Bioequivalence regulation in emerging countries: Example of Moroccan regulations on immediate release formulations and comparison with international guidelines

Study design

As basic design: Single-dose and non- replicate crossover studies are recommended. Under certain circumstances, provided the study design and the statistical analysis are scientifically sound, other well-established models can be considered: parallel design for active ingredients with very long half-lives and replicated crossover design for highly variable drugs (ASEAN, 2015; CDSCO, 2005; EMA, 2010; GCC, 2011; Haidar et al., 2008; HC, 2012; Japan, 2012; Midha et al., 2005; SADC, 2015; Tothfalusi et al., 2009; US-FDA, 2003). There is also the possibility in some countries to perform studies in two stages that require a statistical adjustment (adjusted confidence interval CI to avoid alpha risk inflation) and a specific analysis. This two-stage approach is not commonly used in comparison to the classical replicated crossover designs.

Dose: single or multiple

Moroccan recommendations are identical to those of other countries: single fasted administration is the standard. In some specific case, like in Europe and GCC, the realization of a multiple-dose study, for an immediate release form, is acceptable if a single dose study cannot provide enough information or cannot be performed (EMA, 2010; GCC, 2011). These are: (i) if bioanalysis problems related to the low limit of quantification exists, a multiple-dose study is performed in healthy volunteers (ii) if the study cannot be performed in healthy volunteers for safety reasons and in cases where single-dose study is not possible in patients, the bioequivalence study is then a multiple-dose study carried out in patients. For Health Canada, the same dose of each product should be used, preferably as single dosage form units (HC, 2012). According to ASEAN, CDSCO, and SADC, single-dose studies are recommended (ASEAN, 2015; CDSCO, 2005; SADC, 2015).

Subject selection

In Morocco as in all other countries, to reduce variability unrelated to product differences, bioequivalence studies should be conducted in healthy volunteers unless the drug has safety concerns (e.g., anti-cancer drugs, potent CNS drugs, etc.). Subjects are chosen based on criteria such as age and body mass index (BMI). Volunteers should generally be between 18 and 55 years of age and a BMI of 18.5–25 or 30 kg/m². It is recommended to include subjects of both sexes if possible.

Inclusions of female subjects

Morocco, EMA, Health Canada, ASEAN, GCC, and SADC consider the risk to women of childbearing age when conducting bioequivalence studies (ASEAN, 2015; EMA, 2010; HC, 2012; GCC, 2011; SADC, 2015) but do not prohibit their participation if there is no risk (for example efficacious contraception). In addition to the previous recommendations, CDSCO adds that women taking contraceptives should normally not be included (CDSCO, 2005). US-FDA does not give specific guidance on precautions to be taken during the inclusion of female subjects in studies (US-FDA, 2003). For some drugs dedicated to only one sex, the corresponding sex will be used (for example, female hormonal contraception will be tested in women).

Phenotyping and/or genotyping

According to Moroccan regulations, phenotyping and or genotyping of subjects can be studied for safety reasons or for pharmacokinetic reasons. These recommendations are identical to those of EMA, GCC, and ASEAN (ASEAN, 2015; EMA, 2010; GCC, 2011). US-FDA and Health Canada do not provide any information on phenotyping (HC, 2012; US-FDA, 2003). According to CDSCO, SADC phenotyping and/or genotyping of subjects should be considered for exploratory bioavailability studies and all studies using parallel group design (CDSCO, 2005; SADC, 2015).

Number of subjects

The number of subjects to be included in the bioequivalence study should be based on a calculation of the appropriate sample size. Like US-FDA, Health Canada, Australia, ASEAN, and WHO, Moroccan regulations specify that the number of evaluable subjects in a bioequivalence study should not be less than 12 (EMA, 2010; HC, 2012; US-FDA, 2003; WHO, 2016). For the GCC, a number of 24 healthy volunteers are needed; a number less than 24 can be accepted (with a minimum of 18) when it is statistically justified (GCC, 2011). For CDSCO, the minimum number of subjects should not be less than 16 unless it is justified for ethical reasons (CDSCO, 2005). In case of large variability, in order to reduce the number of subjects, replicate cross-over studies are recommended (EMA and US-FDA) (EMA, 2010; US-FDA, 2003).

Conduct of bioequivalence study

In Morocco, the study should be standardized for fluid intake, diet, and exercise to minimize the variability of all factors except the test products. The regulations agree on an administration of the drug product with a standardized volume of water, which is in general between 150 and 250 ml. In case of product that can be taken without water (oral disintegrating tablet for example), the administration of water with the drug is prohibited. For immediate-release solid oral forms, studies are conducted on an empty stomach unless they are required to be taken during a meal in the Summary of Product Characteristics. For fasting study, a sufficient fasting state is required, usually greater than 8 hours. Fasting is considered to provide discriminatory conditions. Similar recommendations are present in many countries.

Table 1. Summary of Moroccan regulations compared to international guidelines. [Click here to view]

For immediate-release forms, there are types such as microemulsions and solid dispersions for which studies require two conditions: fasting and fed (US-FDA, EMA, and GCC) (EMA, 2010; GCC, 2011; US-FDA, 2003). In this case, it is acceptable to perform two crossover studies of two distinct periods or a four-period crossover study. There are no Moroccan recommendations regarding these forms. For fed studies, a hyperlipidic and hypercaloric diet is recommended (800 to 1,000 Kcal of which 50% from fat).

For concomitant use of other medications, only contraceptives are permitted by EMA and GCC, whereas CDSCO excludes contraceptive use. Most regulations do not address the subject (contraception). Moroccan regulations foresee the possibility of concomitant drug administration to a subject when this is unavoidable, such as during the occurrence of adverse events or to all subjects for safety reasons, provided the possible effects on the results of the study are analyzed (e.g., naloxone in case of study on opiate derivatives) like for example in the EMA guideline.

Posture and physical activity

Like EMA and US-FDA, Morocco does not provide specific instructions on posture or physical activity. According to Health Canada, subjects should not be allowed to recline until at least 2 hours after drug ingestion. Physical activity and posture should be standardized as much as possible to limit effects on gastrointestinal blood flow and motility (HC, 2012). For CDSCO, it is important to standardize post-dosing postures as well as physical activities (CDSCO, 2005). According to ASEAN, GCC, and SADC, posture and physical activity should be standardized because the bioavailability of an active fraction of a dosage form may be dependent on gastrointestinal transit times and regional blood flows (ASEAN, 2015; GCC, 2011; SADC, 2015).

Sampling

In general, the plasma concentration at the time of administration till the last concentration observed at time t [AUC_(0–t) ] should cover at least 80% of the area under the curve of plasma concentration extrapolated to infinity [AUC _(0–∞)]. In case of immediate release form, EMA specifies that the AUC can be truncated at 72 hours. The terminal elimination half-life should be calculated with a number of points greater than or equal to 3 or 4 according to the guidelines (EMA, 2010). US-FDA and China recommend that 12 to 18 samples at least should be collected for most drugs (US-FDA, 2003). The C_max must not be the first sampling point.

The washout period should be sufficient to ensure that drug concentrations are below the lower limit of bioanalytical quantification or 5% of C_max in all subjects at the beginning of the second period. This duration is generally estimated at least five times the mean terminal half-life of the drug. This is to allow the body to eliminate practically the entire dose previously administered and to avoid having an overlap of plasma concentrations of the active ingredient in both periods.

Bioanalytical methods

The validation principles and procedures to be followed are listed but not detailed or referenced in Moroccan regulations unlike in Europe, USA, or Canada (EMA, 2011; HC, 2012; US-FDA, 2018).

Enantiomer and isomers

The quantification of the isomer (s) with enantio-selective methods is recommended if their pharmacokinetic behaviors are different or in case of particular toxicity.

Parent compound or metabolites

The assessment of bioequivalence should be based on the concentration of the parent compound or in the case where this is impossible, on the concentration of its metabolite(s). For inactive pro-drugs, demonstration of bioequivalence for the parent compound is recommended. However, for some pro-drugs with low plasma concentrations and rapidly metabolized, bioequivalence study with the parent compound is difficult to demonstrate. In this situation, it is acceptable to demonstrate bioequivalence with the main active metabolite without measuring the parent compound, provided all available data are available to justify that the exposure to the metabolite will reflect that of the parent compound and that the formation of this metabolite is not saturable at therapeutic doses. These recommendations are unanimous about this subject.

The use of urinary data

It is acceptable to use the cumulative quantities of the active ingredient in the urine to determine the degree of exposure in the case where it is impossible to measure accurately the plasma concentration profile of this active ingredient as a function of time. EMA, US-FDA, and GCC also allow the use of urinary data, with the above-mentioned limitations, in the establishment of bioequivalence (EMA, 2010; GCC, 2011; US-FDA, 2003) subject to the accurate determination of the rate of initial elimination (which can characterize C_max) in addition to the cumulative quantities.

Endogenous substances

According to Moroccan regulations, one should proceed either to subtract the average of the individual endogenous concentrations or subtract the individual AUCs of the endogenous substance so that the calculated pharmacokinetic parameters refer only to the additional concentrations provided by the administered drug. Similarly, according to EMA, calculation of pharmacokinetic parameters should be performed using baseline correction (EMA, 2010). In case of non-linear baseline (circadian cycle), subtraction of blood levels corresponding to the absence of drug administration should be made. In this case, a three-arm crossover study is performed: no drug versus reference treatment versus test treatment. The recommendations of the GCC are identical to those of EMA (GCC, 2011). In rare cases where substantial increases from baseline endogenous levels are observed, a baseline correction may not be needed (Dissanayake, 2010; EMA, 2010). CDSCO requires that, when validating the bioanalytical method, specificity and selectivity data should be generated to demonstrate that the assay does not interfere with endogenous compounds (CDSCO, 2005). In order to distinguish added drug from endogenous baseline, it is possible for Europe to overdose the subjects providing the absence of health risk.

Pharmacokinetic parameters, statistical analysis, criteria, and limit of acceptance

With a single-dose study, the main parameters are C_max, AUC (0–t) and AUC (0–∞) or AUC (0–72 hours). The analysis starts with an ANOVA on log-transformed parameters. The model of ANOVA includes sequence, subject (sequence), period, and treatments as effect; Morocco as EMA preferred a fixed model while US-FDA is using a mixed random model. The 90% CI of the ratio test/reference is calculated based on the residual variance and must be included within the predefined limits. The limit of acceptance of test/reference ratio of pharmacokinetic parameters is 80.00% to 125.00% rounded to two decimal places. The regulatory authorities with the exception of SADC (SADC, 2015), which sets a wider range for C_max (75.00%–133.00%), globally accept these limits. The criteria for accepting the pharmacokinetic parameters are detailed in Table 2.

For narrow therapeutic index drugs, the 90% CI is reduced to 90.00%–111.00% for C_max and AUC. In case of a replicated design for highly variable drug, the limits of CI can be broadened for C_max based on the intra subject coefficient of variation CV of the sole reference formulation starting at 30% up to a maximum corresponding to 50% of variability (80.00%–125.00% at 30% to 69.84%–143.19% for ≥50%) (EMA, 2010; Morocco, 2012). Rules of enlargement are different between EMA, HC, and US-FDA.

Table 2. Pharmacokinetic Parameters and Acceptance Criteria for immediate release formulations. [Click here to view]

Complementary in vitro data to be provided

Dissolution and content data should be provided for batches tested in vivo, in the quality control medium, and in the three pHs: 1.2, 4.5, and 6.8 (and pH 3–5 in Japan due to achlorhydric patients). At least two batches of reference product must be tested. If the content differs by more than 5% between the test drug and the reference, an explanation must be given and the AUC and C_max parameters must be corrected by the contents before statistical analysis. In case of different results between in vitro and in vivo, in vivo prevails. However, the discrepancy must be explained.

Waiver of in vivo bioequivalence studies (Biowaiver)

According to the pharmaceutical forms

International regulations are unanimous regarding biowaivers of solutions, at time of administration, intended for parenteral, oral, or local use. These drugs have active ingredients at the same molar concentrations and excipients that are substantially similar qualitatively and quantitatively. Moroccan regulations adopt the same rules.

According to the different dosage strengths of a drug

In Morocco, for different strengths of a drug of the same formulation whose pharmacokinetics is linear in the therapeutic range, the qualitative composition is the same, manufactured by the same producer on the same site and at least the highest strength of which has undergone a bioequivalence study are dispensed from bioequivalence studies provided the dissolution curves are similar. In case of non-similarity of the composition, several bioequivalence studies are required. These recommendations are similar to the majority of international guidelines with some clarifications (for example, EMA does not grant biowaiver for the same production site).

A pharmacokinetic is considered linear by EMA if the differences in the AUC/dose are less than 25% between the different doses. In case of linear pharmacokinetics in the therapeutic range, the highest strength is recommended for bioequivalence studies. If this higher strength could lead to side effects that compromise subject safety, a lower dosage may be used. In the case of non-linear pharmacokinetics, two possibilities exist: either under linearity, the lowest and the highest strengths must be tested or in over linearity, the highest strength must be used.

According to the biopharmaceutical classification system (BCS)

This classification is based on the aqueous solubility at three pHs: 1.2, 4.5, and 6.8 of the highest therapeutic dose per intake in immediate release and intestinal permeability of the active ingredient. For non-narrow therapeutic index drugs, the equivalence between the generic drug and the reference drug takes into account comparative composition including active pharmaceutical ingredient and makes use of dissolution studies in vitro at the three pH values cited above in controlled and strict condition (for example, USP Type I at 100 rpm or Type II at 50 rpm) and in quality control method. Like EMA and Health Canada, Morocco grants exemptions for BCS class I and III drugs while China, ASEAN, and Saudi Arabia grant them just for class I (ASEAN, 2015; HC, 2012; 2014; SFDA, 2012). US-FDA directive broadens the exemption from Class I to Class III. Japan does not adopt this classification system for the time being. It has to be noticed that International Council on Harmonisation (ICH) M9 (including Japan) is on step 2 draft and is forecasted to be adopted in 2019. This ICH M9 provides clear indication on composition rules, dissolution processes to support bioequivalence surrogate.

In vivo–in vitro correlation (IVIVC)

The standard definition of IVIVC is recognized in Morocco as a predictive mathematical model describing the relationship between an in vitro property of an oral pharmaceutical form and a relevant in vivo response (plasma concentration of the active ingredient or the quantity of the active ingredient absorbed). In this case, derogations may be granted for changes in formulae, manufacturing processes, production sites, etc. To waive in vivo bioequivalence studies, IVIVC studies should be Level A studies that establish a close relationship (i.e., point-to-point) between the in vitro dissolution rate and the in vivo entry rate (absorption).