ich m7 overview: predicting, assessing, and controlling ... · • degradants produced via stress...
TRANSCRIPT
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ICH M7 Overview: Predicting,
Assessing, and Controlling
Mutagenic Impurities from
Degradation
Steven W. Baertschi, Ph.D.
Baertschi Consulting, LLC
http://baertschiconsulting.com/
May 24-25, 2018
Lhasa 2018 Pharmaceutical Industry and
Regulators Symposium
Brasilia, Brazil
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Acknowledgments
• PhRMA Limited Duration Key Initiative Team, ICH M7
• Stephen Miller, US-FDA
• Stephen Raillard, Xenoport
• Chris Riley, Riley and Rabel Consulting
• Bernard A. Olsen, Lilly-retired, currently a consultant
• Joel Bercu, Gilead
• Robert Jolly, Lilly
• Dave Elder (GSK), Mark Kleinman (GSK), Mark Mowery
(Merck); Andrew Teasdale (AstraZeneca), Dave DeAntonis
(Pfizer), Karen Alsante (Pfizer)
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Introduction
• History / Background
• Definitions, Regulatory framework
• Short Overview of ICH M7
• Developing strategies / approaches to predict and
assess potential mutagenic deg products
• Predicting “actual” degradation products in a short
timeframe
• Structure alerts and Degradation pathways
• How likely will there be a “problem”?
• Expected Frequency
• Conclusions
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Quote from ICH Q3A and Q3B
• Degradation products present at a level of not
more than (≤) the identification threshold
generally would not need to be identified.
However, analytical procedures should be
developed for those degradation products that
are suspected to be unusually potent, producing
toxic or significant pharmacological effects at
levels not more than (≤) the identification
threshold.
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EMEA / CHMP “Guidelines on the limits of Genotoxic Impurities”,
CPMP/SWP/5199/02; EMEA/CHMP/QWP/251344/2006, London, UK, 28
June 2006.
• Quotation from EMEA guideline on GTI’s: “As stated in the Q3A guideline, actual and potential impurities most likely to arise during synthesis, purification, and storage of the new drug substance. This summary should be based sound scientific appraisal of the chemical reactions involved in the synthesis, impurities associated with raw materials…and possible degradation products. This discussion can be limited to those impurities that might reasonably be expected based on knowledge of the chemical reactions and conditions involved.”
• Guided by existing genotoxicity data or the presence of structural alerts, potential genotoxic impurities should be identified.”*
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FAST FORWARD TO TODAY…
ICH M7
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ICH M7 Guideline: Step 4 published July
2014; full implementation January 2016
• Title: “Assessment and Control of DNA Reactive
(Mutagenic) Impurities in Pharmaceuticals to
limit potential carcinogenic risk”
• Guideline Objective: This guideline outlines recommendations for assessment and control of mutagenic impurities (to levels that are expected to pose negligible carcinogenic risk) that reside or are reasonably expected to reside in final drug substance (DS) or product (DP), taking into consideration the intended conditions of human use.
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Guideline General Framework
Sections 1-4Scope etc.
Section 5:Impurity
Assessment
Section 6:Hazard
Assessment
Section 7:Risk
Characterization
Section 8:Control
Section 9:Documentation
What impurities need
to be assessed? – actual,
potential, degradation products
Is the impurity
mutagenic?
QSAR + Ames
What is the
acceptable intake?
(TTC, compound
specific, less than
lifetime exposures)
Expectations, options
for impurity control,
lifecycle
Expectations
for regulatory
filings
Scope,
General Principles
Considerations for
Marketed Products
**Slide from Stephen Miller, US-FDA, presented at AAPS Short Course on
Assessment and Control of Mutagenic Impurities, Oct 25, 2015, Orlando, FL
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Scope: Intended
• New drug substances and new drug products in clinical development and subsequent application for marketing
• Certain post approval submissions of marketed products and to new marketing applications (drug substance previously approved):• Changes to the drug substance
• Changes to the drug product
• Changes in clinical use
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Scope: Not Intended
• Biological/biotechnological, peptide, oligonucleotide, radiopharmaceutical, fermentation products, herbal products, and crude products of animal or plant origin, excipients used in existing marketed products, flavoring agents, colorants, perfumes
• Drugs covered by ICH S9 (advanced cancer indications) or where the drug substance itself is genotoxic and exposure to a mutagenic impuritywould not significantly alter the overall cancer risk.
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Considerations for Marketed Products
Category (Section) Guidance for Re-Evaluation
Changes to Drug Substance (4.1)
• Post approval submissions with changes in synthesis or process conditions after the starting material
• Not required for changing drug substance site of manufacture, raw materials supplier
Changes to Drug Product (4.2)
• New or higher levels of existing mutagenic degradation products when product submission involves change e.g., composition, manufacturing process, dosage form
• Not required for changing site of manufacture
Changes to Clinical Use (4.3)
• Changes in clinical dose or duration of use, change in indication e.g., life-threatening disease to non-life threatening disease or less serious condition
Other Considerations (4.4)
• (Q)SAR alert alone does not warrant re-evaluation, unless it is a structure of ‘cohort-of-concern’ (CoC)
• Cause for concern: 1) New mutagenicity or carcinogenicity data for impurity; 2) Newly discovered impurity that is a mutagenic carcinogen or mutagen
Lifecycle (8.5) • Newly identified impurities in products approved after issuance of M7 would be assessed for mutagenicity
**Slide from Stephen Miller, US-FDA, presented at AAPS Short Course on Assessment
and Control of Mutagenic Impurities, Oct 25, 2015, Orlando, FL
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Table 2: Acceptable Daily Intakes for an Individual
Impurity (during clinical development and at
marketing)*
Duration of treatment
< 1 month>1 - 12
months>1 - 10 years
>10 years to lifetime
Daily intake[µg/day]
120 20 10 1.5
• Duration of treatment intended to apply to “great majority of patients” (Section 7.3.2.)
• Intermittent dosing – can be based on the total number of dosing days
• Compound-specific AI can be adjusted proportionally for shorter durations
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Table 2: Acceptable Daily Intakes for an Individual
Impurity (during clinical development and at
marketing)*
Duration of treatment
< 1 month>1 - 12
months>1 - 10 years
>10 years to lifetime
Daily intake[µg/day]
120 20 10 1.5
• Duration of treatment intended to apply to “great majority of patients” (Section 7.3.2.)
• Intermittent dosing – can be based on the total number of dosing days
• Compound-specific AI can be adjusted proportionally for shorter durations
Maximum Daily Intake = 1.5 ug/day (Threshold of Toxicological Concern
(TTC))
Applicable to compounds if there is insufficient evidence for a
threshold-related mechanism
Original calculation assumes life-time exposure of 70 years
Based on potential cancer risk of 1 in 100,000
Compare with actual life-time cancer risk of ~40%*41% → 41.001%
*Based on rates from 2006-2008, 41.21% of men and women born today will
be diagnosed with some form of cancer at some time during their lifetime.
http://seer.cancer.gov/statfacts/html/all.html#risk
E. J. Delaney, “An impact analysis of the application of the threshold of toxicological concern
concept to pharmaceuticals”, Reg. Tox. Pharmacol., 49, 107-124 (2007)
The Cliff of
Regulatory
Concern!
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Naked Eye vs Hubble TelescopeHubble Deep Field
Hubble Ultra-Deep Field
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Naked Eye vs Hubble TelescopeHubble Deep Field
Hubble Ultra-Deep Field
Take home message: The more sensitive
the analytical technique / detector, the more
we will “see”.
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Table 3: Acceptable Total Daily Intakes for
Multiple Impurities*
• *For 3 or more Class 2 and 3 impurities specified on the drug
substance specification (during clinical development and at
marketing).
• For combination products, each active ingredient should be
regulated separately.
• Impurities with compound-specific or class-related acceptable
intake limits (Class 1) should not be included in the total limits of
Class 2 and Class 3 impurities.
• Degradation products would be controlled individually and a
total limit would not be applied.
Duration of treatment
< 1 month >1 - 12 months >1 - 10 years>10 years to
lifetime
Total Daily Intake
[µg/day]120 60 30 5
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Options for Control of Impurities
• Synthesis prior to SM will generally be managed under the applicant’s quality system
• Removal of impurity can be monitored through starting material, intermediate, or drug substance specifications, or assured by the manufacturing process controls themselves
Starting
Material
Synthetic
Intermediate
A
Synthetic
Intermediate
B
Drug
Substance
Etc.
**Slide from Stephen Miller, US-FDA, presented at AAPS Short Course on Assessment
and Control of Mutagenic Impurities, Oct 25, 2015, Orlando, FL
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Control Options (8.1)
Option 1: Monitor the impurity in the drug substanceAcceptance criterion at or below the TTC
Option 2: Monitor the impurity in intermediate, starting material or in-process control
Acceptance criterion at or below the TTC
Option 3: Monitor the impurity in intermediate, starting material or in-process control
Acceptance criterion above the TTC, with demonstrated understanding of fate and purge and associated process controls
Option 4: Design robust process controls to reduce the risk of impurity level above the TTC to negligible
“Especially useful for those impurities that are inherently unstable, or those impurities introduced early in the synthesis and are effectively purged”
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And now for the hardest part…!
Degradation
Products Process
Impurities
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From ICH M7: 5. DRUG SUBSTANCE AND DRUG
PRODUCT IMPURITY ASSESSMENT
• Actual and potential impurities that are likely to arise
during the synthesis and storage of a new drug
substance, and during manufacturing and storage of a
new drug product should be assessed.
• The impurity assessment is a two-stage process:
• Actual impurities that have been identified should be
considered for their mutagenic potential.
• An assessment of potential impurities likely to be present
in the final drug substance is carried out to determine if
further evaluation of their mutagenic potential is required.
• The steps as applied to synthetic impurities and
degradation products are described in Sections 5.1 and
5.2, respectively.
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Questions
• What defines “potential”? “likely”, “reasonably
expected”?• Sound scientific appraisal and reasonable expectation
• Degradants produced via stress testing are considered, by
Q1A(R2) definition, “likely”
“Stress testing helps to determine the intrinsic stability of the molecule by
establishing degradation pathways in order to identify the likely
degradation products and to validate the stability-indicating power of the
analytical procedures used… Examining degradation products under stress
conditions is useful in establishing degradation pathways and developing and
validating suitable analytical procedures. However, such examination may not
be necessary for certain degradation products if it has been demonstrated that
they are not formed under accelerated or long-term storage conditions.
--ICH Stability Guideline Q1A(R2):
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Questions
• What defines “actual”? • Degradation products formed under accelerated or long-term
storage conditions (see quote below)
“Stress testing helps to determine the intrinsic stability of the molecule
by establishing degradation pathways in order to identify the likely
degradation products and to validate the stability-indicating power of the
analytical procedures used… Examining degradation products under
stress conditions is useful in establishing degradation pathways and
developing and validating suitable analytical procedures. However,
such examination may not be necessary for certain degradation
products if it has been demonstrated that they are not formed
under accelerated or long-term storage conditions.”
--ICH Stability Guideline
Q1A(R2):
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ICH M7: 5.2 Degradation Products
• Actual degradation products: include those
observed above the ICH Q3A/B reporting
threshold during storage of the drug substance in
the proposed long-term storage conditions and
primary and secondary packaging.
• Potential degradation products: include those that
form above the ICH Q3A/B identification threshold
during accelerated stability studies (e.g.,
40°C/75% relative humidity for 6 months) and
confirmatory photo-stability studies as described
in ICH Q1B…yet to be confirmed…under long-
term storage…in the primary packaging.
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ICH M7: 5.2 Degradation Products
• Knowledge of relevant degradation pathways
can be used to help guide decisions on the
selection of potential degradation products to be
evaluated for mutagenicity e.g., from
degradation chemistry principles, relevant stress
testing studies, and development stability
studies.
It is clear that ICH M7 is expecting MORE than just
looking at “actual” degradation products (Q3A/B
thresholds) and performing a mutagenicity
assessment.
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Piecing Together What ICH
M7 says about “Potential”,
“Reasonably Expected”,
and “Likely to Arise”….
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Proposed Process
Flow for Assessing
Degradants in API /
DP
Scheme 1 from “Strategies to
address mutagenic impurities
derived from degradation in drug
substances and drug products”,
Kleinman MH et al., Org. Proc.
R&D, Org. Process Res.
Dev. 19, 11, 1447-1457 Article
ASAP, DOI:
10.1021/acs.oprd.5b00091
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Building Knowledge of Deg Pathways:
“Theoretical” / Hypothetical
• Proposed Construct:
• Chemistry principles = Theoretical (or “Hypothetical”)
• based on scientific principles (either personal
knowledge or from the literature).
• Theoretical / hypothetical would mean that it has
not been demonstrated with data.
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What is the state of our ability to predict
Degradation Pathways based on Chemical
Principles?
In Silico / Hypothetical
Real world Real world
In Silico / Hypothetical
In Silico / Hypothetical
Real world
In Silico / Hypothetical
Real world
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• More chemistry- 445 transformations projected for 2016.1.0 knowledge base
• Excipients• ~120 “excipients” or counterions.
Continuing Improvements: Zeneth 7 and Knowledge Base (2016)
45 new and 47 improved transformations
Improved calc of “likelihood”
Separation of counterions and excipients
Compatibility upgrades
– Windows 10 and latest drawing packages
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How well does Zeneth work?
Benchmarking Study in 2014
• “In silico prediction of pharmaceutical degradation pathways: a
benchmarking study”, Kleinman et al., Mol. Pharm., 11, 4179-4188
(2014).
• Involved GSK, Lilly, Pfizer, Amgen, Merck, and Lhasa.
• 27 Drug Substances, 191 known deg products (long-term, accelerated, and
stress)
• Also process against “historical” knowledge bases (2009.1, 2009.2, 2010.2, 2011.1, 2012.1.1, 2012.1.3/2012.2.0)
• Evaluation of coverage(positive predictions)
• Evaluation of overprediction(“unconfirmed positive” predictions)
• Evaluation of predictive progress in time
80 transformations →277 transformations
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Summary of Benchmarking
0%
50%
100%
2009.1.0 2009.2.0 2011.1.0 2011.2.0 2012.1.1 2012.2.0
80 183 277
54%
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Why we can’t rely on Theoretical / “Hypothetical”
Predictions…
• The relationship between Idealized and Realistic Degradation
Knowledge Landscapes: Hypothetical predictions can be
MUCH larger than “reality”…
• Hypothetical Predictions “miss” many real world degradation
pathways/products
Zeneth
See “In silico prediction of pharm
deg pathways: a benchmarking
study”, Mol. Pharm. (2014) 11(11),
4179-88.
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How about Stress Testing as a
Predictive Tool?
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For more details see Baertschi, S.W. “Pharmaceutical Stress Testing: Predicting Drug
Degradation”, Chapter 2, 2nd Edition, Informa Healthcare, 2011.
•Hydrolytic --> high humidity and solution stressing
Acid/Base: pH’s 1-13 at RT up to 70 C, 1-2 weeks
•Thermolytic --> heat / humidity
70 C, high (75%) and low (20%) humidity, 2-4 weeks (DP and API)
•Photolytic --> exposure to appropriate light source(s)
Expose solid and solutions to both visible and UV light in excess of ICH
minimum confirmatory exposure (2-5 fold excess recommended)
•Oxidative --> oxidative degradation can be complex.
Peroxides – 0.3% hydrogen peroxide, RT, 1-3 days.
Radical-initiator – e.g., VAZO 52, 2-3 days, 30C.
Cu(II) and Fe(III) – 1-2 mM, 1 day, RT – 40C.
Why we CAN rely on well-designed stress
testing…benchmarking data from 15 Lilly cmpds
Using Stress Testing to Predict Real World Degradation: Four
Main Pathways
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Important Questions
1. Do we / should we elucidate structures of deg
products observed during stress testing?
--No clear regulatory mandate – up to individual company
--On what basis? “Major” or “Significant” deg products?
-- When in relation to the timeline?
2. How do we define “Major” in stress testing
studies?
3. How do we determine which stress testing-
derived deg. products are relevant to the drug
product?
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Question 2. Defining “Major”
• Stress to end point or to 10-20% degradation
• Define “major” as 10% or more of total
degradation and >25% of largest individual
➢For more details or comparison, see:
➢Alsante et al., Adv. Drug Deliv. Rev. (2007) 59:29-37
➢Kleinman et al., Org. Process Res. Dev. 19, 11, 1447-1457;
DOI: 10.1021/acs.oprd.5b00091
• Typically, 6-12 degradation major deg products
are observed (average 8.2, Lilly benchmarking
data)
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Question 2. Defining “Major”
➢Kleinman et al.,
Org. Process Res.
Dev. 19, 11, 1447-
1457; DOI:
10.1021/acs.oprd.
5b00091
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Question 2. Defining “Major”
➢Kleinman et al.,
Org. Process Res.
Dev. 19, 11, 1447-
1457; DOI:
10.1021/acs.oprd.
5b00091
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Predicting Degradation Profiles from Stress
Testing: Data from 15 Lilly Compounds
12445
“Knowledge
Space”“Control
Space”
“Design Space”
▪Observations:
➢ 36% of Major Stress Degradants formed under “real world”
conditions (45/124 = 36%)
➢8.2 Major Stress Degradants per API
➢No Surprise Degradants outside of Knowledge Space!!
What DOES FORM in final DP
under proper packaged
conditions, long term stability
What CAN FORM in the DP (40/75
or 25/60, no special packaging /
open conditions)ALL STRESS TESTING
results, including Excip.
Compat. and Formulation Stress
Testing
39
Dow LK,* Pack BW, Hansen MM, and Baertschi SW,
J. Pharm.Sci.,102(4), 1404-1418 (2013).
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42
How well do the (Q)SAR Methods
Work for Predicting Mutagens?
• For Process Impurities, approx. 55% of (Q)SAR
(DEREK and Ashby-Tennant predicted positive) were
Ames Positive when tested
• If you remove Boronic Acid Derivatives → ~52%
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• There are certain functionalities that are
considered alerting structures for mutagenicity*
• Which alerting structures are the most common
to drug degradation, and what are the most
common degradation pathways leading to these
structures?
Alerting Structures*: Concerns for Common
Degradation Products
*(a) J. Ashby, R.W. Tennant, Mutat. Res. 204 (1988) 17–115;
(b) Benigni and Bossa, Mutation Research 659 (2008) 248–261, Table 2
(31 structure alerts contained within “Toxtree 1.50” software)
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44
Frequency of Alerting Structures in
the Drug Degradation Database
• A drug degradation database (no longer active)
http://d3.arxspan.com, contained the structures of
more than 393 drugs and 1200 related deg.
products.
• The database was analyzed using ToxTreeTM
software* for the presence of alerting structures.
*Benigni and Bossa, Mutation Research 659 (2008)
248–261, Table 2 (structure alerts contained within
“Toxtree 1.50” software)
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45
Frequency of Alerting Structures in
the Drug Degradation Database
Total # of
Degradants with
AlertsAlerts Shared with
parent
Total # of Degradants with
Unique Alerts
Total # of DegradantsProcessed
356 201 155 1021
35% 20% 15%
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Summary of Analysis: Risk of Producing an
Alerting Structure from Drug Degradation
• ~15% of degradation products have alerting structures
unique from the parent (as found in database)*
• A smaller percentage were flagged as toxicity alerting
from analysis using DEREKTM or MultiCASETM (~5-8%)**,
which take into account not only the presence of an
alerting structure but also apply more sophisticated rules
and machine learning.
• Roughly 50% of these alerting structures can be
expected to be Ames positive
*Raillard, S.P., Bercu, J., Baertschi, S.W., and Riley, C.M. “Prediction of Drug
Degradation Pathways Leading to Structural Alerts for Potential Genotoxic
Impurities”, Org. Proc. Res. and Dev., 14, 1015-1020 (2010).
**Nigel Green, J. Thom Deahl, J. Bercu, Bob Jolly, et al., manuscript in
preparation
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Most Common Alerting Structures From
Drug DegradationStructural Alert and
Corresponding ToxTree™ Alert Number
Number of hits in Degradants
Number of unique hits in Degradants*
Aldehydes (SA 11) 40 34α, β-Unsaturated Carbonyls (SA 10)**
126 30
Primary Aromatic Amines, Hydroxyl amines and its Derived Esters (SA 28)
93 23
Heterocyclic,Polycyclic Aromatic Hydrocarbons (SA 19)
15 13
Epoxides and Aziridines (SA 7) 17 12
Nitro Aromatics (SA 27) 25 6Aromatic ring N-Oxides (SA 26)
6 6
Aliphatic Halogens (SA 8) 12 6
Total 334 130
% of Total Alerts 93.8 83.9
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N
OH
N
O N+
O-
N
A
A
Aminoaryls and alkylated aminoarylsAza-aryl N-oxides
A
N-Hydroxyaryls
A
A
N-Acylated aminoaryls
Purines or Pyrimidines, Intercalators, PNAs or PNAHs
Group 1: Aromatic Groups
Group 2: Alkyl and Aryl Groups
O
N
OH
NO
N
O NH2
O
NO2
A H A A
A
AA
A
Aldehydes N-Methylols N-Nitrosamines Nitro Compounds Carbamates (Urethanes)
O NH O C (or S)
AA
Epoxides
A A
O
Propiolactones
PropiosultonesAziridines
Halogen
S or N
N or S Mustards
(beta haloethyl)
N N
R
A
A
A
Hydrazines and
Azo Compounds
Group 3: Heteroatomic Groups
EWG
Michael-reactive
Acceptors
P
O
OR
S
O
OR
Alkyl Esters of
Phosphonates or Sulfonates
Halogen
Halo-alkenes
Halogen
A
Primary Halides
(Alkyl and aryl-CH2)
Legend: A = Alkyl, Aryl, or H
Halogen = F, Cl, Br, I
EWG = Electron withdrawing group (CN, C=O, ester, etc)
Structural Alerts for Mutagenicity
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Predicted Probability of Finding a
Potential Mutagenic Deg Product…
• If, on average, 8 major stress degradants are
identified per API through Stress Testing….
Between~33-66% of all APIs will require one of the degradants to have an Ames test conducted
i.e., 8% DEREK positive means 2 out of 24 degradants (3 APIs x 8 degs per API)
Between ~16-33% of all APIs will give rise to a positive Ames result for one of the degradants
1 out of 24 degradants is predicted to be Ames positive. (Significant analytical effort will be required – TTC detection, aged / stressed samples.)
Between ~4-12% of all APIs are predicted to have 1 confirmed Ames positive degradant that forms in the drug product
36% stress degradants observed on stability in historical DPs
Analytical
resources required
Synthetic and/ or
isolation resources
required
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Determining “Relevancy” of Potential Degradants:
Using Semi-Empirical Modeling Outlined in M7
• ICH M7: 8.4 Control of Degradation Products
• “For a potential degradation product that has been characterized as mutagenic, it is important to understand if the degradation pathway is relevant to the drug substance and drug product manufacturing processes and/or their proposed packaging and storage conditions. A well-designed accelerated stability study(e.g., 40°C/75% relative humidity, 6 months) in the proposed packaging, with appropriate analytical procedures is recommended…”
• “Alternatively, well designed kinetically equivalent shorter term stability studies at higher temperatures in the proposed commercial package may be used…”
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Determining “Relevancy” of Potential Degradants
(Translating from “Potential” to “Actual”)
• ICH M7: 8.4 Control of Degradation Products
• “Based on the result of these accelerated studies, if it is anticipated that the degradation product will form at levels approaching the acceptable limit under the proposed packaging and storage conditions, then efforts to control formation of the degradation product is expected.”
• …“In these cases, monitoring….in long term primary stability studies…is expected unless otherwise justified.”
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“Well-designed kinetically-equivalent”
shorter study
• Kinetically-Equivalent Accelerated Study: • Use higher temperatures and leverage the Arrhenius
relationship to equate higher temperatures to long term storage conditions
k = A * exp(-Ea / RT)
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Using the Arrhenius Relationship:
k = A * exp(-Ea / RT)• “Well-designed kinetically equivalent”: Use higher temperatures
and leverage the Arrhenius relationship to equate higher
temperatures to long term storage conditions
➢ Determining the Ea (energy of activation) is often not practical
• Leverage the 6 months at 40C/75%RH to 2 years at 25C/60%RH
assumption
➢ This assumes a conservative Energy of Activation assumption of 17 kcal/mol (71
kJ/mol).
➢ Use the actual Ea if it is known or can be obtained (average for Solid Oral Dosage
forms appears to be around 29 kcal/mol*)
• Target thermal / humidity equivalent (or greater) of 6 months at
40C/75%RH
*Data from more than 100 studies; Waterman KC. Accelerated Stability Assessment
Program (ASAP): Using science to set shelf-life. Presented at the AAPS workshop on
Stability Testing in Pharm. Dev., AAPS Annual Meeting Nov 14, 2010: New Orleans, LA
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See USP <1079> for Mean Kinetic Temperature Calculation
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Humidity considerations
• Relative humidity is a critical parameter
• Two options:
1. Build RH into the Arrhenius equation (e.g., by applying
the “Accelerated Stability Assessment Program”
principles*)
ln k = ln A - Ea / RT + B(RH)
• OR…
2. Maintain the same %RH at the elevated stress
temperatures• Consider a degradation reaction with an Ea of 19.87 kcal/mol (USP
<1150> MKT) as an example. A stress testing study at 70°C / 75% RH
for 11 days would yield the kinetic equivalence of 40C / 75% RH for 6
months.
*Waterman KC, Adami RC 2005. Accelerated aging: Prediction of chemical stability of pharmaceuticals. Int J Pharm
293:101-125; Waterman KC, Carella AJ, Gumkowski MJ, Lukulay P, Macdonald BC, Roy MC, Shamblin SL 2007.
Improved Protocol and Data Analysis for Accelerated Shelf-Life Estimation of Solid Dosage Forms. Pharm Res 24:780-
790
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Photostability considerations
• ICH Q1B Photostability Guideline
• Confirmatory photo-exposure (1.2 million lux-h and
200 W-h/m2) is, in some fashion, analogous to 6
months at 40C/75% RH
• Proposal: photo-stressing of drug substance and
product for 2X ICH to define major
photodegradants (potential).
• 1 x ICH in packaging to define “relevance”.
• Mitigation strategy for photo-induced degradants
(protection from light via packaging) is more
straightforward than heat/humidity.
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ICH M7 is COMPLEX…
…Especially when dealing with
Degradation Products
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Overview of Deg Product
Mutagenic Risk Assessment
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Summary / Conclusions
• The prediction and assessment of degradation-
derived GTIs is complex
➢Many companies are struggling with development of sound,
practical, relevant strategies
➢ The field of Degradation Chemistry is still too immature and
complex to allow RELIABLE predictions a priori (Hypothetical
/ Theoretical)
➢ Two main options for a company to define “Potential”: (1)
Well-Designed Stress Testing and/or (2) Accelerated Stability
Studies (including photostability)
➢ Using “well-designed” accelerated stability studies and
Arrhenius kinetics can help focus on “relevant” or “actual”
degradants (i.e., those that will form on accelerated / long-
term stability studies, properly packaged)
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Summary / Conclusions
• Analysis of over 1100 known degradation
products suggest that degradation of drugs may
lead to unique mutagenic structure alerts in ~5-
8% of the degradation products.➢ Roughly 50% or less of these alerting structures expected to be
Ames positive (roughly 2-4% overall)
➢ Using a Stress Testing → Potential Deg Product approach,
➢~8 deg products per API will be identified
➢~4-12% of all APIs are predicted to have 1 confirmed Ames
positive degradant that forms in the drug product
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Impact of M7: Some of the
Significant Questions to Consider
1. What strategies will your company embrace to meet the
expectations of M7?
--Strategy for structural identification of impurities?
2. Do you / should you elucidate structures of deg
products observed during stress testing?
--No clear regulatory mandate – up to individual company and
regulatory agency expectations
--On what basis? “Major” or “Significant” deg products?
--How do you define “Major” in stress testing studies?
-- When in relation to the timeline?
--Stress testing strategy results in Identification of about 3-4X
more than “actual” degs, but enables timely mitigation
--How significant is the risk to discovering a problem late in the
timeline?
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Impact of M7: Some of the
Significant Questions to Consider
3. How do you determine which stress testing-derived
deg. products are relevant to the drug product?
4. Do you have access to two complementary in silico
tools?
5. What about degradants formed in the GI tract? Who
owns the GUT?!
6. Does your company have a strategy and the
expertise to be able to discharge risks of potential
deg products known to be mutagenic?
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Thank you!!!
See baertschiconsulting.com
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Back-up Slides
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Option 1: Stress Testing –> Potential
• Specifics of stress conditions need to be defined
• Stress testing needs to include both DS and DP
• Photostability needs to be included, and exposure should be
more than 1 x ICH Q1B
• Strategy for identification of deg products needs to be defined
• Consideration should also be given to deg pathways leading
to identified deg products.
• If a pathway implies an intermediate with alerting structure,
consideration should be given
• For oral dosage forms, consider what happens in the“gut”(!)
• An important an often overlooked area
• Don’t overlook just because it isn’t spelled out in M7…!
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Option 2: Accelerated Stability and
ICH Q1B Photostability → Potential
• Minimal or no packaging protection for DS/DP
• If we limit to only properly packaged DS/DP, it can be
argued this only uncovers “actual” degradants
• DS/DP Photostability (Q1B confirmatory) should be included
with direct exposure
• Identification threshold? M7 indicates “potential” to be
aligned with Q3A/B ID threshold, but I would recommend
using “reporting threshold” as a conservative measure
• Consideration should also be given to deg pathways leading
to identified deg products.
• If a pathway implies an intermediate with alerting structure,
consideration should be given
• For oral dosage forms, consider what happens in the “gut”(!)
• An important an often overlooked area
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Daily Dose (mg)
ICH Identification
Thresholds (%)
Maximum Concentration of Genotoxic Degradants Calculated from the Proposed FDA Staged-TTC Values
(%)
DS DP <14 days (120 µg)14 days to 1 month
(60 µg)1-3 months (20
µg)3-6 months
(10 µg)6-12 months
(5 µg)>12 months
(1.5 µg)
3000 0.05 0.1 0.004 0.002 0.00067 0.00033 0.00017 0.00005
1000 0.1 0.2 0.012 0.006 0.002 0.0001 0.0005 0.00015300 0.1 0.2 0.04 0.02 0.0067 0.0033 0.0017 0.0005
100 0.1 0.2 0.12 0.06 0.02 0.01 0.005 0.0015
30 0.1 0.2 0.4 0.2 0.067 0.033 0.017 0.005
10 0.1 0.2 1.2 0.6 0.2 0.1 0.05 0.015
3 0.1 0.5 4 2 0.67 0.33 0.17 0.051 0.1 0.5 12 6 2 1 0.5 0.15
0.3 0.1 1 40 20 6.7 3.3 1.7 0.5
Green: Standard HPLC-UV method will likely be suitable for controlling GTI
Orange: Standard HPLC-UV method may be suitable, but a more sensitive (e.g., LC-MS) method may be
required
Red: A more sensitive (e.g., LC-MS) method may be required for controlling GTI
Analytical Sensitivity Required as a Function
of Dose
68