Currently, cell and gene therapy commercial operations use Batch bioreactors which comprise a fixed volume and a limited number of cells and result in low vector yields and low vector stability at 37°C. Internal and published studies from commercial operations achieve total lentiviral vector yields around 2E+10 TU/L. Most recently, perfusion bioreactors have been adopted by commercial manufacturers which perfuse fresh media and remove waste materials at a controlled rate lead to higher cell densities as well as which results in increased vector production.

TFF Perfusion bioreactors using low shear recirculation pumps have been used to increase HEK293 cell densities up to 80 million cells per mL by continuously perfusing fresh media and removing waste metabolites. While standard hollow fibre filters used in ATF perfusion trap viral vectors inside the bioreactor, the tubular membrane VHU filter module together with a low shear Levitronix^® pump allows the continuous transfer of unstable vectors such as Lentivirus to 2-8°C which leads to improved stability of the vector and results in higher yields and improved vector quality compared to batch processes. Total yields up to 6E+11 TU/L or 30-fold higher than batch have been achieved with stable producer cell lines.