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Rapidly emerging as an important therapeutic tool for the treatment of cancer, oncolytic viruses (OVs) can be specifically engineered for tumor cell selectivity, capable of lysing cancerous cells or delivering a therapeutic payload, while further soliciting immune response. The effectiveness of OVs is still largely being demonstrated in clinical trials, with now over 120 clinical trials utilizing OVs in 2021.
Although OVs offer significant advantages to patients, including opportunity to avoid more invasive treatment options such as the need for invasive surgical therapies or side effects of radiation therapy, this modality faces unique challenges surrounding development and manufacturing at required scale. As a result, careful consideration, and sometimes trial and error is required in developing robust processes and procedures for establishing efficient and productive processes required to ensure a commercially-viable product.
In our third release in our three part series, Chief Scientific Officer of Vibalogics, Kai Lipinski, explores a critical consideration regarding starting cell and virus seed banks utilized to generate Oncolytic Viruses through infection-based production processes. He highlights the many considerations that developers and manufactures will need to make early regarding these starting substrates at the center of OV production.
Cell and Virus Bank Generation for OV Production
For OV development and manufacturing, robust processes for cell and virus banking are essential for establishing well produced and characterized starting materials used throughout the life of an OV production process. Master cell or virus banks (MCB/MVSS) are derived from the expansion of a cell or virus clone, and Working banks (WCB/WVBs) can then be made following establishment of the completed master.
Avoiding safety and regulatory risks in bank establishment relies on producing high-quality banks under GMP conditions and robust quality control procedures. This will ensure appropriate starting material is in place for the production process as it progresses in scale and maturity in clinical and commercial phase.
Considerations in Planning
There are many considerations that OV manufacturers will need to be aware of when establishing cell and virus banks.
Determine parameters and bank size
Developers must carefully consider key parameters of the cell and virus banks for each starting material. A typical MCB will be established with 300–500 vials, with WCBs comprising 500–1000 on average. Comparable vial numbers would be expected for master virus banks. Further considerations to be reviewed include:
- Clear understanding of substrate source and origin
- Prior exposure to animal-derived components
- Clonality and well-characterized seed materials
- Bank size – projected future use and needs
- Minimum cell density or minimum virus titer
- Filling volumes
- Recovery after a freeze-thaw cycle
- Timeline readiness for GMP manufacturing
- Requirements of Permitting, Shipping & Logistics
Perform pre-GMP feasibility studies
Banking feasibility studies of starting materials prior to GMP production is an important step in risk mitigation to prevent unexpected occurrences later on. The aim of these studies is to make sure that cell expansion and viability, and system productivity is acceptable for GMP by performing a non-GMP verification run. This is performed by taking your cells through early culture through a number of passages, or by performing a full process simulation for the cell or virus bank.
Other studies can include ensuring dimethyl sulfoxide (DMSO) in cell and virus bank formulation does not pose unacceptable toxicity and determining if controlled freezing and thawing can maximize cell recovery.
Characterize cell and virus banks
There are strict regulatory expectations for the testing of production cell and virus banks. It is therefore essential that preparation of the sampling plan and release testing panel are also considered in the manufacturing of starting material to ensure compliance with relevant regulations.
The release and characterization panel will be dependent on the cell line, virus seed, and whether any animal-derived product has been used in production (including fetal bovine serum). Testing may also require non-infected control cells to determine presence of adventitious agents for full characterization (2-4).
It is recommended to consult with your regulatory agency to confirm the specified testing parameters of your substrates, especially if using a novel cell or virus. Common testing per regulatory guidance includes:
- Identity
- Microbial Safety (Sterility, Mycoplasma)
- Adventitious Virus Safety (InVitro/Vivo, PCR-based)
- Retrovirus Detection (TEM, PBRT)
- Testing for Specific Viruses of the Substrate Origin
- Performing Genetic Stability / Construct Confirmation (Restriction Digest, Sequencing)
Amplify Virus seed material
Occasionally, insufficient material is produced in the first production run, therefore manufacturers may consider a further amplification step for the virus seed during the starting cell expansion for the drug substance (DS). If this is required, the infectious titer of this material must be available at the time of batch infection.
Consider long-term storage conditions
In a best-case scenario, the culture medium used will be sufficient to ensure cell stability during freezing, storage at long-term, and thawing. However, in some cases additional excipients may be required. Other long-term storage considerations include determining the best containers for cell banks (typically cryovials) and viral seeds (cryovials or glass vials) and planning for additional needs of material used in the characterization and quality control testing as well as stability studies.
Key Conclusions
Cell and virus banks are valuable assets that must be generated to facilitate consistent production of OV products from the initiation of the manufacturing process and reaching into many years of commercial manufacturing. With many considerations being required to ensure quality and regulatory compliance, the expertise and experience provided by a specialized OV contract service partner can be invaluable.
Explore our Virotherapy Insider: Deep Dive into GMP Manufacturing of Oncolytic Viruses, to review the critical steps involved in OV development, manufacturing, testing, and the important considerations that must be made throughout.
https://vibalogics.com/resources/gmp-manufacturing-of-oncolytic-viruses-critical-steps-and-key-considerations
- Cook M, Chauhan A. Clinical Application of Oncolytic Viruses: A Systematic Review. Int J Mol Sci. 2020;21(20):7505. Published 2020 Oct 12.
- https://file.wuxuwang.com/yaopinbz/EP3/EP3_1998__13.pdf
- https://www.ema.europa.eu/en/ich-q5a-r1-quality-biotechnological-products-viral-safety-evaluation-biotechnology-products-derived
- https://www.fda.gov/media/76255/download
About Vibalogics
Since 2003, Vibalogics has operated as a specialized global Contract Development and Manufacturing organization (CDMO) offering process and analytical development, manufacturing, testing, and fill-finish services to innovators developing transformational virotherapy products. From its headquarters and commercial facility in Boxborough, MA, USA and operations in Cuxhaven, Germany, Vibalogics supports its customers in the development and commercialization of oncolytic viruses, gene therapies and viral vaccines.
