Biotherapeutics require specialized manufacturing approaches when compared to synthetic chemical entities because the process used to synthesize the 3-D structure of the molecule defines its pharmacological activity and its associated value as a medical product. In practice, this involves the culture conditions of the host organism used to express the molecule and potential changes that may occur to the chemistry of the active components during recovery and purification. These changes can include both conformational changes in the structure as well as alterations due to protease and other enzymatic action. In these cases, moieties can be clipped selectively from the tertiary drug skeleton, or changes can occur in the degree of glycosylation due to enzymatic or chemical hydrolysis. Individually and/or collectively these can have a profound effect on the pharmacological activity and bio availability of the drug.
For protein therapeutics it is now routine to see examples of cell lines biosynthesizing products in the greater than 3 g/L range with examples of greater than or equal to 8 g/L now been reported at various conferences. With these levels of performance the types of options for manufacturing strategy both multiply and increase the potential for a paradigm shift away from conventional approaches. However, as with all industrial bioprocesses, the age old issue of recovery and downstream processing is there to bring stargazers back to earth since recovery of one’s favorite protein therapeutic is not so straightforward and the complexity for this has the potential to increase with increasing expression levels.
These points notwithstanding, during the preceding 10 years we have witnessed an explosion in the interest of using single use and disposable technologies for the production of a variety of biological products. In many respects, this is being driven by the increasing availability of new materials and components that the supplier industry has generated. This has allowed drug developers to explore new avenues that previously were only available and relevant to bench scale research and development scientists. The case for disposables in a therapeutic arena is now well established and includes many points. In terms of operating costs, using single use disposable technological solutions similarly offers some potential for a reduction in operating costs when it comes to manufacturing both clinical and commercial batches of material. This has been well documented elsewhere.(1) Some of these points are listed in Table 1. (Note this is not intended to be an all-inclusive list.)
Part of the attraction for the use of such systems has been the potential to use them to make small amounts of drug product that might be suitable for preclinical and clinical testing. Prior to the availability of these systems this would have only been possible using very substantial facilities to produce the material needed.
The net result of this situation is that universities, institutions and the plethora of small start-up companies have been able to generate GLP/GMP quality material for testing, thus allowing many new potential candidates to be developed. In some cases, this has been for marginal diseases and in others for potential biowarfare countermeasures than might not have been possible through a conventional approach.
However, in relation to vaccine manufacturing this is a very complex process that requires significant investment in process, equipment, facilities, development and operational capabilities and regulatory strategies. It is with this in mind that it is perhaps appropriate to look at the vaccine manufacturing sector in relation to the wider biotherapeutics industry in which single use disposable technologies have been deployed.
As one looks at the vaccine production and compares it to the whole biotherapeutics sector, it becomes apparent that it is perhaps more than a subset of the sector and instead a discrete area with unique issues. At the current time (for civilian vaccines) there is a split between egg-based production for vaccines like influenza and bacterial fermentation for products such as DPT (diphtheria, pertussis, tetanus). Both of these types of product are based on old technologies and processing strategies and so may not become future targets for single use/disposable platform based technology processes because of the very substantial regulatory process involved in obtaining licenses for these products with new processes. A large proportion of this would be to demonstrate clinical efficacy through new trials since showing equivalency for biological involving antigens (which may be a rather ill-defined process mix) is difficult.
However, for new virus particle based vaccines using cell culture methods, very strong possibilities exist to use new technologies to develop and produce them especially where potencies are high and production volumes necessary to meet these titers are modest.
If one looks at respondent’s data from a recent survey, Table 2 (1), which separates information about single use disposables as a subset of the whole biotherapeutics market, there are some interesting results even though some are common to the whole biotherapeutics sector. Some particularly important drivers for vaccine responders appear to be:
1. reduced start up time
2. reduction in cleaning fluids
3. a decrease in documentation
4. ability to get better sterile samples
5. reduction in hazardous waste disposal
6. more convenience using disposable filters
Currently many licensed bacterial vaccines are made in relatively large quantities requiring sizeable fermenters to generate sufficient quantities of antigens. Many are then purified and/or suspended using an adjuvant like aluminum hydroxide. Production costs for these antigens is quite large and the market price for many of these is extremely low, so manufacturers often campaign manufacturing to produce significant quantities of material which is then held at the bulk concentrate level. This may be a formulated bulk. These suspended formulations pose their own issues with disposable technologies and this casts a doubt over their sustainability for these types of product.
Considering some other factors, to provide better clinical convenience, the trend for vaccine availability has been to provide multivalent products such as DPT (diphtheria, pertussis, tetanus) rather than single valent antigen products. These single valent antigens are conjugated together to form the final product and it is these conjugation steps that are the aspect of the process which takes time and adds to the cost of goods for the product. In the case of vaccines like Prevnar®, one sees a very large number of individually processed antigens all conjugated together, which is extremely complex, making the total production cycle quite lengthy.
As a result, when one looks at this compared to the production of a bio therapeutic single entity like Remicade®, for example, the impact of a change in front end production technology for civilian vaccines has perhaps less impact than for a high potency single entity therapeutic which requires purification and formulation. However, in the case of special situations such as a pandemic or bioterrorist attack there may be some additional new variables which could make these types of change possible using single use/disposable options.
Robert House, President of Dynport Vaccine Company, believes that these technologies may well prove to have value as an additional production methodology for the manufacture of countermeasures for unknown threats. Currently the National Strategic Stockpile is amassing many countermeasures for unknown or identified threats but in a case where infrastructure is damaged in some way and conventional systems are unavailable then some limited production of agents for a localized deployment could be made using this type of approach in portable production factories. The advantages then would be logistical since this would enable one to turn on and initiate production quickly, to reload quickly, and changeover campaigns for different threats. For this application, Dr. House believes single use disposable systems are value-added in terms of providing a solution.
Why are single use systems gaining a foothold and what makes them important?
There’s a reason why industry has gravitated towards this type of approach and it has much to do with the idea that you can take a bench scale idea and translate it to a size using linear principles to produce enough of the product for it to be useful as a therapeutic agent. Most biotherapeutics are highly potent moieties and require very small amounts of active ingredient to produce a therapeutic dose. Also the therapeutic categories that these agents are designed to address are (with some exceptions), relatively modest perhaps with the exception of certain monoclonal antibody drugs and other fusion protein drugs.
However, does this still hold true for vaccine production? Perhaps the story is different for existing and new vaccines and for clinical and commercial manufacturing, for example. The same might be true for satisfying the needs for normal civilian requirements as opposed to a pandemic situation and/or the countermeasures required for bioterrorist threats and/or incidents as noted by Dr. House.
When it comes to vaccines it is not always quite so simple and straightforward as the volumes required for many commercial vaccines require sizeable volumes to produce consistently active antigens.
That said for the new vaccine products there is a move away from more traditional methods of production in favor of single use bioreactors/bag technology solutions. System suppliers such as Hyclone, Sartorius Stedim, and Xcellerex are at the forefront of these innovations and there are now many examples of vaccines being produced from cell culture using such systems.
Reviewing the field, we see that viral vaccines are often made using a variety of cell lines including: Vero, MDCK, MRC 5, BHK and CHO.
These are often Anchorage dependent cells lines using micro carriers as part of the production process. Frequently, production of these vaccines requires biocontainment level 2/3 conditions and production volumes tend to be quite modest in the 500 to 2000 L capacity size.
For these types of vaccines, single use disposable technologies have proven attractive for the following reasons:
1. due to the potential for fast turnover
2. due to a reduction in capital investment
3. due to simplified opportunities for bio safety containment
4. production in clean rooms and elimination of WFI
5. the potential for a reduction in downstream processing requirements and reduced handling
Following the H1N1 pandemic in 2009 influenza vaccines are now being produced by cell culture as are a number of other vaccines. In some cases, this has involved the rapid adoption of single use technology employing single use bioreactors and wave bags in addition to other modular single use recovery technologies. For example, Novavax produces a cell generated influenza vaccine using the Xcellerex XDR disposable system. Another example is also the Acambis ACAM2000 smallpox vaccine which is made in a Vero cell line using disposable production technology. Smallpox vaccine is also being made by the Danish company Bavarian Nordic using a modified vaccinia Ankara (MVA) called Imvamune using a disposable integrated platform based on the Sartorius Stedim platform. This material is being supplied as part of a 20 million dose ($2B) contract with BARDA destined for supplying the National strategic stockpile.
Rabies vaccine is being produced by Sanofi Pasteur using Vero cells in a 200 L scale disposable bioreactor from Nucleo PG-ATM1 and claim very significant time savings (up to 70%) in production using disposable systems.
These virus mediated vaccines are frequently produced using disposable systems since they frequently work well with anchorage dependent cells. Such systems can include stackable Cell Factories. Others such as wave bags provide gentle low shear environments that are suitable for microcarriers.
Recently GSK (GlaxoSmithKline) reported a comparison study for a viral vaccine manufactured using several systems (2)
1. Wave bag by GE
2. Sartorius Stedim culti bag STR
3. Xcellerex XDR
4. Hyclone SUB by Thermo Fisher
Using the systems GSK generated very attractive results and performed cost comparative analysis for a greenfield site using single use disposable systems versus a conventional vaccine plant.
The results of the study showed that for a disposable plant it was possible to:
1. generate a 35% saving on the facility investment costs
2. reduce the number of plant FTEs to 30% of a conventional plan
3. reduced direct costs on a cost per dose basis by 75% over conventional plant
4. generate an overall saving of 50% for operational running costs over conventional plant
These types of results appear to be common for these types of systems and have been reported elsewhere.(3)
The industry is clearly moving in this direction but the key question is whether or not this is sustainable and applicable as an across-the-board solution.
Fig 1. Illustrates Xcellerex single use systems in place with modular DSP units
for vaccine production.
So what are future trends?
Like all new technology platforms, it is likely that single use disposable systems will play an increasingly important role in the development and manufacture of vaccine products.
For all systems they will have an increasing role in supporting functions such as media and buffer bags, for filtration and some DSP operations including chromatography.
For mature licensed products it is unlikely that we will see a turnover in production methodology that sees replacement of conventional bioreactor technology since the process is heavily integrated as part of the licensing process. Owing to the fact that the vaccine business is an integrated component of the wider pharmaceutical industry which is very conservative, one is unlikely to see radical changes in technology platforms that might disturb operating performance that could stimulate renewed regulatory activity. That notwithstanding, it is conceivable that support functions connected with media preparation buffer preparation disposable filters and containers may be integrated as part of existing manufacturing methodology in such a way as not to upset or change existing technology platforms or stimulate renewed regulatory/licensing questions.
For these types of vaccine products where volume production is required, many large company players in the vaccine industry believe that there are significant gaps in experience both in terms of product capability, quality manufacturing issues at shop floor level and supply chain challenges that warrant caution before making wholesale claims about total replacement of conventional stainless steel manufacturing plants.
There is a lack of design and operational modeling experience as well as logistics in terms of how to operate a fully disposable commercial plant. For this reason, it is unlikely that regulatory agencies such as the FDA will readily approve processes and facilities using such platforms until sufficient experience and data is presented to assure both safety and reliability when compared to known conventional alternatives.
With little or no standardization in components and technologies at the present time there is a wave of opinion in the mature vaccine industry that some issues such as particulate generation from disposables as well as concerns about leachables and extractables may slow down the universal adoption for vaccine adoption that is predicted in some quarters.
For systems that require 30 to 40 turns per year, Tom Warf of BARDA believes that disposable systems are not cost effective. In terms of time to market they may be suitable for an initial launch but until some of the issues previously discussed are addressed, he feels the gaps in operational knowledge are too broad for reliable production. Operating above a thousand liters on a regular basis with so many moving parts and no mature operational supply chain model, the level of uncertainty and risk is too high for sustainable production of a volume regulated vaccine product.
For savings to become a real cost driver there needs to be a significant advantage to convert to a single use technology platform especially where the value of the vaccine product is high otherwise and the gains will rapidly evaporate upon the loss of a single batch.
On the bright side, propriety technology associated with non-Anchorage dependent cell lines for flu vaccine may drive success in the future although the large part of this acceptance will be based upon a demonstration of sustainable success at commercial scale and this will not come easily given the costs.
Other issues will surely include a requirement for closer collaboration between users and suppliers in relation to the plastic film materials used in single use disposable technology platforms as both current experience shows that this is by no means free of issues. With this type of factor in play, it is unlikely in the current regulatory climate that agencies such as the FDA will give carte blanche approvals without appropriate reassurance in terms of safety and product consistency.
In terms of small dose vaccine products and clinical supply manufacturing. There is clearly an opportunity here where the types of issues and concerns associated with bulk manufacturing become less of a problem and where the advantages of rapid changeover become truly material in benefit.
As noted earlier, for products such as those associated with threat countermeasures, there is more of an immediate opportunity as the constraints lend themselves more favorably to these types of approaches.
In conclusion, it is fair to speculate that the future looks bright for single use/disposable technology platforms vaccine production but it will not necessarily be universal until basic engineering quality principles are fully in place to guarantee supply chain availability and reliability. Like all biotherapeutics, vaccine production requires reliable sustainable systems to assure manufacturing quality and at this moment in time this is not in place for an idea that is still in its infancy.
1. 9th Annual Report & Survey of Biopharmaceutical Manufacturing, BioPlan Associates Inc, April 2012.
2.Disposable bioreactors for viral vaccine production. Jean Francois Chaubard et al
Biopharm; Nov 2010
3.Biological Products Manufacturing Challenges: Now and in the Future.
Mong,M. ISPE Managing knowledge through Science and risk assessment. Strasborg,France, 25 Sept-1 Oct 2009. www.ispe.org/cs/2009_strasborg_conference/pqli
Prevnar is a registered trademark of Wyeth LLC. Marketed by Pfizer Inc.
Remicade is a registered trademark of Janssen Biotech Inc.