The Benefits and Limits of Disposable Technologies In Manufacturing Protein Therapeutic

• Rentschler Biotechnologie

Over the last decade disposable equipment has become an integral part of many biologics manufacturing processes. But it should not be forgotten that this revolution started more than 20 years ago in research labs with the introduction of small scale prepacked columns and the the single-use, wave-rocking bioreactor introduced in 1999.¹ Initially there was no complete large scale disposable process available covering the steps from cells to a fully purified drug substance, but rather hybrid solutions dominated the landscape. In the following years the whole value stream could be established in a fully disposable configuration.² But what are the driving forces to implement single use equipment? Obviously, cost, time, quality, and safety are important parameters to consider in this evaluation (Figure 1).

 Figure 1. Benefits and limits of disposables

Benefits

Let us first focus on the benefits that accompany the utilization of disposables. Typically, disposable facilities are more quickly assembled and require a lower capital investment and smaller footprint due to the reduced complexity derived from the absence of cleaning and sanitization installations. The eliminated need for CIP/SIP saves on the one hand time, in the form of faster product changeover procedures, and on the other hand labor for performing the steps and cleaning validation plus the savings from lower energy and water consumption. The lack of complicated utilities also lowers the cost and effort for qualification and maintenance. However, it must be taken into account that the full benefits of single-use only come into play when hybrid solutions still requiring some CIP/SIP abilities are omitted. Particularly in the context of a multiproduct facility the lower risk of cross contamination is contributing to the operational speed. Therefore single-use facilities have significantly shorter downtimes thus increasing efficiency and batch output per year. Factories combining disposable systems and modular construction can be up to one year earlier on-line than conventional facilities, thus starting the return of investment 25% faster.³

The simple reconfiguration and assembly of mobile and disposable equipment allows optimal customization of processes and increases the flexibility of the production site that is no longer configured to one type of process only. An additional level of flexibility and footprint reduction within downstream processing can be achieved by using modular instrumentation that can be applied for chromatography and filtration.

The currently implemented welding technology for coupling of upstream equipment and the availability of sterile connectors for downstream purposes including disposable sampling enables the establishment of fully closed systems thus reducing the overall microbial contamination risk. As a consequence, fully closed processes can run in lower classified cleanrooms additionally reducing cost for air conditioning utilities. Here the ballroom concept comes into play that relies on a large manufacturing area without fixed equipment or hard piping and minimal segregation of processing steps.⁴

Other drivers are connected to the current portfolio mixture of biologics. Despite the fact that antibodies are still the fastest growing and largest segment of therapeutic proteins, two other product groups have a huge impact on the utilization of disposables. The first group contains the examples of biosimilars. According to a recent publication, disposable facilities are attractive for biosimilars, because the market is shared between multiple biosimilar versions of the initial originator molecule, therefore not requiring a huge centralized production plant. A further advantage could be the fast and cost efficient expansion of capacity by simply copying the facility on site or by duplicating the disposable manufacturing site in geographic proximity to the end user, thus benefiting from lower transportation costs and potential governmental incentives to establish local biologics manufacturing.⁵

The other group of molecules highly amenable to disposable systems are those being used in indications that require less material to support fewer patients (e.g. orphan diseases) or treatments with highly active molecules with lower-dose, less-frequent or non-chronic administration. The first commercial fully disposable upstream process was approved to manufacture Velaglucerase alfa, an enzyme replacement therapy treatment for the rare Type 1 Gaucher disease.⁶ This process is a continuous process, indicating a potential niche for single-use. Continuous processes could be one way to escape the scale limitations of disposable systems but require a cell retention device either based on sedimentation or filtration. Small scale fully disposable continuous processing represent a paradigm shift towards a potential facility of the future.⁷

Limits

Currently the largest commercial available bioreactors have a capacity of 3500 L.⁸ The size restrictions are mainly attributable to the achievable oxygen transfer rates that depend on the maximum tolerated pressure of the welded seams and the energy transfer of the mixing system consisting of impellers and spargers. Furthermore the insulating plastic material of the reactor bag blocks efficient heat transfer thus reducing the effect of the thermal jacket. Scale limits on the downstream side can be observed for column dimensions, and flow rates of single-use chromatography skids. Currently the largest available prepacked column offers a 60 cm diameter.⁹

In order to guarantee interruption-free procedures, a sufficient inventory of single use material must be established on site in order to balance long delivery lead times from the suppliers. A consolidation of suppliers may potentially lead to a monopoly situation that could bring the users under a cost pressure and dependency from a single source. However, a too large inventory might not be used up during its shelf live thus causing additional cost. The shelf life is dependent on the stability of the plastic ware and its sterility. Sterility is an important issue, as the disposables arrive sterilized for immediate application forcing the end user to rely on the supplier’s quality assurance. A re-sterilization of larger assemblies at site is usually impossible as the available methods like autoclaving or treatment with steam are not applicable. Therefore, a careful balance between storage on site, consumption, delivery and lead times must be maintained. The initial savings in capital investment might at some point be exceeded by the repetitive cost for plastic ware and single-use consumables. Furthermore there will be costs involved in the waste management of huge amounts of disposables.

Time saved during the reduced efforts for installation qualification might be needed for supplier audits, qualifications and the collection of material certificates instead. Another complication is the still low level of standardization and compatibility of disposable materials from different vendors. Therefore the Standardized Disposable Design (SDD) initiative has started to generate a database of more than 250 assembly designs from different sources.¹⁰

Extra work is needed for evaluating the leachables and extractables risk that could represent the most critical class of impurities which are not present as a factor of concern in stainless steel facilities. Some standardization of testing has been introduced during the last few years¹¹ as it became apparent that some compounds from singleuse bags could negatively impact cell growth.¹² Therefore it seems worthwhile to establish a standardized assay that proves that the tested material has no negative influence on the cell behavior and is comparable to other products.¹³ Other risk factors derived from the use of disposables are particulates as leftovers or impurities from production which are critical in the final protein manufacturing steps where no further filtration is present.¹⁴

The lack of hard piping requires transportation of large volumes of buffers in mobile containers. This is not value generating work which might additionally create a new source of errors by connecting the wrong buffers and could be a safety challenge as heavy weights are moved around and connecting tubing might be generating trip hazards. Furthermore this buffer transport and storage impacts the dimension of walkways and storage areas as well as the static prerequisites of buildings. Alternatively just in time production and delivery to the site of use could eliminate some space requirements but puts more pressure on logistics.

The multiple manual procedures when placing bags into containers or bioreactor frames can increase the risks of leakage thus compromising the bioburden safety of the overall process. But leakage can also be caused by failures during bag manufacturing which are hard to detect when the holes are located at the incomplete seams or punctures being introduced during transportation. Further issues in the manipulation can occur when connectors or tubings are ripped off during transportation of full containers or mixing vessels. Other quality issues related to single use materials comprise the separation of film layers.

Conclusion

In the meantime, disposables have been widely applied by the bioprocessing industry. But still the fully disposable process from cell to drug substance is a relatively rare approach as the mainstream is represented by hybrid processes mixing steel and plastic equipment or large scale manufacturing with steel only facilities. Early singleuse adopters were contract manufacturing organizations (CMO) as they extraordinarily benefit from the improved flexibility, faster product turnover rates, lower risk of cross contaminations in multiproduct facilities and better and faster returns on investments. In the case of product owing companies it is probably more important to have a facility suitable to the type of product. That means for certain molecules like biosimilars or particularly drugs with small patient populations disposable processes might be advisable. The current renaissance of continuous processes might further fuel the trend of single-use applications, as the scale limitations are no longer relevant. It will be interesting to see if some of the restrictions of disposables will be overcome by intelligent solutions of suppliers. A similar impact on the future of single-use processes will be derived from the currently ongoing standardization initiatives.

References

1. Singh, V. The Wave Bioreactor Story. Wave Biotech LLC, Somerset (2005).
2. Shukla, A. & Gottschalk, U. Single-use disposable technologies for biopharmaceutical manufacturing. Trends Biotechnol. 31, 147–54 (2013).
3. Levine, H. L. et al. Single-Use Technology and Modular Construction. Bioprocess Int. 11, 40–45 (2013).
4. Wolton, D. A. & Rayner, A. Lessons Learned in the Ballroom. Pharm. Bioprocess. 34, 1–5 (2014).
5. Campbell, J. & Ribault, S. Single-use technology enables flexible factories. Bioprocess Int. 14, 60–64 (2016).
6. Shire. Shire Announces European Approval Of Manufacturing Facility For VPRIV^® (Velaglucerase Alfa). Press release (2012).
7. Klutz, S. et al. Developing the biofacility of the future based on continuous processing and single-use technology. J. Biotechnol. 213, 120–130 (2015).
8. Caffrey, K. & Smith, E. ABEC Introduces the Industry’s Largest Single Use Bioreactors. Press Release (2015).
9. Rogge, P., Müller, D. & Schmidt, S. R. The Single-Use or Stainless Steel Decision Process. Bioprocess Int. 13, 10–15 (2015).
10. Wolton, D. A., Heaven, L., McFeaters, S. & Kodilkar, M. Standardization of disposables design. Bioprocess Int. 13, 21–23 (2015).
11. Ding, W., Madsen, G., Mahajan, E., O’Connor, S. & Wong, K. Standardized Extractables Testing Protocol for Single-Use Systems in Biomanufacturing. Pharm. Eng. 34, 1–11 (2014).
12. Hammond, M. et al. A cytotoxic leachable compound from single-use bioprocess equipment that causes poor cell growth performance. Biotechnol. Prog. 30, 332–337 (2014).
13. Tappe, A., Cutting, J., Hammond, M. R., Nunn, H. & Kline, S. The case for a standardized assay to test suitability of single-use systems in cell culture applications. Bioprocess Int. 14, 10–13 (2016).
14. Johnson, M. W. Understanding Particulates in Single-Use Bags. Bioprocess Int. 12, 22–28 (2014).