Evaluating Freeze–Thaw Processes in Biopharmaceutical Development

level: interMediate R egulations mandate that biopharmaceutical product quality be controlled throughout manufacturing, storage, transportation, and delivery to patients (1). Operations often include freezing and thawing of a bulk drug substance, dilution of that purified substance to a target concentration, filtration, filling into a selected container–closure system, additional processing (e.g., lyophilization), inspection, packaging, storage, transport, and delivery (2). Freezing is a common processing step used to maintain stability and quality of a drug substance during development and production of biopharmaceutical products. It is generally agreed upon that freezing drug substance maximizes productivity and reduces overall production costs by decoupling bulk solution manufacture and storage steps from final product manufacture. Freezing provides f lexibility and cost savings by enabling batch processing: Large volumes of an expensive biological drug substance can be frozen in batches to allow the drug product to be manufactured based on real-time commercial or clinical demands. Freezing a drug substance before drug product manufacture also reduces microbial growth risk and eliminates mechanical (agitation) stresses during transportation. Most important, this allows for a longer shelf life. Freezing decelerates chemical degradation (because reaction kinetics depend directly on temperature) and physical degradation (immobilizing drug substance in a frozen matrix limits protein–protein interactions) (3–13). Furthermore, application of freeze–thaw processes extends to storage of process intermediates, allowing for longer hold steps between manufacturing operations. Although freezing is considered to be a conservative approach, frozen storage is one of the most efficient and reliable methods to minimize protein interactions with container–closures and extend the shelf life of biological products in solution-based formulations (13). Drug substance (typically stored in plastic bottles or single-use plastic bags) is exposed to various interfaces on contact with container–closure systems. Likewise, drug product often is filled into multiple-component container–closure systems, such as vials or prefilled syringes with rubber stopper closures (2). Interactions with container surfaces (e.g., glass or polymers) and other constituents (e.g., silicone oil) can significantly influence drug substance and drug product stability. Such interactions may be further exacerbated with mechanical stresses such as agitation during transportation. Freezing can limit exposure of a protein to those interfaces and prevent shippingand storage-related solution instabilities. Overall, freezing can be leveraged to maximize protein stability throughout a supply chain. However, additional controls may be needed to limit the number of freeze–thaw cycles that occur at clinics, pharmacies, or depot sites to that supported by available stability data. Doing so ensures that product quality is not compromised.