National Standard GOST R 57679-2017 of Russia
"Bioequivalence Study of Medicinal Products"

This standard is aimed at optimization of design, performance and evaluation of bioequivalence studies of immediate release systematically acting dosage forms. Bioequivalence study of the medicinal product is a type of the clinical study of the medicinal product to be conducted to determine a rate of absorption and clearance of one or several active pharmaceutical ingredients, an amount of the medicinal product reaching the systemic blood, whose results allow drawing a conclusion on bioequivalence of a generic medicinal product in any particular dosage form and dosage corresponding to the form and dosage of the reference medicinal product.

The bioequivalence concept serves as a basis for the procedures of state registration of generic medicinal products, i.e. medicinal products that have a similar qualitative and quantitative composition of active substances in the same dosage form as the reference medicinal product, whose bioequivalence or therapeutic equivalence to the reference medicinal product has been verified in relevant clinical studies. Different salts, esters, isomers, isomer mixtures, complexes or derivatives of the active substance are recognized as the same active substance, if their safety and (or) efficacy do not significantly differ. Various immediate-release dosage forms for oral use are recognized in bioavailability studies on the same dosage form (from a biopharmaceutical point of view).

Bioequivalence studies are required when changes are made to the Marketing Authorization Application of an authorized medicinal product (in particular, when changing the composition of excipients, production technology, production site, consolidation or disaggregation of the industrial-scale batch, etc.), at the pre-authorization stage with a significant change in the composition, production technology of the medicinal product (if the main non-clinical and clinical trials were performed with unchanged medicinal product and it is necessary to extrapolate the obtained data on safety and efficacy to the modified medicinal product), when changing the immediate-release dosage form to the modified-release dosage form, the development of FDC-FPPs, and in the other cases.

Two medicinal products, containing the same amount of the active substance, are considered bioequivalent if they are pharmaceutically equivalent or pharmaceutically alternative and their bioavailability (by rate and extent), after being used in the same molar dose, falls within the predetermined allowable limits. The specified limits are set to ensure the comparability of biopharmaceutical properties of the dosage form in which the medicinal products are produced in vivo (that is, their comparability in efficacy and safety).

To determine the absorption rate and extent in bioequivalence studies, a plasma concentration-time curve is commonly used. Particular pharmacokinetic parameters and predetermined limits of their tolerances allow estimating the bioequivalence of pharmaceutical products. AUC (an area under the concentration-time curve) reflects a degree of exposure. С_mах (maximum concentration in plasma) and t_max (time of achievement of the maximum concentration in plasma) are parameters affected by a rate of absorption of the active substance from the dosage form.

The purpose of this document is to determine requirements for designing, conducting and evaluating the bioequivalence studies. It also dwells upon the conditions providing for replacement of in vivo studies with in vitro studies.

This standard is applicable only to medicinal products for human use of chemical origin but not to biosimilars, medicinal products of vegetable origin.

This standard covers dosage forms with immediate release of the systematically acting active ingredient, contains recommendations for planning and conducting bioequivalence studies, as well as defines criteria when bioavailability studies are not required (additional dosages, particular dosage forms and/or based on the biopharmaceutical classification system).

The standard does not contain a recommendation for planning and conducting clinical studies with the use of pharmacodynamic and clinical end points in those cases when bioequivalence cannot be confirmed based on the active substance concentration.

The required amount of studies and their design shall be determined and justified by physical and chemical and pharmacokinetic properties of the active substance and proportionality of the composition of the studied medicinal product and a reference drug. In particular, the pharmacokinetics linearity, the need to conduct a study depending on food intake, the analysis of enantiomers, and the feasibility of studies on additional dosages (see subsections 2.1, 2.5, and 2.6 of this standard) should be taken into account.

The registration dossier (Module 2.7.1 of the common technical file) shall contain a list of all related studies (irrespective of their results) conducted with the studied medicinal product, e.g. bioequivalence studies, to compare the studied medicinal product (characterized by the same composition and process) and a reference drug¹. The registration dossier (Module 5 of the common technical file) shall contain full reports on all essential studies, except for pilot studies that can be provided with brief synopses. Full reports on pilot studies shall be submitted upon the request of the regulatory body. Module 2.7 also needs to include synopsis for the reports of bioequivalence and comparative bioavailability studies conducted at the medicinal product development stage. No information on bioequivalence studies conducted otherwise than with a reference drug shall be provided.

¹ Reference drug means a medicinal product that is authorized in the Russian Federation for the first time, quality, efficiency, and safety of which are confirmed by the results of preclinical studies of medicinal product and clinical studies of medicinal products conducted according to the requirements of Federal Law N 61-FZ dated April 12, 2010 "On Circulation of Medicinal Products" in relation to medicinal products for human use (Art. 18, Parts 6, 7) or according to the requirements of Article 12 of the mentioned Federal Law in relation to medicinal products for veterinary use. Federal Law N 61-FZ dated April 12, 2010 "On Circulation of Medicinal Products" (as amended by Federal Laws No. 429-FZ dated December 22, 2014, No. 241-FZ dated July 13, 2015) is used for evaluating bioequivalence or therapeutic equivalence, quality, efficiency, and safety of generic medicinal products (Art. 4, clause 11).

The study design should be planned in such a way that the effect of the dosage form and composition of the medicinal product on its pharmacokinetic parameters can be distinguished from the effect of other factors.

2.1.1. Standard design

When comparing two medicinal products, it is recommended to conduct a randomized, two-stage, cross-over study in two groups with a single dose. Stages should be separated by a washout period sufficient to reduce the active substance concentration below the bioanalytical determination threshold in all subjects at the beginning of the second study stage. As a rule, it is enough for a washout period lasting five periods of the active substance half-life.

2.1.2. Alternative design

In some cases, provided that the study design and statistical analysis are scientifically justified, the alternative generally accepted designs can be considered: parallel — for substances with a long-term half-life period t_1/2; repeated (replicate design) — for substances with highly variable pharmacokinetic parameters (see subsection 2.10 of this standard).

If, due to intolerance, taking a single dose by healthy volunteers is unacceptable, and it is impossible to conduct a single dose study in patients, it is allowed to conduct a repeated dose study in patients.

In rare cases, where insufficient sensitivity of the analytical procedure prevents an accurate determination of the active substance concentration in plasma after taking a single dose, and its steady-state concentration is high enough to obtain accurate values, as an alternative to a single dose study, it is acceptable to conduct a study with multiple intake of the medicinal product. However, taking into account a lower sensitivity of studies with multiple intake of the medicinal products for identification of differences in С_mах, they can be conducted only if there are convincing proofs of impossibility to improve sensitivity of the analytical method and impossibility of precise measurement of the concentration of the initial active ingredients after a single intake of the medicinal product even by use of supra-therapeutical doses (see subsection 2.6 of this standard). Taking into account modern possibilities of bioanalytical methods, a failure to perform precise and right measurements of the parent compound is quite a rare case. Conducting a study with multiple intake of the medicinal product instead of a single dose due to insufficient sensitivity of the analytical procedure is permissible only in exceptional cases.

In the steady-state concentration studies, the washing out period after taking the previous product may overlap the increased concentration in the second stage (provided that the duration of such an increase is rather long and not less than five final f_1/2).

2.2.1. Reference medicinal product

The reference medicinal product is represented by the medicinal product that is initially registered in the Russian Federation, whose quality, efficiency and safety are proved based on the results of preclinical studies of medicinal products and clinical studies of medicinal products in accordance with the set requirements. Data on the selected reference product and justification of this selection are provided in the registration dossier on the investigational medicinal product.

By study of bioequivalence of a generic product (including additional subsequent doses of a generic product that is already registered), the investigational medicinal product is compared with the respective dosage form of the reference medicinal product if it is available in the market.

In case there are several dosage forms of the original product registered according to the procedure of registration of generic products (with application of the bioequivalence concept) in the market, it is recommended to use a dosage form of the original product, in which it was first registered and which was used during clinical studies, as a reference drug to confirm its efficiency, safety (if available in the market).

The justification of selection of the reference medicinal product for bioequivalence study, it is required to consider the assay results for the active ingredient and data on dissolution thereof. In the batch to be used as an investigational medicinal product, the quantitative content (established using the analytical procedures proposed for the standard quality tests of the investigational product (specified in the normative document on quality control and registration dossier) should not differ by more than 5 percent from the quality indicator of the reference product batch (in the absence of proper justification). The procedure for selecting a reference medicinal product shall be documented in terms of data of assay and dissolution test for future bioequivalence study. When choosing a reference product batch for bioequivalence studies, it is recommended to study several batches of the reference medicinal product.

2.2.2. Tested drug

The investigational medicinal product used in the bioequivalence study shall not differ from the medicinal product that will be supplied to the pharmaceutical market, which shall be comprehensively analyzed, its representativeness shall be justified.

For example, for oral solid dosage forms:

a) if there are no proper justifications, the samples of the investigational medicinal product should be selected from a batch comprising at least 1/10 of the industrial-scale batch, or 100000 units of dosage forms, depending on which of the volumes is larger;

b) the production of the used medicinal product batches should provide a high degree of confidence that the medicinal product and its manufacturing process can be reproduced on an industrial scale.

The batch size intended to confirm the bioequivalence, less than 100000 units is possible, provided that this is the proposed industrial-scale size, and the subsequent scaling of industrial-scale batches is not expected;

c) regulation of critical quality indicators of the investigational medicinal product, such as dissolution test, and inclusion thereof into the specification should be performed based on the results of tests of a product batch used during bioequivalence study, whose bioequivalence is confirmed;

d) the medicinal product samples from additional pilot and (or) industrial-scale batches submitted for authorization should be compared with samples from the batch used in the bioequivalence study; they should have the comparable in vitro dissolution profiles under suitable EDT conditions (see Appendix 1 to this standard). Equivalence dissolution tests shall be performed for the first three industrial batches of the investigational drug. If upon submission of an application for registration, industrial batches have not been manufactured yet, the batch shall be released into circulation before completion of the equivalence dissolution test. The results of tests of the first three industrial batches shall be provided at the request of the regulatory body, and in case the dissolution profile is different the results shall be submitted with specification of particular measures aimed at settling the issue occurred.

For other immediate release dosage forms, representativeness of a batch of the investigational medicinal product used during bioequivalence study shall be justified in the similar way in respect of industrial batches.

2.2.3. Packaging of comparable medicinal products

The investigational and reference medicinal products shall be packaged individually for each study subject and study period before shipping them to the investigator (clinical) site or at the investigator site itself. Packaging (including labeling) should be carried out in accordance with the Rules of the Union's Good Manufacturing Practices. Foreign investigational centers shall perform packaging in accordance with the Good Manufacturing Practices that is compatible with the requirements of the Good Manufacturing Practice of the Russian Federation.

It is necessary to provide for the possibility of accurate identification of the medicinal products used by each subject in each study period. In this regard, it is necessary to document in detail the packaging, labeling and administration of the medicinal products to study subjects. Such documents shall contain a description of all measures implemented to prevent and identify possible drug administration measures. It is recommended to use the tear-off labels.

2.3.1. Number of subjects

The number of subjects enrolled in the bioequivalence study should be based on a proper calculation of the sample size. The number of subjects enrolled in the bioequivalence analysis should be not less than 12.

2.3.2. Selection of subjects

Subjects for bioequivalence study shall be selected so as to ensure an opportunity of identifying clinically important differences between medicinal products. To reduce the variability of results not caused by differences between the medicinal products, the studies shall be carried out among healthy volunteers, except when the medicinal products are an obvious threat to their health, and make such studies unethical. In most cases, the in vivo studies among healthy volunteers to establish differences between the compared medicinal products are considered acceptable and allow extrapolating the study results to populations of patients to whom the use of a reference product is approved (elderly, children, patients with renal or hepatic failure, etc.).

The study protocol shall clearly state the inclusion and non-inclusion criteria for study subjects. Study subjects shall be at least 18 years old with a body mass index of 18.5 to 30 kg/m², if possible.

The compliance of subjects with the selection conditions shall be confirmed by laboratory tests, medical histories and examination. Depending on the product therapeutic category and safety profile, it is necessary to conduct special studies and take appropriate precautions before, during and after the study. The gender of the subjects is irrelevant, but the risk to women of reproductive age shall be taken into account. Subjects, if possible, should be non-smoking; alcoholism and drug addiction (including a history) are criteria for their non-inclusion. In some cases, for reasons of safety or due to pharmacokinetic features, the phenotyping and/or genotyping of study subjects shall be provided.

With a parallel study design, the compared groups should be comparable in all significant variables that may affect the active substance pharmacokinetics (including age, body weight, gender, ethnicity, smoking, belonging to "fast" or "slow" metabolizers). This is an important prerequisite for validating the results of such studies.

If the tested active substance causes the adverse reactions and/or pharmacological effects being the unacceptable risks to healthy volunteers, subject to taking the necessary precautions and establishing appropriate monitoring, the patients may be enrolled in the study.

2.4.1. Ensuring standardization of study conditions

To minimize the variability of all the factors affecting the results, except for properties and characteristics of comparable medicinal products, the study conditions shall be standardized, and therefore the diet, fluid intake and exercises shall be standardized.

Medicinal product intake time shall be set in advance. If there is no justification, the subjects should not eat at least 8 hours before the medicinal product intake. Since fluid intake can affect the passage of oral medicinal products through the stomach, the investigational and reference medicinal products shall be washed down with a standard volume of fluid (150 mL to 250 mL). Within 1 hour before and 2 hours after the product intake, fluid intake is prohibited, otherwise free drinking mode is established. After the medicinal product intake, food consumption is prohibited for 4 hours. The diet and meal time after the medicinal product administration shall be standardized for a sufficient period of time (e.g., 12 hours).

If the study is to be carried out after a meal, the medicinal product and the food shall be taken in accordance with the package leaflet (or summary of product characteristics) of the used reference medicinal product. In case such details in the package leaflet of the reference medicinal products are missing, the subjects should start eating 30 minutes before the medicinal product intake (meal time — 30 minutes).

To neutralize an effect of duration of the medicinal product intestinal passage and intensity of the regional blood flow, it is required to standardize a body position and physical activity of the subject during the study.

During a certain period before and during the study, the study subjects should refrain from eating and drinking, which may affect the cardiovascular, digestive, liver and/or kidney function (e.g., alcoholic beverages or certain juices, such as a grapefruit juice). Subjects should not take any concomitant medications (including herbal medications) during the relevant period before and during the study. At the same time, the use of contraceptives is allowed. In case any associate medicinal products shall be consumed and they are prescribed to the subject to eliminate unfavorable events (e.g. a headache), study reports shall contain data on such associated drug therapy (e.g. a dose and a period of consumption) as well as assessment of its possible impact on the study results. In exceptional cases, for reasons of safety or tolerability, all study subjects shall be prescribed the concomitant medications (e.g., opioid receptor antagonists, antiemetics). In this case, it is required to assess and minimize a probability of distorting the study results due to drug interaction and an impact on the bioanalytical methods.

The medicinal products, which, in accordance with the package leaflet general of the reference medicinal product, should be used only in combination with another medicinal product (e.g., some HIV protease inhibitors are used only in combination with Ritonavir), are allowed to be taken both separately and in combination with the recommended product.

When studying the bioequivalence of endogenous compounds, it is necessary to monitor the factors affecting their background (e.g., strict control of food intake).

2.4.2. Sampling time

To accurately describe the plasma concentration-time profile, it is necessary to take a sufficient number of samples. To accurately estimate the maximum exposure, it is necessary to provide for the frequent sampling near the estimated t_max. In particular, the sampling procedure should be designed so that C_max is not the first point on the concentration-time curve. The number of samples taken should also be sufficient to provide a reliable estimate of the exposure duration of the active agent. This is achieved when AUC_(0-t) overlaps at least 80 percent of AUC_(0-∞). To obtain a reliable estimation of the terminal elimination rate constant (necessary for a reliable estimation of AUC_(0-∞)), at least 3–4 samples should be taken during the terminal phase. As an absorption phase for the oral immediate release medicinal product does not exceed 72 hours, to compare an exposure degree, as an alternative to AUC_(0-t), AUC reduced up to 72 hours (AUC(_0-72h) can be used. So for any immediate release medicinal products, sampling within no more than 72 hours is required irrespective of t_1/2.

In studies with multiple product intake, to accurately determine AUC_(0-τ), the "predose" sample shall be taken directly (within 5 minutes) before the product administration, and the last sample — within 10 minutes at the end of the specified dosing interval.

If urine is selected as the biological material in which the active substance content is determined, it shall be collected for at least 3t_1/2 of the active agent.

Besides, urine collection shall also be performed within no more than 72 hours. To determine the excretion rate, the intervals between sampling in the absorption phase should be as short as possible (see also subsection 2.5 of this standard).

The scheme of sampling during study of bioequivalence of endogenic compounds shall ensure determination of their background content for each subject at each study stage. As a rule, the background content shall be determined through analysis of 2–3 samples before the drug intake. Sometimes, to take into account the circadian fluctuations in the background endogenous compound, it is required to regularly determine its concentration within 1–2 days before the medicinal product administration (see also subsection 2.5).

2.4.3. Medicinal product intake under fasting and fed conditions

Usually, the bioequivalence studies are carried out under fasting conditions, since it is believed that this corresponds to the highest sensitivity to detect differences between the comparable medicinal products. If in the package leaflet of the reference product it is recommended to use it under fasting conditions or regardless of food intake, the bioequivalence studies shall be carried out under fasting conditions. In case the reference product leaflet package implies that the drug shall be administered solely after a meal, during bioequivalence study products shall be taken after a meal.

However, for certain dosage forms (e.g. micro-emulsions, solid dispersions), bioequivalence is studied both before and after a meal except for those cases when the package leaflet provides for the drug intake either strictly before or after a meal.

In case the study shall be conducted by administration of the product both before and after a meal, two separate crossover studies can in two groups and one crossover study in four groups of subjects can be conducted.

In conditions when the medicinal product is taken after a meal, its composition should comply with the recommendations of the package leaflet of the reference medicinal product. If it does not contain any recommendations on this matter, the food should be high-caloric (800 – 1,000 kcal), and high-in-fat (about 50 percent of the total calories). Proteins should account for 150 kcal, carbohydrates — 250 kcal, and fats — 500–600 kcal. The food composition in the reporting documents shall be described with specification of proteins, fats and carbohydrates (in grams, absolute and relative content of calories (%)).

2.5.1. Pharmacokinetic properties

To determine pharmacokinetic properties, the actual sampling time should be used. In the bioequivalence studies with a single dose of the medicinal product, the test pharmacokinetic parameters include AUC(₀-_t), AUC(_0-∞), a residual area, С_mах and t_max. In case of sampling within 72 hours and by an adequate concentration for assay of the active ingredient in the 72-hour point, values of AUC(_0-∞) and the residual area may not be specified in the reporting documents, it is acceptable just to include the values of AUC reduced in the 72-hour point (AUC(₀-_72h)). Moreover, values of the terminal elimination rate and t_1/2 can be described.

For immediate-release medicinal products in steady-state bioequivalence studies, it is necessary to determine AUC_(0-τ), С_max,ss and t_max,ss

When using urine as a biological material, it is necessary to determine Ae _(0-t) and, if possible, R_max.

Beadless model methods are used to determine the pharmacokinetic properties in bioequivalence studies. The use of compartment models is unacceptable.

2.5.2. Parent compound or its metabolites

2.5.2.1. General recommendations

In most cases, the bioequivalence assessment should be carried out by determining the parent compound concentration, since to detect differences between the medicinal products in terms of the absorption rate C_max of the parent compound is usually a more sensitive parameter than C_max of its metabolite.

2.5.2.2. Inactive prodrugs

During bioequivalence study of inactive prodrugs, it is recommended to also determine pharmacokinetic parameters for a parent compound. It is not required to determine the concentration of the active metabolite. However, in case of a considerably low concentration of certain prodrugs in plasma and their quick clearance from blood, it is acceptable to assess bioequivalence by parameters for the main active metabolite without measuring a concentration of the parent compound. In this standard, the parent compound being an inactive prodrug means a compound with no or very low pharmacological activity.

2.5.2.3. Use of metabolite parameters instead of parameters for an active parent compound

It is not recommended to use pharmacokinetic indicators for metabolite as replacement of data on an active parent compound to assess equivalence. Such replacement is allowed only in case unambiguous proofs of an impossibility to increase sensitivity of the analytical method of the parent compound assay and lack of an opportunity of precise measurement of the parent compound concentration by a single intake of the medicinal products are provided, even in case of supra-therapeutic doses application (see subsection 2.6 of this standard). Taking into account modern possibilities of bioanalytical methods, a failure to perform precise and right measurements of the parent compound is quite a rare case. Replacement of the pharmacokinetic parent compound data with data on its metabolite is allowed only in exceptional cases. In case of use for bioequivalence assessment based on metabolite data, it is required to include into the registration dossier all available data confirming that the metabolite exposure (expressed in the form of AUC) reflects an exposure of the parent compound and, at therapeutic doses, the metabolite formation is not a saturable process.

2.5.3. Enantiomers

Usually, the non-stereospecific bioanalytical procedures are allowed. However, when all of the following conditions are met, it is necessary to measure the concentration of each enantiomer:
- enantiomers have different pharmacokinetic properties;
- pharmacodynamic properties of enantiomers vary significantly;
- enantiomer exposure ratio (expressed as AUC) varies with the absorption change.

Besides, it is required to measure concentration of each enantiomer if the above listed data are missing. If only one of the enantiomers has a pharmacological activity (pharmacological activity of the second enantiomer is low or completely absent), it is sufficient to confirm the bioequivalence only for the pharmacologically active enantiomer.

2.5.4. Use of urine as a biological material

If it is impossible to reliably determine the plasma concentration-time profile of the parent compound, it is acceptable to use data on urinary excretion to determine the exposure value as a substitute for plasma concentration. In this case, it's required to clearly justify use of urine as a biological material by the maximum exposure value determination. If it is possible to obtain reliable information about plasma C_max, to assess bioequivalence these data shall be presented along with the exposure value obtained using urine. When using urine as a biological material, the applicant shall provide all available information confirming that urinary excretion reflects plasma exposure.

2.5.5. Endogenous substances

In case of study of endogenic active ingredients, pharmacokinetic parameters shall be calculated with an adjustment according to their background content so as the calculated pharmacokinetic parameters should be related to an increase in concentration obtained as a result of the drug administration. For the purpose of reliable measurement of increase in concentration of the investigational substance if compared with the background concentration thereof, which is determined by the drug administration, one can apply supra-therapeutic doses under the condition of acceptable tolerance thereof. In case no exposure difference after administration of different doses of the endogenic substance has been demonstrated, it shall be determined either in the pilot study or within the framework of one of the stages of the main bioequivalence study with the use of different doses of the reference drug in order to confirm suitability of the dose selected for bioequivalence study and to ensure identification of possible differences between the compared medicinal products.

In the study protocol, it is necessary to determine in advance and describe the method used to adjust for the background content of the endogenous substance. As a correction, it is preferable to use the standard subtraction: either the average concentration of the endogenous substance, determined before taking the medicinal product, or the average AUC is subtracted. Occasionally, when the endogenous substance concentration after taking the product exceeds significantly the background, a correction for background content of the endogenous substance is not required.

In the bioequivalence studies of endogenous substances, it is not possible to directly assess the carry-over effect; therefore, special care shall be taken in choosing the duration of the wash-out period.

If several dosages are subject to authorization, then depending on the composition proportionality between the different dosages and other properties of the medicinal product, it is sufficient to conduct a bioequivalence study for one or two dosages. The choice of dosage (strengths) for study depends on the linearity of the active substance pharmacokinetics.

If the pharmacokinetics are non-linear (an increase in AUC disproportionately to the dose taken), the suitability of different dosages for determining potential differences between the comparable medicinal products may vary. Linearity of pharmacokinetics is recognized not exceed 25 percent, if the difference between dose-adjusted average AUCs for the test dose (dose used in the bioequivalence study) and the dosage(s) for which the bioequivalence study is not planned. To assess the linearity, the applicant shall study and critically evaluate all available scientific literature in terms of dose proportionality. Linearity is ascertained, if the differences between dose-adjusted AUCs are within ± 5 percent.

If the bioequivalence for the highest sensitivity dosages with respect to establishing differences between the comparable medicinal products is confirmed, the in vivo bioequivalence studies with other dosages are not required.

2.6.1. General criteria of the biowaiver for different

In case of the statement that there is no need to conduct a bioequivalence study for additional dosages, the following conditions shall be met:

a) manufacturing process of the medicinal products with different dosages is the same;

b) the qualitative composition of the medicinal product with different dosages is the same (this requirement does not apply to dyes and flavors);

c) the composition of medicinal products with different dosages should be quantitatively proportional: the relationship between the content of the active substance(s) and each of the excipients is the same for all dosages (this requirement does not apply to membranes of immediate-release medicinal products, capsules, dyes and flavors).

If the quantitative proportionality of the composition is absent, the specified condition is considered to be fulfilled when the conditions "i" and "ii" or "i" and "iii" are observed in respect of the test dosage(s) subject to bioequivalence studies:
i) the quantitative content of active substance(s) does not exceed 5 percent of the tablet core weight, the capsule content weight;
ii) the quantitative content of the tablet core excipients or the capsule content is the same for all the dosages recorded, only the active substance content changes;
iii) the quantitative content of fillers varies depending on the active substance content; the quantitative content of the remaining core excipients or the capsule content for the dosages in question remains unchanged;

d) data on comparative dissolution kinetics test confirm the absence of the need for additional in vivo bioequivalence studies.

2.6.2. Linear pharmacokinetics

If the conditions described in paragraphs a)–d) hereof are met, it is sufficient to conduct a bioequivalence study for a single dosage.

Typically, the bioequivalence study is conducted to the highest dosage. For medicinal products with linear pharmacokinetics, provided that the pharmaceutical substance is highly soluble (see Appendix 3), the bioequivalence studies can be carried out with lower dosages. Choosing a lower dosage can also be justified from the standpoint of safety or tolerability, when the use of the highest dosage in healthy volunteers is unacceptable. In addition, if the analytical procedure sensitivity does not allow to accurately measure the concentration of the active ingredient when taking the highest dosage, a higher dose of the medicinal product is allowed (it is preferable to use several tablets with the highest dosage). Exceeding the maximum therapeutic dose is allowed only if it is well tolerated by healthy volunteers and there are no restrictions on the absorption or solubility extent of the active ingredient taken in such a dose.

2.6.3. Non-linear pharmacokinetics

If, in a therapeutic range, the extent of AUC increase for the medicinal products with non-linear pharmacokinetics is proportionately greater than the extent of increase in dose, the bioequivalence study is usually carried out with the highest dosage of the medicinal product. As in the case of medicinal products with linear pharmacokinetics, the choice of a lower dosage can be justified from the standpoint of safety of subjects and tolerability of products, when the use of the highest dosage in healthy volunteers is unacceptable. Due to the low sensitivity of the analytical procedure, similar to medicinal products with linear pharmacokinetics, higher doses of medicinal products with non-linear pharmacokinetics are also allowed.

The bioequivalence study of medicinal products in which therapeutic ranged AUC increases less than the corresponding dose increase, in most cases, is required for the highest and lowest dosages (or for the dosage, the pharmacokinetics of which are in the linear range), If non-linearity is not due to low solubility, but explained, for example, by vector saturation and the conditions of biowaivers specified in paragraph a)–d) hereof are met, and the comparable medicinal products do not contain any excipients affecting the motility of gastrointestinal tract or carrier proteins, the bioequivalence study with the smallest dosage (or a dosage, the pharmacokinetics of which is in the linear range) is sufficient. The selection of other dosages may be justified by the low sensitivity of the analytical procedure, when conducting the study with the lowest dosage is impossible or using the highest dosage in healthy volunteers is unacceptable from the standpoint of safety or tolerability.

2.6.4. Bracketing

If the bioequivalence study is required for more than 2 dosages, for example, due to differences in the composition proportionality, an approach is used that allows one to limit the study of extreme variants. In this case, it is allowed to conduct two bioequivalence studies if the doses selected for study are presented by extreme values, e.g. with the minimal and maximum content of the active ingredient or fundamentally differing by content (when the content differences of other doses are less than this difference).

In case the bioequivalence study implies a study by administration of drugs in two doses before and after a meal (as a result of non-linear absorption or deviations from the content proportionality), it is acceptable just to conduct a study before and after a meal for one dose. No need to conduct the study on an empty stomach or after meal for other dosages (biowaiver) may be justified by data of the literature and/or pharmacokinetics data obtained from studying the test dosage conducted on an empty stomach and after meal. When selecting the study conditions (on an empty stomach or after meal), for studying the remaining dosages, preference is given to conditions that are most sensitive in identifying possible differences between the comparable medicinal products.

2.6.5 Fixed-dose combination finished pharmaceutical products

For all fixed-dose combination finished pharmaceutical products (FDC-FPPs), the conditions of composition proportionality provided for above should be met. When calculating the quantitative content of each active substance in the fixed combination, other active substances should be considered as excipients. Each layer of bilayer tablets can be considered independently.

The biological part of bioequivalence studies shall be conducted in accordance with the Good Clinical Practices (GLP) applied in the sphere of circulation of medicinal products.

To obtain reliable study results and adequate interpretation thereof, it is required to conduct a comprehensive assessment of the used bioanalytical methods, perform full validation thereof and document them. In each analytical run within the study, it is necessary to confirm the method feasibility using the quality control samples.

The main characteristics of the bioanalytical procedure for ensuring the acceptability and reliability of obtained analytical data are: selectivity, lower limit of quantification, response function (calibration curve form), accuracy, precision, and stability.

Since the detectable concentration of the analyte before taking the medicinal product should be 5% of C_max or less, the lower limit of quantification of the method shall ensure the determination of concentrations ≤ 5 percent of C_max (see subsection 2.8 "Carry-over Effects").

In the study protocol, it is necessary to provide for the possibility of incurred sample reanalysis. Under normal conditions, the incurred sample reanalysis due to pharmacokinetic reasons is unacceptable, which is especially important for bioequivalence studies, as this may distort the study results.

Persons performing the sample analysis should not be aware of the investigational medicinal products taken by the subjects.

A correction for assay differences between the batches of investigational and reference medicinal products in bioequivalence studies for pharmacokinetic parameters usually is not allowed. However, in exceptional cases when differences between batches of the reference medicinal product and investigational drug do not exceed 5% (see subsection 2.2), such adjustment is acceptable. The correction, along with the assay results of the active ingredient in the studied product shall be reflected in the study documents.

2.8.1. Selection of subjects for the study result analysis

Whenever possible, all subjects who have taken the drug product should be included in the statistical analysis. However, the subjects participated in a cross-sectional study with lacked data on both the investigational medicinal product and the reference medicinal product, or the subjects participated in the parallel study with lacked data from a single stage should not be included in the analysis.

Data processing of all subjects, who took the medicinal product, is necessary to carry out by the same methods. The study protocol is not allowed to include in the analysis of data on the " spares" of volunteers only to replace the data of excluded subjects. Even during the study there was no drops out, it is necessary to include all subjects who took the drug in the analysis. Thus, it is not allowed to include spares undergoing the bioequivalence study procedures separately from the main sampling.

In a study with more than 2 comparison groups (for example, a three-period study with 2 reference products or a four-period study on fasting and after meals), the analysis for each pair being compared should be performed only after the pre-exclusion of data not related to the comparison groups.

2.8.2. Subject exclusion criteria

For an objective assessment of the randomized study results, the follow up and management of all subjects shall be carried out in accordance with the same rules. These rules should not depend on the medicinal product taken or the outcome, so the decision on the subject exclusion from the statistical analysis shall be made before the laboratory analysis of samples.

Any reason may be a criterion for excluding subjects, if it is described in advance in the study protocol, and the decision on exclusion was made before the sample analysis. However, due to a decrease in the statistical power of the study, as well as with the necessary minimum of 12 subjects, the exclusion of the latter should be avoided.

Acceptable exclusion criteria for subjects are vomiting or diarrhea, which can distort the results of the analyte concentration measurement. In exceptional situations, the simultaneous use of other medicinal products can also serve as an exclusion criterion.

The study protocol shall describe in advance the acceptable exclusion criteria for subjects. If a situation arises that is interpreted as an exclusion criterion, information about it shall be entered into an individual registration card during the study course. The exclusion of subjects based on predetermined criteria shall be clearly reflected and listed in the study report.

Due to the inability to separate the effect of medicinal products from other factors affecting the pharmacokinetics, the exclusion of data based on statistical analysis or for pharmacokinetic reasons is not allowed. Exceptions to this rule are:

a) subjects in whose plasma the reference product concentration is not determined or is determined only in small amounts. The plasma analyte concentration in a subject is recognized as very low if its AUC does not exceed 5 percent of the geometric mean AUC of the reference product (calculated without taking into account the subject's data with the emissions). The exclusion of data for this reason is allowed only in isolated cases, and as a whole it concerns the reliability (validity) of the conducted study;

b) subjects with a non-zero initial concentration of the analyte greater than 5 percent of C_max. Such data shall remove from the bioequivalence study (see "Carry-over Effects").

For immediate-release medicinal products, the abovementioned situations may arise if the subjects do not observe the study regime or in an insufficient wash-out period. To prevent such situations, in the first case, it is necessary to examine the subject's oral cavity to make sure that the medicinal product has been swallowed, in the second – to provide for a sufficient wash-out period. The biological samples of subjects excluded from the statistical analysis should be analyzed, and their results should be provided in the study report (see subsection "Data submission" hereof).

As specified in subsection 2.4, AUC(₀-_t) shall cover at least 80 % AUC(_0-∞). Nevertheless, if this rule is not fulfilled, the subjects should not be excluded from the statistical analysis. However if AUC(₀-_t) does not cover 80 % AUC(_0-∞) in more than 20% of cases, the results of such study shall be questioned. This requirement does not apply to studies with a sampling duration of 72 hours or more, when AUC_{(72 h)} is used instead of AUC_(0-t).

2.8.3. Analyzed parameters and acceptance limits

In the bioequivalence studies with a single dose of the medicinal product, the test pharmacokinetic parameters include: AUC_(0-t) or AUC_{(0-72 h)}, respectively, and С_max. The ratio of these parameters of the investigational medicinal product to the reference medicinal product should be in the range of 80.00 to 125.00 percent with a 90 percent confidence interval. The range limits shall be rounded to two decimal places.

The test items of bioequivalence studies for the immediate-release medicinal products with the determination of steady-state concentration include AUC_(0-τ) and C_max,ss, which should be within the specified intervals.

If urine is used as a biological material, Ае_(0-t) should be in the range described for AUC_(0-t), and R_max – in the range for C_max.

The statistical evaluation of t_max is not required. However, if it is indicated that fast clearance is of clinical important and affects the start of action or leads to any unfavorable reactions, there shall be no considerable differences in t_max and its variability between the investigational and reference medicinal products.

The acceptance bioequivalence limits of medicinal products with a narrow therapeutic range should be narrowed (see subsection 2.9 hereof). For medicinal products with a high variability of C_max, if there is an appropriate justification, these limits can be extended (see subsection 2.10).

2.8.4. Statistical analysis

As a main criterion for bioequivalence, 90 percent confidence intervals are used for the ratio of geometric mean test pharmacokinetic parameters of the investigational and reference medicinal products. Such an approach is equivalent to two unilateral checks of a zero hypothesis regarding lack of bioequivalence (non-bioequivalence) at a 5-percent level of significance for each test.

Comparison of the test pharmacokinetic parameters is carried out using the analysis of variance (ANOVA). Logarithmic transformation of data shall be performed before that. Then carry out an analysis of variance and on the basis of its results build the confidence intervals (in a logarithmic scale) to find the differences between the comparable medicinal products. The obtained confidence intervals are inversely transformed to construct the desired confidence intervals for the ratio of means in the original (not converted) units. The use of non-parametric statistical analysis methods is not allowed.

In the study protocol, it is necessary to foresee the choice of a specific statistical analysis model. Statistical analysis should take into account the sources of variability that can affect the test variable. In this model of analysis of variance, it is customary to use such factors as sequence, subject of sequence, period, and a medicinal product. For all of these factors, fixed and not random effects should be used.

2.8.5. Carry-over effects

It is not allowed to use the carry-over test results to make any decisions that affect the analysis (e.g., analysis of data obtained only from the first study period). The probability of carry-over can be directly taken into account when taking a biological fluid sample before the medicinal product administration in the second study period (and, if applicable, in subsequent ones).

If the concentration before the medicinal product administration exceeds 5% of C_max, information received from the subject in this period shall be excluded from the statistical analysis. This means that in a two-period study, such a subject drops out of the analysis. Continuation of the study is unacceptable, if the number of subjects to be analyzed is less than 12. This approach is not applicable to the endogenous compound study.

2.8.6. Two-stage bioequivalence study design

The bioequivalence studies can be conducted in two stages. At the first stage, a study is conducted on the initial (primary) group of subjects with an analysis of results obtained. If the bioequivalence is not confirmed, an additional group can be collected and the results obtained in both groups can be combined for final analysis. If such an approach is chosen, certain measures need to be taken to keep the probability of type I error unchanged for the entire study, and the statistical criteria for stopping the study should be clearly defined before it begins. The analysis of data obtained during the first stage can be considered as an intermediate one, and both analyzes should be carried out at corrected significance levels. For confidence intervals, a corrected probability of at least 90% should be used. For example, the use of 94.12% confidence intervals for both analyzes at the first stage and for the combined data of the first and second stages would be acceptable, but there are many other options, and the choice of which significance level (α) to use for the intermediate analysis is the sponsor's prerogative. The protocol shall provide in advance the two-stage study design along with the corrected significance level.

When analyzing the combined data obtained during the two stages, the "stage" factor should be included in the analysis of variance model.

2.8.7. Data submission

For each comparable medicinal product mentioned in the reporting documents, it is required to provide all values of individual concentrations and pharmacokinetic parameters along with descriptive statistical data, including a geometric mean, a median, an arithmetic mean, a standard deviation, a variation ratio, maximum and minimal values. Individual concentration-time curves should be presented on linear and logarithmic scales. It is necessary to describe the method of obtaining pharmacokinetic parameters from the source data and the number of points in the terminal logarithmic phase used to estimate the rate constant of terminal elimination (which is used to reliably estimate AUC 0-∞)).

As the main results of the statistical analysis of test pharmacokinetic parameters, the point estimates and 90% confidence intervals for the ratio of mean values should be indicated.

The standard result tables of analysis of variance, including the results of statistical tests for all effects in the model used should also be applied.

The report shall be detailed so that the pharmacokinetic and statistical analyzes could be reproduced, i.e. it is required to include a precise sampling time after administration of the medicinal product, concentrations of the active ingredient, values of pharmacokinetic parameters for each subjects at each study stage and a randomization scheme.

It is necessary to describe in detail all cases of drop-out and exclusion. If possible, for each such subject it is necessary to present data on the concentration and pharmacokinetic parameters in a separate document, but not to include them in the overall statistical analysis.

The bioanalytical method shall be assessed and documented before the start of the bioequivalence study (a validation report before the study start). It is necessary to submit a bioanalytical report as part of the final bioequivalence study report. It should include a brief description of the used bioanalytical procedure, results for all calibration solutions (standards) and quality control samples. It is required to submit a sufficient number of chromatograms or other source data covering the entire concentration range for all calibration solutions (standards) and quality control samples, as well as test (active) samples (all chromatograms and other primary data of at least 20% of subjects with relevant quality control samples and calibration solutions/cycle standards related to the specified subjects).

If several studies have been carried out with respect to a specific dosage of a certain medicinal product, some of which confirm its bioequivalence, and some do not, the entire set of data should be considered as integral. Only the studies stipulated by section 2.1 of this standard shall be considered. The presence of studies confirming the bioequivalence is not a reason to consider studies in which it is not confirmed. It is required to carefully analyze all the results and justify the presence of bioequivalence. Alternatively, in addition to individual studies, where possible, a generalized analysis of all studies is allowed. It is unacceptable to summarize studies that do not confirm the presence of bioequivalence, if there are no studies confirming the bioequivalence.

The allowable limit for AUC of the medicinal products with a narrow therapeutic range should be narrowed to 90.00 – 111.11%. Since C_max occupies a special place in terms of efficacy, safety and concentration monitoring of the analyte, the allowable interval for this parameter should also be narrowed to 90.00 – 111.11%. It is impossible to provide a comprehensive definition of medicinal products with a narrow therapeutic range so a decision to referral of the active ingredient to this group shall be made individually based on clinical peculiarities of effect and application of such medicinal product.

If the intra-individual variability of the pharmacokinetic parameter exceeds 30%, such medicinal products are recognized as highly variable. If it is supposed that the medicinal product may have a high variability in absorption rate and (or) extent, it is recommended to conduct studies with replicative cross-design.

Assessment of С_mах of highly variable medicinal products, a greater difference in С_mах is considered clinically insignificant (if confirmed by a strict clinical justification, it can be performed with application of extended intervals). In this case, the acceptance criterion for C_max can be extended to 69.84 - 143.19%. In order to expand the acceptance criterion, the bioequivalence study design should be repeated (with the use of replications) and it shall confirm that C_max variability of the reference product does indeed exceed 30% in the study. It should be proved that the calculated intra-individual variability is reliable, and not due to emissions. The possibility of permissible interval extension shall be specified in advance in the study protocol.

A degree of the interval extension is determined based on the intra-individual variability results obtained during the bioequivalence study with the use of the weighted average calculated according to this formula: [U, L] = е^[±kS]_WR) where U is an upper limit of the acceptability range, L is a bottom limit of the acceptability range, k~ is a regular constant accepted as 0.760, and S_WR is an intra-individual standard deviation of logarithmically transformed values of С_mах of the reference drug.

The table below shows the examples of bioequivalence recognition calculated on the basis of the procedure depending on the varying degree of variability of the medicinal product pharmacokinetic parameters.

The ratio of geometric mean pharmacokinetic parameters should be in the range of 80.00% to 125.00%.

The expansion of acceptable bioavailability limits based on intra-individual variability does not apply to AUC, the boundaries of which, regardless of variability, should be in the range of 80.00% to 125.00%.

When re-designing, use a 3 or 4-stage cross study design.

The equivalence dissolution test (hereinafter, the EBT) is briefly described in Appendix 1, including the main requirements to the repeatability similarity factor application, f₂-criterion).

3.1. In vitro equivalence dissolution test as an addition to study

It is required to provide the EDT results of the investigational and the reference medicinal product batches used in the bioequivalence study in three different buffer media (usually at pH 1.2, 4.5, and 6.8) and the medium to be used in the medicinal product release control (quality control medium included in the specification (normative document on the product quality control)). The study of some dosage forms, for example, orally disintegrating tablets, shall be carried out in various conditions. The report on study results should be presented in the form of profiles of the dissolved amount proportion in time, indicating the mean values and summary statistics.

In the absence of other justifications, the specification (normative document on the product quality control) for quality control in terms of "Dissolution" parameter of the investigational medicinal product, should be compiled on the dissolution profile of the investigational medicinal product batch, which confirmed the bioequivalence of the reference medicinal product (see Appendix No. 1).

If the results of EDT carried out with different batches do not confirm the bioequivalence previously proved in vivo studies, they rely on the in vivo study results. However, it is necessary to study and explain the reasons for this discrepancy.

3.2. Equivalence dissolution test for additional dosage biowaiver

The validity of not conducting any additional in vivo bioequivalence studies shall be confirmed by properly conducted EDT. Unless otherwise indicated, it is necessary to study the dissolution at different pH values (usually at pH 1.2, 4.5 and 6.8). For all the provided batches, it is required to confirm the comparability of in vitro dissolution profiles between the additional dosages and the dosages from the batches used in the bioequivalence study under all conditions (see Appendix No. 1).

With pH values, at which complete dissolution cannot be achieved for any of the dosages, the EDT conditions of dosages may vary. However, to confirm that this is due to the properties of the active substance, and not the dosage form, it is required to compare it with the appropriate reference product dosage. Moreover, it is allowed to confirm the compatibility of profiles for the similar doses (e.g., between two tablets with a dosage of 5 mg and one tablet with a dosage of 10 mg).

4.1. Study report on a bioequivalence study

The bioequivalence study report should contain all the necessary information about the study protocol, study and its analysis conduction. The report shall be drawn up in accordance with the ICH guidelines for generating a report on the clinical study and signed by the researcher.

The report shall include full name of the responsible researchers, their place of work, study site and duration, certificates or conclusions drawn on the audit results (if available).

The report should contain the confirmation that the choice of the reference drug meets the set requirements. In particular, it is necessary to indicate its trade name, strength, dosage form, batch number, manufacturer, shelf life and country in which the reference drug was purchased.

The report should indicate the name, composition, size and batch number, date of manufacture and, if possible, shelf life of the investigational medicinal product.

Certificates of analysis of the investigational and reference medicinal products used in the study are attached to the report as an Appendix.

Information on concentrations, pharmacokinetic parameters and statistical analysis results shall be submitted to the extent stipulated by "Data submission" in subsection 2.8.

4.2. Other data provided in the registration dossier

The dossier shall include a signed official document confirming that the quantitative content and technology of manufacturing of the investigational drug used during the bioequivalence study and the drug released into circulation are not different. Besides, it is required to attach the results of the comparison dissolution test (see subsection 3.2).

The bioanalytical method validation report shall be submitted, which shall be included into Module 5 of the drug registration dossier.

Upon request, you shall provide data (for example, in the form of an electronic text file with data separated by commas or spaces, or an Excel file, or in another format as agreed with the authorized body) sufficient to reproduce the pharmacokinetic and statistical analysis, including data on sampling time, drug concentration, pharmacokinetic parameters of each subject in each period and randomization schedule.

When changing the previously approved composition or production technology that may affect the bioavailability, the in vivo bioequivalence studies shall be conducted, unless otherwise justified. Any justification submitted should be based on general principles, in particular, those specified in Appendix No. 3, or when establishing the acceptable (level A) in vitro – in vivo correlation (IVIVC).

If the bioavailability of the modified medicinal product has been previously studied and the acceptable (level A) correlation is set between in vivo pharmacokinetic parameters and in vitro dissolution kinetics, while the in vitro dissolution profile is comparable between the modified and previously approved medicinal product under the same test conditions used to establish the correlation, the bioequivalence study is not required (see Appendix No. 1).

When changing the Marketing Authorization Applications for the products that are generic (e.g., original, new combinations, well-studied use), to conduct the bioequivalence study and EDT a previously approved drug with the same composition, manufacturing site, packaging, etc. is used as a reference.

When changing the Marketing Authorization Application for a generic drug, a commercially available reference drug batch is used as a reference (comparator, control) for bioequivalence studies. If the medicinal product is not available on the market, the comparison is allowed to be carried out with a previously approved formulation (investigational generic drug) with the presentation of the corresponding justification.

Pharmaceutical equivalence: Medicinal products are deemed pharmaceutically equivalent if they contain an equal amount of active ingredients in the same dosage form that meet the same or compatible standards. Pharmaceutical equivalence may not ensure bioequivalence as differences in the content of excipients and/or manufacturing technologies can result in quick or slow absorption and/or dissolution.

Pharmaceutical optionality: Pharmaceutically optional medicinal products means medicinal products in the form of different salts, simple or compound ethers, isomers or mixes thereof, sets or derivatives of the active ingredient or products differing by their pharmaceutical form or dosage.

Pharmacokinetic parameters:

Ae(_0-f)) the total content of unchanged active substance in urine collected from the moment of intake to time t;

AUC(_0-t) the area under the plasma concentration-time curve from the moment of intake to collection of the last blood samples with an identifiable concentration of the active ingredient in the time point t;

AUC(_0-t) the area under the plasma concentration – time curve from the moment of intake to infinity;

AUC(_0-t) the balanced AUC within the interval between two subsequent drug intakes;

AUC(_{0-72 h}) the area under the plasma concentration – time curve from the moment of intake to 0-72 hours;

С_mах maximum plasma concentration;

C_max,ss steady-state maximum plasma concentration max.ss* 1;

residual area: the supposed area (AUC(_0-∞) – AUC(_0-t)/AUC(_0-∞);

R_mах: maximum urinary excretion rate m a-d;

t_max: time to reach C_max,ss;

t_max,ss: time to reach C_max,ss;

t_1/2: plasma elimination half-life.

1.1. General aspects of in vitro equivalence dissolution test

When developing the composition of a medicinal product, the comparative dissolution kinetics test (EDT) serves as a tool for determining the biopharmaceutical properties of a medicinal product, that is, properties that can affect bioavailability. Upon completion of the formulation of the drug and the manufacturing process, EDT is used to control the quality of scaling and industrial batches to ensure both the consistency of the quality of the batches and the comparability of dissolution profiles with the batches used in the reference clinical studies. Moreover, in some cases, the EDT may serve as a substitute for bioequivalence studies.

The EDT can be used for different purposes:

a) Quality Review of Medicinal Product(s)
- to characterize the batches used in bioavailability studies (bioequivalence) and support clinical trials to substantiate specifications (regulatory document on quality control);
- as a tool for quality control of a batches of medicines in order to confirm the constancy of production;
- to characterize the reference drug used in bioavailability studies (bioequivalence) and supporting clinical studies;

b) to replace bioequivalence studies:
- to confirm (in individual cases) similarity of different compositions of the investigational medicinal product and reference medicinal product (biowavers, e.g. in case of amendments, changes in the composition during development of the medicinal product, and generic drugs (see section 3 of the standard and Appendix 3));
- to establish the constancy of the quality of a batches of drugs (test and reference drug) on which the choice of the appropriate batches will be based for use in vivo studies.

Analytical methods shall be developed for each medicinal product on the basis of general and (or) particular pharmacopoeial requirements. In case it is impossible to fulfill the set requirements and/or they do not reflect a process of in vivo absorption (bio-relevance), it is permissible to use alternative methods, provided that they have sufficient discriminatory ability, that is, the ability to catch the difference between batches with acceptable and unacceptable bioavailability of the drug in vivo. It is always necessary to take into account current information (including the interaction of drug characteristics based on the biopharmaceutical classification system and the type of dosage form.

In order to obtain complete dissolution profiles, the intervals between sampling should be quite frequent (at least every 15 minutes). During the period of maximum change in the dissolution profile, sampling is recommended to be carried out even more often. To build the correct dissolution profile of rapidly dissolving drugs, which are completely dissolved in 30 minutes, samples shall be taken every 5 or 10 minutes.

If the active substance is highly soluble, it is assumed that bioavailability problems will not arise if, in addition, the dosage form dissolves rapidly at physiological pH values, and excipients do not affect bioavailability. On the contrary, if the active substance is sparingly soluble or slightly soluble, the solubility of the dosage form may become a factor limiting the rate of absorption. A similar situation occurs if the excipients affect the release and subsequent dissolution of the active substance. In such cases it is necessary to conduct EDT in different conditions with the appropriate sampling scheme.

1.2. Comparability of dissolution profiles

The EDT results and the conclusions based on them (for example, in support of a biowaiver) are considered correct if the construction of the dissolution profile was based on a sufficient number of time points.

In addition to the requirements set out in section I of this Appendix, for immediate-release dosage forms, a comparison should be made at a time point of "15 minutes" to find out if complete dissolution occurred before gastric emptying.

If more than 85% of the active substance (of the nominal amount) is dissolved within 15 minutes, the dissolution profiles are considered comparable without further mathematical data processing.

If 85% of the active substance is dissolved within 30, but not 15 minutes, then 3 time points are necessary during sampling: before the expiration of 15 minutes, at the 15th minute and at the point when the release rate is about 85%.

Comparability of dissolution profiles can be determined using f₂ by the following formula above.

When using this formula, it is necessary to determine the degree of release of the active substance from the investigational medicinal product and the reference medicinal product.

The assessment of the similarity factor (convergence) is based on the following conditions:

a) the minimum number of time points is 3 (not counting the zero point of selection);

b) for both compared drugs the same time points are chosen;

c) for each time point, a minimum of 12 values of the degree of release of the active substance for both drugs are necessary;

d) for each of the compositions no more than one case of exceeding the average value of the degree of release of 85% is allowed;

e) the relative standard deviation (coefficient of variation) for the degree of release of the active substance in the first time point of any of the drugs should not exceed 20%, and in all subsequent drugs no more than 10%.

The acceptance criterion for the similarity factor (f₂) is from 50 to 100, which confirms the comparability of dissolution profiles.

In the case of non-compliance with the acceptance criterion for f₂, dissolution profiles can be compared using alternative methods (for example, calculating the difference factor f₂, Weibull distribution function or comparing release rates at different time points (for example, using Student's t-test)).

Alternative methods for calculating by f₂ are considered acceptable if they are statistically correct and their use is sufficiently justified.

It is necessary to determine in advance and justify the limits of acceptability of the comparability criterion, but they should not exceed 10%. In addition, the variability of dissolution between the data of the investigational and reference medicinal product should also be comparable, but lower variability for the test drug is acceptable.

It is necessary to provide a justification that the statistical software has been validated.

It is necessary to give a detailed description and explanation of all actions taken during the study, with the presentation of the relevant summary tables.

Besides the standard recommendations concerning bioequivalence studies of immediate release dosage forms, the appendix contains general recommendations for study of different dosage forms and particular types of dosage forms with immediate release of the active ingredient.

If the investigational medicinal product contains a different salt, ester, stereoisomer or their mixture, another complex compound or derivative of the active substance compared to the reference medicinal product, the bioequivalence shall be confirmed with in vivo bioequivalence studies. However, if the active ingredient of the investigational medicinal product is identical to the active ingredient of the reference medicinal product (or contain salts with similar properties according to the criteria of section 3, Appendix 3), in several cases described below and in Appendix 3, no bioequivalence study in vivo is required.

2.1. Oral systemically acting, immediate release dosage forms

In the absence of conditions for biowaiver (see Appendix No. 3) in terms of such dosage forms as oral tablets, capsules and suspensions, the bioequivalence studies are required. For orally disintegrating tablets and oral solutions, the special recommendations are described below.

2.2. Orally disintegrating tablets

Orally disintegrating tablets (hereinafter – ODTs) are intended for rapid dissolution in the mouth. If the active substance is also soluble in saliva and able to be absorbed through the mucous membrane of the oral cavity, the time of drug intake and its contact with the mucous membrane are important factors. After swallowing the active substance released from the coated ODTs, depending on the product composition, the gastrointestinal absorption also occurs. If it can be confirmed that the active substance is not absorbed from the oral cavity, but requires swallowing for the gastrointestinal absorption, the medicinal product can meet the biowaiver criteria based on the Biopharmaceutical Classification System (BCS) (see Appendix No. 3). If this cannot be confirmed, the bioequivalence study in humans shall be conducted.

If ODTs are an additional (new) dosage form and (or) expansion of the dosage range for a different oral drug formulation, a three-period study shall be conducted to evaluate the use of orally disintegrating tablets, with or without concomitant use of water. However, if the bioequivalence between ODTs taken without water and the reference medicinal product washed down with water, is shown in a two-period study, the bioequivalence of ODT washed down with water is considered proven.

If the ODT with respect to the reference medicinal product, which is an ODT, is a generic or hybrid drug, the following requirements should be followed at study planning:

a) if the reference medicinal product is acceptable both to wash down and not wash down with water, the bioequivalence study should be carried out without taking water, since this is more appropriate for the method of product administration in real conditions. This is especially important if the active substance is dissolved and absorbed from the oral cavity. If bioequivalence without water is confirmed, bioequivalence with simultaneous fluid intake is considered proven;

b) if the reference medicinal product is either washed down or not washed down with water, the bioequivalence study shall be carried out under appropriate conditions (with a standard two-period cross-design);

c) if the reference medicinal product is either washed down or not washed down with water, and the investigational medicinal product is intended for both routes of administration, the comparison shall be carried out, taking the investigational medicinal product by washed down or not washed down with water, while the medicinal product is used in accordance with the recommended method (three-period 3 groups study in 6 sequences).

In studies on ODTs, if the latter is not washed down with water, it is recommended immediately before taking the product to moisten the oral mucosa with 20 mL of water. Fluid intake for 1 hour after the product administration is prohibited.

The bioequivalence study with respect to films dispersed in the oral cavity, films or cheek tablets, sublingual tablets and chewable tablets shall be carried out by analogy with the ODTs. The bioequivalence study should be carried out in accordance with the recommended route of administration of the investigational medicinal product.

2.3. Oral solutions

If the investigational medicinal product is an oral aqueous solution and contains the same concentration of the active substance as the authorized solution, then bioequivalence studies are not required. However, if excipients can affect the gastrointestinal motility (e.g., sorbitol, mannitol, etc.), absorption (e.g., surfactants or compounds that affect carrier proteins), dissolution and absorption processes (e.g., cosolvents) or in vivo stability of the active substance and if the differences between the content of excipients are not properly justified by other data, bioequivalence study is conducted. The requirements to oral solution excipients are similar to the biowaiver conditions (see Appendix 3).

If bioequivalence of the investigational medicinal product, which is an oral solution, should be confirmed in relation to another immediate-release medicinal product, a bioequivalence study shall be conducted.

2.4. Fixed-dose combination finished pharmaceutical products

The requirements to study of combination finished pharmaceutical products are set by other documents. The biowaiver conditions for FDC-FPPs are set out in Part V of Appendix No. 3.

2.5. Oral systemically acting, immediate release dosage forms

This subsection covers, in particular, the rectal dosage forms. For them, the bioequivalence studies are usually required. If the medicinal product is a solution containing the active substance in the same concentration as the authorized medicinal product with the same qualitative and similar quantitative content of excipients, a biowaiver is possible (thus, similar requirements for oral solutions can be used).

The provisions of this section do not apply to inhaled medicinal products used to treat bronchial asthma and chronic obstructive pulmonary diseases, as well as hormonal sprays for nasal use.

2.6. Parenteral solutions

If the investigational medicinal product is an aqueous solution for intravenous administration and contains the same active substance as the authorized product, the bioequivalence study is usually not required. However, if one of the excipients is able to interact with the active substance (for example, with the formation of complexes) or otherwise affect its distribution, metabolism and excretion, the bioequivalence study is required. It can be avoided if the compared medicinal products contain approximately the same amount of excipients and it has been properly proven that the differences in their content do not affect the active substance pharmacokinetics.

For other parenteral routes of administration, for example, intramuscular and subcutaneous, if the investigational medicinal product has the same type of solvent (for example, an aqueous or oily medium), contains the same active substance in the same concentration and the same excipients in similar amounts as the authorized one, no bioequivalence studies are required. Moreover, the bioequivalence study of aqueous solutions with approximately the same content of excipients is not required, if the latter do not affect the viscosity.

2.7. Liposomal, micellar and emulsion dosage forms for intravenous administration

Liposomal dosage forms: pharmacokinetic features of liposomal products for intravenous administration require special approaches to confirm the bioequivalence that are not provided for in this standard.

Emulsions: the emulsions are generally not subject to a biowaiver procedure.

However, if the following conditions are met, the biowaiver procedure is possible:

a) the dosage form is not intended for controlled release and/or controlled distribution (vector delivery);

b) the administration route and rate coincide with those for the authorized medicinal product.

In such cases, the qualitative and quantitative composition of the medicinal product should not differ from the authorized one; It is necessary to provide reasonable data confirming the high similarity of physicochemical properties, including the fractional composition of the dispersed lipid phase and other significant characteristics of the emulsion, including surface properties (e.g., ζ-potential and rheological properties).

Lipid-based medicinal products for intravenous parenteral nutrition: if reasonable data on the comparability of physicochemical properties are presented for these medicinal products, a biowaiver procedure is possible. Differences in the composition can be justified by the properties and indications for use of such dosage forms.

Micelle-forming drugs: micellar solutions for intravenous administration can be considered as "complex" solutions, so they do not fall under the biowaiver.

However, if the following conditions are met, the biowaiver procedure is possible:

a) when diluting a medicinal product in accordance with the recommendations for its route of administration, the micelles undergo the rapid disintegration, and the dosage form is not intended for controlled release or distribution;

b) the administration route and rate coincide with those for the authorized medicinal product;

c) excipients do not affect the distribution, metabolism and elimination of the active substance.

In such cases, qualitative and quantitative composition of the micellar solution immediately before administration should not differ from the authorized medicinal product; It is required to provide reasonable data confirming the similarity of physicochemical properties. For example, the critical concentration of micelle formation, the ability of the dosage form to solubilize (e.g., Maximum Additive Concentration), the free and bound fraction of the active substance and the size of micelles.

These rules also apply to minor changes in the qualitative or quantitative composition of the medicinal product, provided that such changes do not affect the qualitative or quantitative composition of surfactants.

2.8 Modified-release dosage forms of systemic action

2.8.1. Modified-release dosage forms for oral or transdermal use

Modified-release dosage forms for oral or transdermal use require the bioequivalence studies in accordance with the set requirements.

2.8.2. Modified-release dosage forms for intramuscular and subcutaneous administration

When confirming bioequivalence in relation to suspensions or other dosage forms intended to modify the release of the active substance upon its intramuscular or subcutaneous administration, the requirements for confirming the bioequivalence of extravascular modified-release dosage forms (e.g., transdermal) are applied, according to the set requirements.

2.9. Topical medicinal products used topically or externally

Recommendations for the test of topical medicinal products (with oral, nasal, pulmonary, ocular, dermal, rectal, vaginal, etc. administration) are stipulated by other regulatory documents.

If an investigational medicinal product which is a solution (for example eye drops, nasal spray (except for hormonal nasal sprays) or a solution for external use) has the same dissolution medium (water or oil) and has the same concentration of the same active ingredient as a registered medicinal product, there is no need to confirm their equivalency. Minor differences in the content of excipients are allowed provided that significant pharmaceutical properties of the investigational and reference medicinal products are identical or similar. Any qualitative or quantitative differences in the content of excipients must be justified within the context of their effect on therapeutic equivalence. If there are no grounds for it, method and routes of administration must comply with those of the registered medicinal product.

If there is a risk of systemic adverse reactions due to systemic absorption after topical administration of topical medicinal products, it is necessary to measure systemic exposure. It is necessary to confirm that systemic exposure of the investigational medicinal product does not exceed that of the reference medicinal product, that is, the upper limit of the 90% confidence interval must not exceed the upper limit of bioequivalence acceptability (125.00%).

None of topical medicinal products used topically or externally can be regarded as a generic medicinal product as they are all classified as hybrid medicinal products.

2.10. Gases

If the medicinal product is a gas for inhalation, the bioequivalence studies are not required.

3.1. General provisions

A biowaiver based on the biopharmaceutical classification system (BCS) aims to reduce the number of in vivo bioequivalence studies, i.e. it can serve as a substitute for in vivo bioequivalence. In vivo bioequivalence studies can be avoided if in vivo equivalence is confirmed by valid in vitro data.

BCS-based biowaiver is limited to oral immediate-release medicinal products in solid dosage forms of systemic action, containing highly soluble active substances with predictable absorption in humans, provided that these active substances have a wide therapeutic range (see subsection 2.9 of the standard). However, it is not applicable to sublingual, cheek dosage forms and modified-release dosage forms. For orally disintegrating dosage forms, this approach is applicable if absorption from the oral cavity is excluded.

BCS-based biowaiver is designed to set bioequivalence between the specific investigational and reference medicinal products. The biowaiver concept principles can be applied to confirm the bioequivalence of generic drugs, extensions of original medicinal products, when changes are made to the bioequivalence dossier, to set bioequivalence between the medicinal products used in the initial clinical trials, as well as medicinal products introduced to the market.

3.2. General requirements

BCS-based biowaiver is applicable to an immediate-release medicinal product, provided that all of the following requirements are met:

a) the active substance is highly soluble and undergoes full absorption (BCS class I) (see section 3);

b) taking into account the special requirements (see subsection 4.1), the in vitro dissolution characteristics of the investigational and reference medicinal products are defined as very fast (> 85% within 15 minutes) or fast (85% within 30 minutes);

c) the qualitative and quantitative composition of excipients that can affect the bioequivalence is the same. At the same time, it is advisable to use the same excipients in comparable quantities (see section 3);

d) there are no risks associated with the probability to accept the erroneous conclusion about the possibility of using the biowaiver procedure, taking into account the therapeutic index value and clinical indications for the active substance as part of the medicinal product.

BCS-based biowaiver is also applicable to an immediate-release medicinal product, provided that all of the following requirements are met:

a) the active substance is highly soluble and undergoes the limited absorption (see section 3);

b) taking into account the special requirements (see subsection 4.1), the in vitro dissolution characteristics of the investigational and reference medicinal products are defined as very fast (> 85% within 15 minutes);

c) the qualitative and quantitative composition of excipients that can affect the bioequivalence is the same. At the same time, it is advisable to use the same excipients in comparable quantities (see subsection 4.2);

It should be more critical to assess the fulfillment of conditions (for example, the site of absorption, the possibility of interaction with carrier proteins at the site of absorption, the composition of excipients, and therapeutic risks) for BCS class III medicinal products than BCS class I medicinal products.

3.3. Active substance

To describe the properties of the active substance covered by the biowaiver concept, clear abstract literature data can be enough.

If the active substances of the investigational and reference medicinal products are the same, the biowaiver is possible. The biowaiver is also possible if the investigational and reference medicinal products contain different salts, provided that they belong to BCS class I (high solubility and full absorption; see subsections 3.1 and 3.2). If the investigational medicinal product contains esters, stereo-isomers and their mixtures, complexes or derivatives of the active substance of the reference drug, the biowaiver is impossible, because the differences can lead to different bioavailability not detected by experiments used in the BCS-based biowaiver concept.

The active ingredient shall not be characterized by a narrow therapeutic range (see clause 2.9.1 of the standard).

3.3.1. Solubility

It is required to establish and analyze the pH-solubility profile of the active substance. The active substance is recognized as highly soluble if at 37 ± 1 °C its maximum single dose (for an immediate-release medicinal product) is completely dissolved in 250 ml of buffer solution with pH ranged from 1 to 6.8. This requires a study with at least 3 buffer solutions of different pH in the above range (preferably at pH 1.2; 4.5 and 6.8) and, if possible, at pKa, if pKa is within the specified pH range. To unambiguously determine the solubility classification property, it may be necessary to repeat the tests at each pH (for example, a shaking method or another suitable one). pH of the solution should be determined before and after adding the active substance to the buffer.

3.3.2. Absorption (penetrability)

When applying for the medicinal product authorization as a BCS-based biowaiver, it is recommended to confirm the total absorption of the active substance in humans. For this purpose, total absorption means absorption ≥ 85%. total absorption is usually caused by high penetrability of the active substance through the intestinal barrier.

The presence of complete absorption should be based on human studies. As a justification, it is allowed to use the results of the following studies:
- absolute bioavailability;
- inventory balance.

When using the inventory balance method to calculate the absorbed fraction, it is required to ensure that the metabolites taken into account when calculating the absorbed fraction were formed after absorption. In this regard, when calculating the total radioactivity excreted in the urine, it is required to ensure that no partial degradation or biotransformation of the unchanged active substance has occurred in the gastric or intestinal juice. Phase I (for example, oxidation) or phase II (for example, conjugation) responses of metabolism can occur only after absorption (not in the gastric or intestinal juice). Thus, based on data from inventory balance studies, absorption is recognized as total, if the total parent compound content in the urine and its metabolites (past phase I and (or) phase II metabolism) in urine and feces is ≥ 85% of the dose taken.

In addition, the highly soluble active substances with incomplete absorption (BCS class III) may also fall under the biowaiver if certain requirements for the medicinal product composition and in vitro dissolution profile are fulfilled (see subsection 4.2 "Excipients"). When classifying compounds as BCS Class I and the absence of substantiated evidence in favor of their complete absorption, more stringent requirements are also placed on them.

The established bioequivalence between immediate-release aqueous and solid dosage forms of some oral compound is taken as confirmation, because it indicates that the limitation of absorption due to the dosage form properties of the (immediate release) medicinal product is insignificant. In vitro qualitative permeability studies, including with reference standards, also argue in favor of the results obtained in vivo.

3.4. Medicinal product

3.4.1. In vitro equivalence dissolution test management

When studying the medicinal product properties, it is required to prove the immediate release and comparability of the investigational medicinal products, i.e. to confirm the in vitro equivalence dissolution kinetics between the investigational and reference medicinal products at physiological pH values under experimental conditions. However, it is not possible to establish an in vitro/in vivo correlation. The in vitro dissolution kinetics should be studied in pH range of 1.0-6.8 (at least at 3 pH values: 1.2, 4.5, and 6.8). Additional studies may be required at pH with the lowest solubility of the active substance (a justification should be provided to ensure that such studies are not required). The use of any surfactants is not allowed.

The investigational and reference medicinal products shall meet the requirements stipulated by subsection 2.2 of the standard. In accordance with these requirements, it is recommended to conduct a study with respect to more than 1 batch of investigational medicinal products.

In vitro equivalence dissolution tests should comply with the pharmacopeial requirements. Tt is necessary to provide a detailed description of the study conditions and analytical procedures, including data on their validation. For statistical validity, each experiment is recommended to be carried out with 12 samples of the medicinal product. The standard study conditions are as follows:
- apparatus: paddle stirrer or basket;
- volume of the dissolution medium: – 900 mL or less;
- dissolution media temperature: 37±1°С
- rotation speed: paddle stirrer – normally 50 rpm, basket – normally 100 rpm;
- sampling schedule: e.g., at 10, 15, 20, 30 and 45 minutes;
- buffer solutions: pH 1.0-1.2 (usually 0.1 M HCl or imitation of gastric juice without enzymes), 4.5 and 6.8 (or imitation of intestinal juice without enzymes), pH value should be monitored regularly. Pharmacopeial buffer solutions should be used;
- other conditions: no surfactants. The use of enzymes is allowed for gelatin capsules or gelatin-coated tablets.

It is required to submit a full analytical report of equivalence dissolution test (EDT) i vitro, including a study protocol, data on studied batches and comparison batches, a detailed description of experimental conditions, results of validation of the used methods, individual and average values, as well as relative statistical parameters.

3.4.2. Evaluation of in vitro equivalence dissolution test results

Medicinal products are recognized as very soluble if 85% of the claimed content of the active substance dissolves within 15 minutes. In this case, the dissolution profiles of the investigational and reference medicinal products are considered comparable without further mathematical calculations.

If the dissolution process with the release degree of 85% of the claimed content of the active substance lasts more than 15 minutes, but does not exceed 30 minutes, then it is necessary to prove the absence of significant differences (comparability). To confirm compatibility of dissolution profiles of the studied and reference medicinal products, the f₂ criterion (see Appendix 1) and other suitable tests are used. However, an explanation of differences in dissolution profiles from clinical or therapeutic point of view is impractical because the dissolution test does not reflect the in vitro/in vivo correlation.

3.4.3. Excipients

Although, the effect of excipients contained in the immediate-release dosage forms on the bioavailability of highly soluble and completely absorbed active substances (i.e. belonging to BCS class I) is considered unlikely, it cannot be completely excluded. In this regard, in all cases (including with the active substance of BCS class I) of the investigational medicinal product it is recommended to use similar amounts of the same excipients as in the reference medicinal product.

In order to exclude various effects on membrane carriers, one of the biowaiver conditions with regard to active substance of BCS class III is the absence of differences in quality and high comparability in the quantitative composition of excipients.

Usually, it is necessary to use standard quantities of well-studied excipients along with the active substances of BCS class I or III, as well as to analyze and explain their possible effect on bioavailability and/or solubility. It is necessary to describe the purpose of each of the excipients with the justification that the amount of each of them is in an acceptable range. It is necessary to describe all excipients that can affect the bioavailability (e.g., sorbitol, mannitol, sodium lauryl sulfate and other surfactants), indicating their effect on:
a) gastrointestinal motility;
b) susceptibility to interaction with the active substance (for example, complexation);
c) penetrability of the active substance;
d) interaction with membrane carriers.

The qualitative and quantitative composition of excipients proven to affect the bioequivalence of the investigational and reference medicinal products should be the same.

3.4.4. Fixed-dose combination finished pharmaceutical products

The BCS-based biowaiver for immediate-release FDC-FPPs is possible if all active substances belong to BCS class I or III, and excipients meet the requirements set by subsection 4.2. In other cases, the in vivo bioequivalence studies are required.