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Mar 1, 2006 (Vol. 26, No. 5)

Purification Woes Upstage Upstream Gains

Cooperation Is Necessary to Break the Downstream Logjam and Reap the Benefits

  • New technologies in upstream biopharmaceutical production continue to increase yields and protein product quantities at the bioreactor. However, these higher titers, larger yields, and shorter production times are not always making it through as end-product.

    As improvements in upstream manufacturing continue to show results, the slower advancements in downstream purification have created a bottleneck (see GEN, January 1, 2006, p. 1).

    The mass of product that needs to be recovered is getting higher and higher, says Joanne Beck of Abbotts (www.abbott.com) bioresearch center. The entire purification train is slowly becoming a bottleneck.

    Biopharmaceutical manufacturing capacity and production purification problems are adversely affecting about 51% of biopharmaceutical developers and contract manufacturers, according to the 3rd Annual Report and Survey of Biopharmaceutical Manufacturing by BioPlan Associates.

    As you get higher titers and lower volumes, youre going to get higher biomass to deal with as well, pointed out Duncan Low, Amgens (www.amgen.com) scientific director of process development at a conference of biomanufacturers in Boston. He noted that, in the 1980s, titers from 550 mg/L were common. In the future, volumes of 1020 g/L are expected.

    However, an exponential improvement in titer volumes may not lead to greater overall efficiencies, because increased biomass will exceed the capacity of downstream protein purification, especially the chromatography and filtration steps. This will lead to repeat chromatography steps for high-volume bioreactor runs.

    At a certain point, the number of chromatography cycles required will outstrip all the gains achieved by the greater bioreactor capabilities. Its mass-driven, explained Low. If you want to put 28 kilos in a column, youre going to need one thats twice as big as one that would take 10 kilos.

    As Low suggested, downstream bottlenecks are raising industry eyebrows with the protein purification process receiving considerable attention. More than half of the respondents to the BioPlan survey of 187 manufacturers worldwide, indicated that there was an opportunity to improve this step. For an industry that has annual returns of $87 billion and depends on these downstream steps, success could result in millions more in returns.

    Chris Conroy, Acambis (www.acambis. com) supervisor of viral manufacturing, agrees. He sees trouble on the horizon for protein purification. With these higher titers and more biomass, purification is going to become considerably more difficult in the future. Its simply harder to filter these volumes and put them through the columns.

    In the production of most biopharmaceuticals, retaining the biological activity of large volumes of proteins and maintaining consistency is critical to manufacturing success. The high level of consistency required is both expensive and unwieldy. Moreover, the processes that are proven on the lab bench must work as well, scaled-up to the production floor.

    Protein purification weighs in at about 50 percent of the workload of making and formulating the product, says Erica Shane, director of process biochemistry at Medimmune (www.medimmune.com). There is room for improvement, especially with cell cultures that have higher titers.

    One manufacturer surveyed felt that the biggest problems in the capture step are the binding capability of the protein A and the specificity of protein A for Mabs. The multitude of different properties makes the pretreatment of the purified broth to the column a significant issue.

  • Areas of Improvement

    The areas in need most of improvement are the clarification and microfiltration steps, ultrafiltration, affinity chromatography, and anion and cation exchange chromatography. This is not surprising given the higher degree of equipment reliability, required in processing biopharmaceutical products. In biopharmaceuticals, each batch is valuable, and the consequences of a manufacturing failure are costly.

    The filters themselves are a considerable limiting factor, said survey respondents. Filter fouling can be particularly troublesome because it can lead to the aforementioned losses, as well as longer run times, possible product safety issues, and the resultant regulatory exposure.

    Filter cost is another area that manufacturers point to as a major concern. Nearly 64% of the respondents surveyed felt that cost was an issue. However, it was interesting to note that only 11% of respondents felt that cost was a significant problem. This suggests that, since cost isnt a very significant issue with a majority of people, performance may be a more significant problem.

    Filters are some of the most expensive raw materials and any way we can reduce the number of filters used, reduces our costs, says Shane.

    Another bottleneck that may prove more difficult to overcome is that of the contract manufacturer. When the in-house capacities are overloaded, and a producer needs the assistance of a contract manufacturer, the protein purification capacity of the contractor may determine where the outsourcing goes.

    If you have to go to a contractor, the rate limiting factor is the size of their purification area, says Shane. This may prove to be a need that opportunistic contract manufacturers can take advantage of by adopting newer technologies to enable them to take on producer overloads.

  • Potential Improvements

    One improvement that may rupture the bottleneck is membrane chromatography. Currently in use by many in the upstream analytical phases, membrane chromatography has many benefits over column chromatography, including good flow rates, high capacities, and newer membranes that have produced sharper resolutions.

    Membranes are faster than columns, says Ian Sellick, director of marketing of Pall Life Sciences (www.pall.com). Membranes are the future of chromatography and soon they will be part of the main purification stage. Also, Sellick says that membranes can do in minutes what columns do in hours.

    The future purification solution that I find most exciting is disposable membranes, adds Conroy. These large disposable membrane columns increase speed, as well as flow rate. He notes that some of the efficiency comes as a result of the prepackaged kits that eliminate the repacking required by columns so that rinsing is all thats required.

    Recent developments in technology, such as high capacity chromatography and membranes, came as the result of vendors working with manufacturers to understand their processes and needs. Shane points to several instances where vendors came to Medimmune to understand what they were looking for in the purification process to develop new products and technology. One instance involved the need for a filter that could double as a buffer. Today, several vendors offer filters that have fast fill rates with buffers with low-clog solutions.

  • What the Future Holds

    To improve their downstream performance, many manufacturers are increasingly focusing on improvements to reliability and consistency of their production.

    In a licensed GMP production facility a companys implementation flexibility can be limited. The improvements typically need to happen early in process development. According to one manufacturer, if you really want to improve commercial output, start early and focus on continuous improvement.

    Many of these changes will be initiated in the process development area rather than in commercial production. Many manufacturers filed for their processes more than 10 years ago; to make production changes requires substantial effort to stay in compliance.

    On the bright side, there are a number of protein A column alternatives in development that promise to perform better, use higher pH, are more durable and more cleanable, yet have similar efficiency and better binding capacity. These factors will be critical in the future.

  • Solution through Cooperation

    One way to break the bottleneck and reap the benefit of upstream gains is through vendor and manufacturer cooperation. They will need to partner to reduce the operating costs of filtration, improve yield, and assure continued improvements and cost reductions.

    A roadblock to this may be in the difficulties associated with intellectual property. In biopharmaceutical process development, many manufacturers would like to work together more closely. Resolving the intellectual property roadblock may be the key to breaking through current and future downstream purification bottlenecks. Until then, protein purification may be the biggest obstacle on the road to higher yields.



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