Continuous Manufacturing of Active Pharmaceutical Ingredients: Current Trends and Perspectives

Abstract The pharmaceutical industry has traditionally employed batch processing as a means of synthesizing active pharmaceutical ingredients (APIs) on a commercial scale. Batch manufacturing enables API synthesis in large quantities in order to meet regulations. Yet, this strategy remains cumbersome, is labor‐intensive, and creates complex logistical networks. In recent decades, batch API processing has gradually eroded American economic competitiveness and has led to the offshoring of API manufacturing from the United States. Today it is estimated that +80% of APIs are manufactured overseas. [1] Meanwhile, disruptions from the Coronavirus Disease (SARS‐CoV‐2) have exacerbated weaknesses in the global supply chain, culminating with widespread shortages of critical life‐saving drugs. [2] These shortages have emphasized the importance of reshoring drug manufacturing to the U.S. and fostered a regulatory landscape that seeks advanced methods of API manufacturing in order to bolster America's supply chain resiliency. [3] Recently, increased attention has been directed towards continuous drug manufacturing to enable nonstop API production within modular stand‐alone flow systems. Continuous manufacturing (CM) facilitates modular automation, offers new avenues towards process intensification, and even enables in‐line analytical monitoring from raw materials to packaged products. This strategy offers better conversion, increased safety, reduced waste, and overall cost savings versus traditional batch‐style processing. The rise of advanced API manufacturing, coupled with the current regulatory landscape, offers a rare window of opportunity to convert traditional batch pharmaceutical processes into continuous, streamlined production systems to on‐shore API manufacturing and eliminate drug shortages. This review will outline the current state‐of‐the‐art in the CM of APIs and will highlight the translation of chemistry and unit operations from batch processes to modular CM systems.