Cynthia A. Challener is a contributing editor to Pharmaceutical Technology.

Cynthia A. Challener

The choice of possible mixing and blending equipment for the preparation of solid and semisolid dosage formulations is extensive. Therefore, the first step in a successful mixing process is to select the most appropriate equipment. “The choice of mixing equipment is greatly dependent on the products/materials being mixed. Therefore, good blending and mixing equipment will be determined by how suitable the configuration of the blender is for the powders being mixed,” says Wilf Sangüesa, product manager for Quadro Engineering’s IDEX Material Processing Technologies Group.

Specifically, good blending equipment for solid dosage formulations offers a large filling span at constant blending performance and provides homogeneous distribution of the API within the formulation using gentle blending conditions that do not lead to destruction of the particles or granules, according to Tobias Borgers, head of marketing for L.B. Bohle. Adds Pär Almhem, president of ModWave: “The mixer or blender must achieve the specified quality of the final product in a very short time using a very stable and repeatable process and with minimal residual product in the machine and good cleanability.”Some of the different types of mixing equipment used for the preparation of solid and semisolid dosage formulations include ribbon and tumble blenders for dry-powder blends, multishaft mixers for transdermal drug/adhesive mixtures, and double planetary mixers for the processing of wet granulations and viscous gels. “Performance characteristics, such as the shear input, cleanability, ease of discharge, flexibility in terms of batch size and viscosity, vacuum capability, temperature control, and scalability, vary from one mixer design to another and depend on the properties of the particular application as well as the mixing objective itself,” explains Christine Banaszek, an application engineer at Charles Ross & Son Company.

Flexibility is becoming increasingly important as well, notes Sangüesa “The better blending systems are the ones that are able to mix a wide number of powders so that fewer blenders are required in a given facility. Because blending can be a costly and labor-intensive step, equipment also must be efficient and provide the maximum yield possible with few trap points and proper surface finishes that allow the maximum amount of powder to flow out upon completion of the mixing process. Systems also need to readily integrate with upstream/downstream equipment.”

Sangüesa has observed that the drive to reduce the number of components needed to perform a task has been greatly influenced by rising costs for not just capital investment, but also by increasing processing costs, such as cleaning, maintenance, space constraints, safety, product losses, and so on. One solution has been the introduction of blending systems that utilize the same holding recipient (i.e., intermediate bulk container, or IBC) to do both blending and at its completion, product transfer. “In the past,” he says, “powders had to be loaded from an IBC or Supersack to a blender and then, once the mixing was completed , transferred back. Each step adds the potential for powder losses, segregation, operator exposure, higher space needs, and more pieces to clean and maintain. By having the powders inside the IBC, blending them without further handling and then taking the IBC to its next process, many of these concerns and costs are greatly reduced. Companies, such as Matcon have innovative approaches in this area.”

New mixer designs have also been introduced that have also had an impact. For semisolid formulations, for instance, Banaszek points to double planetary mixers with improved mixing efficiency and diminished contamination risk. “We have developed a custom-fabricated and sealed gearbox that protects the drive assembly from all product contact, including solvent vapors. Newer design helical blades also prevent the ‘climbing’ issue commonly experienced with traditional rectangular planetary stirrers. These blades generate a unique mixing action; each sweeping curve firmly pushes batch material forward and downward, keeping it within the mixing zone at all times,” she notes.

Ekato Corp. has also introduced new technology for highly viscous materials, such as those used for the production of softgel and hard shell capsules. “Softgel capsule formulations often undergo several physical property changes during mixing, such as from a liquid to a paste or even a solid-like material and then back to a paste again. Such systems require very powerful mixers,” observes process systems sales engineer Rainer Engenhart. The company has adapted its high-torque, high-viscosity mixers to meet the specific sanitary requirements of the pharmaceutical industry and developed customized solutions that include ergonomic loading of solids materials with a low melting point into a hot vessel, elevated designs that allow for gravity transfer of the finished bulk into transfer tanks, and in-place cleaning systems for quick changeovers from one formulation to another.

Most importantly, the systems address the critical needs for high shear mixing combined with excellent de-aeration in both the shell and fill materials, according to Engenhart. For capsules, if air bubbles remain in the shell material, they can create pinholes that can be sources of potential leaks, while entrapped air in the fill materials can cause fill weight issues. In oral strip products, even a tiny amount of trapped air can lead to the generation of large pores during the drying process. In addition, in capsules, if moisture remains in the fill material, it can migrate from the interior and cause degradation of the water-soluble shell, leading to a loss of integrity.

“We have found that the solution for good de-aeration is to bring the bubbles to the surface while pulling a vacuum on the system to remove the air. Because air bubbles can’t move in the very viscous materials used for the production of softgels, we developed a shear laminar flow impeller that gently moves them to the surface (without breaking them into smaller bubbles), where they are removed under a strong vacuum. “

Other developments have also had an impact on the mixing and blending equipment used for solids and semi-solid formulations. For Borgers, the ability to conduct online analysis of blend homogeneity has helped manufacturers better understand blending behavior and made it possible to detect properly the required blending time. Ekato has found that determination of the end point of mixing using inline techniques such as viscosity, pH, and particle size analysis, but on a bypass loop, enables increased automation. 

Meanwhile, for Almhem and Reiner Lemperle, director of sales with Lödige Process Technology, the shift to continuous processing has been a notable development. “This approach allows the use of smaller equipment, which translates to less expensive production space, reduced product losses, and fewer material surfaces to clean, and eliminates scale-up issues, because the only factor is running time.” Lödige has developed a solution for continuous mixing, granulation, and drying that can be used for continuous mixing with a throughput of up to 200 kg/h, and for granulation and drying from 5 to 30 kg/h.


Despite these advances, there are still numerous ways in which blending and mixing of solid and semisolid formulations can be improved. Engenhart believes that even higher batch size flexibility is needed to increase efficiency and productivity in the mixing and blending of both solid and semisolid dosage forms. Currently, some Ekato mixing systems can efficiently mix batch sizes that are in the range of 10–25% of the maximum batch size that can be processed in a specific size of equipment. Engenhart is confident that these limitations can be pushed further.

For Sangüesa, the main issue is segregation. “Blenders can do a great job to ensure that all the powders, even those with varying densities, particle shapes, flow characteristics, etc., are thoroughly mixed inside the blender. But the moment those powders are either discharged or transferred out, segregation can occur,” he explains. “Depending on the surface finish, for example, some powders will flow better than others, thus negating the very benefits the blender had achieved. As powders flow out, there is always the concern that some of the ingredients will no longer be represented in the same percentage throughout the batch.”

To address issues such as segregation, Borgers would like to see more simulations of blending processes. He believes the ability to effectively simulate different mixing and blending processes will lead to the development of more effective approaches to scale-up of processes and help address equipment transfer questions. “Fortunately, advances are being made in simulation software, and I am thus hopeful that useful software tools will be available in the near future.” 

At the same time, there are a growing number of specialty products and “individual drugs” that are produced in much smaller quantities. “Scaling down production throughput to these small volumes is a challenge. The mixing and blending equipment needed for these niche products looks a lot different than the existing units in use today,” Lemperle notes. To help its customers, Lödige has introduced a mixer designed for batch sizes down to 0.5 kg/batch. Engenhart adds that many of these specialty semisolid formulations, including softgels and oral strip products, involve exceptionally high viscosity materials that require special mixing conditions. 

Furthermore, there is a trend toward the use of non-animal-based shell materials for softgel capsules, and these materials are more challenging to work with, according to Engenhart. In addition to having higher melting temperatures that require an even tighter allowable process parameters during mixing and transfer, these newer shell materials are often of even higher viscosity than conventional materials, and thus higher shear mixing is necessary to adequately disperse some of the solids raw materials.


There are also general challenges related to the selection of appropriate mixing and blending equipment. Because many mixing technologies today overlap in use and function such that certain formulations can be produced in more than one distinct type of mixer, making sure that the mechanical and physical aspects of the equipment enable safe, repeatable, and sanitary mixing is very important, according to Banaszek. “More often than not, there is no all-purpose, off-the-shelf solution,” she says. 

In addition, manufacturers that are using inherited equipment or procedures because they have worked in the past may actually be at a disadvantage and limiting their production capabilities. “With the greater understanding of mixing and blending processes that we have today, combined with the advances in mixing technology and new equipment, it is generally beneficial in such cases to reevaluate the existing mixing strategy to determine if it is efficient,” Banaszek observes. She concludes that, to identify the best mixer or blender for a particular formulation, it helps to partner with a reliable mixer supplier that offers long-term experience, rental, and testing resources. 

Articles

Effective blenders provide efficient, homogeneous mixing and de-aeration for a wide range of formulations.

Optimizing the Selection of Mixing Equipment

Many biological APIs are not stable in aqueous solutions, making preparation of shelf-stable sterile formulations difficult or impossible. Removal of the water at low temperature is a gentle method for overcoming this issue. To achieve effective lyophilization processes, careful selection of ingredients and knowledge of their properties and behavior at different temperatures is necessary. Parenteral manufacturers are benefiting from the use of process analytical technology (PAT) and increased automation. High hopes are also placed on controlled ice nucleation technology, with the first commercial product implementations expected soon.

An effective solution for improved stability


For parenterals, the preferred product presentation is a sterile, ready-to-use solution, largely because of ease of use. For many drugs, protein pharmaceuticals in particular, the active ingredient is not stable enough in an aqueous solution to make a sterile solution formulation feasible, according to Steven L. Nail, a senior research scientist at Baxter Biopharma Solutions. Robert Sever, business development manager for life sciences and laboratories at Praxair, also notes that freeze-drying is a relatively gentle method for obtaining the desired shelf life while maintaining the efficacy of the product, which can be more difficult with other options, such as spray-drying.

There are additional benefits as well. “Not only can shelf life be extended from weeks or months to years, but because the product has long-term stability, it can be produced in larger batch sizes, which provides economies of scale,” observes Isobel Cook, a principal scientist at Biopharma Technology. Freeze-dried products also do not require a carefully controlled environment during shipment, which is a cost savings, according to lyophilization consultant Larry Ulfik of Applewood Scientific.

“As importantly,” Ulfik says, “the final product is whole and complete, meaning it can be produced under sterile conditions with dosage accuracy, even when only miniscule amounts of API are required, such as for cytotoxic anticancer formulations and vaccines. The finished lyophilized vial is in its own sterile boundary and protected from environmental gases, moisture, and particulate contamination, and thus remains sterile over the entire expiry period and perhaps even beyond without using antibacterial-mold preservatives.” By freeze-drying parenterals, it is also possible to ensure that the API is in its preferred crystalline or amorphous form and helps speed up the time to market for complex and unstable products.


These benefits only accrue, of course, if the appropriate lyophilization conditions are used. Determining these parameters can be a challenge, though, given the various ingredients found in parenterals formulations. “In general, the composition of the formulation is critical in achieving the desired product quality attributes,” Nail states. “The formulation may include a buffer, a bulking agent, a stabilizer, and (perhaps) a surfactant.” Excipients can also provide stability to complex molecules by replacing the water in the matrix so that the molecular structure of the API is retained after reconstitution, according to Ulfik. For proteins, the stabilizer is generally a disaccharide, which protects against damage to the API, often due to unfolding caused by the stresses associated with freezing, with the drying process, or even reconstitution. 

Excipients can also be added to adjust the critical temperature. “The lower the freezing temperature, the longer the cycle time; excipients are thus often added that can raise the critical temperature,” explains Cook. In fact, the idea is to dry the product at as high a temperature as possible without exceeding the critical, or collapse, temperature where the microstructure established during freezing has the potential to collapse due to viscous flow of solutes during primary drying when the ice is sublimed away. Shorter cycle times are important for controlling costs, which are a major consideration given freeze-drying is a very expensive process, according to Sever.

Knowledge of the formulation and its effect on the API during lyophilization can be obtained using appropriate analytical techniques, such as differential scanning calorimetry, freeze-drying microscopy, Karl Fischer analysis, X-ray diffraction, Raman spectroscopy, infrared spectroscopy, gas chromatography/liquid chromatography analysis, and final inspection via noninvasive methodologies, according to Ulfik. 


Although freeze-drying technology tends to advance at a slow pace, some incremental advances in vial design have been beneficial, according to Cook. Examples include vials that can be stoppered and crimped in the freeze-dryer for improved seal integrity and enhanced glass systems for reduced breakage and cycle times and improved quality.

The use of PAT in recent years has had a significant impact. “Devices that monitor the global moisture levels of drying products to ensure that the process endpoint is reached consistently are an important example,” says Ulfik. Nail points to tunable diode laser absorption spectroscopy (TDLAS), a near-IR-based in-process flow meter that gives an instantaneous reading of the mass flow rate of water vapor during drying. “We use this instrumentation as a part of our quality-by-design approach to freeze-dry process development,” he notes. Nail, however, has found that TDLAS suffers at present from poor quantitative accuracy in large-scale equipment, but expects improvements as the understanding of vapor flow in the freeze-dryer increases.

The implementation of advanced sterile practices enabled by the burgeoning isolator and robotization industries has also allowed automated loading and unloading of freeze-dryers.”With this technology, the product, container, closure, and sealing cap are never exposed or manipulated by operators after sterilization at a cost that is competitive with and less risky than conventional methods in classified facilities,” Ulfik explains. He notes that the important benefit of this isolator technology is an overall improvement in product quality and worker safety.

The technology attracting the most attention, however, is controlled ice nucleation. Using current freezing methodology, ice nucleation occurs randomly and often at very low temperatures. According to Sever, the vial-to-vial nucleation variability leads to heterogeneity in ice structure, which can impact critical product and process attributes, leading to sub-optimal processes and challenges in scale-up.  Very cold nucleation temperatures can significantly reduce the primary drying rate. “The reduction is due to the fact that vials that freeze at lower temperatures have smaller ice crystals, which leave smaller pores behind when they sublime, thus slowing the drying rate.” Praxair has developed a technology that makes it possible to ensure nucleation at not only a specific temperature for all vials, but generally at warmer temperatures than previously possible.  “Such controlled nucleation has the potential to make both the freezing process and the drying process more consistent and efficient,” observes Nail.

Praxair has worked with freeze-dryer manufacturers to make the controlled nucleation technology readily available to the industry. SP Scientific provides laboratory scale freeze-dryers equipped with the new technology; both SP Scientific and GEA Lyophil can provide the technology on new or existing freeze-dryers at pilot and manufacturing scales. Sever notes that the technology has been demonstrated to be effective at manufacturing scales with no scale-up issues. Although no commercial process has yet adopted controlled nucleation, many are looking to implement the technology in the near future. Nail adds that there are several approaches to controlled nucleation that are currently under development that will benefit the industry. 


In addition to ice-nucleation issues, there are several other limitations of the current freeze-drying process that need to be addressed, including protein/nucleic acid stabilization in the solid state, heat transfer, vial-fogging, high-concentration formulations. Improvements are also desired in the reconstitution process, the scale-up process, and characterization and analysis tools. “Each drug formulation has its own unique characteristics, and therefore its own set of issues depending on those properties,” asserts Cook. 

In general, though, Nail sees a real need for better screening techniques to quickly identify the most promising formulations, particularly for protein pharmaceuticals since, in general, solid state stability is very much affected by the composition of the formulation. Nail also believes that the inefficiency of current freeze-drying technology is a serious issue. “Freeze-dryers basically need to be redesigned to make heat transfer more efficient by taking more effective advantage of thermal radiation.” Ulfik notes that there have been improvements in shelf fabrication methodologies that have contributed to increased heat transfer uniformity.

He adds, though, that inexpensive workable, noninvasive methods for measuring product conditions in all areas of the freeze-drying shelf stack are still needed to ensure that the product process envelope can be maintained over each and every product vial in the entire freeze-dryer load. “The shelf position in the dryer can have an effect during processing. Knowing these influences will reduce risks to product efficacy and overall customer safety, and of course save tossing batches if the control system can maintain conditions based upon these individualized measurements,” Ulfik states.

Improvements in technologies for cleaning in place and sterilization are also needed. Ulfik believes that the use of sterilizing gas rather than steam at high pressure is promising and expects that sterilization gases that remain as ideal gases will ultimately replace the use of hydrogen peroxide vapor.


Manufacturers and users of freeze-dryers are also investigating other improvements as well. “Users of lyophilizers want engineered solutions to the problems they face to maintain product process envelopes. That can include tempered jacketed chambers to reduce chamber-heat gain to edge-of-shelf vials, solutions for choked flow during processing, the use of non-hardwired temperature sensors during validation, and non-temperature-based methods for robustly determining process endpoints. Additional improvements include streamlining of the interiors and operation of freeze-drying systems.

With respect to formulating parenterals for freeze-drying, drug manufacturers are exploring different buffer types and concentrations to minimize pH effects on product integrity during freezing and reconstitution, according to Ulfik. The use of more complex excipients, such as amino acids and glass-forming polysaccharides, is also increasing.

Meanwhile, some pharmaceutical companies are entering into what has previously been thought to be forbidden territory and are exploring drying above the critical temperature of the frozen solid. “Drug manufacturers are looking for ways to reduce the cycle time and lower the cost of freeze-drying. Raising the temperature is one way to do so,” Sever explains. “What is most interesting is that it has been found in some cases that the stability and reconstitution properties of the freeze-dried formulations are acceptable despite the potential for collapse of the cake microstructure.”

New characterization technologies are also under development. Baxter is closely following optical coherence tomography, which offers potential improvement over current methodology for freeze-dry microscopy, according to Nail. Biopharma Technology, meanwhile, has investigated headspace moisture analysis. “Moisture analysis is very important in freeze-drying because moisture impacts product quality and storage stability. An approach based on headspace analysis is beneficial because it is both rapid and non-destructive and accurately indicates whether the product is within the specified moisture range, which can be critical for biologics,” Cook says.

Finally, Sever believes that one of the biggest challenges is educating practitioners of freeze-drying technology about recent scientific advances so that they can be put into commercial practice. There has been significant effort to develop effective process modeling  tools and describe robust process design strategies that can help reduce the amount of trial and error needed to optimize lyophilization, but they are not yet widely being used in the industry today,” he says.

As an important method for improving the stability of parenterals, lyophilization is fairly well understood, but can still benefit from several advancements in the technology.

Lyophilization Technology: Slow Progress but Hopeful Outlook

The characteristics of particles–whether formulated into a suspension, capsule, or tablet–can have a tremendous impact on the performance of a drug product. Particle analysis is, therefore, a critical tool for drug manufacturers throughout the drug development and commercialization process. Ian Treviranus, product line manager for particle characterizationwith HORIBA Scientific, spoke with Cynthia Challener, editor of the 

Pharmaceutical Sciences, Manufacturing & Marketplace Report

, about different particle-characterization techniques and recent developments in the field.

Pharmaceutical Sciences, Manufacturing and Marketplace Report:

 Why is particle-size analysis important in the pharmaceutical industry? 

 Particle characteristics can have a tremendous impact on the behavior of an API and/or a formulated drug product. Smaller particles tend to dissolve more rapidly and thus have higher bioavailability. A uniform particle size (narrow particle-size distribution) will similarly improve performance compared to drugs with a random distribution of particle sizes. The appropriate surface charge is important for preventing aggregation and agglomeration of particles in suspensions and emulsions, and therefore impacts stability. The surface area of a solid dosage drug plays a role in its dissolution profile. The properties of coatings applied to particles (i.e., thickness, uniformity) also affect drug performance. Finally, processability can be impacted, such as in tableting systems, where particles with certain shapes exhibit much better flow behavior than others.

 For what applications in the pharmaceutical industry is particle-size analysis useful/valuable and what technologies are typically used?

 Particle characterization is critical throughout the entire drug development and commercialization process. Because particle properties play such a major role in the performance of both APIs and formulated products, these characteristics must be determined in the earliest stages of drug development. Once particle properties are defined in an FDA submission, the manufacturer must ensure that those specifications are met as the drug progresses through clinical trials and on to commercial production. Often, not only the specified methods, but the same instruments (makes and models) are used at each stage to ensure consistent analysis results.

The two most common technologies used in the pharmaceutical industry for particle characterization are laser diffraction (LD) and dynamic light scattering (DLS). LD is useful for particles ranging from tens of nanometers to a few millimeters while DLS is appropriate for particles that are a few nanometers to about one micrometer in diameter. Other techniques include optical image analysis, surface area analysis, and sedimentation analysis.

LD and DLS are used to determine particle size, particle-size distribution, and particle dispersion in a formulated tablet or capsule as well as to measure the properties of tablet and particle coatings. More recently, laser diffraction has proven to also be applicable to the evaluation of protein agglomeration. DLS, meanwhile, can be used to determine the zeta potential of particles in suspensions or emulsions. The zeta potential is a measurement of the difference in the charge on the surface of a particle and the background; a higher number indicates greater stability and reduced likelihood of agglomeration. Optical imaging techniques are used for particle-shape analysis while surface-area analysis provides information on the porosity of a tablet, which affects its dissolution rate.

 What recent developments in particle analysis technology are being applied in the pharmaceutical industry, and what advantages/benefits do they provide? 

 Much of the advances in particle-analysis technology occur on an incremental basis through cooperation between instrument manufacturers and their pharmaceutical industry customers. With laser diffraction, iterative small improvements in polishes, light sources, detectors, computer algorithms, and noise subtraction add up over time to new capabilities for new applications. For example, laser diffraction previously was discounted as a technique for the determination of protein agglomeration. Today, however, LD performance has been shown to indeed be suitable for the reliable quantification of protein aggregation, even at very low concentrations.

For dynamic light scattering, there have been significant improvements with respect to its use for the determination of zeta potentials. The interest in zeta potential measurements has grown rapidly in recent years, and instrument manufacturers have responded by making incremental improvements in DLS to improve performance.

The need to properly characterize nanoparticles is also driving interest in newer technologies, especially in Europe. Since 2011 when the European Commission Joint Research Center (JRC) published its definition of nanoparticles and recommended the use of number-based analyses, which involve looking at individual nanoparticles, something that LD and DLS cannot do, there has been growing interest in methods such as nano tracking analysis (or nanoparticle tracking analysis, NTA) and nanocoulter counters. There is an expectation that the JRC definition will eventually become regulation in Europe, and the US will ultimately adopt something similar. Nanoparticle characterization is an issue for any product that contains nanoparticles that will be used by consumers, including medicines that are ingested or applied to the skin in some way.

 What issues/limitations remain with particle size analysis in the pharmaceutical industry today, and what efforts are being made to address them? 

 The holy grail of particle analysis is to develop instruments that can cover a wider range of particle sizes or types, provide as much new information as possible, and do so in one instrument that is easy to use. For example, HORIBA is working to combine its experience in spectroscopic chemical identification with its particle-characterization systems. Marrying particle-size analysis with optical analysis and/or surface area analysis is another opportunity that the industry is exploring.

With respect to limitations, protein-aggregation analysis remains a real challenge. There is no one instrument at this time that can provide quantitative results over the entire size range from the smallest protein to the larger aggregate. Many biopharmaceutical customers are also looking for improvements in zeta potential analysis systems. One major flaw of this analytical method is the fact that, when the electric fields are applied to the samples, currents are generated. Pharmaceutical customers were reporting both variability in results for repeated tests and a trending of results in one direction, indicating that samples were being destroyed or degraded. Damage to sample cells is also a problem. Both can be extremely costly, particularly if it means larger sample sizes are required and the material is not recoverable for further analysis. 

This issue is one that HORIBA has chosen to tackle. By replacing the precious metal electrodes typically used for zeta potential measurements with specially designed pressed graphite electrodes, it is possible to conduct the analysis with a much lower electric field. As a result, only a weak current is generated that does not damage the sample cell or the sample, which provides consistent results that our customers can have confidence in. Furthermore, the graphite electrodes are extremely durable and don’t need to be replaced for the lifetime of the instrument. 

Iterative and multiple incremental advances in particle-characterization technology are making a difference in pharmaceutical analysis applications.

Particle Characterization is Critical for Drug Performance

Cell-culture media is critical to the production of biologic drugs, including cell and gene therapies. Initially, media makers focused on increasing yield and productivity for protein-based applications. Today, productivity is high enough that downstream processing has become the bottleneck. Media manufacturers have thus turned their attention to improving the consistency and quality of protein expression. For therapeutic cells and viruses, yield and productivity continues to be a critical area of focus in addition to downstream processing. Several leading producers spoke with Cynthia Challener, editor of the 

, about their efforts with respect to media development. Participants included Melanie Brandl, head of global marketing for cell culture media and supplements at EMD Millipore; Gautam Choudhary, associate vice-president, Gibco Cell Culture Bioproduction with Life Technologies; Willem Folkerts, clinical technologies portfolio and global marketing head, and Alexis Bossie, head of media R&D , both with Lonza Bioscience; and Bruce Lehr, director of cell sciences and development with SAFC.

Optimization of performance
Pharmaceutical Sciences, Manufacturing and Marketplace Report:

 What are the major trends in the development of cell-culture media today?

 All suppliers are moving toward chemically defined formulations that are also made from animal-origin free (AOF) components. Additionally, there is a growing trend toward the development of optimized platforms for media trains and a continued drive toward greater process yields through higher producing titer systems.

 The focus has switched to product quality and the determination of how different media characteristics affect product quality, such as glycosylation patterns. This issue is of particular importance for biosimilar manufacture, where a major requirement is the ability to demonstrate that the biosimilar matches the branded drug as much as possible. Other trends include a growing interest in flexible manufacturing processes and the use of disposable equipment and the emerging use of perfusion systems.

Media and feed platforms are developed to ease fast optimization of each fed-batch process respecting different cell-clone requirements. The success of the platform is linked to the formulation, but is also strongly dependent on the quality and safety profiles of cell-culture raw materials. Improvements in the solubility of single components are targeted to increase concentration levels and media performance.

 For protein media, which is well-established, the focus is on optimization for platform cell lines to give high yields and desired protein characteristics, such as aggregation, glycosylation, and folding. For stem-cell media, and particularly pluripotent or mesenchymal stem cells, the media needs to be designed so that the desired highly specialized cells proliferate but do not differentiate until they are supposed to. The industry is driving towards xeno-free formulations here as well. Primary cells also require highly specialized media that provides proliferation without loss of function.

Pharmaceutical Sciences, Manufacturing and Marketplace Report: 

What approaches are being adopted to address upstream manufacturing process/material issues?

 Raw materials have to undergo defined qualification processes to secure quality, origin, and consistency in their manufacturing, including evaluation of serial amplification assays to check impurity impacts, trace elements, and the effect that individual components have on product quality. Beyond standard vendor qualification, EMD Millipore applies its pharmaceutical ingredient qualification expertise to bring the raw-material topic to the next level.

Verification of raw materials is necessary to ensure that they are not only of the required grade, but also “fit-for-use,” meaning ensuring that the raw materials function as needed. Today, Lonza is doing a lot more testing, particularly related to building capabilities for cell characterization and determination of how media impacts cell performance. Some of the tests include evaluation of cell-surface markers and the production of cytokines, growth factors, and other cell products that are indicative of cell behavior.

 Pharmaceutical industry customers want the therapeutic cells manufactured in clinical trials to be the same as those produced on a commercial scale. Therefore, an understanding of the impact of culture media is very important for obtaining better consistency from batch to batch. 

 At Life Technologies, we have a robust vendor- management program. Individual components are scored for risk and processes have been put in place to mitigate any concerns. Additionally, analytical tools are employed to verify the composition of components.

 Raw materials have become critical to media manufacturing and development. Pharmaceutical companies want more transparency, so they can follow the complete supply chain. In response to this growing need, SAFC has developed novel biological assays and evaluation technologies to ensure that all raw materials are appropriate for cell-culture applications. We are also collaborating closely with our customers and suppliers and working to develop methods for identifying all of the chemicals in formulated media, which can consist of up to 70 components.

 What advances in cell- culture media can be expected in the near future? What about long term?

 Pharmaceutical companies are looking for improved efficiency with respect to the formulation of chemically defined media for fed-batch operations. They are looking for good base media that can be used throughout production with their platform cell lines and use tweaks to feeds to optimize each different cell line. With the increased use of perfusion, there is also a need for media that is formulated specifically for those processes

 In cell therapy, there is a move away from adherent technologies to the use of suspension systems that are similar to the systems used for protein production. The use of suspension systems will enable easier scale-up and also reduce the cost of manufacturing. These systems will require different media, particularly given the fragile and sensitive nature of the cells.

Base cell-culture media continue to be improved upon, but there will likely be a point reached when the incremental benefits are minimal. However, functional additives focused on product quality, titer, and product safety look to become the focus for the future. 

 Efforts are being made to achieve complete elimination of undefined components and at the same time gain better knowledge about the individual components and how they impact product quality. We also expect to see novel ingredients that dissolve easier and have better uptake profiles as well as improvements in the ability to control cell metabolism (e.g., lactate control). Other approaches are to make media safer with respect to any type of adventitious agents such as viruses, which is economical on the upstream side of the process.

 What activities has your company pursued recently with respect to cell-culture media?

 Most recently, Lonza formed a collaboration with Sartorius Stedim Biotech (SSB) in which SSB will assume global sales and marketing of media and buffers used in the manufacture of protein-based therapeutics and vaccines while Lonza will continue to carry out development and manufacturing of these products. The media will be packaged in ready-to-use, prefilled SSB sterile single-use bags. The ability to offer fully integrated single-use solutions for the entire cell-culture process provides a real benefit to customers. 

 Lonza has also been awarded two separate contracts by the National Institutes of Health Center for Regenerative Medicine to produce induced pluripotent stem cells (iPSCs) for research purposes and clinical grade under current good manufacturing practices. 

 EMD Millipore recently launched a new CHO media product as part of our platform development effort that offers a complete solution for cell-culture batch, fed-batch, and perfusion processes. Produced as a top quality dry powder in our cGMP-compliant manufacturing facility, it has shown equivalent or superior cell growth and production compared to several other commercially available media and demonstrated impressive purity and consistency, which is an important consideration in optimizing bioprocess control, especially in the rapidly emerging biosimilars production market.

 Life Technologies has developed and launched a pH-neutral, highly-concentrated additive designed to keep specific productivity high late in culture. This additive is also designed to have minimal impact on product quality. We also continue to expand our media format by adding highly-concentrated additives that not only enhance titer but are also easy to use. 

 SAFC’s Zinc Finger technology allows for genetic manipulations so that certain genes that control glycosylation (related to molecule antigenicity) can be knocked out and cell lines improved. We are also developing targeted integration as an improvement over random integration. It can speed up the process and enables control of gene placement for more controlled expression, which leads to both performance and regulatory benefits. 

To meet our customers’ expectations for more efficient media development, we have adopted high-throughput systems for the rapid screening of hundreds of combinations of media products and feeds. The use of multivariate analysis and a design of experiment approach are also making it possible to identify key components and their impacts on media performance and protein quality.

With high productivity achieved, makers of cell-culture media are working to optimize product quality through better understanding and control of raw materials and production processes.

Media Makers Focus on Quality

Although taste-masking is more often associated with pediatric and geriatric liquid formulations, the APIs used in solid dosage drugs often have a very bitter flavor as well. Tablets and capsules are swallowed whole, thus masking the taste of the ingredients involves prevention of dissolution before the pill reaches the stomach. Nigel Langley, head of technical sales for pharma ingredients and services at BASF Pharma Ingredients and Services, discussed the two approaches to taste-masking of solid and semisolid dosage drugs with Cynthia Challener, editor of the Pharmaceutical Sciences, Manufacturing and Marketplace Report.

Choice of protection
Pharmaceutical Sciences, Manufacturing and Marketplace Report:

 What are different methods that can be used to achieve a taste-masking effect for solid and semisolid dosage forms?

 There are two approaches to taste-masking of solid and semisolid drugs, and both involve coating the product in some way with a polymer. The goal of the coating is to prevent disintegration and release of the drug into the mouth or throat so the taste buds are never exposed to the API.  In one method, a sustained-release polymer system is used, and in the other, an instant-release polymer that exhibits pH-dependent solubility ensures that the drug remains whole until swallowed. These polymer coatings can be applied to the entire tablet or capsule, or to crystals, granules, or other particulates used to manufacture the final dosage form.

 What factors must be considered when selecting a taste-masking excipient for a particular API/formulated drug?

 APIs themselves can be acidic. Most polymers that have pH-dependent solubility characteristics are basic. Therefore, the choice of polymeric coating type can be influenced by the nature of the API. It is, however, possible to apply a barrier coating to the tablet or particle before the pH-dependent coating is applied if this type of taste-masking system is preferred. 

What is the chemistry of the different types of taste-masking polymers? How does each type generally work?

 Our [BASF] pH-dependent polymer is based on acrylate chemistry and is an aqueous dispersion of a copolymer comprised of methyl methacrylate and diethylaminoethyl methacrylate. This coating is stable at neutral pH, and thus does not dissolve in saliva, which generally has a pH of 6.8-7.2. Below pH 5.5, however, the polymer will form salts. Thus, in the stomach, where the pH is typically 1.2, but can be a little higher in people who suffer from acid reflux, the coating reacts with biosalts, becomes soluble, and the drug is released. In fact, the coating operates in the opposite manner to an enteric coating.

Sustained-release coatings work because they can be formulated with both water- insoluble and water-soluble polymers, the latter of which is referred to as a pore former. The sustained release behavior of the coating can be tuned by varying the amount of pore former and therefore customized to meet the release profile required for a specific solid dosage drug.

  Different polymer types have been used as sustained release coatings, including cellulose-based resins. BASF’s polyvinylacetate water-insoluble film former is offered as a 30% dispersion in water. Our water-soluble pore former is a polyvinyl alcohol-polyethylene glycol graft copolymer with polyethylene glycol (PEG) units incorporated into the backbone that impart flexibility.

 What specific new technology has BASF developed and how is it an improvement over current products? What might be expected in the future?

 The instant-release technology from BASF is unique in that, even though the acrylate copolymer is basic, it has a very bland odor. At least one other pH-dependent taste-masking product on the market smells strongly of ammonia, which is quite offensive in the manufacturing setting. In addition, BASF’s polymer hides very bitter tastes at a reduced coating thickness compared to other products on the market. It also prevents moisture uptake, which is an added benefit for sensitive solid dosage formulations. Furthermore, because it is a dispersion in water, no organic solvent is required for spraying of the coating.

These advantages, in fact, led Colorcon to recognize our acrylate technology as the best-in-class reverse enteric polymer for taste-masking, according to general manager for film coating Kamlesh Oza. As a result, BASF and Colorcon have been in a collaboration since October, 2011 for the development of film-coating systems using BASF’s polymer. Colorcon has developed a preformulated additive system for use with the BASF coating that lowers the number of materials to be dispensed by 50% and reduces the preparation time by almost 40%, thus enabling efficient preparation and application for taste-masking of solid and semisolid dosage forms. 

The pH-dependent technology was introduced two years ago and has attracted a lot of interest. It takes quite some time for pharmaceutical customers to adopt a new excipient and get a product approved by the FDA, but we are working closely with our customers to reach that goal.

The trick to taste-masking in solid dosage forms is to never let the taste buds have a chance.

Ignorance is Bliss in Solid Dosage Taste-Masking

In parenteral manufacturing, filtration is used for particulate control, depyrogenation, and sterilization. Russell Madsen, president of the Williamsburg Group, group leader of the Parenteral Drug Association (PDA) Filtration Interest Group, and member of the editorial advisory board of 

, discusses why filtration is important in parenteral drug manufacturing and related initiatives of the PDA Filtration Interest Group.

Pharmaceutical Sciences, Manufacturing & Marketplace Report:

 Why is filtration such a critical issue for parenterals?

 Patient safety requires parenteral products to be sterile and free from objectionable levels of particulate matter and endotoxins.  Filtration is used to remove particulates, for depyrogenation, and for sterilization of aseptically produced parenteral products.  Each of these functions has different control parameters and processing requirements. From a risk-based perspective, sterility assurance is the most critical of these filtration processes. Filtration also can be used to remove viruses from biopharmaceutical process streams and products.

 What are the major techniques that are used for filtration of parenterals, and what are the benefits and limitations of each?

 Broadly, there are three major techniques: depyrogenation, prefiltration, and sterilizing filtration.

Depyrogenation is accomplished by means of ultrafiltration, reverse osmosis, microfiltration using charged filters, and charge-modified depth filters. Prefiltration is used to control the particulate and microbial levels reaching the final filter. 

 Prefiltration can occur in several stages; for example, a depth filter can be followed by a membrane filter. Controlling particulate and microbial levels prior to sterilizing filtration minimizes the potential for blocking or clogging the final filter in a properly designed system with adequate capacity, [thereby] ensuring filtration efficiency and minimizing changes between pre- and postfiltration diffusive flow integrity test values. The use of two sterilizing-grade filters in series is a special case where the first sterilizing-grade filter acts as a prefilter to stringently control the microbial level presented to the second, final filter.

Sterilizing filtration is used to remove all viable microorganisms from the product stream when other sterilization methods, such as moist-heat terminal sterilization, cause unacceptable levels of product degradation. Stringent controls, including knowledge of the prefiltration bioburden, sterilization of the filter, its housing and associated tubing, and filter-integrity testing, are required to ensure sterility of the filtrate. Validation studies demonstrating the ability of any particular combination of filter, product, and processing conditions to produce a sterile filtrate are required. Typically, these validation studies employ 

 (if viable in the product) at a challenge level of 1 x 10

 of effective filter area in the product to be filter-sterilized.  If the standard challenge organism is not viable, other options are available. (See 

, PDA Technical Report No. 26 (Revised 2008) for details and recommendations.)

Presterilized, single-use filter assemblies

 What recent advances have been made in filtration technology and how are they addressing some of the aforementioned issues? What might be in development?

 Regulatory agencies, such as FDA and EMA, have stressed the need to have detailed knowledge of the prefiltration bioburden to demonstrate microbiological control of the manufacturing process. The presterilization bioburden should not exceed the limit established during product development and validation of the sterilizing filtration process.

The use of presterilized, single-use filter assemblies simplifies the set-up and sterilization of the filtration system, especially where multiple filters are used in series. This approach is consistent with the increasing use of single-use processing equipment, such as chromatography capsules, processing and holding bags, and sterile connectors, to minimize the risk of cross-contamination while providing operator protection from potent and toxic biopharmaceutical process streams.

Presterilized capsule filters minimize the risks of improper set-up and assembly of filter housings, leaking O-rings, and eliminate the need for sometimes complex and difficult-to-validate steam-sterilization of the assembled units. In addition, single-use sterilizing filter capsules are increasingly available in sizes, configurations, and membrane materials that directly replace conventional stainless-steel housings and cartridge filters while providing increased sterility assurance and minimizing risk.

The future will see increasing use of single-use equipment, including sterilizing filters, tangential flow units, and purification columns. It is conceivable that someday sterile, out-of-the-box systems will be available for parenteral production encompassing compounding to filling.

Prefiltration poststerilization integrity testing

Pharmaceutical Sciences, Manufacturing & Marketplace Report: 

Why is prefiltration poststerilization integrity testing so important? What are the issues that must be addressed?

 While the European GMPs require prefiltration poststerilization testing of sterilizing filters, the US aseptic processing guidance is largely silent on such testing.  However, both documents require post-use integrity testing.

Pre-use poststerilization integrity testing (PUPSIT) is intended to show that a filter in its housing, having been subjected to a sterilization process, passes a validated integrity test and has not been damaged during sterilization.  In most cases, the filter has already been subjected to one or more presterilization integrity tests: by the filter manufacturer prior to sale and by the user after having been placed in its housing and flushed prior to sterilization. The purpose of such testing is to demonstrate that the filter is integral and has the appropriate pore-size rating.

However, PUPSIT often requires exposing the downstream side of the filter to atmospheric pressure, potentially compromising the sterility of the unit. From a risk-based perspective, this approach therefore makes little sense as long as the sterilization process for the filter has been validated and shown not to damage or cause loss of integrity of the sterilized filter. If, in fact, the sterilization process damaged the filter, the damage would be detected during post-use integrity testing, minimizing the importance of PUPSIT.

PDA published an article “Pre-use/Post-sterilization Integrity Testing of Sterilizing Grade Filters” in the September–October issue of the 

PDA Journal of Pharmaceutical Science and Technology

.  The article recommends that the PUPSIT decision should be “. . . made by the filter user upon thorough, documented risk-based analysis in accordance with ICH guidelines.” PDA is planning a research project designed to evaluate the risks associated with PUPSIT and the likelihood that damage to the filter caused by sterilization would not be detected in post-use integrity testing.

 What issues is the US PDA Filtration Interest Group tackling in 2013? What do you anticipate might be issues that the group will address over the longer term?

For 2013, the next US PDA Filtration Interest Group (IG) meeting will be held on April 16 at the Peabody Orlando Hotel in Orlando, Floridia.  There will be four presentations followed by a discussion of topics of general interest.  Monica Cardona, Pall Corporation, will present “Safety Considerations for Gas Filtration in High Temperature and Oxygen Enrichment Applications.” Mandar Dixit, Sartorius Stedim North America, will discuss “Optimizing Total Cost of Ownership for Membrane Filtration.”  The title of Lia Jeffrey’s presentation, EMD Millipore Corporation, is “Retention of Mycoplasma and Small Microorganisms,” and Leesa McBurnie, Meissner Filtration Products, will provide an update on the activities of PDA’s 

Longer term, the IG [Interest Group] is likely to continue to address PUPSIT issues and support discussions on that topic with European and American regulatory agencies.  Single-use filtration technologies and devices will be prominent topics for discussion.

Russell Madsen, group leader of the Parenteral Drug Association (PDA) Filtration Interest Group, discusses technical and regulatory considerations in filtration for parenteral drug manufacturing