Thailand draws a critical line between two types of generic applications. Which side of that line your product is on determines whether a bioequivalence study is required, and misclassifying costs months.
Thailand's registration framework draws a distinction between two types of generic applications based on when the comparator product was first approved by Thai FDA:
References an originator or comparator product whose first Thai FDA approval was granted after B.E. 2534 (1991). Requires a full bioequivalence study demonstrating that the generic product is bioequivalent to the reference product. This is the pathway applicable to the vast majority of foreign manufacturers registering generic products in Thailand today, since most modern reference products were approved after 1991.
References an originator whose comparator was first approved by Thai FDA before B.E. 2534 (1991). Does not require a bioequivalence study. This pathway is largely historical and applies to a narrow set of very old reference products. Most foreign manufacturers will not qualify for this pathway.
Confirming whether a specific comparator was first approved before or after B.E. 2534 (1991) requires checking Thai FDA's registration records. A product's first approval date in the EU, US, or other markets does not determine its classification in Thailand. The relevant date is the Thai FDA approval date for the comparator product used as the reference.
Thai FDA requires bioequivalence studies that meet the ASEAN Guideline for the Conduct of Bioavailability and Bioequivalence Studies. This guideline is broadly aligned with ICH E5, WHO bioequivalence guidance, and EMA BE standards, with ASEAN-specific provisions.
A two-period, two-sequence crossover design for single-dose studies is the standard approach. Fasted-state studies are required for most immediate-release oral dosage forms. Fed-state studies may additionally be required for products where food significantly affects absorption, or for modified-release formulations. Steady-state designs may be appropriate for certain modified-release or combination products.
The 90% confidence intervals for the primary pharmacokinetic parameters (AUC and Cmax) must fall within 80.00 to 125.00% for the test-to-reference ratio. For highly variable drugs, a reference-scaled average bioequivalence approach may be applicable under the ASEAN guideline provisions for this category.
The bioanalytical method used to measure drug concentrations must be validated according to accepted international standards (EMA, US FDA, or ICH M10 guideline). The validation report is required in Part IV of the ACTD submission. An unvalidated method, or a method that fails validation criteria, invalidates the study data and requires a repeat study.
The bioequivalence study must be conducted at a facility operating under Good Clinical Practice (GCP). Studies conducted at recognized CROs in regulated markets with documented ICH-GCP compliance are generally acceptable, provided the GCP declaration and investigator qualifications are included in the submission.
Not all new generic applications require an in-vivo bioequivalence study. Thai FDA recognizes biowaiver criteria under the ASEAN guideline for specific circumstances.
Biowaivers based on Biopharmaceutics Classification System (BCS) criteria are available for BCS Class I drugs (high solubility, high permeability) where the test product is highly similar to the reference in formulation and shows rapid dissolution, and for BCS Class III drugs under specific conditions. The biowaiver application must include complete dissolution profiling data comparing the test and reference products at multiple pH values, in addition to the BCS characterization data for the drug substance.
When a new generic application covers multiple strengths of the same product, a bioequivalence study conducted on the most sensitive strength (typically the highest or the one with the least favorable dissolution profile) may support a biowaiver for other strengths, provided the formulations are proportionally similar and dissolution profiles are comparable.
Biowaiver eligibility analysis should be completed early in the development process. A product that qualifies for a BCS-based biowaiver saves the significant cost and time of a clinical study. The biowaiver justification is submitted as part of Part II of the ACTD dossier.
Generic ACTD dossiers follow the same 4-part structure as new drug dossiers, with the following characteristics specific to generic applications:
Thai-language administrative and product information documentation, including labeling mock-ups and the Thai product information document. The product information for a generic must align with the approved product information for the reference product on the Thai market. Divergences in indication, dosage, or warnings from the approved Thai reference labeling require justification.
Full quality documentation for both the drug substance and drug product. Stability data must meet ASEAN Climate Zone IVa or IVb requirements (typically 40°C / 75% RH for long-term stability, with 12 months of data at submission and commitment to full shelf-life data). The dissolution method must be validated and discriminating.
For generics, Part III typically consists of a literature-based summary relying on the established safety profile of the active substance. Bridging to the reference product's nonclinical data is acceptable for most standard generic applications. New studies are not normally required.
The bioequivalence study report is the centerpiece of Part IV for new generics. The comparator product details must be documented: Thai FDA registration number, the lot number and batch certificate used in the study, and the justification that the selected comparator is the Thai FDA-approved reference product. If the study used a comparator sourced outside Thailand, the justification for comparator equivalence must be submitted.
Generic applications face a 120-business-day review target from the date of screening acceptance, not from the submission date. End-to-end, including screening, the timeline typically runs 12 to 18 months for a well-prepared dossier.
Generic-specific failure points beyond the general issues that affect all applications:
If the bioequivalence study was conducted using a comparator that Thai FDA does not accept as the reference product, the BE data cannot be used and a new study is required. Comparator confirmation should be obtained before the study is commissioned, not after the data is in hand.
Deviations from the ASEAN guideline design requirements (crossover design errors, inappropriate sampling time points, insufficient washout period, analytical method not validated to the required standard) invalidate the study data. Thai FDA will reject a study that does not meet design requirements regardless of the outcome.
Thai FDA may require the reference product used in the BE study to be the product currently registered and sold in Thailand. If the study used a comparator sourced from a different market (for example, the EU reference product), a comparator equivalence justification must be submitted demonstrating that the two sourcing-market products are the same formulation. Without this justification, the study data may be questioned during review.
VeroPharma Group assesses generic classification, comparator status, and biowaiver eligibility before the registration strategy is set. We confirm comparator acceptability with Thai FDA before advising a client on whether an existing bioequivalence study can be used, and we prepare ACTD dossiers with the dissolution, stability, and bioequivalence documentation that Thai FDA reviewers expect.
A misclassified generic or an unaccepted comparator adds months and the cost of a new study. These are preventable outcomes, and we prevent them by doing the assessment first.