Injectable Biologics

For now, most biologics are administered via the intravenous or subcutaneous route, both requiring the injectable dosage form. The increasing use of biologics has stimulated innovations in novel injectable drug delivery systems. The conventional intravenous formulation is not suitable for biologics delivery due to its high viscosity, higher dosage volume, higher molecule size, and protein stability. Therefore, the formulation development of injectable biologics must take into consideration of the afore-mentioned factors. Further, future product innovation will likely focus on self-injectors, wearable drug delivery and needle-free injectors.

Two commercially available biologic formulations are injectable liquid or powder for injection, while microemulsion, suspension (for vaccine) or pellet (for implant) are occasionally used. Powder for injection is prepared through a freeze-drying process, which is briefly described as follows: The first step is to lower the temperature to the eutectic point, to freeze the protein solution. This is followed by primary drying at -40°C to remove crystallized water. Lastly, the temperature is raised from -40°C to eutectic point, and then to ambient temperature, to effectively remove water bound to the protein or excipients. The freeze-drying process is crucial as the condition of temperature, pressure and cycling time affect not only the quality but safety (immunogenicity) of the lyophilized product.