Continuous manufacturing (CM) has become a contentious topic in the modern pharmaceutical lexicon, driven by divergent definitions—from perfusion and flow chemistry to fully integrated systems.

In biologics production, CM is an emerging technology aimed at improving yields, reducing costs, and streamlining production processes. However, despite its recent media attention, misconceptions remain about what constitutes true continuous manufacturing in biologics production. While several companies have adopted elements of CM—often upstream perfusion or perfusion with capture on affinity resin (with or without surge tanks)—few can claim an end-to-end process. A truly continuous process is one in which both upstream and downstream operations are connected and integrated, with no interruptions in flow all the way to Chrom 3. This approach yields compounded benefits that deliver significantly higher returns than perfusion and perfusion with capture alone.

Fed-batch or perfusion production on the other hand has isolated stages requiring product transfers, intermediate testing, and downtimes that slow production and introduce inefficiencies. By integrating key operations, such as capture chromatography and anion/cation exchange chromatography into a continuous, connected system enables true continuous mode manufacturing, optimizing productivity and reducing costs.

Primary variations of continuous manufacturing processes

The industry currently employs three primary variations of continuous manufacturing processes:

1. Semi-Continuous (Hybrid): This method combines elements of both batch and continuous manufacturing, and only certain stages operate continuously, while others follow traditional batch techniques. For instance, some setups may use perfusion, harvesting daily for downstream processing while maintaining a bioreactor with fresh media. Others may connect the protein capture stage and pause the flow before proceeding with subsequent downstream steps, which are completed sequentially. 

2. Individual Continuous Operations: Companies in this category retrofit continuous components into their existing batch processes, creating a hybrid system. This enhances efficiency but doesn’t deliver a fully integrated solution. For example, some manufacturers operate multiple fed-batch bioreactors in series with a single downstream process.

3. Fully Connected Continuous Manufacturing (FCCM): The most advanced form of continuous manufacturing, FCCM provides an uninterrupted, end-to-end process from seed to final purification. Enzene, a CDMO, has validated a fully connected continuous platform that integrates all unit operations—from perfusion to Chromatography 3 (Chrom 3). Unlike other processes, FCCM eliminates the need for holding tanks or intermediary steps, streamlining the workflow and significantly improving efficiency and consistency throughout the manufacturing process. 

The benefits of FCCM extend far beyond productivity gains. A significant advantage is the marked improvement in yield. In continuous perfusion cell culture, fresh media is added to the cells daily while spent media is removed, allowing the protein/antibodies produced to move directly into downstream steps. This approach prevents degradation in cell culture and minimizes the chances of protein aggregation, resulting in enhanced product quality and output. Product degradation is mitigated by ensuring the protein of interest does not remain in a mixture with other proteins that could cleave it over time. This leads to up to ten-fold increase in biologics productivity compared to traditional batch processes.

Moreover, FCCM also enhances product quality by minimizing exposure to hold times and environmental fluctuations, resulting in greater stability and consistency in complex biologics, such as bispecific antibodies and fusion proteins.

Cost efficiency is another major benefit. The integrated nature of FCCM reduces the need for large bioreactors and storage tanks, lowering the overall footprint and capital expenses. Enzene’s platform achieves 40-50% savings in the cost of goods sold, even for complex molecules, and has a 70% smaller operational footprint compared to traditional methods.

Additionally, FCCM offers exceptional scalability and flexibility. It is designed to efficiently scale up production, enabling the manufacture of larger quantities of biologics, such as monoclonal antibodies (mAbs), at lower per-gram costs compared to traditional methods. This scalability and cost efficiency make FCCM a versatile solution for various production needs.

How is continuity maintained?

In a FCCM setup, both upstream and downstream steps are seamlessly integrated into a continuous process, eliminating traditional batch-mode interruptions. At the heart of the upstream process is a perfusion system, where a bioreactor continuously produces the product which is subsequently taken out of the bioreactor using an Alternating Tangential Flow (ATF) system. This ATF system filters out the product without removing the cells, allowing them to remain in the bioreactor at high density (up to 60–120 million cells/mL), thus maintaining high cell viability and productivity.

Once taken out of the bioreactor, the product immediately enters the downstream process. Instead of pausing between stages, like many setups that rely on hold tanks after capture step, Enzene’s FCCM synchronizes every step in real time. While one Protein A chromatography column is loaded with the bioreactor’s output, a second column in parallel undergoes washing, elution, and cleaning, preparing it for the next cycle. This precise timing eliminates hold times, allowing the entire process to flow continuously without interruption (Figure 1).

While other setups may similarly use 4, 8, or even up to 16 Protein A capture columns followed by a holding step, Enzene has optimized the process to use only two Protein affinity columns without the need for hold tanks, allowing all operations to remain in a continuous flow-through mode.

By connecting all stages from perfusion to viral inactivation, along with further downstream steps of anion and cation exchange chromatography, the process is fully integrated and occupies a much smaller physical footprint than traditional systems. This is achieved by using time synchronization between process unit steps and integrating the unit operations. The process parameters are in turn optimized to get maximum possible fixed volume out of unit operations either in flow-through mode or binding mode.

This allows the platform to produce impressive volumes, achieving between 5 to 15 kg of product from a 500-liter bioreactor at 320 L working volume. It operates with a 1.5 bioreactor volume perfusion rate and can complete production within approximately 30 days, depending on the molecule and titer. With EnzeneX 2.0, the target is to achieve 40 kg per batch, by scaling up from 500L to 1000L bioreactors and new high titre producing cell lines, with a cost per gram of antibody production as low as $40.

A compelling example of FCCM’s superiority comes from our work with a bispecific interleukin molecule. Initially developed using a fed-batch process, the molecule faced significant stability issues and poor yield. Transitioning to the FCCM platform resulted in an eight-fold increase in productivity and marked improvements in stability and quality, highlighting FCCM’s advantages and versatility in handling complex biologics. As the biologics pipeline expands to include novel formats like bispecifics, tri-specifics, and fusion proteins, FCCM will be instrumental in overcoming challenges related to stability, yield, and scalability.

Regulatory guidelines for continuous manufacturing

As the industry embraces these advancements, regulatory authorities, including the FDA, have updated their guidelines to reflect the increasing recognition of continuous manufacturing. The agency acknowledges the significant benefits of CM in enhancing product quality and consistency, as well as providing greater control over production processes. Its guidelines advocate for the adoption of CM, underscoring its superiority over traditional batch methods, particularly within the framework of quality-by-design (QbD) principles.

International regulatory bodies such as the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) have in fact developed specific guidelines, like ICH Q13, to assist drug manufacturers in implementing CM for both drug substances and drug products. 

As these guidelines become established and the advantages of CM become more evident, it is inevitable that more manufacturers will transition to continuous manufacturing to leverage the significant benefits this technology offers over fed batch, but few may have the resources or expertise to develop fully continuous systems.

While continuous manufacturing offers significant advantages, it also requires rigorous validation to meet evolving regulatory standards. Achieving success in this area involves considerable investment and careful process validation. For instance, it took Enzene several years to optimize the process and then to be able to transition 30 fed-batch processes to a fully connected continuous manufacturing platform resulting in the production of commercial products. 

As the biologics industry evolves with more complex molecules and treatments like bispecific antibodies and fusion proteins, the demand for efficient and scalable manufacturing processes will rise. Continuous manufacturing is often seen as a solution, but not all CM approaches provide the same benefits. FCCM platforms, by integrating upstream and downstream processes into a seamless flow, offer enhanced flexibility and process control. They can achieve higher yields, lower costs, and improved product quality, making them essential for addressing the challenges posed by complex biologics and emerging therapies.

Russell Miller is Vice President of Global Sales and Marketing at Enzene Biosciences.