Abstract
Quality by Design (QbD) is a transformative and systematic approach to developing top-tier pharmaceutical products, ushering in a departure from traditional trial-and-error methods toward a more science-based, risk-oriented, and holistic strategy. Central to QbD implementation is the meticulous development of formulations and manufacturing processes, consistently fulfilling predefined quality objectives. The core objective of QbD remains unwavering — to guarantee the steadfast alignment of the final pharmaceutical product with predetermined quality attributes, thereby mitigating batch-to-batch variations and potential recalls. This article succinctly explores the multifaceted application of QbD methodology within the pharmaceutical industry. Emphasizing its pivotal role in research and development, manufacturing, quality control, and quality assurance, the discussion navigates through the strategic deployment of QbD elements and tools. Amidst the evident advantages of QbD, challenges persist in its widespread adoption within the pharmaceutical sector and regulatory frameworks. This article sheds light on the regulatory landscape that currently governs the implementation of QbD in these crucial stages of pharmaceutical processes. For that reason, this review article aims to provide researchers, scientists, and industry professionals with a thorough introduction to QbD so they may adopt this methodical approach to developing and producing high-quality pharmaceutical products, always in compliance with the underlying regulations.
Introduction
Ensuring pharmaceutical product quality is a top priority for industries, driven by the need to safeguard patient safety and ensure the efficacy of products. As a result, the pharmaceutical sector stands as one of the most highly regulated industries worldwide (1). Traditional drug development has historically relied on trial-and-error procedures focused on creating a product that satisfies all regulatory requirements, rather than simplifying and improving the development process (Fig. 1). This method is often labor-intensive, costly, and prone to batch failures due to process variability (2). While it has enabled the commercialization of numerous drugs, this method’s inefficiencies call for a more systematic approach to quality assurance (3, 4).
The concept of Quality by Design (QbD) emerged in the manufacturing industry over 25 years ago, and it started to receive significant attention from the pharmaceutical industry in the early 2000 s due to its potential to improve the efficacy, quality, and safety of pharmaceutical products (2, 5). The U.S. Food and Drug Administration (FDA) first introduced QbD notions between 2001 and 2004, and described it as a proactive tool designed to introduce quality into the pharmaceutical product from the start, while improving the processes of development, manufacturing, and regulation (6) (Fig. 1).
The pharmaceutical sector was first formally exposed to the notion of QbD in 2005 with the publication of the International Conference on Harmonization (ICH) Q8 guideline (Pharmaceutical Development) (5, 7). The guideline emphasized the importance of understanding both the product and the manufacturing process to establish a solid manufacturing method that could reliably and consistently produce high-quality products (7,8,9). Since then, QbD has gained importance in the pharmaceutical industry, with global regulatory agencies advocating for its adoption (6, 7). Nowadays, QbD is considered an integral component of pharmaceutical development, and even more, a strategy that should be included in all new drug applications (2, 6, 8).
When compared to traditional quality control methods, which mostly rely on end-product testing, where quality is assessed at the end of production, often resulting in waste, inefficiencies, and costly regulatory setbacks when specifications are not met, QbD represents a paradigm change. Instead, QbD places a strong emphasis on integrating quality into all phases of the product lifecycle, with an emphasis on proactive design and control. It understands that quality must be incorporated into a product from the start, based on sound scientific concepts, rather than examined or tested at the end (5).
Studies indicate that QbD can reduce development time by up to 40% by optimizing formulation parameters before full-scale manufacturing. Additionally, its ability to define and control a robust design space has led to fewer batch failures, reducing material wastage by up to 50% in some reported cases.
At the core of QbD lies the systematic identification and management of critical quality attributes (CQAs) and critical process parameters (CPPs) (5, 10) (Fig. 1). CQAs are the fundamental features of a product that must be incorporated to guarantee its performance, effectiveness, and safety. These characteristics are closely related to the final pharmaceutical product’s therapeutic advantages, stability, and manufacturability (5). CPPs, on the other hand, are the process factors that have a big impact on CQAs. For the manufacturing process to be optimized and consistent product quality to be attained, it is essential to comprehend the cause-and-effect relationship between CPPs and CQAs (5, 11).
QbD uses Design of Experiments (DOE), a powerful tool for process optimization. By planning and executing experiments, collecting data, and analysing results statistically, DOE allows for the systematic evaluation of process parameters (12). This structured approach helps experts identify key sources of variability and determine the optimal conditions needed to achieve the desired product quality features. Controlling these critical variables within clearly defined limits reduces the risk of product failures, inconsistencies, and batch rejections.
Another key element of QbD is the development of a Quality Target Product Profile (QTPP) (2, 13), which outlines the therapeutic goals, safety requirements, and intended product characteristics (14). It guides all phases of product development, enabling a comprehensive and scientifically informed approach to formulation and process design. QTPP streamlines decision-making processes and assures consistency and quality across the product lifecycle by aligning all stakeholders around a unified quality target (5, 14). Recognizing QbD’s potential to improve the quality of pharmaceutical products, regulatory bodies have offered recommendations to support its use (9). The European Medicines Agency (EMA) and the U.S. FDA have both released regulatory frameworks that stress the significance of a methodical and scientific approach to pharmaceutical research and manufacture (7, 15, 16).
In recent years, Analytical Quality by Design (AQbD) has gained prominence as an extension of QbD principles into analytical method development. AQbD aligns with the principles outlined in ICH Q14, ensuring that analytical methods are robust, reproducible, and regulatory-compliant throughout the product lifecycle. This approach establishes a Method Operable Design Region (MODR) to improve method performance while minimizing method variability, an essential factor for regulatory approval (15, 17,18,19). Despite these benefits, QbD requires extensive upfront investment in experimental design, data collection, and regulatory documentation, which can be challenging. However, as regulatory agencies increasingly favor QbD-based submissions, its long-term advantages in process efficiency, regulatory flexibility, and patient safety outweigh the initial implementation challenges (20).
In this comprehensive review, the objective is to thoroughly explore the significant role played by QbD in the pharmaceutical industry, focusing on its application across fundamental domains — research and development, manufacturing, quality control, and quality assurance. By examining the integration of scientific principles, risk assessment (RA), statistical methodologies, and DOE, the aim is to provide a nuanced understanding of these and other foundational concepts.
Drawing on diverse case studies and real-world scenarios, this work illustrates how QbD emerges as a transformative strategy within the pharmaceutical industry, leveraging meticulous scientific analysis and a holistic, science-based overview of the entire pharmaceutical process. Ultimately, QbD stands as a revolutionary framework poised to elevate pharmaceutical products by ensuring patient safety, enhancing product quality, and aligning seamlessly with regulatory standards. This review highlights how QbD principles refine and advance the pharmaceutical development processes.
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Duarte, J.G., Duarte, M.G., Piedade, A.P. et al. Rethinking Pharmaceutical Industry with Quality by Design: Application in Research, Development, Manufacturing, and Quality Assurance. AAPS J 27, 96 (2025). https://doi.org/10.1208/s12248-025-01079-w
Read also our introduction article on Quality by Design (QbD) here:
