ABSTRACT:
Background: Generic pharmaceutical products such as letrozole, a nonsteroidal aromatase inhibitor used in hormone receptor-positive breast cancer, must be registered through markedly different dossier formats across regulatory regions, creating duplication of effort and inconsistent review experiences for manufacturers pursuing multi-region approval. Objective: This review critically compares the International Council for Harmonisation Common Technical Document (CTD) and the ASEAN Technical Dossier (ATD) formats for letrozole generic submissions, identifies structural, procedural and data-depth differences, and proposes strategies to support regional harmonisation. Methods: A qualitative, comparative regulatory analysis was conducted using publicly available ICH and ASEAN guidance documents, regulatory assessment reports, and peer-reviewed literature. Illustrative, compiled examples of quality and stability data presentation were used solely to contrast documentation style between the two formats and do not represent a specific marketed product's proprietary dossier. Results: The CTD demonstrates a more standardised, modular structure with mandatory electronic (eCTD) submission in most ICH-aligned jurisdictions. The ATD, although modelled on the CTD, permits considerable regional flexibility that produces inconsistent data expectations, administrative requirements and electronic-submission practices across ASEAN member states, contributing to less predictable review timelines relative to ICH-aligned regions. Conclusion: Addressing ATD variability through clearer regional guidance, strengthened regulatory capacity, and standardised electronic-submission infrastructure could shorten approval timelines and improve market access for letrozole and comparable generic products across ASEAN markets.