Mechanism of collapse of amorphous-based lyophilized cake induced by slow ramp during the shelf ramp process

Predictive model for the surface melting and puffing of freeze-dried amorphous materials

It is thought that surface melting and puffing of freeze-dried amorphous materials are related to the difference between the surface temperature (Tsur) and freeze-concentrated glass transition temperature (Tg') of the materials. Although Tg' is a material-specific parameter, Tsur is affected by the type and amount of solute and freeze-drying conditions. Therefore, it will be practically useful for preventing surface melting and puffing if Tsur can be calculated using only the minimum necessary parameters. This study aimed to establish a predictive model for the surface melting and puffing of freeze-dried amorphous materials according to the calculated Tsur. First, a Tsur-predictive model was proposed under the thermodynamic equilibrium assumptions. Second, solutions with various solute mass fractions of sucrose, maltodextrin, and sucrose-maltodextrin mixture were prepared, and three material-specific parameters (Tg', unfrozen water content, and true density) were experimentally determined. According to the proposed model with the parameters, the Tsur of the samples was calculated at chamber pressures of 13, 38, and 103 Pa. The samples were freeze-dried at the chamber pressures, and their appearance was observed. As expected, surface melting and puffing occurred at calculated Tsur > Tg' with some exceptions. The water activity (aw) of the freeze-dried samples increased as the Tsur - Tg' increased. This will have resulted from surface melting and puffing, which created a covering film, thereby preventing subsequent dehydration. The observations suggest that the proposed model is also useful for predetermining the drying efficiency and storage stability of freeze-dried amorphous materials.

Lyophilization of Small-Molecule Injectables: an Industry Perspective on Formulation Development, Process Optimization, Scale-Up Challenges, and Drug Product Quality Attributes

Lyophilization is a pivotal manufacturing process to obtain a stable drug product that is unstable as a ready-to-use formulation. Some formulations may require the addition of drug-specific excipients such as stabilizers, buffers, and bulking agents to support the cake appearance and ensure long-term stability of the drug product. Optimization of the lyophilization process parameters at each stage including freezing and primary and secondary drying is important because these parameters can have a direct impact on the process efficiency (shortened cycle time) and product performance (cake appearance and homogeneous moisture content). Several parameters of the formulation, including properties of the active pharmaceutical ingredient, excipients, solvent system, and container closure, determine the success of lyophilization. Development, scale-up, and transfer of the lyophilization cycle are challenging; hence, a comprehensive understanding of the critical parameters related to the formulation, lyophilization process, and lyophilizer design allows designing a quality drug product. One approach for a successful transfer of the lyophilization cycle between the laboratory and commercial-scale lyophilizer is using vial heat transfer coefficient and ice slab test to establish a maximum sublimation rate. This review provides a general overview of the lyophilization process and discusses several key considerations and product development aspects of formulation, process optimization, container closure system, scale-up principles, and drug product quality attributes from the industrial viewpoint. Grapical abstract.

Use of a temperature ramp approach (TRA) to design an optimum and robust freeze-drying process for pharmaceutical formulations

Freeze-drying, until now, has been a process that was designed using a trial and error experimental approach. This approach is often material and time consuming, and the resulting freeze-drying processes are neither optimum nor robust. Accordingly, the objective of this study was to develop a simple-to-use and experimental-based approach to design an optimum and robust freeze-drying process for any given formulation. The temperature ramp approach (TRA) detailed in this study involves the implementation of a customized design of experiments (DoE) to perform few (three or four) experiments using a given drug formulation. The DoE results are analyzed to define optimum processing conditions (i.e., shelf temperature and chamber pressure) based on a predefined range of target product temperature for primary drying, which could be defined from formulation characterization at its frozen state. In this study, a successful freeze-drying process of two model formulations using the TRA was designed. Verification experiments at the optimum processing conditions showed excellent agreement in both product temperature and sublimation rate with the values obtained using the TRA. Thus, the TRA detailed in this study offers a significant advantage to reduce development time and material, and enhance the efficiency and robustness of the resulting freeze-drying process.