The global biopharmaceutical market has witnessed a transformative shift with the emergence of biosimilars—biologic medical products highly similar to an already approved reference biologic. By offering more affordable therapeutic alternatives, biosimilars expand patient access to life-saving treatments for conditions such as cancer, autoimmune diseases, and diabetes. However, producing a biosimilar is far from trivial; it demands rigorous manufacturing processes to ensure comparability in safety, efficacy, and quality. At the heart of this manufacturing challenge lies downstream processing (DSP), the suite of purification and isolation steps that transform crude harvests into final, high-purity drug substance. Recent advances in DSP are not only reducing costs and timelines but also enabling manufacturers to meet ever-stricter regulatory expectations with greater confidence.

Fundamentals of Downstream Processing

Downstream processing encompasses every unit operation that occurs after the bioreactor harvest. Its primary objective is to isolate the target protein—typically a monoclonal antibody (mAb), fusion protein, or therapeutic enzyme—from a complex mixture of host cells, cell debris, media components, and product-related impurities such as aggregates, fragments, or variants. The process generally follows a logical sequence:

  • Harvest and clarification: Removal of whole cells and large debris via centrifugation, depth filtration, or a combination thereof.
  • Capture: Initial recovery and concentration of the product, most commonly using affinity chromatography (e.g., Protein A resin for mAbs).
  • Viral inactivation and intermediate purification: Steps such as low-pH incubation to inactivate enveloped viruses, followed by orthogonal polishing chromatography (ion exchange, hydrophobic interaction, or multimodal).
  • Polishing and final purification: Removal of remaining impurities, aggregates, and viral particles via additional chromatography and filtration (e.g., anion exchange, flow-through mode).
  • Viral filtration and concentration: Use of nanometer-pore filters to clear non-enveloped viruses, followed by ultrafiltration/diafiltration (UF/DF) to achieve the target concentration and buffer composition.
  • Formulation and final fill: Adjustment of excipients and sterile filtration before filling into final containers.

Each step must be optimized for yield, purity, and robustness. Even minor deviations can lead to batch failures or product inconsistency, which is particularly critical for biosimilars because regulators require a high degree of similarity to the reference product over the entire lifecycle. Consequently, DSP is often the costliest and most time-consuming segment of biosimilar manufacturing, driving the need for continuous innovation.

Recent Advances in Downstream Processing

The past decade has seen remarkable progress in DSP technologies, many of which are now being adopted across the biosimilars industry. These advances can be grouped into four main categories: single-use systems, improved chromatography, automation and continuous processing, and advanced filtration.

Single-Use Technologies

Single-use (disposable) equipment—including bioreactors, mixers, bags, tubing, and filters—has become a cornerstone of modern bioprocessing. For DSP, the shift to single-use systems brings tangible benefits:

  • Reduced cross-contamination risk: Since contact materials are used only once, the risk of carryover between batches is essentially eliminated. This is particularly valuable when switching between different biosimilar products in a facility.
  • Shorter changeover and setup times: Disposable flow paths replace fixed piping and cleaning validation, dramatically reducing turnaround time between campaigns.
  • Lower capital investment: Facilities designed for single-use DSP require less stainless steel, fewer clean-in-place (CIP) systems, and reduced water-for-injection (WFI) infrastructure.
  • Increased flexibility: Single-use skids and chromatography columns can be reconfigured quickly for different product titers or process scales.

Leading suppliers such as Cytiva, Thermo Fisher, and Sartorius now offer single-use chromatography columns (e.g., ReadyProcess columns) and single-use tangential flow filtration (TFF) assemblies. Biosimilar manufacturers have been quick to adopt these platforms because they allow rapid scale-up from early development to commercial production without the delays of hard-piped fabrication.

Improved Chromatography Techniques

Chromatography remains the workhorse of protein purification, and recent innovations have pushed the boundaries of what is possible in both capture and polishing steps.

High-capacity and alkali-tolerant resins: Next-generation Protein A resins now offer binding capacities exceeding 60 g/L and can withstand repeated exposures to 0.5 M NaOH for cleaning, reducing resin replacement frequency and operational costs. For polishing, high-capacity ion-exchange and hydrophobic interaction (HIC) resins enable smaller column volumes and faster flow rates.

Multimodal (mixed-mode) chromatography: Resins that combine multiple interaction modes—such as ion exchange and hydrophobic interactions or hydrogen bonding—can achieve superior selectivity in a single step. For example, a multimodal capture step can simultaneously remove aggregates, host cell proteins, and DNA, potentially replacing two or more conventional columns. This is particularly advantageous for biosimilars because it reduces the number of unit operations and shortens overall processing time.

Continuous chromatography: True continuous capture systems, such as periodic counter-current chromatography (PCC), allow simulated moving bed operation that uses multiple smaller columns sequentially saturated and eluted. This dramatically increases resin utilization (often from 60–70% to >95%) and reduces buffer consumption up to 40%. Continuous chromatography is increasingly being paired with steady-state perfusion bioreactors to form the core of integrated continuous bioprocessing (ICB) trains. The FDA has expressed support for continuous manufacturing, and several biosimilar makers are already exploring ICB for late-stage pipelines. Biopharm International regularly features case studies on ICB adoption.

Automated and Continuous Processing

Automation and process control have matured to a point where whole DSP trains can be operated with minimal human intervention. Advances include:

  • Skid-based automation: Modern DSP systems are equipped with programmable logic controllers (PLCs) and distributed control systems (DCS) that manage flow rates, pH, conductivity, and column switching automatically. Built-in sensors provide real-time process data, enabling alarm-driven response and process trending.
  • Robotics and automated buffer preparation: Automated liquid handling systems can prepare buffers in-line, reducing manual error and improving consistency across batches.
  • Fully integrated continuous downstream lines: In a continuous DSP train, harvest, capture, viral inactivation, polishing, and UF/DF are linked directly without intermediate hold tanks. This reduces product residence in stainless steel vessels, minimizes aggregation, and shortens overall processing time from days to hours. Leading integrated platforms—such as the GE FlexFactory (now integrated into Cytiva) and the KrosFlo system—are being used successfully for biosimilar production in both academic and industrial settings.

Automation not only improves reproducibility but also facilitates the collection of high-quality process data, which is essential for regulatory filings and process validation. With more data points per batch, manufacturers can apply statistical control and ensure consistent quality across lots—a critical requirement for biosimilar comparability.

Advanced Filtration Methods

Filtration is applied at multiple points in DSP: depth filtration for clarification, sterile filtration before and after formulation, and virus filtration as a dedicated viral clearance step. Recent advances have targeted higher throughput, tighter pore size distributions, and new membrane materials.

  • Next-generation depth filters: Multi-layer depth filters with graded density and optimized charge can remove both large debris and fine particulates with higher capacities (up to 500 L/m²). Some designs incorporate active binding ligands to capture host cell proteins and DNA directly on the filter medium, reducing the burden on subsequent chromatography steps.
  • Improved virus filters: Virus-retentive filters are now available with log reduction values (LRVs) >4 for both small (<20 nm) and large (>50 nm) viruses. Newer designs use asymmetric membranes that maximize flow while maintaining high retention. For biosimilars, which often require robust viral clearance strategies, these filters allow manufacturers to achieve the necessary safety margins with shorter processing times.
  • Tangential flow filtration (TFF) for concentration and buffer exchange: Advances in TFF cassettes include more uniform flow distribution and linear scale-up, enabling predictable performance from bench to commercial scale. Single-pass TFF (SP-TFF) technology allows continuous concentration and diafiltration within a single unit, reducing equipment footprint and product hold times.

PDA (Parenteral Drug Association) provides extensive technical resources on filtration validation and viral clearance for biosimilar products.

Impact on Biosimilars Production

Collectively, these advances are reshaping the economics and technical feasibility of biosimilar manufacturing.

Cost reduction: Higher resin utilization, smaller column volumes, and reduced buffer consumption from continuous chromatography can lower DSP costs by 30–50%. Single-use equipment reduces cleaning and maintenance costs, while automation cuts labor requirements. Lower costs ultimately translate into more affordable drug pricing for health systems.

Faster development timelines: Platform DSP processes using single-use devices and standardized resins allow biosimilar developers to move from clone selection to clinical material in 12–18 months rather than the traditional 2–3 years. Because a biosimilar developer must perform extensive analytical and functional comparability with the reference product, a shorter manufacturing timeline means they can initiate clinical studies sooner.

Improved product quality and consistency: Real-time process monitoring and automated control minimize batch-to-batch variability. Consistent removal of impurities and aggregates ensures that the biosimilar closely matches the reference product’s purity profile, which is essential for regulatory approval under the comparability exercise (EMA Guideline on Similar Biological Medicinal Products; ICH Q5E).

Regulatory compliance: Many of the newer technologies—particularly single-use systems and continuous processing—align with regulatory expectations for quality by design (QbD) and process analytical technology (PAT). The ability to show a well-controlled, validated DSP platform simplifies submissions to the FDA and EMA. ICH Q5E explicitly emphasizes the need for robust control over downstream steps to demonstrate comparability.

Future Directions

While the progress to date is impressive, the DSP field continues to evolve rapidly. Three emerging trends promise to further enhance biosimilar production: deeper integration of process analytics, modular and personalized approaches, and greener processing methods.

Integration of Process Analytical Technology (PAT)

PAT refers to real-time measurement of critical quality attributes (CQAs) and critical process parameters (CPPs) during production. In DSP, non-invasive spectroscopic tools (Raman, UV, near-infrared) and at-line analytical methods (HPLC, mass spectrometry) can provide immediate feedback on product concentration, aggregation state, and impurity levels. The goal is to create adaptive control loops that automatically adjust process conditions—such as elution gradient or filtration pressure—to maintain quality within the design space. Several contract development and manufacturing organizations (CDMOs) have already demonstrated PAT-based control for biosimilar capture steps, and the industry is moving toward closed-loop continuous DSP systems where no manual intervention is needed. Biotechnology Advances publishes regular reviews on PAT applications in bioprocessing.

Modular and Personalized Biosimilar Production

As the biosimilar market matures, there may be demand for highly customized or small-batch production—for example, biosimilars for rare diseases or pediatric formulations. Modular DSP skids built from standardized single-use components can be rapidly configured to manufacture different products without extensive facility renovation. This “plug-and-play” architecture would allow a single facility to produce multiple biosimilars simultaneously or in rapid succession, lowering the fixed cost per product. While still in the early concept stage, modular DSP is being evaluated by several CDMOs for niche applications.

Sustainable Processing Methods

Environmental sustainability is becoming a key differentiator for biomanufacturers. Traditional DSP consumes large volumes of water (especially for CIP and buffer preparation), generates significant liquid waste, and uses resins that must be incinerated after their limited lifetime. Green initiatives include:

  • Buffer reuse and water recycling: In continuous DSP, buffers can be recycled through closed loops after purification, reducing overall WFI demand by up to 60%.
  • Resin reuse with intensive cleaning: New alkali-stable resins can withstand hundreds of cleaning cycles, reducing the volume of spent resin sent to landfills.
  • Greener solvents and ligands: Researchers are exploring bio-based eluents (e.g., arginine or histidine buffers) that are less toxic and fully biodegradable. Next-generation Protein A mimetics—non-protein ligands that are chemically synthesized—offer reduced environmental footprint compared to Protein A produced from bacterial fermentation.
  • Energy reduction: Single-use systems often require less energy for heating and cooling than stainless steel vessels, and continuous processing reduces hold times and associated energy for refrigeration.

These sustainability improvements not only benefit the planet but also reduce operating costs, making biosimilar production more economically viable in regions with limited water or energy infrastructure. The BioPharma Reporter frequently covers sustainability initiatives in the biopharma sector.

Conclusion

Downstream processing is the backbone of biosimilar manufacturing, and recent advances in single-use technology, chromatography, automation, and filtration have dramatically improved the efficiency, cost, and quality of these steps. By adopting continuous processing, real-time monitoring, and greener methods, biosimilar producers can accelerate timelines, reduce costs, and maintain the high standards demanded by regulators. As research continues, we can expect even more integrated and flexible DSP platforms that will further broaden patient access to affordable biologics around the world. The future of biosimilars is not just about lower prices—it is about achieving therapeutic equivalence with greater manufacturing consistency and environmental responsibility.