Aggressive conditions during primary drying as a contemporary approach to optimise freeze-drying cycles of biopharmaceuticals.

Freeze-drying is the method of choice to dry formulations with biopharmaceutical drugs, to enhance protein stability. This is usually done below the glass transition temperature of maximally freeze-concentrated solutions (T'), to avoid protein aggregation, preserve protein activity, and obtain pharmaceutically 'elegant' cakes. Unfortunately, this is a lengthy and energy-consuming process. However, it was recently shown that drying above T' or even above the collapse temperature (T) is not necessarily detrimental for stability of biopharmaceuticals, and hence provides an attractive option for freeze-drying cycle optimisation. The goal of the present study was to optimise the freeze-drying cycle for a model IgG monoclonal antibody (20 mg/mL) in sucrose and sucrose/glycine formulations, by reducing primary drying time. To study the impact of shelf temperature (T) and chamber pressure on product temperature (T), one conventional and five aggressive cycles were tested. Aggressive conditions during primary drying were achieved by increasing T from -20 °C (conventional cycle) to 30 °C, with chamber pressure set to 0.1 mbar, 0.2 mbar or 0.3 mbar. These combinations of T and chamber pressure resulted in T well above T', and in some cases, even above T, without causing macrocollapse. Other critical quality attributes of the products were also within the expected ranges, such as reconstitution time and residual water content. Physical stability was tested using size exclusion chromatography, dynamic light scattering, and micro-flow imaging. All of the lyophilised samples were exposed to stress and the intended storage conditions, with no impacts on the product seen. These data show that implementation of aggressive conditions for the investigated formulations is possible and can significantly contribute to the reduction of primary drying times by up to 54% (from 48 to 22 h) in comparison to conventional freeze-drying.