogenicity increases, the level of testing should also increase
Samples tested more frequently
More thorough characterization

7. Clinical immunogenicity testing strategy 3-tiered approach
Screening assay
Tier 1: 5% false-positive  ADAs present?
Reactive
Negative
Confirmatory assay
Negative
Tier 2: Are the detected
ADAs specific for the drug?
Confirmed Positive
Titer
Neutralizing Assay
 Characterization
Negative
Tier 3: Do the specific ADAs possess neutralizing capacity?
Confirmed Positive
Titer
Correlation ? with
clinical observations

8. How to determine the screening cut point?
SCP = level of response above which a sample is defined to be reactive (potential positive) and below which is probably negative
Upper negative limit of 95% is recommended = risk-based approach (more appropriate to have 5% false-positive than false-negative)

9. How to determine the specificity cut point?
Used to confirm the presence of ADA in sample found above the SCP
Competitive inhibition by addition of the therapeutic protein in sample
% inhibition calculated between sample measured unspiked and spiked with an excess of drug
Sample is confirmed positive if its %inhibition is > Confirmation cut point (CCP)
0.1% of false-positive
Measured signal > SCP
=> Reactive sample
Addition (spike) of an excess of drug in sample
Decrease of measured signal
=> Sample confirmed as positive if %inhibition > CCP
Important: Suitability of the Cut-point needs to be re-assessed once baseline samples from patients become available

10. Clinical Immunogenicity reporting

11. Reporting of Clinical ImmunogenicityData
Currently there is a lack of standardization in the terminology used for the collection, analysis, and presentation of immunogenicity results in clinical trial reports, regulatory documents (IND, IMPD) and product labels
The aim of the initiative “Harmonization of the Reporting of Clinical Immunogenicity Data” is to foster a unified approach to assessing and describing immunogenicity (globally, but at least on company level)
It is based on latest recommendations and “white papers”

12. Kinetics of the ADA response
Reporting of Clinical Immunogenicity Data Sample Status / ADA Attributes / Subject Status *
Kinetics of the ADA response
ADA incidence
*Evaluable subjects should also have a baseline sample. If baseline sample is missing, it should be treated as if negative.

13. Reporting of Clinical Immunogenicity Data Treatment Boosted ADA
Treatment-boosted ADA: Pre-existing ADA that were boosted to a significant higher titer following drug administration than the baseline
A difference in titer values between 2 samples representing at least two titer steps is considered significant. For example at least a 4-fold increase in titers for 2-fold or a 9-fold increase for a 3-fold serial dilution schema would be required
2-fold dilution scheme:
1:2
1:4
1:8
1:16
example:
3-fold dilution scheme:
1:3
1:9
1:27
1:81
9-fold increase
4-fold increase

14. Reporting of Clinical Immunogenicity Data ADA Incidence/Prevalence
Subject status is used to calculate:

15. Reporting of Clinical Immunogenicity Data Kinetics of the ADA Response
Focus on treatment-induced ADA
A separate evaluation for the kinetics of treatment-boosted ADA might be performed in case a high number of pre-existing ADAs are detected
Onset of ADA:
Time period between the initial administration of the biologic drug and the first instance of treatment-induced ADA
Report the “median time to ADA development” and the quartiles Q1 and Q3
Duration of ADA:
Longevity of treatment-induced ADA
Only calculated for subjects with at least two positive ADA samples
Report the median duration of an induced ADA response and IQR

16. Reporting of Clinical Immunogenicity Data Kinetics of the ADA Response
Important note: Categories listed below are independent from the dosing- and sampling regimen
Transient ADA response
Persistent ADA response
Indeterminate ADA response

17. Kinetics of the ADA Response Transient Response
Transient ADA response:
Treatment-induced ADA detected only at one sampling time point during the treatment or follow-up observation period (excluding the last sampling time point)
Treatment induced ADA detected at two or more sampling time points during the treatment (including follow-up period if any), where the first and last ADA-positive samples (irrespective of any negative samples in between) are separated by a period less than 16 weeks and the last time point is negative 4 8 12 24 48 36
week
Half-life of endogenous IgGs: days
=> a transient immune response (IgGs) is expected to be eliminated at the end of 5 x t1/2 (~16 weeks)

18. Kinetics of the ADA Response Persistent Response
Persistent ADA response:
Treatment induced ADA detected at two or more sampling time points during the treatment (including follow-up period if any), where the first and last ADA-positive on-treatment sample (irrespective of any negative samples in between) are separated by at least 16 weeks 4 8 12 24 36 48
week
Half-life of endogenous IgGs: days
=> a transient immune response (IgGs) is expected to be eliminated at the end of 5 x t1/2 (~16 weeks)

19. Kinetics of the ADA Response Indeterminate Response
Indeterminate ADA response
Only the last sampling time point is positive and all previous samples are negative
The last two samples are positive but separated by a period less than 16 weeks 4 8 12 24 36 48
week

20. Case presentations

21. Case 1: Growth hormone Phase II trial
Single patient with transient antibodies
Characterization: Neutralizing
Adverse events: No AEs suspected to be caused by the drug

22. Case 1: Growth hormone Originator (Genotropin®)

23. Efficacy response -- patient efficacy response (IGF-I)
--efficacy response of the dose cohort (IGF-I)
Confirmed NaB time-point

24. Case 1: Growth hormone For evaluation:
History?
HCV antibodies at screening tested positive but negative on retest
Relevance?
Clinical impact?

25. Case 2: Interferon beta
Biosimilar interferon-beta for multiple sclerosis
Hypersensitivity reported with a few weeks after initiating treatment
The patient was interferon naive
Investigator assessed the event as severe and definitely related
Patient discontinued from the trial

26. Case 2: Interferon beta 1a Originator (Avonex®)
4.4 Special warnings and precautions for use
4.8 Undesirable effects

28. Case – Interferon beta
No neutralizing antibodies detected – but consider the limitations of antibody assays
Actions to be considered:
History
Follow-up
Clinical
Laboratory
Rechallenge with the IMP?

29. Thank you for your attention