The Challenges
In response to the ongoing development of new and ever more complex biotherapeutics, more controllable, efficient methods for freezing and thawing of product have become increasingly desirable, particularly between downstream processing and the fill and finish stage. As details of critical vaccine development and subsequent storage and transport are discussed throughout more mainstream channels, this need has been highlighted further.
The science behind freezing appears to be simple but for complex drug substances requiring a frozen state, any technology needs to be assessed to ensure that parameters such as consistent quality, potential for degradation, and homogeneity post-thawing, are scrutinized. This typically occurs during process validation.
The benefits of freezing include prolonging shelf-life of the bulk product by lowing degradation and helping to assure product quality and drug potency. The freezing process itself is an area of focus but the processes surrounding it should be equally sound, ensuring frozen drug substances can be protected safely and reliably during storage and shipping. In all these areas the gap between the current needs of the biopharmaceutical industry and traditional solutions is real and growing but not always acknowledged. This is changing and the requirement for freeze-thaw platforms, with sufficiently integrated biocontainers and robust shipment solutions, that adequately protect, fill and freeze valuable product, has rapidly increased with product demand.
Traditional Static Freezing
For years, static freezers have predominantly been the equipment of choice, but studies have shown that they can be responsible for up to 56% loss of potency in product1. This activity loss can be directly equated to how a product freezes or thaws and the effect that parameters, such as freeze/thaw rate and the type of technology utilized, have on each process.
The traditional static freezing mechanism is characterized by different rates of freezing within a liquid product and is considered to be ‘slow freezing’ which can adversely impact drug substance quality. A slower freezing process leads to formation of longer ice crystals. These crystalline structures can cause tension, which in turn can destroy up to 20% of proteins contained within a product. Additionally, slow freezing allows the cold temperatures to penetrate the substance from the outside in, which can lead to an expansion of the core and potential damage to the surrounding material.
Another potential threat to product quality is the effect of cryoconcentration, a naturally occurring phenomenon during liquid freezing where concentration of active material is different throughout the solid or liquid phase of the partially frozen mixture. During traditional freezing methods, solubility of buffer solutes, inclusive of the active proteins, decreases as temperature decreases. As such, these solutes/proteins can become excluded from the growing formation of ice crystals and migrate in front of the phase change, becoming trapped in all regions of the block as the liquid freezes. The negative effect of cryoconcentration is its potential to cause denaturation, whereby some proteins lose their structure and functionality; an undesirable effect when consistency in product homogeneity and product activity is the end goal. Cryoconcentration may also lead to aggregation and precipitation, potentially impacting yield, quality and activity.
CRYOCONCENTRATION: The concentration of a material in the solid or liquid parts of a partially frozen mixture. |
Intelligent, Controlled Plate Freezing
A rapid freezing process ensures homogeneity and applies to multiple products including vaccines, mAbs and viral vectors, where consistent quality and defined shelf-life are the highest priority. Rapid freezing minimizes crystallization, reduces the potential for contamination and product loss. Efficient freezing can be achieved through advanced technologies characterized by swift, controlled processes and maximized freeze area to volume ratios. Typically, this is best achieved using two-dimensional single-use biocontainers where simultaneous freezing of both sides of the biocontainer is achieved using plate freezers; essentially a freeze-thaw platform that facilitates direct transfer of the cold to the liquid (removal of heat) in a controlled manner. The effective result is more homogenous freezing kinetics which prevents expansion of the core and the type of damage seenwith traditional static freezing methods.
Although it would be true to say that cryoconcentration can never be completely eliminated, studies have shown that plate freezing technology achieves the best results because the rapid and homogenous freezing process deters the accumulation of proteins and anti-bodies in the center of the biocontainer.
Traditional Product Freezing and the Concerns of Today’s Biomanufacturers
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Loss of product, product instability and potential damage to biocontainers, brought about by increasingly complex handling stages, are the three main concerns often voiced by biopharmaceutical manufacturers when asked about product freezing.
Product freezing has become an increasing necessity for many drugs reaching the marketplace. With product instability and decreased shelf-life being acknowledged, the challenges faced by biomanufacturers are naturally encouraging movement towards controlled freezing and complete management of the process. End-to-end solutions that ensure rapid bulk fill of drug substance, controlled freezing and thawing, and robust storage of frozen biocontainers during transit, significantly reducethe potential for damage that can occur through insufficient handling.
Pall® Freeze & Go Solutions which utilize Allegro™single-use biocontainers in combination with RoSS* freeze-thaw platforms offer exciting new possibilities in terms of controlled drug substance filling, freezing, transport and thawing, preserving the quality and potency of any frozen drug substance.
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(1) Bezavada Ashish, et al.: “Use of Blast Freezers in Vaccine Manufacturing”,Bioprocess International(October 1, 2011). https://bioprocessintl.com/manufacturing/monoclonal-antibodies/