Active pharmaceutical ingredients
Evaluation of quality and interchangeability of medicinal products
Training workshop for evaluators from National Medicines
Regulatory Authorities in East Africa Community
10-14 September 2007, Dar Es Salaam, Tanzania
Presented by
Rutendo Kuwana
What is an API?
Active Pharmaceutical Ingredient (API)
A substance or compound that is intended to be used in
the manufacture of a pharmaceutical product as a
therapeutically active compound (ingredient)
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Active Pharmaceutical Ingredients
Presentation approach
Collect and interpret available information on the APIs (pre dossier studies),
such as:
 Literature, all aspects (chemical/physical)
 Monographs in pharmacopoeia (example: ARVs)
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Active Pharmaceutical Ingredients
Some definitions
Enantiomer
cpds with same molecular formula as substance but differ in spatial
arrangement of atoms and are non-superimpossable mirror images
Polymorphism – occurrence of different crystalline forms of the same
substance
Degradation product – molecule resulting from chemical change in
substance due to e.g. light, temperature, pH, water, reaction with
excipient, immediate container/closure
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Active Pharmaceutical Ingredients
Some definitions (2)
Impurity – any component of the medicinal product which
is not the chemical entity defined as the active
substance or an excipient of the product
Identified Impurity – an impurity for which structural
characterisation has been achieved
Unidentified degradation product – an impurity defined
only by qualitative properties e.g. Rt
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Active Pharmaceutical Ingredients
Available information on API
Applicants should collect and analyse available
information of the API in a systematic approach
Some outcomes:






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Sound scientific understanding of the API, with respect to
properties, stability, specifications, etc.
Assists in API manufacture and DMF compilation
Sound choice of API manufacturer (source)
Assists in dossier compilation
Important for FPP pharmaceutical development
Reduction of time / cost
Active Pharmaceutical Ingredients
Literature information on API
Standard works / series / books – such as:



(Analytical) Profiles of Drug Substances and Excipients [eds:
Florey / Brittain – 31 volumes]
The Merck Index (for structures, properties)
Pharmaceutical Codex (12th edition) (“old” APIs)
Journals through search facilities such as

International Pharmaceutical Abstracts, Chemical Abstracts,
Analytical Abstracts & internet
Pharmacopoeial monographs (current)
Analysis of structure & stereochemistry
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Active Pharmaceutical Ingredients
Information from
literature and structures
 APIs which are organic compounds, have unique
chemical structures & stereochemistry
 These structures, together with the solid/liquid state
conditions, are basically responsible for chemical and
physical properties of the APIs
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Active Pharmaceutical Ingredients
Information from literature & structure:
Rifampicin
hydrolysis (to 25-desacetyl)
Oxidation
to N oxide
light sensitive
oxidation
(to quinone)
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Active Pharmaceutical Ingredients
hydrolysis
(to 3-formyl)
Information from literature & structure
Rifampicin (discussion - 1)
Oxidation

Hydroquinone group



Tertiary amine



Moderately prone towards oxidation (to N-oxide)
Enhances solubility in acid medium
Oxidation enhanced by


10 |
Main degradation of API (to rifampicin quinone)
Enhances solubility in alkaline medium
Metal ions
Low pH
Active Pharmaceutical Ingredients
Information from literature & structure
Rifampicin (discussion - 2)
Hydrolysis

Hydrazone (imine) group


Hydrolysis to 3-formyl rifamycin
25-acetyl (ester) group

Hydrolysis to 25-desacetyl rifampicin (minor)
Light sensitive

Due to conjugation in molecule (unsaturated)
Storage of bulk raw material (BP/Ph.Eur.):

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Store under nitrogen in an airtight container, protected from light at
temperature of ≤ 25ºC
Active Pharmaceutical Ingredients
Information from literature & structure
Isoniazid
Small molecule (quite stable)





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Basic amino functions
Primary amine - reacts with aldehydes/lactose
see presentation: FPPs – formulation problems?
Can hydrolyze under stress conditions to e.g. isonicotinic acid & hydrazine
Oxidize in presence of strong oxidants (e.g. permanganate), with metals as
catalyst
Active Pharmaceutical Ingredients
Information from literature & structure
Indinavir sulfate
Basic amino atoms (2)
forms H2SO4 salt
ethanol in crystal
Unstable
 2 main degradation products
– moisture and temp. sensitive
– acid / base enhanced
– Intra-molecular reaction
+
Kreutz, J. Pharm. Biomed. Anal., 19,
725-735 (1999) and Crixivan® EPAR
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Active Pharmaceutical Ingredients
Literature support
Literature information used in the dossier should always be
accompanied by
Full traceable reference citations, for instance:

Devani, M.B., Shishoo, C.J., Doshi, K.J. & Patel, H.B. Kinetic
studies of the interaction between isoniazid and reducing sugars.
Journal of Pharmaceutical Sciences, 74, 427-432 (1985)
Photocopies of publication or relevant pages
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Active Pharmaceutical Ingredients
Properties of APIs
Scenarios:
API not described in BP, Ph., JP, Ph.Eur., or USP (non compendial)
API described in BP, Int.Ph., JP, Ph.Eur.,or USP
(compendial)
Information from literature (important)
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Active Pharmaceutical Ingredients
Properties: non-compendial APIs
 Proof of structure/stereochemistry correctness
– Single crystal X-ray structure (sufficient) or
– Spectrometric data (IR, 1H & 13C NMR, MS, etc.): QA certified
copies of the spectra and tabulated data with
• assignments against structure
or
• correlation against API spectral data from peer reviewed literature,
preferable innovator publication (in tabulated form!!). Strongly
recommended
 Physico-chemical properties
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Active Pharmaceutical Ingredients
Properties: Compendial APIs

Physico-chemical and other relevant properties, e.g.
– Solubility in water (effect of pH), other solvents such as ether,
ethanol, acetone and dichloromethane
– pKa, partition coefficient
– Existence/absence of polymorphs and pseudo-polymorphs e.g.
solvates (with XRPD, DSC, IR)
• e.g. Rifampicin polymorphs I and II
• See Nevirapine (later in this presentation)
– Hygroscopicity e.g. Ethambutol hydrochloride in FDC tablet
– Particle size
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Active Pharmaceutical Ingredients
Properties for Compendial APIs
Example: solubility of TB APIs
API
Water
CHCl3*
Ethanol
Rifampicin
Water: Slightly 1,2
pH 7.5: 0.3% 2
pH 5.3: 0.4% 2
pH 2.0: 10% 2
Freely 1,2
Slightly 2
Ethambutol 2HCl
50% 2
0.1% 2
20% 2
Ethambutol base
Sparingly 2
Very 2
Isoniazid
14% 1
0.1% 1
2% 1
Pyrazinamide
1.5% 1
0.7% 1
0.6% 2
1 Merck Index 13th ed
2
Pharmaceutical Codex 12th ed
* Dichloromethane has similar properties to chloroform as solvent, but preferred for safety
reasons
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Active Pharmaceutical Ingredients
Properties APIs
Example: solubility protease inhibitors (mg/ml)
Medium
Saquinavir
Ritonavir
Indinavir
Nelfinavir
Amprenavir
Water
mesilate
2.2
0.001
sulfate
>100
mesilate
4.5
mesilate
0.19
pH 7.4
0.036
0.005
0.07
very low
0.06
pH 6.8
pH 6.5
0.19
0.073
pH 4.8
pH 4.0
pH 3.5
pH 2.6
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0.3
0.007
60
0.5
4.5
Properties Compendial APIs
Pseudo-polymorphism nevirapine
Int. Ph. monograph Nevirapine (anhydrous & hemihydrate)

Identification test C
Carry out the examination as described under “Spectrophotometry
in the infrared region”.
–
–
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For the anhydrous substance, the infrared (IR) absorption spectrum
is concordant with the spectrum obtained from anhydrous
nevirapine RS or with the reference spectrum of anhydrous
nevirapine
For the hemihydrate, the IR absorption spectrum shows a
characteristic sharp absorbance at about 3503 cm−1; after heating
the test substance for one hour at 140°C and cooling, the IR
absorption spectrum is concordant with the spectrum obtained from
anhydrous nevirapine RS or with the reference spectrum of
anhydrous nevirapine
Active Pharmaceutical Ingredients
Properties Compendial APIs
Pseudo-polymorphism nevirapine (2)
Interpretation of this IR identification test:

Nevirapine anhydrous (one test)
–
IR spectrum against nevirapine anhydrous RS

Nevirapine hemihydrate (two tests, conform to both)
1. IR spectrum shows signal at 3503 cm-1 (water) and
2.
Heat converts the hemihydrate to the anhydrous form
•
IR spectrum against nevirapine anhydrous RS
- ½H20
Nevirapine, ½H20
————>
Nevirapine
heat
The reaction is not reversible at room temperature
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 no O-H signal
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4 000
10
3 000
1415.32
2 000
W av e num be rs (c m -1 )
789.12
1 000
761.66
621.49
697.56
829.44
803.62
436.32
655.88
551.88
540.26
499.65
523.67
1 000
462.39
576.06
710.87
999.24
975.13
965.33
956.63
830.56
794.26
464.43
780.82
767.11
844.92
819.45
894.68
1144.79
1168.40
698.40
434.50
588.58
711.86
500.03
548.23
619.51
652.23
939.89
1117.27
1107.16
1092.50
1071.57
1050.96
1027.00
998.51
979.36
1272.70
1244.44
1221.94
1295.94
1491.86
1459.55
1411.84
1381.78
1351.84
1600.74
1582.33
1654.00
959.84
60
941.75
1107.27
1091.16
1074.82
1048.30
1167.32
1153.13
40
1025.40
1258.94
1210.77
1950.21
2 000
885.03
1289.19
1243.06
1384.34
1354.95
30
2088.38
2065.49
3 000
1487.86
80
2320.66
40
1465.35
20
2916.77
2861.41
55
1568.92
50
3062.78
3007.45
2218.44
1983.68
2070.73
2599.59
2515.27
1961.46
1945.48
1913.05
70
1586.57
60
1927.40
(do not match)
3502.85
75
2583.59
2505.28
2456.46
 Spectra not concordant
2698.58
4 000
2914.76
2861.26
45
3011.59
O-H signal (water)
1647.72
 no crystal water
50
3124.51
3503 cm-1
3062.45
3193.26
Nevirapine ½H20
3294.95
%Trans mittanc e
3893.86
85
3189.89
Nevirapine anhydrous
%Trans mittanc e
IR-spectra
95
90
80
65
W av e num be rs (c m -1 )
5 00
11 0
10 0
90
70
5 00
Route(s) of synthesis
Scenarios:
 API not described in BP, Int.Ph., JP,Ph.Eur., or USP (noncompendial APIs)
 Specifications of raw materials and intermediates used in the
synthesis of non-compendial APIs
 API described in BP, Int.Ph., JP, Ph.Eur.,
or USP (compendial APIs)
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Active Pharmaceutical Ingredients
Route(s) of synthesis (cont.)

Requirements: The synthesis should
–
–
–
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lead to the correct structure, stereochemistry and crystal
form & size (if relevant)
be well controlled and validated (GMP)
produce an API which meets acceptable standards of
quality, including limits of impurities (organic, inorganic,
residual solvents)
Active Pharmaceutical Ingredients
The information required for the synthesis of the API may depend on
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
Is a valid CEP is available? - no synthesis information
required. CEP must however have all appendices and
applicant to submit other info not covered by CEP

Is the quality of the API controlled by a monograph in an
acknowledged pharmacopoeia?

No official monograph is available for quality control
- Detailed information required e.g. Open Part of DMF (from API
manufacturer)
- Also signed declaration from API manuf that synthesis and purification
are as described in the dossier
Active Pharmaceutical Ingredients
Synthesis non-compendial APIs
 A flow diagram of the synthesis process
 including structures & stereochemistry of starting materials & intermediates;
reagents; catalysts; solvents
 A full description of each step / process, including:









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Reaction conditions (temp., time, moisture control, etc.)
Quantities of reagents/solvents
Size of production scale
Purification of intermediates
Final API purification method / crystallisation / solvent(s)
Reprocessing (has to be justified, validated)
Process controls
Validation of critical steps, e.g. aseptic processes
Discussion of (possible) process impurities
 Organic, residual solvents and catalysts/inorganic
Active Pharmaceutical Ingredients
Specifications of raw materials and intermediates used in synthesis
Provide specifications for


starting materials and intermediates (if isolated)
reagents, solvents & catalysts
Class 1 solvents should not be used (ICH Q3C)

Benzene, Carbon tetrachloride, 1,2-Dichloroethane,
1,1-Dichloroethene & 1,1,1-Trichloroethane
Provide a declaration on the use/non-use of material of animal or
human origin (TSE)

Risk of Transmitting Animal Spongiform Encephalopathy Agents
(WHO TRS 908, Annex 1 or EMEA/410/01 Rev.2)
To limit impurities in the API (Safety reasons)
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Active Pharmaceutical Ingredients
WHAT IS A STARTING MATERIAL?
 Contributes an important structural part of the API
 Available in free trade
 Compound well defined in chemical literature (name, chemical
structure, chemical and physical properties, and impurity profile)
 Synthesized by commonly known process
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Active Pharmaceutical Ingredients
RE-DEFINITION OF STARTING MATERIAL
MARKS THE START OF THE MANUFACTURING
PROCESS DESCRIBED IN AN APPLICATION
 Manufacturing steps before are not described
 Manufacturing steps before need not be performed in accordance
with GMP
 Changes in manufacturing steps before need not be reported to
Agency
EACH BRANCH OF A SYNTHESIS WILL BEGIN WITH
ONE OR MORE STARTING MATERIALS
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Active Pharmaceutical Ingredients
INDINAVIR
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CHEMICAL SYNTHESIS
•
Indinavir is a chiral molecule with 5 stereogenic centers
•
Only stereoisomer observed in the API is the 4-(R)-epimer.
•
It is stereoselectively prepared in six steps.
•
The enantiomeric purity of the API and other ingredients is
ensured by the route of manufacture and quality control on
intermediate products (starting materials and intermediate
indinavir free base) rather than a test for specific rotation.
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Active Pharmaceutical Ingredients
CHEMICAL EQUIVALENCE (1)
 The stereochemistry is well under control during the synthesis
 Racemization after the synthesis is extremely unlikely
 Formation of epimers cannot be excluded but should be detectable by
the purity tests applied.
 Potential impurities from synthesis, stereoisomeric impurities and
degradants have been identified. Minimised or removed by control on
the reaction parameters and in-process controls
 High humidity, which leads to formation of degradants, is avoided.
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Active Pharmaceutical Ingredients
CHEMICAL EQUIVALENCE (2)
 The API is very pure
 The limit for any single impurity is not more than 0.1 %
 limit for the sum of all impurities is not more than 0.5 %
 Due to the high doses to be given in clinical use (> 2 g/day),
the qualification threshold as defined in the ICH guideline on
impurities, is 0.05 %.
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Active Pharmaceutical Ingredients
PHYSICOCHEMICAL EQUIVALENCE
Indinavir Sulfate Ethanolate
 Freely Soluble In Aqueous Solutions
 PARTICLE SIZE Not Critical
 No POLYMORPHISM
 POOR FLOWABILITY
 Relatively Loose Bulk Density
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Active Pharmaceutical Ingredients
API STABILITY TESTS
 Indinavir is highly hygroscopic at relative humidity above 60
%
 In the presence of moisture and/or elevated temperatures, the
API undergoes conversion to an amorphous material or to a
hydrate crystal form and to the formation of degradation
products i.e. lactone and several unidentified impurities occur
 HVAC SYSTEM SHOULD MAINTAIN A RELATIVE
HUMIDITY OF ≤ 33% AT 25OC
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Active Pharmaceutical Ingredients
NEVIRAPINE
CHEMICAL STRUCTURE
H3C
N
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Active Pharmaceutical Ingredients
O
H
N
N
N
CHEMICAL STRUCTURE
 Nevirapine does not contain an assymetric carbon
atom (a chiral centre)
 The nitrogen in position 11 shows weekly basic
properties
 Other functional groups are not very reactive under
everyday manufacturing environmental conditions
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Active Pharmaceutical Ingredients
CHEMICAL INFORMATION
C15H14N4O (anhydrate for tablets)
266.30
C15H14N4O·1/2 H2O (hemihydrate
for oral suspension)
275.35
CAS number: 129618-40-2
NEVIRAPINE is lipophilic (partition coefficient 83) and is
essentially nonionized at physiologic pH. As a weak base
(pKa 2.8), NEVIRAPINE is known to be soluble at acidic pH
values.
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Active Pharmaceutical Ingredients
PHYSICO-CHEMICAL INFORMATION
 Aqueous solubility (anhydrate) (90 μg/ml at 25°C).
 NEVIRAPINE anhydrous is a white to off-white
crystalline powder.
 No potential toxicity was found in intermediates found in
the synthesis of NEVIRAPINE
 NEVIRAPINE is milled in order to obtain an acceptable
particle size distribution.
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Active Pharmaceutical Ingredients
SPECIFICATION, STABILITY
 Innovator results showed that Nevirapine is highly stable even
under stressed conditions over a 24 month study period
 No degradants were detected and all the results remained
within the specifications.
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DESK CONCLUSION
Critical API parameters:

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Particle size of the micronized drug substance
Active Pharmaceutical Ingredients
API specifications
API not described in BP, Int.Ph., JP, Ph.Eur., or USP (non-compendial
APIs)
API described in BP, Int.Ph., JP, Ph.Eur.,
or USP (compendial APIs)
General note
An API has only one set of specifications applicable at release
and throughout the re-test period
–
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an FPP may have two sets of specifications – release and shelf-life
Active Pharmaceutical Ingredients
Specifications: Non-Compendial APIs
ICH Q6A (new APIs and products) – for instance:

Requires justification for proposed specifications

Impurities to be characterised and limits set


synthesis and degradation according to ICH Q3A(R)
residual solvents according to ICH Q3C

Analytical methods with validation

Preparation and potency determination/specification of primary
and secondary (working) standards, with CoAs
Valid CoAs for at least 2 batches
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Active Pharmaceutical Ingredients
Non-compendial APIs
Typical set of specifications

Appearance/description

Identification (at least one specific, e.g. IR spectrum)

Moisture content (or LOD: moisture + residual solvents)

Impurities
- Related organic substances (synthesis or degradation)
 specified
 unspecified and
 total organic impurities
- Inorganic impurities, including catalysts
- Residual solvent(s)

Assay

Additional parameters important for specific API

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such as particle size, polymorphic form, microbial limits
Active Pharmaceutical Ingredients
Specs: Compendial APIs

The current monograph always applicable

Additional critical specifications that are not included in
monograph e.g.
–
–
–

particle size & polymorphic form
synthesis related impurities resulting from specific process which
may be additional to monograph
residual solvents (specific to process)
Valid CoAs for at least 2 batches required
CEP normally states tests additional to the monograph
–
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e.g. residual solvents & impurities
Active Pharmaceutical Ingredients
IMPURITIES
 Extraneous contaminant (foreign substances)
 Toxic impurities
 Concomitant components
 Signal impurities
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Classes of Impurities
Organic
Inorganic
Residual solvents
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Active Pharmaceutical Ingredients
Organic Impurities
May arise during manufacturing process and storage
 Starting materials
 By products
 Intermediates
 Degradation products
 Reagents, ligands and catalysts
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Inorganic Impurities
May be from manufacturing process and are normally
known and identified:

Reagents, ligands and catalysts

Heavy metals

Inorganic salts

other materials (e.g. filter aids, charcoal etc.)
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Solvents
Organic or inorganic liquids used during the manufacturing
process
Toxicity generally known, therefore controls achievable
Limits to be based on pharmacopoeial standards or known
safety data
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IMPURITIES
 Identified impurity
 Unidentified impurity
 Specified impurity
 Unspecified impurity
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IMPURITY THRESHOLDS
Maximum
daily dose
<= 2g/day
Reporting Identification Qualification
threshold
threshold
threshold
0.10% or
0.15% or
1mg/day
1mg/day
0.05%
intake
intake
>= 2g/day
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Active Pharmaceutical Ingredients
0.03%
0.05%
0.05%
IMPURITY EQUIVALENCE
 No new impurity is observed in the intermediate
above 0.1%
 No new impurity is observed in api above the
qualification threshold
 Each existing impurity is within its stated limit
 Total impurities are within the stated limit
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Active Pharmaceutical Ingredients
IMPURITY EQUIVALENCE
 Each existing residual solvent is within its stated limit
 New residual solvents, in either an intermediate or the
api, are at or below the levels recommended in the ich
guide
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Active Pharmaceutical Ingredients
IMPURITY EQUIVALENCE
Ideally, impurities should be evaluated in isolated
intermediates immediately following the process step in
which they are produced
The impurity search can be extended to the next
downstream intermediate and the evaluation process
repeated until the final intermediate, even to the api
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Stability testing
Stress testing of API (forced degradation) helps



to identify the likely degradation products and pathways
to establish stability of the molecule
To verify specificity of stability assay method
 Diode array detection for API peak purity !
Stability testing (regulatory) to provide evidence on



57 |
how the quality of an API varies with time
 under the influence of a variety of environmental factors such as temperature,
humidity, and light; and
to establish a re-test period for the API and
to recommended storage conditions
Active Pharmaceutical Ingredients
Stress testing (forced degradation)
Typical conditions
The conditions should


partially (e.g. 10-30%)
decompose the API to
primary degradation
products
Conditions can be
changed to get required
degree of degradation
**
Temperature should not
come closer than 10°C
from melting point
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Active Pharmaceutical Ingredients
Stress factor
Conditions (e.g.)
Humidity
≥ 75% RH (solid)
Heat **
≥ 60°C (solid)
Heat
water
Acid
0.1 M HCl
Base
0.1 M NaOH
Oxidative
3% H2O2
Photolytic
ICH Q1B
Metal ions
(optional)
0.05 M Fe2+ or Cu2+
Stress testing (forced degradation)
Literature

Literature information and/or CEP
–
–
in support of and/or
to replace experimental data
Examples of literature information
1.
2.
3.
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Rifampicin (earlier slides)
 Oxidation, hydrolysis, light sensitivity
Indinavir sulfate (earlier slide)
 Intra-molecular reaction – heat, moisture, acid, base
Efavirenz (see next slides)
 Hydrolysis – pH dependent
Active Pharmaceutical Ingredients
Stress testing (forced degradation)
Efavirenz (1)
 Non-hygroscopic
 4 Polymorphs
• Form 1 pharmaceutical
(EPAR Sustiva®)
 Hydrolysis main degradation
– pH dependent
– Maximum stability at pH 4
– 2 Degradants isolated
• structures elucidated
– Pathways postulated
Maurin, Pharm. Res. 19, 517 (2002)
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Stress testing (forced degradation)
Efavirenz (2)
The data (generated at 60°C) shows that
61 |
–
Efavirenz is quite stable
–
–
Maximum stability at pH 4 (Suspension possible?)
Carbon dioxide formation
(30 mg/ml solution, 100 ml bottle:
1% decomposition ≈ 2 ml CO2
Active Pharmaceutical Ingredients
Efavirenz main route of
degradation
Maurin (2002)
2nd route
+
2
62 |
Active Pharmaceutical Ingredients
1
CO2 (g)
Important Elements

The API must be of required structure & stereochemistry

The physical properties must be well understood, e.g.
–

The synthesis process must be according to GMP to
–
–
63 |
hygroscopicity, crystal properties and solubility
consistently produce an API of required chemical and physical
quality
limit impurities according to defined standards
Active Pharmaceutical Ingredients
Important Elements (2)
The set of specifications should



64 |
be based on validated analytical methods
with appropriate acceptance criteria
to which an API should conform to be considered acceptable
for its intended use throughout the retest period in the
proposed packaging
Active Pharmaceutical Ingredients