21EBTA Novel Engineering Biology Solutions to the Production of Lentiviral Vectors by In vitro Assembly for Gene Therapy

Cell and gene therapy promises great benefits to patients covering a wide range of serious diseases. In the UK alone, clinical trials for such advanced therapy medicinal products (ATMP) continue to rise annually according to the Cell and Gene Therapy Catapult clinical trials database: in 2019 the increase was about 45% and in 2020 the increase was 20% from previous year. According to the Catapult, this represents about 12% of all ATMP clinical trials globally making the UK a global leader in this field of biomedicine. These advanced therapies require carriers to deliver the genes of interest that can help in combatting these diseases.

One of the most commercially promising gene delivery systems are lentiviral vectors (LVs). In the Catapult database, LVs are most commonly used for ex-vivo therapies although early phase studies are also reported for in-vivo therapies. The genes that LVs carry are relatively large and with pseudotyping, i.e., dressing up the LVs with proteins that envelope the surface of the viral particles, LVs can be designed to enter a broader range of cells and deliver the gene of interest. The supply of these gene vectors (i.e., gene carriers like LVs), however remain a major bottleneck in the development of cell and gene therapies (UK Government Report: 2016 Advanced Therapies Manufacturing Taskforce Report).

Cost-efficient gene therapy vector manufacture is needed to realise wide applications of and easy access to cell and gene therapy with recommendations from the 2016 ATMP Taskforce Report to invest in viral vector manufacturing capacity and capability. To address viral vector supply issues during commercial manufacture, vector production methods need to change to an industrialised process that is robust and consistently delivers high yielding gene vectors. There is a huge incentive to improve lentiviral vector production through engineering biology. This can be achieved via novel construction of LVs by bringing together the different major parts of functional vector: the viral particle and the envelope proteins. The establishment of these techniques to create and characterise this new mode of LV production system could improve recovery yields during bioprocessing. The proposed research, which builds on recent developments in engineering biology of LVs, aims to create and characterise the production, recovery, and purification of these novel LVs.

The cost-effective, simplified platforms for LV manufacture and associated technologies we develop in this work will help improve bioprocessing efficiencies. Therefore, the increase in product yield will eventually help to meet demand for LV supply. This will increase availability of gene vectors and make gene and therapies easier to reach the market. This has a huge potential benefit for many patients. More broadly, LVs are also widely used outside gene and cell therapy field from basic biology to drug screening. Our innovations in LV technology will support a wide range of research and development, therefore generally contribute to biological science and technology innovations.

The aim of the research is to create and characterise a novel lentiviral vector (LV) production system for robust bioprocessing. Our proposed project will focus on the engineering, production, concentration, purification, and formulation of these novel LV products. The proposed research builds on three recent developments in engineering biology of LVs: (1) the establishment of stably produced bald (devoid of viral envelope proteins) LVs; (2) the cell-free, in vitro assembly of pseudotyped lentiviral vectors; and the (3) genetic encoding of biotin mimics in vector packaging cell lines resulting in the establishment of an affinity-based LV purification.

We have shown that it is possible to produce functional LV by mixing two components, namely bald/envelope-less LV and VSV-G protein vesicles (Tijani, PMID: 30182034). We will investigate production scale up of these components using bioreactor technology for adherent cells, optimisation of formulation of these components and their mixture, and integration of downstream processing (DSP) with the two-component admixing process. In order to enhance the DSP, we will incorporate biotin mimetic labelling of bald LV and VSV-G vesicles by engineering producer cell lines, which will allow a single step purification and concentration of the product by an affinity separation as previously described (Mekkaoui, PMID: 30547049).

Advanced bioreactor technology for adherent cells will be used for the scalable production of LVs. The DSP techniques we will examine for the development of robust, efficient and scalable downstream recovery and purification steps include tangential flow filtration and biotin affinity separation.