Case study: seamless process transfer using an in silico bioreactor scaling tool

Introduction:

Cell culture transfer between scales, often referred to as scale-up or scale-down, is a difficult task, often requiring trial and error to predict physical characterization parameters for the bioreactors. Manual scaling is a time-consuming and error-prone process, and it can lead to delays in moving from small-scale to pilot-level production.

Cytiva Bioreactor Scaler is a software platform that predicts bioreactor settings, allowing users to perform in silico experiments that help define key process parameters. Scaler lets you scale right the first time, create less waste, and reduce risk. In this case study, scientists employed Bioreactor Scaler Pro, which offers features such as bioreactor vendor agnostic scaling, multi-day characterization inputs, and design space visualization, to efficiently scale-up a process from mL-scale to L-scale (production level).

Challenge: engineering antibodies at scale

IGM Biosciences (igmbio.com), a clinical-stage biotechnology company, is developing a new class of antibody therapies for treating cancer and autoimmune and inflammatory diseases. The company’s stated interest is to engineer and produce at scale novel antibody molecules that they believe will offer increased therapeutic potential.

In order to achieve an efficient scale-up from mL-scale to 200 L and 1000 L production-scale, the company needed to address the following challenges:

• Short timelines for scale-up to toxicology testing
• Limited experience transferring a process from a mL-scale to pilot-scale bioreactor
• Monoclonal antibody (mAb) product with very sensitive quality profile
• Preference for accelerated scale-up to Cytiva Xcellerex™ XDR-200 and XDR-1000 single-use stirred tank bioreactors without the need for technical, scale-up, and engineering runs

Outcomes:

• Using the Bioreactor Scaler Pro allowed for right-first-time scale-up to production-scale level
• Achieved successful scale-up without resource-intensive technical and engineering batches
• Scaling strategy reduced risk and accelerated timelines to the clinic

Process: Evaluating Cytiva Bioreactor Scaler Pro tool

Bioreactor Scaler Pro employs the following approaches to determine operating parameters in a bioreactor scaling process:

1. Agitation: The most commonly used scaling approach for mammalian bioreactor processes is to adjust the agitation rate to ensure similar power per unit volume (P/V) between different scales. The average P/V is used as a proxy for the local energy dissipation rate.
2. Match the oxygen transfer rate (OTR): It is a function of kLA (mass transfer coefficient for oxygen) and the driving force of the oxygen gradient between liquid phase and gas bubble. The tool calculates the aeration regime so that the OTR requirement of the cell culture is met.
3. Carbon dioxide removal: It is also important to consider the removal of carbon dioxide (CO₂) from the bioreactor. This is crucial, as accumulation of CO₂ in the bioreactor affects the culture negatively by impairing cell viability, potentially impacting product quality and making the culture more acidic. This can in turn cause a dysfunctional acid-base balance in the bioreactor environment. When investigating CO₂ removal in bioreactors, it was found that the most significant factor for CO₂ stripping was the total volumetric gas flow (1). Therefore, a constant volumetric gas flow is calculated across scales.

Results:

To achieve the scale-up and technology transfer to production-scale right the first time, IGM Biosciences used the Bioreactor Scaler Pro digital scaling tool to predict operating parameters for the XDR-200 and XDR-1000 bioreactor runs based on existing small-scale data from the Ambr 250 system from Sartorius. To test the potential of a digital scaling process from mL-scale to 200 L and 1000 L production-scale, they used the Bioreactor Scaler Pro tool to calculate the operating parameters for the agitation and the aeration regimes for the manufacturing-scale bioreactors. They then successfully applied these operating parameters in cell culture runs at scale.

First, with Bioreactor Scaler Pro, they calculated the agitation and aeration regime for the XDR-200 bioreactor. Second, they calculated the aeration regime by applying two major scaling criteria, i.e., maintaining a constant OTR and volumetric gas flow rate (vvm) across scales. Figure 1 shows an overview of the OTR and vvm values for multiple days in the process as an example of results from the Bioreactor Scaler Pro tool. The volume at inoculation in the Ambr 250 was 180 mL while the corresponding volume in the XDR-200 bioreactor was 150 L.

Fig 1. Overview of the OTR and vvm values for multiple days in the process.

The process was successfully performed at both 200 L and 1000 L production-scale, with comparable viable cell densities (VCD), viability, titer, metabolites, as well as desired product quality profiles across scales.

In summary, IGM Biosciences successfully performed scale-up in one step from the Ambr 250 to the Cytiva XDR-200 and XDR-1000 bioreactors. This may help enable the company to reach its clinical milestones quicker than initially anticipated using a traditional scale-up and technology transfer strategy.

Conclusion:

In conclusion, IGM Biosciences was able to perform a direct process transfer from the Ambr 250 bioreactor to the Cytiva XDR-200 and XDR-1000 bioreactors using a digital scaling strategy. This resulted in a significant acceleration of the program to toxicology stage testing and GMP production and by extension, to pivotal clinical studies. They achieved this acceleration without the need for technical, scale-up, and engineering runs, and the scale-up was successful the first time.

“We are a young company with an exciting product portfolio. For us, tox and first clinical production batches are on the critical line for the program. Therefore, we always strive to compress the timelines in this phase of the development. Using Cytiva’s Bioreactor Scaler Pro allowed us to be successful with the first batch in 200 and 1000 L scale, maintaining the desired product quality. This meant a lot for us reaching our clinical targets.”

Saloni Khurana, PhD, Senior Director, Process Development at IGM Biosciences

Learn more about digital bioreactor scaling

References

1. Sieblist C, Jenzsch M, Pohlscheidt M. Equipment characterization to mitigate risks during transfers of cell culture manufacturing processes. Cytotechnology. 2016;68(4):1381-401. doi:10.1007/s10616-015-9899-0.