Control Strategies for Drug Product Continuous Direct Compression-State of Control, Product Collection Strategies, and Startup/Shutdown Operations for the Production of Clinical Trial Materials and Commercial Products

Continuous manufacturing (CM) has emerged in the pharmaceutical industry as a paradigm shift with significant advantages related to cost, efficiency, flexibility, and higher assurance of quality. The inherent differences from batch processes justify examining the CM control strategy more holistically. This article describes the current thinking for the control and implementation of CM, using the example of a direct compression process and taking into consideration the ICH Q10 definition of "state of control" and process validation requirements. Statistical process control using control charts, sources of variation, process capability, and process performance is explained as a useful concept that can help assess the impact of variation within a batch and indicates if a process is in state of control. The potential for time-variant nature of startup and shutdown with CM is discussed to assure product quality while minimizing waste as well as different options for detection and isolation of non-conforming materials due to process upsets. While different levels of control are possible with CM, an appropriate balance between process control and end product testing is needed depending on the level of process understanding at the different stages of development from the production of clinical supplies through commercialization.