Mechanical Characterization of Vial Strain During Freezing and Thawing Operations Using Amorphous Excipients.

The purpose of this study was to investigate the mechanical stresses and strains acting on pharmaceutical glass tubing vials during freezing and thawing of model pharmaceutical formulations. Strain measurements were conducted inside of a laboratory-scale freeze-dryer using a custom wireless sensor. In both sucrose and trehalose formulations at concentrations between 5 % and 20 % w/v, the strain measurements initially increased before peaking in magnitude at temperatures close to the respective glass transition temperatures of the maximally freeze concentrated solutes, Tg'. We attribute this behavior to a shift in the mechanical properties of the frozen system from a purely elastic glass below Tg' to a viscoelastic rubber-like material above Tg'. That is, when the interstitial region becomes mechanically compliant at temperature above Tg'. The outputs were less predictable below 5 % w/v and tended to exhibit two separate peaks in strain output, one near the equilibrium melting temperature of pure ice and the other near Tg'. The peaks merged at concentrations between 4 and 5 % w/v where the largest strain magnitude was observed. The strain on primary packaging has traditionally been applied to evaluate the risk of damage or breakage due to, for example, crystallization of excipients. However, data collected during this study suggest there may be utility in formulation design or as a process analytical technology to minimize potentially destabilizing stresses and strains in the frozen formulation.

Practical Advice on Scientific Design of Freeze-Drying Process: 2023 Update.

OBJECTIVE: The purpose of this paper is to re-visit the design of three steps in the freeze-drying process, namely freezing, primary drying, and secondary drying steps. Specifically, up-to-date recommendations for selecting freeze-drying conditions are provided based on the physical-chemical properties of formulations and engineering considerations. METHODS AND RESULTS: This paper discusses the fundamental factors to consider when selecting freezing, primary drying, and secondary drying conditions, and offers mathematical models for predicting the duration of each segment and product temperature during primary drying. Three simple heat/mass transfer primary drying (PD) models were tested, and their ability to predict product temperature and sublimation time showed good agreement. The PD models were validated based on the experimental data and utilized to tabulate the primary drying conditions for common pharmaceutical formulations, including amorphous and partially crystalline products. Examples of calculated drying cycles, including all steps, for typical amorphous and crystalline formulations are provided. CONCLUSIONS: The authors revisited advice from a seminal paper by Tang and Pikal (Pharm Res. 21(2):191-200, 2004) on selecting freeze-drying process conditions and found that the majority of recommendations are still applicable today. There have been a number of advancements, including methods to promote ice nucleation and computer modeling for all steps of freeze-drying process. The authors created a database for primary drying and provided examples of complete freeze-drying cycles design. The paper may supplement the knowledge of scientists and formulators and serve as a user-friendly tool for quickly estimating the design space.

Best Practices and Guidelines (2022) for Scale-up and Technology Transfer in Freeze Drying Based on Case Studies. Part 2: Past Practices, Current Best Practices, and Recommendations.

Scale-up and transfer of lyophilization processes remain very challenging tasks considering the technical challenges and the high cost of the process itself. The challenges in scale-up and transfer were discussed in the first part of this paper and include vial breakage during freezing at commercial scale, cake resistance differences between scales, impact of differences in refrigeration capacities, and geometry on the performance of dryers. The second part of this work discusses successful and unsuccessful practices in scale-up and transfer based on the experience of the authors. Regulatory aspects of scale-up and transfer of lyophilization processes were also outlined including a topic on the equivalency of dryers. Based on an analysis of challenges and a summary of best practices, recommendations on scale-up and transfer of lyophilization processes are given including projections on future directions in this area of the freeze drying field. Recommendations on the choice of residual vacuum in the vials were also provided for a wide range of vial capacities.

Recommended Best Practices in Freeze Dryer Equipment Performance Qualification: 2022.

Best practices for performing freeze dryer equipment qualification are recommended, focusing on identifying methods to quantify shelf thermal uniformity (also known as "shelf surface uniformity"), equipment capability, and performance metrics of the freeze dryer essential to the pharmaceutical Quality by Design paradigm. Specific guidelines for performing shelf temperature mapping, freeze dryer equipment limit testing (the capability curve), and condenser performance metrics have been provided. Concerning shelf temperature mapping and equipment capability measurements, the importance of paying attention to the test setup and the use of appropriate testing tools are stressed. In all the guidelines provided, much attention has been paid to identifying the balance between obtaining useful process knowledge, logistical challenges associated with testing in the production environment vs that at laboratory scale, and the frequency of the testing necessary to obtain such useful information. Furthermore, merits and demerits of thermal conditions maintained on the cooled surfaces of the freeze dryer condenser have been discussed identifying the specific influence of the condenser surface temperature on the process conditions using experimental data to support the guidelines. Finally, guidelines for systematic leak rate testing criteria for a freeze dryer are presented. These specific procedural recommendations are based on calculations, measurements, and experience to provide useful process and equipment knowledge.

Best Practices and Guidelines (2022) for Scale-Up and Tech Transfer in Freeze-Drying Based on Case Studies. Part 1: Challenges during Scale Up and Transfer.

The freeze-drying process scale-up and transfer remain a complicated and non-uniform practice. We summarized inefficient and good practices in these papers and provided some practical advice. It was demonstrated that using the same process set points/times in laboratory and commercial scale dryers may lead to loss of product quality (collapse or vial breakage). The emerging modeling approach demonstrated practical advantages. However, the upfront generation of some input parameters (vial heat transfer coefficient, minimum controllable pressure, and maximum sublimation rate) is essential for model utilization. While the primary drying step can be transferred with a high degree of confidence (e.g., using modeling), and secondary drying is usually fairly straightforward, predicting potential changes in product behavior during freezing remains challenging.

Impact of Annealing and Controlled Ice Nucleation on Properties of A Lyophilized 50 mg/ml MAB Formulation.

We compared "ice-fog" controlled ice nucleation at -6 °C to annealing at the same temperature for a 50 mg/mL monoclonal antibody formulation, using shelf-ramp freezing as a control. Cake structure, drying time, reconstitution time, specific surface area, calculated cake resistance and size exclusion chromatography were all compared. Controlled nucleation resulted in the fastest reconstitution, shortest primary drying, lowest calculated cake resistance, lowest specific surface area and highest moisture content. There was no effect upon the results for size exclusion chromatography. Results for annealing were between those for controlled nucleation and shelf-ramp freezing. All results were consistent with "ice-fog" controlled nucleation at -6 °C having greater impact upon the ice crystal morphology than annealing at the same temperature for 3 h.

Recommended Best Practices for Lyophilization Validation 2021 Part II: Process Qualification and Continued Process Verification.

This work describes the lyophilization process validation and consists of two parts. Part one (Part I: Process Design and Modeling) focuses on the process design and is described in the previous paper, while the current paper is devoted to process qualification and continued process verification. The goal of the study is to show the cutting edge of lyophilization validation based on the integrated community-based opinion and the industrial perspective. This study presents best practices for batch size determination and includes the effect of batch size on drying time, process parameters selection strategies, and batch size overage to compensate for losses during production. It also includes sampling strategies to demonstrate batch uniformity as well as the use of statistical models to ensure adequate sampling. Based on the LyoHUB member organizations survey, the best practices in determining the number of PPQ runs are developed including the bracketing approach with minimum and maximum loads. Standard practice around CQA and CPP selection is outlined and shows the advantages of using control charts and run charts for process trending and quality control. The case studies demonstrating the validation strategy for monoclonal antibody and the impact of the loading process on the lyophilization cycle and product quality as well as the special case of lyophilization for dual-chamber cartridge system are chosen to illustrate the process validation. The standard practices in the validation of the lyophilization process, special lyophilization processes, and their impact on the validation strategy are discussed.

Recommended Best Practices for Lyophilization Validation-2021 Part I: Process Design and Modeling.

This work describes lyophilization process validation and consists of two parts. Part I focuses on the process design and is described in the current paper, while part II is devoted to process qualification and continued process verification. The intent of these articles is to provide readers with recent updates on lyophilization validation in the light of community-based combined opinion on the process and reflect the industrial prospective. In this paper, the design space approach for process design is described in details, and examples from practice are provided. The approach shows the relationship between the process inputs; it is based on first principles and gives a thorough scientific understanding of process and product. The lyophilization process modeling and scale-up are also presented showing the impact of facility, equipment, and vial heat transfer coefficient. The case studies demonstrating the effect of batch sizes, fill volume, and dose strength to show the importance of modeling as well as the effect of controlled nucleation on product resistance are discussed.

Application of First Principles Primary Drying Model to Lyophilization Process Design and Transfer: Case Studies From the Industry.

Lyophilization modeling is well documented in academic circles but has not yet been widely adopted by pharmaceutical manufacturing companies. To facilitate wider adoption and implementation, an accessible ExcelTM-based tool is provided, presenting several fresh examples as a practical introduction to the process of modeling the primary drying phase. Case studies are presented of the tool's application during process development and scale up which highlight business benefits that have been realized by using the model. The authors and contributors are members of the BioPhorum's Lyophilization Workstream and represent several pharmaceutical companies. The current manuscript is intended to serve as a pathway to not only share the collective knowledge on the topic but also accelerate its adoption in the industry.

A Kinetic Model for Spray-Freezing of Pharmaceuticals.

Spray freeze-drying (SFD), which includes spray-freezing into droplets and dynamic vacuum drying, presents a promising alternative approach to manufacture dried pharmaceuticals more efficiently than conventional vial freeze-drying. Without reliable predictive models for the SFD conditions of interest, any respective process development still relies on empirical approaches. In this work, we propose an improved modeling framework to describe the fast freezing (<1 s) that sub-millimeter droplets undergo in the present SFD process. The modeled freezing rate accounts for both the kinetics of ice growth and droplet heat transfer mechanisms. Computational fluid dynamics (CFD) simulations and experiments on bulk spray-freezing are combined to refine and validate the proposed reduced-order model. While this study is limited to water-sucrose solutions, the present modeling approach can be extended to other pharmaceutical excipients. For the cooling rates of interest, model results indicate that droplets with initial sucrose concentration higher than 20% w/w will transit to a glassy state before completion of crystallization and, consequently, devitrification is expected during post spray-freezing manipulation of the bulk material. In practice, such compact model does not only allow quantification of process parameters that cannot be measured in real time but also enable the choice of optimal spraying conditions for production of free-flowing, high-quality frozen droplets that meet the target product profile.

Reconstitution of Highly Concentrated Lyophilized Proteins: Part 1 Amorphous Formulations.

Long reconstitution times before patient administration remain an undesirable quality attribute for high concentration lyophilized protein formulations. In this study, 3 approaches were developed to study reconstitution behavior of lyophilized, amorphous cakes of a highly concentrated monoclonal antibody (mAb) by exploring their wetting, disintegration, and hydration behavior. As the mAb concentration increased from 0 to 83 mg/mL, reconstitution times were longer with poorer wetting, slower hydration, and disintegration rates. Furthermore, the effect of controlling ice nucleation temperature at -5 and -10°C during freezing followed by either conservative or aggressive drying conditions on the reconstitution times was explored in formulations containing 40 and 83 mg/mL mAb. Although no effect of either of the 2 processing conditions was noted at 40 mg/mL, aggressive drying led to faster reconstitution at both the nucleation temperatures with 83 mg/mL mAb. The present study combined with literature data suggests that below a protein-to-sugar ratio of 1, reconstitution was complete within 1 min, and when the ratio was greater than 1, the reconstitution times increased nonlinearly. Disintegration and hydration were determined to be the key mechanisms contributing to the complete reconstitution of the lyophilized, amorphous cakes of the highly concentrated mAb in vials.

Freezing of Biologicals Revisited: Scale, Stability, Excipients, and Degradation Stresses.

Although many biotech products are successfully stored in the frozen state, there are cases of degradation of biologicals during freeze storage. These examples are discussed in the Perspective to emphasize the fact that stability of frozen biologicals should not be taken for granted. Frozen-state degradation (predominantly, aggregation) has been linked to crystallization of a cryoprotector in many cases. Other factors, for example, protein unfolding (either due to cold denaturation or interaction of protein molecules with ice crystals), could also contribute to the instability. As a hypothesis, additional freezing-related destabilization pathways are introduced in the paper, that is, air bubbles formed on the ice crystallization front, and local pressure and mechanical stresses due to volume expansion during water-to-ice transformation. Furthermore, stability of frozen biologicals can depend on the sample size, via its impact on the freezing kinetics (i.e., cooling rates and freezing time) and cryoconcentration effects, as well as on the mechanical stresses associated with freezing. We conclude that, although fundamentals of freezing processes are fairly well described in the current literature, there are important gaps to be addressed in both scientific foundations of the freezing-related manufacturing processes and implementation of the available knowledge in practice.

Bulk Dynamic Spray Freeze-Drying Part 1: Modeling of Droplet Cooling and Phase Change.

In spray freeze-drying (SFD), the solution is typically dispersed into a gaseous cold environment producing frozen microparticles that are subsequently dried via sublimation. This technology can potentially manufacture bulk lyophilized drugs at higher rates compared with conventional freeze-drying in trays and vials because small frozen particles provide larger surface area available for sublimation. Although drying in SFD still has to meet the material collapse temperature requirements, the final characteristics of the respective products are mainly controlled by the spray-freezing dynamics. In this context, the main goal of this work is to present a single droplet spray-freezing model and validate it with previously published simulations and experimental data. For the investigated conditions, the droplet temperature evolutions predicted by the model agree with experiments within an error of ±10%. The proposed engineering-level modeling framework is intended to assist future development of efficient SFD processes and support scale up from laboratory to commercial scale equipment.

Bulk Dynamic Spray Freeze-Drying Part 2: Model-Based Parametric Study for Spray-Freezing Process Characterization.

Spray freeze-drying is an evolving technology that combines the benefits of spray-drying and conventional lyophilization techniques to produce drug substance and drug product as free-flowing powders. The high surface-to-volume ratio associated to the submillimeter spray-frozen particles contributes to shorter drying and reconstitution times. The formation of frozen particles is the most critical part of this dehydration technique because it defines the properties of final product. Based on a previously proposed and validated model, the current goal is to understand the role of various controllable parameters in the spray-freezing process. More specifically, given a set of spraying conditions, the model is used to predict the minimum distance required to cool and freeze the droplets below a temperature that prevents coalescence and product agglomeration. A parametric study is carried out to map the operational limit conditions of the actual spray-freezing column apparatus under consideration. For the spray freeze-drying conditions of interest, model simulations indicate that convection contributes to at least 80% of the total droplet heat transfer and, consequently, that freezing column gas temperature and droplet diameter are the most important process parameters affecting the freezing distance.

Determining Maximum Sublimation Rate for a Production Lyophilizer: Computational Modeling and Comparison With Ice Slab Tests.

Equipment capability is an important factor in scale up and technology transfer for lyophilized pharmaceutical products. Experimental determination of equipment capability limits, such as the maximum sublimation rate at a given chamber pressure, is time-intensive for production lyophilizers. Here, we present computational fluid dynamics modeling of equipment capability and compare it with experimental data for minimum controllable pressure ice slab sublimation tests in a 23 m2 shelf area freeze dryer. It is found that the vapor flow in the production scale is characterized by turbulent effects at high sublimation rates. For the considered freeze dryer configuration, the onset of turbulence occurs at a sublimation rate of 17 kg/h and leads to an increase in the minimum controllable pressure by 3-4 mTorr for the flow rates up to 40 kg/h. Variations in the shelf and duct orientations as well as the valve stroke distance and their effect on the equipment limit and pressure uniformity are also discussed. The minimum controllable pressure measured experimentally agreed within 5% with computational fluid dynamics results. For high vapor sublimation rates at final stages of ice slab testing, the condenser load affects the product chamber pressure control. Estimate of condenser pressure changes because of ice accumulation has been included.

Investigation of Fogging Behavior in a Lyophilized Drug Product.

Vial "fogging" is a common observation in lyophilized biological products and has been reported in the pharmaceutical industry. In addition to unappealing appearance, severe fogging that reaches the shoulder or neck of the vial can potentially compromise the container closure integrity of the vials. In this study, we performed experiments to identify parameters impacting the fogging phenomena in lyophilized drug product vials. Glass vial surface properties were found to have a significant impact on vial fogging. In line with prior published research, the study demonstrates that fogging can be mitigated by using glass vials with hydrophobic surface (such as siliconized vial or TopLyo® vial) and by extending the prefreeze 5°C hold during the lyophilization cycle. Moreover, this study shows that extending the annealing at -5°C or -10°C can also significantly reduce the fogging. Increased formulation viscosity and exclusion of a surfactant can mitigate the fogging behavior of the lyophilized product. The study shows that container closure integrity as determined by headspace analysis and vacuum decay is not compromised for the "fogging" drug product vials for this model monoclonal antibody container using a worst-case model of lyophilized "neck-wet" vials.

Recommended Best Practices for Process Monitoring Instrumentation in Pharmaceutical Freeze Drying-2017.

Recommended best practices in monitoring of product status during pharmaceutical freeze drying are presented, focusing on methods that apply to both laboratory and production scale. With respect to product temperature measurement, sources of uncertainty associated with any type of measurement probe are discussed, as well as important differences between the two most common types of temperature-measuring instruments-thermocouples and resistance temperature detectors (RTD). Two types of pressure transducers are discussed-thermal conductivity-type gauges and capacitance manometers, with the Pirani gauge being the thermal conductivity-type gauge of choice. It is recommended that both types of pressure gauge be used on both the product chamber and the condenser for freeze dryers with an external condenser, and the reasoning for this recommendation is discussed. Developing technology for process monitoring worthy of further investigation is also briefly reviewed, including wireless product temperature monitoring, tunable diode laser absorption spectroscopy at manufacturing scale, heat flux measurement, and mass spectrometry as process monitoring tools.

Next generation drying technologies for pharmaceutical applications.

Drying is a commonly used technique for improving the product stability of biotherapeutics. Typically, drying is accomplished through freeze-drying, as evidenced by the availability of several lyophilized products on the market. There are, however, a number of drawbacks to lyophilization, including the lengthy process time required for drying, low energy efficiency, high cost of purchasing and maintaining the equipment, and sensitivity of the product to freezing and various other processing-related stresses. These limitations have led to the search for next-generation drying methods that can be applied to biotherapeutics. Several alternative drying methods are reviewed herein, with particular emphasis on methods that are commonly employed outside of the biopharmaceutical industry including spray drying, convective drying, vacuum drying, microwave drying, and combinations thereof. Although some of the technologies have already been implemented for processing biotherapeutics, others are still at an early stage of feasibility assessment. An overview of each method is presented, detailing the comparison to lyophilization, examining the advantages and disadvantages of each technology, and evaluating the potential of each to be utilized for drying biotherapeutic products.