Indeed, with the rapid advancement of cell and gene therapy (CGT), viral vectors—such as adeno-associated virus (AAV) and lentivirus (LV)—as well as plasmid DNA (pDNA), have become critical raw materials that occupy a central position throughout the entire CGT product development pipeline.

1. Higher virus clearance capability

• During the production of viral vectors, there is a risk of contamination by exogenous viruses or the presence of replication-competent viruses (such as RCA, Replication Competent AAV).

• Nanofiltration technology, with its precisely controlled pore size (typically ranging from 15 to 50 nm), can effectively retain viral particles while allowing target products—such as plasmids and small-molecule impurities—to pass through. As a result, it has become a critical step in the validation of virus removal processes.

• For plasmid DNA production, although the DNA itself is non-infectious, if it is used for transfection to produce viral vectors, it is essential to ensure that there is no contamination by exogenous viruses. Therefore, stringent nanofiltration control is also required in this case.

2. Protection of product yield and integrity

• Ultrafiltration/dialysis (UF/DF) is commonly used for concentration and buffer exchange, but high shear forces or improper membrane selection may lead to:

  • AAV capsid integrity is compromised;

  • Plasmid DNA undergoes cleavage or aggregation.

• Therefore, it is necessary to optimize membrane materials (such as regenerated cellulose or PES membranes with low protein adsorption) and operational parameters (transmembrane pressure, flow rate, and temperature) to strike a balance between flux and product stability.

3. Process Integration and Scalability Challenges

• CGT products are mostly produced on an individualized or small-batch basis, but the industry is evolving toward automated, closed-loop, and scalable platform processes.

• The nanofiltration/ultrafiltration system must be compatible with Single-Use Technology (SUT) and seamlessly integrated into continuous production processes, thereby reducing the risk of human intervention and cross-contamination.

4. Regulations and quality control requirements are becoming stricter.

• Pharmacopoeias of various countries (such as USP <1047>, EP 5.2.12) and guidelines from the FDA and EMA explicitly require validation of virus removal/inactivation steps.

• The nanofiltration step must provide virus removal data with a log reduction value of ≥4 log₁₀ and demonstrate that it has no adverse impact on the product’s critical quality attributes (CQAs).

Industry Response to Trends

• Development of new membrane materials: such as composite membranes with high throughput, low adsorption, and high-pressure resistance;

• Application of Process Analytical Technology (PAT): Online monitoring of parameters such as transmembrane pressure, turbidity, and UV absorbance to achieve real-time quality control;

• Modular equipment design: Supports linear scale-up from R&D (mL level) to GMP commercial production (L level).