By Giuliana Miglierini
The draft ICH M13A harmonised guideline “Bioequivalence for immediate-release solid oral dosage forms” was endorsed by the International Council for Harmonisation on 20 December 2022 and is now open for consultation. Comments can be forwarded until 26 May 2023; publication of the final document is expected by May 2024.
The new guideline will then be implemented as a European guideline, replacing the current EMA guideline on the investigation of bioequivalence (BE) for oral dosage forms. The ICH M13A is the first of a planned series intended to address scientific and technical aspects of study design and data analysis, so to better support BE assessment both during development and post approval. The guideline covers immediate-release (IR) solid oral dosage forms delivering drugs to the systemic circulation (i.e. tablets, capsules, and granules/powders for oral suspension). Different approaches from those suggested in the guideline are possible, provided they are scientifically justified; applicants are thus encouraged to seek the advice of the relevant regulators in order to share a common approach to development.
Key concepts of the M13 series
The determination of bioequivalence to the originator is a fundamental step in the development of generic and biosimilar medicines. BE plays also an important role for some innovator products, as well as for post-approval changes of formulation and/or manufacturing process. BE is determined in terms of bioavailability of the products under comparison after administration, within predefined limits to ensure safety and efficacy. In vivo BE studies for certain orally administered IR solid oral dosage forms can be waived according to the ICH M9 guideline on Biopharmaceutics classification system (BCS)-based biowaiver, which has already superseded Appendix III of the EMA guideline.
The M13A guideline addresses study design containing multiple comparator products or test products, but not the acceptance of comparator products across different regulatory regions, as this greatly varies according to local legislations. The process of regulatory decision making based on BE is also excluded from the guideline.
The planned M13 series should also include the ICH M13B guideline, focused on biowaiver considerations for additional strengths not investigated in BE studies, and ICH M13C discussing data analysis and BE assessment for highly variable drugs, drugs with narrow therapeutic index, and complex BE study design. It should also address data analysis considerations, for example in the case of adaptive BE study design.
Pharmacokinetics (PK) bioequivalence studies and comparative in vitro dissolution studies are the main tools for BE determination for IR solid oral dosage forms with systemic action. These principles can be also applied to other non-orally administered drug products with immediate action (e.g., certain rectal, inhalation, and nasal drug products), provided BE may be derived from measures of systemic exposure.
The ICH E6 guideline on Good Clinical Practice should also be considered while conducting BE studies, in order to ensure the data integrity of all data generated in the trials.
The main contents of the ICH M13A
Chapter 2 of the ICH M13A guideline discusses the general principles to be used for the establishment of bioequivalence. These include the selection of the study population and the choice of the pharmacokinetic endpoint to be used in the BE studies. Healthy subjects should be the preferred choice, unless there are ethical concerns linked to the safety of the pharmaceutical products under assessment. In any case, inclusion and exclusion criteria should always be clearly reported in the study protocol. The main target of BE studies should be the detection of differences in the in vivo release characteristics between the products. Elements to be considered to select the study population are discussed in the draft guideline.
As for the study design, the recommended suggestion is for randomised, single-dose, two-period, two-sequence crossover studies comparing two formulations, as single-dose studies may better detect differences in the rate and extent of absorption. Multiple-dose studies may be conducted in patients should the single-dose design be not affordable for safety/tolerability or ethical reasons. A parallel design may be indicated for drugs with long elimination half-lives, requiring a prolonged washout period. Alternatives are also acceptable upon scientific justification.
The choice of the test product should be also discussed and justified, and it should be representative of the product to be marketed. As for the comparator, the selection of the batches to be used for BE studies should be based on assay content. The strength of the product to be used in the BE study depends on the dose proportionality in PK and solubility of the analyte.
The draft also indicates standardised fasting conditions should be the preferred choice to run BE studies, as they support a better discrimination between the PK profiles of the product and the comparator. Both fasting and fed BE studies should be conducted for high-risk products, due to their complex formulation design or manufacturing process that may impact differently on their in vivo performance, due to different gastrointestinal (GI) conditions. This is the case, for example, of low solubility drug substances formulated in the form of solid dispersions, microemulsions, lipid-based formulations, nanotechnologies, or other specialised technologies.
Analysis of the parent drug should be the preferred choice to demonstrated bioequivalence. Primary metabolites are considered acceptable in the case of pro-drugs which are rapidly eliminated. Stereoselective assays measuring individual enantiomers should be also considered while assessing chiral drugs.
Specific paragraphs address the setting up of sampling, the need to avoid occurrence of Cmax at the first post-dose sampling time point, the possibility to use truncated AUC for drugs with long half-life and considerations on early exposure.
How to analyse and present data
Specific sections of the guideline discuss how to present and report data obtained from BE studies. The study documentation should include the complete evidence of the protocol, conduct, and evaluation, and it should be written according to the ICH E3 guideline “Structure and content of clinical study reports”.
Unadjusted, measured drug concentrations in a suitable biological fluid should be always provided for both the product and the originator, for each subject participating in the study. Any deviations should be clearly identified. A suggested list of PK’s parameters to be tabulated for each subject-formulation combination is provided, together with summary statistics to be reported. Not less important is the statistical analysis performed on raw data. To this instance, the model of choice for the analysis should be pre-specified in the study protocol. Cmax and AUC(0-t) should be the preferred PK parameters to establish BE.
Chapter 3 discusses specific topics that may impact on the determination of BE. Among these is the presence of endogenous compounds identical to the drug under evaluation, thus requiring the determination of their baseline concentration in the biological fluids of interest. The draft guideline also specifies that both orally disintegrating tablets (ODTs) and chewable tablets should be administered in BE studies according to the comparator product labelling with regard to intake of water. The comparator product labelling should also represent the main reference for BE studies involving tablets, granules, and powders labelled as being only intended to be dispersed in a liquid before administration as an oral suspension. Considerations are also provided for fixed-dose combination products and the dependance of the drug solubility on pH.
