Presented by Cristina Peixoto
Cristina Peixoto is head of downstream process development (Animal Cell Technology) at IBET, Portugal.
IBET is a private, not-for-profit research institute located in Oeiras, Portugal, just outside Lisbon. The institute has performed extensive work in the fields of vaccines and gene therapy. The global vaccine market continues to expand, driven in part by the need for paediatric vaccines in emerging markets. There is a growing interest in the use of viruses to deliver gene therapies, with adenovirus being one of the most commonly used vectors.
IBET has also worked on projects with virus-like particles (VLPs). The US Food and Drug Administration (FDA) has approved VLP vaccines based on nonenveloped viruses. Although a number of enveloped VLP vaccines are in clinical trials, none have yet received FDA approval.
IBET has four strategies to improving downstream processing operations for emerging biopharmaceuticals. First, it may develop new processes and operating approaches, sometimes drawing upon historical methods from other process industries. Second, the institute studies new materials and purification matrices to understand how vaccine manufacturers can use them for virus purification. IBET’s third strategy is to gain a fundamental understanding of processes such as how viruses interact with synthetic membranes. Finally, IBET uses process modeling to optimize purification process performance.
By using those four approaches, IBET was able to develop a semicontinuous multicolumn process for the purification of adenovirus. The multicolumn process gave a sixfold increase in productivity and a 50% increase in recovery compared with a batch process. The DNA and HCP clearance was satisfactory compared with a batch approach.
|Operation Unit||ng DNA/dose||HCP (ppm)||ng Denerase/Dose||Step Recovery VP (%)|
|Initial bulk after cell lysis||1,260||240||8||-|
|Final formulation and sterile filtration||0.4||-||0.018||86|
Table 1: Adenovirus purification at 20 L scale; the specifications were achieved and global recovery yield is not compromised
In a second case study, IBET showed how to improve the purification of VLPs with a multicolumn chromatography approach that increased impurity clearance and yield when compared with the batch process. Operating two chromatography columns simultaneously with one system allowed steady-state operation and an improvement in the specific productivity of the process.
IBET has been able to improve the downstream processing of human mesenchymal stem cells (hMSC) by using a negative-mode expanded-bed chromatography step that provided for cell recoveries that are comparable with existing process configurations, while also improving protein impurity clearance by 10-fold. The hMSCs maintained their immunophenotype and metabolic activity following purification by expanded-bed chromatography.
In a final case study, IBET described a scalable, single-use platform for the purification of adenovirus. The downstream process used Sartobind®Q and Sartobind STIC® membrane adsorbers. IBET showed that the capacity of the Sartobind®Q was extremely high. The Sartobind STIC® membrane, which has a unique primary amine chemistry, was operated in flow-through mode to capture residual nucleic acids. The use of these disposable membranes allowed faster, simpler, and more economical processing than conventional membranes, further limiting the risk of cross contaminations.