By Edgar Piskernik, Peter Thaler, Harald Volland and Estelle Zelter

As the market for biopharmaceutical products rapidly expands, pharmaceutical and biotechnology companies are increasingly turning to Contract Manufacturing Organizations (CMOs) to help streamline their processes. With numerous projects in pipelines simultaneously, outsourcing production to CMOs allows pharmaceutical companies to free up valuable resources and help keep new projects moving forward.

The benefits of outsourcing development and production phases are many and include:
* Eliminating capital investment in potentially underutilized production capacity
* Eliminating long lead time to build and validate a cGMP manufacturing facility
* Avoiding the development and scale-up phases in cGMP environment
* Improving flexibility and speed

In order to maintain successful relationships with their clients, CMOs must ensure completion of projects on time and within budget, and at the high quality demanded by clients.

One main challenge CMOs face today is shortening the time between development and the first Phase 3 production step. In general, we try to shorten time of a product in plant (reduce campaign, focus on validation batch and reduce engineering batch) so any solution improving speed is essential.

In the last few years, process development efforts have led to cell culture productivity increase (titers > 1g/L). As a consequence, early downstream processing steps are more challenging and may sometimes appear to cause a bottleneck.

Depth filters are commonly used for the primary or secondary clarification and have streamlined this step in the process. However, there are still pros and cons to using this traditional technology. Format limitations persist, heavy housing domes require cranes/hoists, pre-use flushing and clean-in-place (CIP) use excessive fluids, and CIP validation work is time consuming.

As a solution, Millipore Corporation has developed a modular, disposable and scalable clarification tool in order to meet CMOs’ requirements of ease of use, scalability, safety and flexibility. Millipore’s Millistak+® Pod platform consists of an expandable holder and modular filters that overcome many operational limitations of traditional stainless steel housings (Figure 1). Pod filters are single-use which reduces the need for CIP procedures. This minimizes costs associated with water usage, cleaning and validation.

The proven filtration performance of Millistak+ HC filter media provides greater flexibility and productivity, improves safety and process economics, and reduces cycle time.

Sandoz Kundl evaluated the Millistak+ Pod filter system in the clarification of a recombinant protein from E. coli fermentation. In the past, Sandoz had used traditional stack disc filters in housings in their clarification steps.

In this study, a Millipore application engineer was involved from the early stage of each step of the process to support the development work. The objective was to clarify a centrate of E. coli fermentation broth. Millistak mini capsules were first used for screening and early sizing. The appropriate media and grade was selected. A pilot step was then performed with a 1.1 m2 Pod and 13 L of product. Confirmation with 1 m2 Pod system was conducted in the manufacturing area by the Sandoz team. This pilot stage was important as the Sandoz team was able to manipulate the system themselves and really get used to working with it. In addition, the clarification step was conducted in parallel with the classical lenticular format, with which more than 100m² of filter area would have been necessary.

Discussions then led to the agreement to incorporate the Pod system into the manufacturing step. E.coli centrate (3000 L) was stored in a holding tank. Thirty Pod modules of 1.1 m2 Millistak-A1HC media (for a total of 33 m²) were installed in a three-rack Pod holder. The whole assembly was flushed prior to use with purified water for about half an hour. The feed was then pumped through the Pod system and finally filtered onto a 5 x 20” 0.2µm sterilizing-grade filter. A flush operation with purified water was conducted post use to recover a maximum of product, and was followed by an air blow down at 1 bar. The filtrate quality from the Pod system was excellent and handling of these disposable filters was easy.

Sandoz has since run several campaigns of numerous batches with the Pod system and obtained excellent results on all batches. The performance of the media, in addition to the advantage of a disposable system, led to increased confidence of the Pod filter technology. The technology was therefore implemented in several other processes as well. The scale-up data provided at early lab and pilot stages were appropriate and the protection of the existing sterilizing-grade filter was very good. Time was saved by avoiding CIP of a housing and analytical control of the cleaning.
Ease of Use

3-rack system filled with 30 x 1.1 m2 Millistak+ Pod filters.
Installation and set up of the Pod system at Sandoz was easy and straightforward. The small footprint saved valuable floor space and the lightweight design eliminated the need for hoists or high ceiling heights. In addition, the holder was on casters which allowed for easy assembly and movement. The operators were trained quickly on the process scale Pod system and appreciated its ease of use.

The hydraulic pump system for the Pod module installation was convenient and robust (Figure 2). Sandoz was confident that the right pressure set point was reached. The pump system eliminated the risk of breaking the filter as has happened in the past with lenticular filters when they are over-tightened.

The design of the Millistak+ Pod system allowed the units to be drained before change-out resulting in lighter devices that were easier to move. In addition, the design and construction of the Pod system can reduce hold-up volume from 30 - 60% over typical configurations of lenticular discs, providing an increase in product yield.

CMOs offer support from preclinical trials up to full scale manufacturing. They process batches from a few liters up to several thousand liters and therefore require a tool with a tremendous amount of scalability.

The Pod platform consists of three Pod filter sizes and two expandable holders. Pod filters are available with 0.11 m2, 0.55 m2 and 1.1 m2 filtration areas. The pilot scale holder can accommodate a single 0.11 m2 Pod filter up to five 1.1 m2 Pods, while the process scale holder expands to hold from five to thirty 1.1 m2 Pod filters.

Because both holders use the same Pod filters, linear scale-up and the flexibility to meet changing process needs is easily achieved. Without changing hardware, the system can be run in serial or parallel configurations, combining two different grades of filtration in one single operation, to meet specific process and batch size requirements of 20 to 12,000 liters.

The development plant at Sandoz is currently equipped with the Pod pilot holder. Once a new project is defined and optimized, moving to the full process scale Pod holder will be simple.

Front view of 3-rack Pod system and hydraulic pump system.
No part of the system (the Pod filter, the adapter) comes into contact with the product. In addition, the self-contained design of the Pod system protects operators from exposure to biohazards, eliminates maintenance and requires no cleaning.

The unique design of the disposable adapters easily connects the Pod filters to the process piping. With the compact, modular design of the Pod system, productivity can be increased, cycle-time is shortened and costs are reduced.

Flexibility is a key parameter for CMOs. Most CMOs offer extensive capabilities in the area of mammalian cell culture as well as in the area of microbial production. Generic platform processes are needed to allow rapid transfer of the process to pilot scale or directly to manufacture.

The Pod system is flexible in terms of surface area and media grade and can be adapted to new products.

Pod expendable devices are available in four different Millistak+ HC media grades specifically developed to accommodate any type of biological feed stream. Millistak+ HC filters incorporate multiple graded density layers of adsorptive positively charged depth filter media. The successively tighter multimedia layers reduce particle loads when cell culture fluids flow through the filter. The more retentive Millistak+ HC media grades incorporate an additional layer of microporous cellulose membrane to protect downstream equipment and membrane filters.

The Millistak+ Pod system is ideal for a wide variety of primary and secondary clarification applications, including cell culture, yeast, E.coli lysates post centrifuge or E.coli refolds. Millistak+HC media is efficient at processing cells culture fluids, which often vary widely in composition and particulate load.

Disposable manufacturing is a significant industry trend that offers important advantages, including reduced cleaning and validation requirements and increased flexibility. In an age of time to market imperative, the Millistak+ Pod platform addresses many of the biopharmaceutical industry requirements where speed, quality and economics are the key for success.

1 Sandoz Kundl, Biochemiestrasse 10, A-6250 Kundl / Tirol Austria 2 Millipore Corporation, 290 Concord Road, Billerica, MA 01821