Drug Testing Results
Toward a generic approach for stress testing of drug substances and drug productsSilke Klick The Impurity Profiling Group has developed a generic approach for conducting stress testing on drug substances and drug products. The proposed strategy is evaluated and verified with historical data and new experiments. Results demonstrate that the proposed approach is reasonable and generates relevant, generally predictive results for the development of a stability-indicating method.
Stress testing is defined as the stability testing of drug substances and drug products under conditions exceeding those used for accelerated testing. Although it is an integral part of the information provided to regulatory authorities in registration application dossiers (ICH Q1A[R2]) (1), details regarding the design of such studies are not covered by regulatory guidance documents (see Reynolds et al. for a review of regulatory guidance on stress testing [2]).
Pharmaceutical companies perform stress testing (also called forced-degradation studies) during preformulation to help select compounds and excipients for further development, to facilitate salt selection or formulation optimization, and to produce samples for developing stability-indicating analytical methods. Stress testing provides information about degradation mechanisms and potential degradation products. This information then can be used to develop manufacturing processes or to select proper packaging. It may also help in preparing reference material of identified degradation products. Although preformulation work is part of early-phase drug development, stress testing often is repeated when manufacturing processes, product composition, and analytical procedures are refined and reach a more final state (3). This is usually the case when a compound enters clinical Phase 3 studies. According to various regulatory guidance documents, results from stress testing should be included in the dossier when a registration application is submitted to regulatory authorities.
This article discusses stress testing according to the regulatory guidance documents, with emphasis on what should be considered for late-clinical phases and for registration application dossiers (e.g., marketing authorization applications or new drug applications). (During early development, other aspects of stress testing may be relevant for various screening purposes, but these are not the primary subject of this article.)
Many pharmaceutical companies have policies such as standard operating procedures or internal guidelines for stress testing. There is no consensus, however, about how much stress is adequate. This fact was recently confirmed in an extensive bench marking study in which information about the design, conditions, procedures, and the organization to oversee stress testing activities was requested from 20 companies (3). The authors concluded that the pharmaceutical companies were applying significantly diversified approaches.
Many researchers have developed stability-indicating methods that involve applying various stress regimes to generate degraded samples. Bakshi and Singh evaluated these studies and concluded that the majority would fall short of meeting ICH and FDA requirements (4). The main issue was that the required stress studies were not performed.
Although the development of a broad range of pharmaceutical compounds requires flexibility in how stress testing is conducted, many companies apply extreme stress conditions. Typically, stress conditions are determined on the basis of the senior scientist's experience or are copied from previously applied example studies on other products. Rationales explaining why certain stress conditions are applied typically are not provided.
Almost no literature can be found in which stress conditions were investigated on their ability to predict the degradation products formed during long-term stability studies of marketed formulations. Some direction regarding the practical conduct and issues related to stress testing under various ICH prescribed conditions has been published (5). This reference described a classification scheme and included decision trees to help select the right type of stress conditions. Although this approach is systematic, the suggested stress conditions seem rather harsh. For example, refluxing the drug in 0.1 N HCl/0.1 N NaOH for 8 h was suggested as a starting condition, which in our opinion would generate irrelevant degradation in many cases.
Representatives from several pharmaceutical companies and Utrecht University (The Netherlands) have collaborated to form the Impurity Profiling Group (IPG). For approximately three years, this group has examined the issues relevant to stress testing of low molecular weight compounds. The main focus of the group has been to generate representative degradation samples for developing stability-indicating analytical methods for both drug substances and drug products. The predictive value of the degraded samples for real-time storage of the final product under long-term and accelerated storage conditions was defined as a measure of the balance between "purposeful degradation" and the formation of irrelevant artifacts that may lead to misinterpretations (e.g., secondary degradation products).
This article reviews the regulatory guidances' exact text related to stress testing and the current practices in participating companies and presents a proposal and verification with practical results of the feasibility of a generic approach toward stress testing.
Overview of regulatory guidance documents
Several regulatory guidance documents mention forced degradation or stress testing of drug substances and/or drug products (1, 6-16). A summary of these has been published (2). To enable a good interpretation of the available guidance documents and to provide the reader with a comprehensive overview, the text of the relevant paragraphs of these guidance documents is provided in the sidebar, "Overview of stress-testing guidance documents."
The ICH stability guideline Q1A(R2) defines stress testing for drug substances and drug products. For drug substances, these tests are studies undertaken to elucidate the intrinsic stability of the drug substance. Such testing is part of the development strategy and is normally carried out under more severe conditions than those used for accelerated testing. For drug products, stress tests are studies undertaken to assess the effect of severe conditions on the drug product. Such studies include photostability testing (see ICH Q1B) and specific testing on certain products (e.g., metered-dose inhalers, creams, emulsions, and refrigerated aqueous liquid products).
In addition to investigating drug substance or drug product stability, stress testing studies may also provide information about degradation pathways and the selectivity of the applied analytical methods. According to the ICH and FDA guidance documents, stress testing is conducted to fulfill three main purposes: to provide a stability assessment of the drug substance or the drug product; to elucidate the possible degradation pathways of the drug substance or the active pharmaceutical ingredient in the drug product; and to investigate the stability-indicating power of the analytical procedures applied for the drug substance and the drug product.
Although the regulatory guidance documents listed in the sidebars define the concept of stress testing, they do not provide detailed information about a stress testing strategy. The experimental conditions to conduct stress tests are described in a general way and the exact stress conditions to be applied are not described. Some guidelines emphasize that the experimental conditions of stress tests depend on the nature of the drug substance and the drug product (1, 9).
The available guidance documents also do not state the extent to which stress tests should be carried out--that is, how much stress should be applied or how much degradation should be aimed for. It is recognized, however, that during stress testing, degradation products can be observed that are not formed during accelerated or long-term stability studies. Hence, these degradation products need not always to be examined (1, 9).
It can be concluded that the available guidance documents allow for performing stress tests on a sound scientific basis. The experimental conditions should be realistic and lead to "purposeful degradation" That is, stress tests should generate representative samples to assess drug substance and drug product stability, provide information about possible degradation pathways, and demonstrate the stability-indicating power of the analytical procedures applied.
Current practice in participating companies
As a starting point for the IPG's discussion about stress testing, participants shared existing strategies for stress testing applied by the participating companies. The approaches were very different. Some companies had standard operating procedures in place in which conditions for stress testing studies were described in detail. Other companies were applying case-by-case approaches that depended on the chemistry of the compound to be evaluated or the dosage form to be developed.
After thoroughly discussing the various procedures, members of the IPG agreed that the companies were applying conditions that in many cases were too drastic and were causing irrelevant degradation. Typical conditions for stress testing in solution included various pH (1-12), high temperatures (> 70[degrees]C), extreme light exposure, or the presence of oxidative or reductive agents. For stress testing in the solid state, applied conditions included high temperatures (> 70[degrees]C) and relative humidity (RH) (>70%). These conditions frequently are set on the basis of tradition rather than scientific rationale.
To investigate the effectiveness and possible shortcomings of typical fast and severe stress conditions, a screening study was set up by one of the participating companies. Fifteen low molecular weight (i.e., non-biologically derived) compounds were studied using a fixed set of 11 commonly applied stress conditions (see Table I). To save time, fast (drastic) conditions were applied (e.g., a maximum two weeks at high temperature for solid stressing and a maximum one day for stress in solution). Because no long-term stability data were available for the test compounds, accelerated storage conditions (six months at 40[degrees]C and 75% RH) provided the relevant degradation products.
The screening study did not include stable compounds in which no degradation products formed under accelerated conditions. The observed degradation was classified into five categories (see Table II).
The category "adequate" is considered optimal and "out of proportion" is considered acceptable. All the other categories are of no additional value and may even be misleading if taken too seriously. The combined results for the set of 11 typical stress conditions are shown in the summary diagram (see Figure 1). The extraordinary observation is that only in a rather small fraction of cases does "adequate" degradation occur with the applied typical stress conditions. The results were combined in one chart because generally the same pie-chart distribution was obtained for each individual stress condition. It was frequently observed that although one stress condition was too soft for one compound, it led to massive degradation for another compound. Apparently, it is still difficult to generate the relevant degradation products with a fixed set of stress conditions. Results indicate that some fine-tuning of applied stress conditions or stress duration will be necessary and that no universal set of stress conditions exists. The large proportion of cases in the "false" category is of particular concern because such studies may give a false idea of achieving relevant degradation.
On the basis of the degree of degradation, one can assume that typically the right amount of stress was applied and, therefore, relevant degradation products could be expected. This was not the case, however. The most probable cause for the high percentage of irrelevant degradation may be the significant difference in the thermodynamics of the applied stress conditions, resulting in degradation pathways other than what is observed during shelf-life stability-testing conditions. According to the IPG, these results demonstrate that degradation from fast stress-testing conditions may be misleading and therefore should be interpreted with precaution.
Results from the screening test show that the typically applied conditions usually generate a lot of irrelevant degradation products, thereby leading to complicated results and a potential for not producing relevant degradation products. In addition, evaluating large numbers of irrelevant degradation products may generate high amounts of workload. The screening study by the IPG, therefore, demonstrates the limited value of using fast and severe stress-testing conditions. Our hypothesis is that for successful stress testing, mild conditions should be used that may result in storage times that are longer than in usual stress testing.
Strategy toward a generic approach
The IPG tried to elaborate an applicable generic approach for stress testing to produce representative samples for developing stability-indicating methods for drug substances and drug products. The initial question was how much stress could be regarded as adequate to generate such samples. The IPG group agreed that the amount of stress applied to a sample should be selected according to what is necessary to achieve "purposeful degradation" An optimal degradation pattern generated during stress testing would show only those degradation products observed at the end of shelf life in regulatory stability studies and those that might appear if the drug substance or drug product is not handled or packed properly (see sidebar, "Requirements for relevant stress conditions").
Chromatograms thus obtained will be representative and not too complicated to evaluate, which may be the case if drastic conditions are applied and many second- and third-generation degradation products are formed.
Stress testing should induce not more than 5-15% degradation of the main compound. A stress test should be stopped when this percentage of degradation is achieved. It is not desirable to generate samples with extensive degradation because of their limited relevance and the formation of secondary degradation products, which would lead to complicated degradation patterns.
One issue to address is how long a stress test should be continued if the target is not achieved. The IPG proposes a maximum of 14 days for stress testing in solution (a maximum of 24 h for oxidative tests) to provide relevant stressed samples for methods development. The group also proposes a three-month period for drug substances in the solid state and drug products, which may be too long for preformulation during early development (e.g., early development screening or salt screening). In such cases, more drastic conditions can be applied to generate results on a shorter course but at a risk that the degradation patterns may not be predictive. In general, to evaluate their relevance, results from stress tests should be compared with results obtained from long-term and accelerated stability studies as soon as they are available.
The IPG developed a generic protocol for stress testing on the basis of the experience and scientific expertise of its participating companies and by taking into consideration the existing regulatory guidance documents. The proposed conditions should be sufficient and should normally induce realistic, predictive degradation. Predominant degradation products obtained under these conditions should be regarded as relevant for developing a stability-indicating method and will provide valuable information about relevant degradation pathways. For this purpose, it is essential to identify the observed degradation products by structure elucidation, especially if they are formed in more than one of the experiments included in the generic protocol. However, common sense should be used when selecting degradation products for identification from a complicated pattern. Identification work should not be mandatory unless a particular degradation product has been shown to be relevant under long-term or accelerated storage conditions.
Finally, the IPG decided that the agreed generic protocol for stress testing should be developed using examples from the participating companies, with evaluation according to both historical data from marketed products and, in some cases, results of new experiments.
Program for stress testing drug substances in the solid state and drug product. The IPG established conditions for stress testing drug substances in the solid state and drug product (see Table III). These conditions are regarded as sufficient to expose a solid-state sample to temperature, humidity, and oxidation (oxidation by open storage) stress. Testing periods are upper limits and studies should be stopped when 5-15% degradation is achieved.
Temperatures higher than those proposed in Table III (e.g., 70-90[degrees]C) can be applied to rapidly generate method development or preformulation samples. This approach, however, may lead to various degradation kinetics and irrelevant degradation products, as demonstrated in the screening experiment. Shorter storage times should be avoided to maintain realistic thermodynamics. Longer storage times are not recommended because such samples are hardly available early in development and should be considered only if no degradation is achieved after three months.
During the evaluation of the generic stress program, a revision of ICH Q3B16 was published, in which light, heat, humidity, acid-base hydrolysis, and oxidation are mentioned as stress conditions to demonstrate the specificity of a stability indicating method for drug product. Light, heat, humidity and oxidation (open storage) are considered to be covered by the conditions listed in Table III. However, acid-base hydrolysis of the drug product is considered as a less relevant stress condition by the IPG members, provided that the information about the degradation of the drug substance obtained under acidic and basic conditions is taken into consideration.
Program for stress testing of drug substance in solution. Conditions for stress testing of drug substance in solution are shown in Table IV. For many final products, especially most solid oral dosage forms, testing the drug substance in solution may be of limited relevance. However, stress testing in solution is generally seen as relevant both for elucidation of degradation pathways and for specificity testing of the analytical method.
Stress testing in solution or in suspension of the drug substance often is conducted at temperatures above ambient (3,5). Such an approach increases the probability of generating irrelevant degradation products, especially secondary degradation products, which was confirmed in the IPG's screening study. After extensive discussion, the IPG proposed not to use elevated temperatures as a means to accelerate degradation.
In special cases, however, testing the drug substance at elevated temperature in solution may be of interest (e.g., to predict stability during autoclaving of a solution). Therefore, testing a drug substance in solution under elevated temperatures should be considered on a case-by-case basis.
Stress testing in solution should be conducted on dissolved samples. Additives may be used to enhance the solubility of compounds with limited aqueous solubility (e.g., cosolvents or cyclodextrins). Caution should be taken in these cases because several additives are not inert agents. Cyclodextrins, for instance, may protect potentially reactive moieties in a molecular structure, whereas cosolvents may affect degradation mechanisms and even induce degradation (e.g., formation of reaction products such as methyl or ethyl esters).
Suspensions are not recommended because degradation might be influenced by the presence of particles, and degradation-sensitive moieties can be protected if a suspension is used. Suspensions may sometimes be justified, however, especially if the formulation is a suspension. The three pH regions given in Table IV may be chosen with flexibility, depending on the pH of the potential formulation, anticipated degradation, solubility, and so forth. Again, not more than 5-15% degradation is the target value. If this amount of degradation is not achieved, the samples may be stored for a longer period of time or at higher temperatures on a case-by-case basis.
Experiments should be performed in the laboratory without protection from daylight. Exposure of solutions in photostability testing chambers will normally lead to much degradation and an overestimation of photosensitivity. If degradation occurs in samples exposed to ambient light, a dark control may be useful to distinguish between photodegradation and other mechanisms.
To test susceptibility to oxidation, 0.1-2% of [H.sub.2][O.sub.2] at neutral pH is the most predictive. A non-neutral pH may be helpful in cases of limited solubility or to distinguish between oxidative and other degradation.
Optional stress conditions for drug substance in solution. Routine testing of radical initiators or transition metals such as [Fe.sup.3+] and [Cu.sup.2+] as initiators or catalysts for oxidative degradation are not generally regarded as relevant, and a case-by-case approach is recommended. This means that the influence of radical initiators or metal ions should be tested if expected to be relevant (e.g., when these constituents are expected to be present in the potential formulation or if a special susceptibility can be anticipated). Testing [Na.sub.2][S.sub.2][O.sub.3] as a reducing agent may be included in stress testing studies in special cases if considered relevant.
Results
The proposed stress testing conditions of the generic approach were evaluated retrospectively by comparing the degradation patterns obtained during real-time storage in regulatory stability studies of marketed products with the degradation patterns obtained by applying the conditions proposed by the generic protocol. Four products developed by their respective manufacturers (companies A, B, C, and D) were compared (see Table V). These compounds represent a range of chemical characteristics that to some extent can be considered to be representative of low molecular weight compounds in the pharmaceutical industry.
The selected test compound from Company A had undergone previous regulatory stability studies and all of its stability data, including degradation pathways, were known and available. Results indicated that all degradation products that were observed in the regulatory stability study were readily detected under the stress conditions of the proposed generic stress testing protocol (see Table V). Degradation products 1, 2, and 3 were relevant. Although some irrelevant degradation products were observed, for example under the oxidative conditions, the number of degradation products was still easy to handle.
The test compound from Company B is registered in most countries and also described in a monograph in the European Pharmacopoeia. The test compound is susceptible to oxidation, and the resulting oxidation product is the only relevant degradation product for drug product stability. It is also included as a named degradation product in the pharmacopeial monograph for the drug substance. Results show that the relevant degradation product is readily formed in the drug substance by several tests in the generic stress-testing protocol (see Table V). The most relevant condition was the forced photostability study, which is required by ICH Q1B (12). Degradation product 1 was also generated in the presence of copper ions and by hydrogen peroxide. Under these conditions the degradation product was not as clearly dominating as in photostability testing, and in the case of hydrogen peroxide, it was not even the largest degradation product. The oxidation of this compound is a well-known feature of the substance class, and hence, the degradation product would be considered as a likely degradation product, even without performing any stress testing.
The drug product of this compound (extended-release tablets) was not tested according to the generic stress-testing protocol. A review of older data indicated that the proposed conditions would not necessarily generate the degradation product. In particular, the tablet coating provides an effective protection against photochemical degradation. However, the degradation product was formed in the drug substance upon stress testing, and the oxidation is well-known for the substance class. Hence, the degradation product has been considered as a most likely degradation product from early development of this product and onward.
A marketed product from Company C was selected as a test compound. Several stability studies have been performed on this compound, and the degradation pathways are known. For the drug substance studies, degradation product I, which is not formed in the crystalline drug substance during long-term and accelerated storage, is formed by stress testing in solution (neutral and alkaline pH), as described in the generic stress-testing protocol.
For drug product studies, degradation product 1 is formed under the influence of humidity and even under long-term conditions when the ratio of active to excipient is worse (data for another dosage strength were not given). In this example, the proposed stress humidity conditions were sufficient to induce degradation.
Company D also chose a well-documented compound with an extensively investigated degradation mechanism. Two main degradation products are known for the various strengths of the marketed product. Degradation product 1 is observed during all long-term stability studies. This degradation product is formed during 3 months open storage at 40[degrees]C and 75% RH of the drug substance, as well as in solution at pH 7. Degradation product 2 is observed during the long-term stability studies at higher temperatures (30 and 40[degrees]C). This degradation product is formed under stress conditions in solution at acidic pH. From these results, one can conclude that both degradation products observed during long-term stability studies were observed with the drug substance in solution during the generic stress-testing protocol.
Results demonstrated that all relevant degradation products observed during real-time stability studies of these four different drug products were formed during the proposed generic stress-testing protocol (see Table V). In general, purposeful degradation that is relevant to the products' stability was obtained. The generated samples were suitable for the development of stability-indicating methods.
Conclusion
Results from stress testing studies are used to assess drug substance and drug product stability, to provide information about possible degradation pathways, and to demonstrate the stability-indicating capability of the analytical methods used. Drastic conditions tend to generate irrelevant degradation in the sample and may lead to methods optimized for the separation of an impurity profile, which is not relevant for an end-of-shelf-life sample.
The IPG developed a generic approach for stress testing of drug substances and drug products. Efforts were aimed to prevent too-drastic conditions and to achieve "purposeful degradation," predictive for what is relevant under long-term and accelerated storage conditions. The proposed stress testing program, which is in line with requirements from the regulatory agencies, was applied to four products developed by the participating companies and evaluated both retrospectively by historic data and by new experiments. Results demonstrated that the proposed generic approach is reasonable and generates relevant, generally predictive results for the development of a stability-indicating method. Some of the conditions included, however, still induce irrelevant degradation.
Stress tests for developing a stability-indicating method should always be designed and evaluated with common sense and chemical knowledge, keeping in mind the manufacturing process and the nature of the final drug product. The proposed generic approach can be used as a starting point to set up a stress testing study, but a case-by-case approach for stress testing is essential to allow flexibility. This is also recognized by the regulatory agencies because very detailed instructions about how to perform stress testing are not given in the available guidance documents.
A general experience in the IPG was that the formal stability study under accelerated conditions is highly predictive for long-term storage and the impurity profile at the end of shelf life. These results should be used as soon as they become available to verify the relevance of the stress testing performed.
Figure 1: The effect of a fixed set of fast and severe
stress conditions on relevant degradation.
Adequate 13%
Out of proportion 10%
Overdone 14%
Soft 29%
False 34%
Note: Table made from pie chart.
Table I: Investigated set of fixed stress conditions.
Temperature Temperature Acid/base/
and moisture Light oxidative
30 min, 1 week 1 h xenon light 2 h 1 M HCI
121[degrees]C 70[degrees] (70-90 klx)
C, ambient
2 weeks 2 h xenon light 2 h NaOH
70[degrees] (70-90 klx)
C, ambient
1 week 35 h UV light 2 h 3%
70[degrees] (~210 W h/ [H.sub.2][0.sub.2]
C, 100% RH [m.sup.2])
2 weeks
70[degrees]
C, 100% RH
Table II: Type of degradation observed with a fixed set of
fast and severe stress conditions.
Category Explanation
Soft No significant degradation and therefore
no relevant degradation products observed
False Fair amount of degradation (<15%), however
no relevant degradation product(s) observed
Adequate Fair amount of degradation (< 151.) and at least
one or all relevant degradation product(s) observed
Out of Between 15 and 100% degradation and at least
proportion one relevant degradation product observed
Overdone Between 15 and 100% degradation, however, no
relevant degradation products are observed
Table III: Storage conditions for stress testing of drug
substance in solid state and drug product.
Storage conditions Testing period *
40[degrees]C, 75% RH; open storage ** 3 months
50-60[degrees]C, ambient RH; open storage 3 months
Photostability; according to ICH according to ICH(67)
* 3 months or 5-15% degradation, whatever comes first.
** For drug substances, typically a thin layer of material is
spread in a petri dish. Open storage is recommended if possible.
Table IV: Conditions for stress testing of drug substance
in solution.
Storage conditions Testing period *
pH [greater than or equal to] 2, room temperature 2 weeks
pH [greater than or equal to] 7, room temperature 2 weeks
pH 10-12, room temperature 2 weeks
[H.sub.2][0.sub.2], 0.1-2% at neutral pH, 24 h
room temperature
* Storage times given or 5-15% degradation, whatever comes first.
Table V: Retrospective evaluation of the
generic stress-testing protocol.
Degradation products observed
Company A
#1 #2 #3 Remark
Drug substance in
solid state
40[degrees]C, 75% RH, 3 [check] [check] [check]
months open storage
50[degrees]C,ambient RH, [check] [check] [check]
3 months open storage
Photostability, [check] [check] [check]
according ICH
Drug substance in solution
pH 1, 3 days, room
temperature
pH 2, 2 weeks, room [check] [check] [check]
temperature
pH 7, 2 weeks, room [check] [check] [check]
temperature
pH 10, 2 weeks, room [check] [check] [check]
temperature
pH 11, 2 weeks, room
temperature
pH 12, 2 weeks, room [check] [check] [check]
temperature
0.1% [H.sub.2][0.sub.2], [check] [check] [check] H, L
24 h, room temperature
1% [H.sub.2][0.sub.2],
24 h room temperature
2% [H.sub.2][0.sub.2], [check] [check] [check] H, L
24 h, room temperature
[Fe.sub.2]+ (0.05 mM), 2
weeks, room temperature.
[Cu.sub.2]+ (0.05 mM), 2
weeks, room temperature
Drug product
40[degrees]C, 75% NP NP NP
RH, 3 months open storage
50-60[degrees]C, ambient NP NP NP
RH, 3 months open storage
Photostability, NP NP NP
according to ICH
Real-time stability
studies of drug product
25[degrees]C, 60% RH [check] -- -- 18 months
30[degrees]C, 70% RH
40[degrees]C, 75% RH
40[degrees]C, 80% RH [check] [check] [check] 18 months
50[degrees]C, [check] -- -- 18 months
uncontrolled RH
Degradation products observed
Company B Company C
#1 Remark #1 Remark
Drug substance in
solid state
40[degrees]C, 75% RH, 3 -- N --
months open storage
50[degrees]C,ambient RH, -- N --
3 months open storage
Photostability, [check] L --
according ICH
Drug substance in solution
pH 1, 3 days, room -- *
temperature
pH 2, 2 weeks, room -- N
temperature
pH 7, 2 weeks, room -- N [check] 3 days
temperature
pH 10, 2 weeks, room [check] 6 h
temperature
pH 11, 2 weeks, room -- N
temperature
pH 12, 2 weeks, room
temperature
0.1% [H.sub.2][0.sub.2],
24 h, room temperature
1% [H.sub.2][0.sub.2], [check] H
24 h room temperature
2% [H.sub.2][0.sub.2], [check]
24 h, room temperature
[Fe.sub.2]+ (0.05 mM), 2 -- N
weeks, room temperature.
[Cu.sub.2]+ (0.05 mM), 2 [check] L
weeks, room temperature
Drug product
40[degrees]C, 75% NP [check]
RH, 3 months open storage
50-60[degrees]C, ambient NP NP
RH, 3 months open storage
Photostability, -- --
according to ICH
Real-time stability
studies of drug product
25[degrees]C, 60% RH [check] 36 months [check] 24 months
30[degrees]C, 70% RH
40[degrees]C, 75% RH [check] 6 months [check] 3 months
40[degrees]C, 80% RH
50[degrees]C,
uncontrolled RH
Degradation products observed
Company D
#1 #2 Remark
Drug substance in
solid state
40[degrees]C, 75% RH, 3 [check] --
months open storage
50[degrees]C,ambient RH, NP NP
3 months open storage
Photostability, -- -- **
according ICH
Drug substance in solution
pH 1, 3 days, room
temperature
pH 2, 2 weeks, room -- [check] H
temperature
pH 7, 2 weeks, room [check] -- H
temperature
pH 10, 2 weeks, room
temperature
pH 11, 2 weeks, room
temperature
pH 12, 2 weeks, room -- -- **
temperature
0.1% [H.sub.2][0.sub.2],
24 h, room temperature
1% [H.sub.2][0.sub.2],
24 h room temperature
2% [H.sub.2][0.sub.2], -- -- **
24 h, room temperature
[Fe.sub.2]+ (0.05 mM), 2
weeks, room temperature.
[Cu.sub.2]+ (0.05 mM), 2
weeks, room temperature
Drug product
40[degrees]C, 75% NP NP
RH, 3 months open storage
50-60[degrees]C, ambient NP NP
RH, 3 months open storage
Photostability, -- --
according to ICH
Real-time stability
studies of drug product
25[degrees]C, 60% RH [check] -- 5 years
30[degrees]C, 70% RH [check] [check] 3 years
40[degrees]C, 75% RH [check] [check] 3 months
40[degrees]C, 80% RH
50[degrees]C,
uncontrolled RH
* pH 1 was chosen for harsher stress conditions because
Compound 1 is stable in acidic media.
** A known degradation product is formed under these stress
conditions. This degradation product, however, is not formed
during the real time stability studies. Key: "[check]" denotes
observed; "--" denotes not observed; "NP" denotes.not performed;
"H" denotes additional degradation products observed at higher
levels than the relevant degradation products mentioned in the
table; "L" denotes additional degradation products observed at
lower levels than the relevant degradation products mentioned
in the table; "N" denotes no significant degradation. observed.
Acknowledgment
We wish to thank Jenny Ottosson for performing the stress testing experiments; Magnus Erickson (AstraZeneca R&D, Molndal, Sweden) and Han Op't Land, Henriette Hamstra, and Pier Hoogkamer (all at Solvay Pharmaceuticals B.V., The Netherlands) for their valuable comments on the manuscript; Laurent Duhau (Aventis, France) for the inspiring discussions; Mark Vermunt and Gerben Wynia for performing the screening study experiments; and Eddy Ruyter (Akzo Nobel, N.V. Organon, The Netherlands) for his comments.
References
(1.) International Conference on Harmonization, "ICH Q1A(R2): Stability Testing of New Drug Substances and Products" Step 5 (2003).
(2.) D.W. Reynolds et al., "Available Guidance and Best Practices for Conducting Forced Degradation Studies," Pharm. Technol. 26 (2), 48-56 (2002).
(3.) K.M. Alsante, L. Martin, S.W. Baertschi,"A Stress Testing Benchmarking Study," Pharm. Technol. 27(2), 60-72(2003).
(4.) M. Bakshi and S. Singh, "Development of Validated Stability-Indicating Assay Methods: Critical Review," J. Pharm. Biomed. Anal. 28, 1011-1040 (2002).
(5.) S. Singh and M. Bakshi, "Guidance on Conduct of Stress Tests to Determine Inherent Stability of Drugs," Pharm. Technol. 24, 1-14 (2000).
(6.) Guidance for Industry: Submitting Documentation for the Stability of Human Drugs and Biologics (FDA, Rockville, MD, 1987).
(7.) Guideline for Submitting Samples and Analytical Data for Methods Validation (FDA, Rockville, MD, 1987).
(8.) Reviewer Guidance: Validation of Chromatographic Methods (FDA, Rockville, MD, 1994).
(9.) Guidance for Industry (Draft): Stability Testing of Drug Substances and Drug products (FDA, Rockville, MD, 1998).
(10.) Guidance for Industry (Draft): CMC Content and Format, INDs for Phase 2 and 3 Studies of Drugs, Including Specified Therapeutic Biotechnology-Derived Products (FDA, Rockville, MD, 1999).
(11.) Draft Guidance for Industry on Analytical Procedures and Methods Validation: Chemistry, Manufacturing, and Controls Documentation (FDA, Rockville, MD, 2000).
(12.) International Conference on Harmonization, "ICH Q1B: Photostability Testing of New Drug Substances and Products," Step 5 (1996).
(13.) International Conference on Harmonization, "ICH Q2A: Validation of Analytical Procedures: Methodology" Step 5 (1994).
(14.) International Conference on Harmonization, "ICH Q2B: Validation of Analytical Procedures: Terms and Definitions," Step 5 (1996).
(15.) International Conference on Harmonization, "ICH Q3A-(R): Impurities in New Drug Substances," Step 5 (2002).
(16.) International Conference on Harmonization, "ICH Q3B-(R): Impurities in New Drug Products," Step 5 (2003).
RELATED ARTICLE: Overview of stress-testing guidance documents.
Standard Title and reference Status Date
ICH Q1A(R2) Stability Testing of New Drug Step 4 February 2003
Substances and Products (1)
ICH Q1B Photostability Testing of New Step 4 November 1996
Drug Substances and
Products (12)
ICH Q2B Validation of Analytical Step 4 November 1996
Procedures: Methodology (14)
ICH Q3A(R) Impurities in New Step 4 February 2002
Drug Substances (15)
ICH Q3B(R) Impurities in New Step 4 February 2003
Drug Products (16)
FDA Guidance Submitting Documentation for February 1987
the Stability of Human
Drugs and Biologics (6)
FDA Guideline Submitting Samples and February 1987
Analytical Data for Methods
Validation (7)
FDA Reviewer Validation of Chromatographic November 1994
Guidance Methods (8)
FDA Guidance Stability testing of Drug
Substances and Drug Draft June 1998
Products (9)
FDA Guidance Analytical Procedures and
Methods Validation (11) Draft August 2000
FDA Guidance INDs for Phase 2 and Phase 3
Studies, Chemistry, May 2003
Manufacturing, and
Controls Information (10)
ICH Q1A(R2): Stability Testing of New Drug Substances and Products
Drug substance. Stress testing a drug substance can help identify the likely degradation products, which can in turn help establish the degradation pathways and the intrinsic stability of the molecule and validate the stability-indicating power of the analytical procedures used. The nature of the stress testing will depend on the individual drug substance and the type of drug product.
Stress testing is likely to be carried out on a single batch of the drug substance, It should include the effect of temperatures (in 10[degrees]C increments [e.g., 50[degrees]C, 60[degrees]C] above that for accelerated testing), humidity (e.g., 75% RH or greater) where appropriate, oxidation, and photolysis on the drug substance.Testing should evaluate the susceptibility of the drug substance to hydrolysis across a wide range of pH values when in solution or suspension. Photostability testing should be an integral part of stress testing.
Examining degradation products under stress conditions is useful for establishing degradation pathways and developing and validating suitable analytical procedures. It may not be necessary, however, to examine for specific degradation products if previous studies have demonstrated that these products are not formed under accelerated or long-term storage conditions.
Drug product. The design of formal stability studies for a drug product should be based on the behavior and properties of the drug substance, the results from stability studies on the drug substance, and the experience gained from clinical formulation studies. The likely changes to storage conditions and the rationale for the selection of attributes to be tested in the formal stability studies should be stated. Photostability testing should be conducted on at least one primary batch of the drug product if appropriate. Standard conditions for photostability testing are described in ICH Q1B.
Any evaluation should take into account not only the assay but also the degradation products and other appropriate attributes. Where appropriate, attention should be paid to reviewing the adequacy of the mass balance and stability and degradation performance.
ICH Q1B: Stability Testing: Photostability Testing of New Drug Substances and Products
Drug substance. Photostability testing should consist of two parts:forced-degradation testing and confirmatory testing. The purpose of forced-degradation testing is to evaluate the overall photosensitivity of the material for method-development purposes and/or degradation pathway elucidation. This testing may involve the drug substance alone and/or the substance in simple solutions and suspensions to validate the analytical procedures, in these studies, the samples should be in chemically inert and transparent containers. For forced-degradation studies, various exposure conditions may be used, depending on the photosensitivity of the drug substance and the intensity of the light sources. For development and validation purposes, it is appropriate to limit exposure and end the studies if extensive decomposition occurs. For photostable materials, studies may be terminated after an appropriate exposure level has been used. The design of these experiments is left to the applicant's discretion although the exposure levels used should be justified.
Under forcing conditions, decomposition products may be observed that are unlikely to be formed under the conditions used for confirmatory studies. This information may be useful in developing and validating suitable analytical methods. If in practice it has been demonstrated that they are not formed in the confirmatory studies, these degradation products need not be further examined.
ICH Q2B: Validation of Analytical Procedures: Methodology
Drug substance/drug product. If impurity or degradation product standards are unavailable, specificity may be demonstrated by comparing the test results of samples containing impurities or degradation products with a second well-characterized procedure;e.g., pharmacopeial method or other validated analytical procedure (independent procedure).As appropriate, this should include samples stored under relevant stress conditions (light, heat, humidity, acid-base hydrolysis, oxidation).
ICH Q3A(R): Impurities in New Drug Substances
Drug substance. The applicant should summarize the actual and potential impurities most likely to arise during the synthesis, purification,and storage of the new drug substance. This summary should be based on sound scientific appraisal of the chemical reactions involved in the synthesis, impurities associated with raw materials that could contribute to the impurity profile of the new drug substance, 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. In addition, the applicant should summarize the laboratory studies conducted to detect impurities in the new drug substance. This summary should include test results of batches manufactured during the development process and batches from the proposed commercial process, as well as the results of stress testing (see ICH Guideline Q1A on Stability) used to identify potential impurities arising during storage. The impurity profile of the drug substance batches intended for marketing should be compared with those used in development and any differences discussed.
ICH Q3B(R): Impurities in New Drug Products
Drug product. Analytical procedures should be validated to demonstrate specificity for the specified and unspecified degradation products. As appropriate, this validation should include samples stored under relevant stress conditions: light, heat, humidity, acid/base hydrolysis, and oxidation.
FDA Guidance for Industry: Submitting Documentation for the Stability of Human Drugs and Biologics
Drug substance. A program fur the stability assessment might include storage at ambient temperature and under stress conditions. Stress testing conditions ordinarily include temperature (e.g., 5,50, and 75[degrees]C), humidity, where appropriate(e.g., 75% or greater) and exposure to various wavelengths of electromagnetic radiation (e.g., 190-780 nm UV and visible ranges), preferably in open containers, where applicable. It is also suggested that the following conditions he evaluated in stability studies on solutions or suspensions of the bulk-drug substance: acidic and alkaline pH, high-oxygen atmosphere, and the presence of added substances under consideration for product formulation.
Drug product. Stress testing the drug product helps identify potential problems during storage and transportation and provides an estimate of the expiration-dating period.
FDA Guideline for Submitting Samples and Analytical Data for Methods Validation
Drug product. Information supporting the suitability of the methodology for the dosage form. Generally, this should include the following: A degradation schematic for the active ingredient in the dosage form, where possible (e.g., products of acid-base hydrolysis, temperature degradation, photolysis, and oxidation).
FDA Reviewer Guidance: Validation of Chromatographic Methods
Drug substance. Submission of data from stress testing the drug substance using acid and base hydrolysis, temperature, photolysis and oxidation according to the Guideline for Submitting Samples and Analytical Data for Methods Validation is recommended.
FDA Guidance for Industry: Stability Testing of Drug Substances and Drug Products
Drug substance/drug product. Stress testing helps determine the intrinsic stability characteristics of a molecule by establishing degradation pathways to identify the likely degradation products and to validate the stability-indicating power of the analytical procedures used. Stress testing provides data about the forced-decomposition products and decomposition mechanisms of the drug substance. The severe conditions that may be encountered during distribution can be covered by stress testing definitive batches of the drug substance. These studies should establish the inherent stability characteristics of the molecule such as the degradation pathways and lead to identification of degradation products and hence support the suitability of the proposed analytical procedures. The detailed nature of the studies will depend on the particular drug substance and type of drug product.
This testing is likely to be carried out on a single batch of a drug substance. Testing should include the effects of temperatures in 10[degrees]C increments above the accelerated temperature test condition (e.g., 50[degrees]C, 60[degrees]C) and humidity, where appropriate (e.g., 75% or greater). In addition, oxidation and photolysis on the drug substance plus its susceptibility to hydrolysis across a wide range of pH values when in solution or suspension should be evaluated. Results from these studies will form an integral part of the information provided to regulatory authorities. Light testing should be an integral part of stress testing.
Some degradation pathways can be complex and under forced conditions, decomposition products may be observed that are unlikely to be formed under accelerated or long-term testing. This information may be useful in developing and validating suitable analytical methods, but it may not always be necessary to examine specifically for all degradation products if, in practice, it has been demonstrated that these are not formed.
FDA Guidance for Industry: Analytical Procedures and Methods Validation
Drug substance/drug product. Degradation information obtained from stress studies (e.g., products of acid and base hydrolysis, thermal degradation, photolysis, oxidation) for the drug substance and for the active ingredient in the drug product should be provided to demonstrate the specificity of the assay and analytical procedures for impurities. The stress studies should demonstrate that impurities and degradants from the active ingredient and drug product excipients do not interfere with the quantitation of the active ingredient.
FDA Guidance for Industry: INDs for Phase 2 and Phase 3 Studies, Chemistry Manufacturing, and Controls Information
Drug substance. Performance of stability-stress studies with the drug substance early in drug development is encouraged because these studies provide information crucial to selecting stability indicating analytical procedures for real-time studies. If not performed earlier, stress studies should be conducted during Phase 3 to demonstrate the inherent stability of the drug substance, potential degradation pathways, and the capability and suitability of proposed analytical procedures. Stress studies should assess the stability of the drug substance in different pH solutions, in the presence of oxygen and light, and at elevated levels of temperatures and humidity. These one-time stress studies on a single batch are not considered part of the formal stability program.
Drug product. For certain drug products, one-time stress testing can be warranted to assess the potential for changes in the physical (e.g., phase separation, precipitation, aggregation, changes in particular-size distribution) and/or chemical (e.g., degradation and/or interaction of components) characteristics of the drug product. The studies could include testing to assess the effect of high temperature, humidity, oxidation, photolysis and/or thermal cycling.
RELATED ARTICLE: Requirements for relevant stress conditions.
* Should lead to the degradation of the main compound, but not more than 5-15%
* Should lead to a good predictability of degradation pathways (i.e.; a low probability of "drastic" or "false" degradation)
* Should he conducted for no longer than three months
* To whom all correspondence should be addressed.
S. Klick, PhD, is a team manager, Analytical Developement, at AstraZeneca R&D (MoIndal Sweden), tel. +46 31 7761758, fax +46 31 7767337, Silke.Klick@astrazeneca.com. P.G. Muijselaar, PhD, is a senior analytical scientist and T.K. Gerding, PhD, is a manager, Sector Chemical & Pharmaceutical Development, at Solvay Pharmaceuticals (The Netherlands). J. Waterval, PhD, is a group leader, Department of Pharmaceutics at Akzo Nobel, N.V. Organon (The Netherlands), tel. +31 412662070, fax +31 412662524, Joop.Waterval@organon.com. T. Eichinger, PhD, is a deputy global director, Analytical Sciences Department and C. Korn, PhD, is a manager, Analytical Development, Sanofi-Aventis Frankfurt (Germany). A.J. Debets, PhD, is a general manager of Organon Development GmbH, Akzo Nobel (Germany). C.E. Sanger-van de Griend, PhD, is an associate principal scientist, Analytical Development, at AstraZeneca (Sodertalje, Sweden). C. van den Beld, PhD, is the section head, Pharmaceutical Development Section/PDD at Yamanouchi Europe BV (The Netherlands). G.W. Somsen, PhD, is an associate professor and G.J. De Jong, PhD, is a professor, Pharmaceutical Analysis, Utrecht University (The Netherlands).
COPYRIGHT 2005 Advanstar Communications, Inc.
COPYRIGHT 2005 Gale Group
|
