Modeling of the lyophilization process, based on the steady-state heat and mass transfer, is a useful tool in understanding and optimizing of the process, developing an operating design space following the quality-by-design principle, and justifying occasional process deviations during routine manufacturing. The steady-state model relies on two critical parameters, namely, the vial heat transfer coefficient, Kv, and the cake resistance, Rp. The classical gravimetric method used to measure Kv is tedious, time- and resource-consuming, and can be challenging and costly for commercial scale dryers. This study proposes a new approach to extract both Kv and Rp directly from an experimental run (e.g., temperature and Pirani profiles). The new methodology is demonstrated using 5% w/v mannitol model system. The values of Kv obtained using this method are comparable to those measured using the classic gravimetric method. Application of the proposed approach to process scale-up and technology transfer is illustrated using a case study. The new approach makes the steady-state model a simple and reliable tool for model parameterization, thus maximizes its capability and is particularly beneficial for transfer products from lab/pilot to commercial manufacturing.
Keywords: cake resistance; freeze-drying; lyophilization; lyophilization modeling; scale-up; technology transfer; vial heat transfer coefficient.