The key steps for QbD implementation include: identification of the product attributes that are of significant importance to the product's safety or efficacy (i.e., target product profile and critical quality attributes); design of the process to deliver these attributes; a robust control strategy to ensure consistent process performance; validation and filing of the process demonstrating the effectiveness of the control strategy; and finally, ongoing monitoring to ensure robust process performance over the lifecycle of the product (10, 11). Risk assessment and management, raw material management, use of statistical approaches and process analytical technology (PAT) provide a foundation to these activities.
There are many significant differences that contrast a QbD-based process and product development from traditional practices. In the traditional approach, the process defines the product, and as a result, the process needs to be performed within narrow operating ranges to get consistent product quality. In QbD, the product defines the process, so as long as the process stays within the defined design space, product quality is acceptable. Product specifications in the traditional approach are set based on process performance, and regulators expect them to be narrowed after enough process history has been established. On the other hand, in QbD, product specifications are set based on process and product knowledge and this allows them to be kept wider, resulting in greater operational flexibility. The regulatory filing in the traditional approach describes the process and presents data on product characterization.
The focus is on presenting the status quo . In a QbD filing, the focus is instead on process and product knowledge. Data are presented to explain how the process affects the quality attributes (QA) of the product and how the QA affect the safety and efficacy of the product. Postapproval support through product lifecycle requires high maintenance in the traditional approach. The regulatory burden is high for process changes and, therefore, process improvements are few.
Many postapproval supplements are focused on alleviating repeat violations of the approved ranges and limits even though these violations do not necessarily affect product quality. Many postapproval supplements introduce new filling lines and manufacturing sites for similar processes. In a QbD paradigm, the regulatory burden is low because there are wider ranges and limits based on product and process understanding. Changes within these ranges and limits do not require prior approval. Resolution of nonconformances is faster because the required process knowledge already exists.
REGULATORY IMPLICATIONS OF QBD
QbD cannot exist without an effective quality system that oversees and manages process variability and product quality through appropriate control strategies, documentation, data trending and analysis, risk assessment, and continuous review. It is a living system that incorporates gained knowledge and historical experience to effect updates and changes whenever and wherever necessary. From the regulatory side, FDA develops the expertise to understand and assess QbD elements. Decisions are made based on science and risk to patient safety and are documented under the umbrella of an effective quality system. Knowledge is managed effectively to serve as reference in the future. Precedents and regulatory decisions are recorded and managed. Data and trends are collected and analyzed to identify any patterns or trends for specific categories of products or similar products even after drug approval. Metrics are developed to understand the impact of regulatory decisions. Under the QbD paradigm, the success or failure of a marketed pharmaceutical product is assessed to incorporate lessons learned into future reviews of drug applications.