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.

Accelerated Storage for Shelf-Life Prediction of Lyophiles: Temperature Dependence of Degradation of Amorphous Small Molecular Weight Drugs and Proteins.

Prediction of lyophilized product shelf-life using accelerated stability data requires understanding the temperature dependence of the degradation rate. Despite the abundance of published studies on stability of freeze-dried formulations and other amorphous materials, there are no definitive conclusions on the type of pattern one can expect for the temperature dependence of degradation. This lack of consensus represents a significant gap which may impact development and regulatory acceptance of freeze-dried pharmaceuticals and biopharmaceuticals.

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.

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 graphical design space for the primary drying phase of freeze Drying: Factors affecting the dried product layer resistance.

An emerging approach to process development of a lyophilized pharmaceutical product is to construct a graphical design space for primary drying as an aid to process optimization. The purpose of this paper is to further challenge the assumption in earlier work that the maximum values of the resistance of dried product layer, R, is approximately constant and is independent of process conditions within the "acceptable" region of the design space. Three model formulations containing bovine serum albumin as the model protein were chosen to represent: (a) an amorphous system, (b) a crystalline system, and (c) a mixed system where both an amorphous and a crystalline component were present.

Mannitol hemihydrate in lyophilized protein formulations:Impact of its dehydration during storage on sucrose crystallinity and protein stability.

The high propensity of mannitol to crystallize in frozen solutions along with its high eutectic temperature enabling higher primary drying temperatures makes it a good bulking agent. In protein formulations, addition of a sugar (sucrose) that has the ability to remain amorphous throughout processing as well as storage is imperative to retain the protein in its native state. It is well known that in the presence of amorphous excipients and protein, mannitol can crystallize as a mixture of anhydrous polymorphs - α-, β- and δ-forms and a hemihydrate form [mannitol hemihydrate (MHH); CHO·0.

Equipment Capability Measurement of Laboratory Freeze-Dryers: a Comparison of Two Methods.

The objective of this investigation was to evaluate two methods for measuring the maximum sublimation rate that a freeze-dryer will support-the minimum controllable pressure method and the choke point method. Both methods gave equivalent results, but the minimum controllable pressure method is preferred, since it is easier, faster, and less subjective. The ratio of chamber pressure to condenser pressure corresponding to the onset of choked flow was considerably higher in this investigation (up to about 20:1) than in previously published reports.

Stability of Freeze-Dried Protein Formulations: Contributions of Ice Nucleation Temperature and Residence Time in the Freeze-Concentrate.

Controlling ice nucleation, at a fixed higher temperature, results in larger ice crystals, which can reduce the ice/freeze-concentrate interface area where proteins can adsorb and partially unfold. Moreover, limited work has been done to address any effects on short-term stability due to a slow ramp or long isothermal hold after the ice nucleation step. The objective was to evaluate the effect of the ice nucleation temperature and residence time in the freeze-concentrate on in-process or storage stability of representative proteins, human IgG, and recombinant human serum albumin.

Freeze-Dryer Equipment Capability Limit: Comparison of Computational Modeling With Experiments at Laboratory Scale.

The equipment capability curve is one of the bounding elements of the freeze-drying design space, and understanding it is critical to process design, transfer, and scale-up. The second bounding element of the design space is the product temperature limit beyond which the product collapses. The high cost associated with freeze-drying any product renders it crucial to operate using the most efficient cycle within the limits of the equipment and the product.

Experimental Aspects of Measuring the Vial Heat Transfer Coefficient in Pharmaceutical Freeze-Drying.

One of the current methods for cycle optimization in primary drying to is develop a graphical design space based on quality by design (QbD). In order to construct the design space, the vial heat transfer coefficient (K) is needed. This paper investigated experimental factors that can affect the K result, examined the relationship between the batch average K and K values for individual vials, and recommended best practices for measuring K.

The Influence of Mannitol Hemihydrate on the Secondary Drying Dynamics of a Protein Formulation: A Case Study.

The objective of this research was to study the atypical secondary drying dynamics observed during the freeze-drying of a formulation consisting of mannitol, disaccharide, and sodium chloride, where "bursts" of water vapor release were observed during secondary drying as detected by comparative pressure measurement. "Thief" samples were removed at the end of primary drying and during secondary drying as the shelf temperature was increased in a stepwise fashion. These samples were examined by X-ray powder diffraction and thermal analysis.

Lyophilized Drug Product Cake Appearance: What Is Acceptable?

Cake appearance is an important attribute of freeze-dried products, which may or may not be critical with respect to product quality (i.e., safety and efficacy).

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.

Process and Formulation Effects on Protein Structure in Lyophilized Solids Using Mass Spectrometric Methods.

Myoglobin (Mb) was lyophilized in the absence (Mb-A) and presence (Mb-B) of sucrose in a pilot-scale lyophilizer with or without controlled ice nucleation. Cake morphology was characterized using scanning electron microscopy, and changes in protein structure were monitored using solid-state Fourier-transform infrared spectroscopy, solid-state hydrogen-deuterium exchange-mass spectrometry, and solid-state photolytic labeling-mass spectrometry (ssPL-MS). The results showed greater variability in nucleation temperature and irregular cake structure for formulations lyophilized without controlled nucleation.

A proposed rationale and test methodology for establishment of acceptance criteria for vacuum integrity testing of pharmaceutical freeze dryers.

A scientific rationale is proposed for the establishment of acceptance criteria for leak rates in pharmaceutical freeze dryers. A method was developed to determine the quantity of air that could leak into any lyophilizer from the outside while still maintaining Class 100/Grade A microbial conditions. A lyophilizing product is assumed most vulnerable to microbial contamination during secondary drying, when mass transfer of water vapor from product to condenser is minimal.

Sucrose lyophiles: a semi-quantitative study of residual water content by total X-ray diffraction analysis.

Total X-ray Powder Diffraction Analysis (TXRPD) using transmission geometry was able to observe significant variance in measured powder patterns for sucrose lyophilizates with differing residual water contents. Integrated diffraction intensity corresponding to the observed variances was found to be linearly correlated to residual water content as measured by an independent technique. The observed variance was concentrated in two distinct regions of the lyophilizate powder pattern, corresponding to the characteristic sucrose matrix double halo and the high angle diffuse region normally associated with free-water.

Experimental determination of the key heat transfer mechanisms in pharmaceutical freeze-drying.

The study is aimed at quantifying the relative contribution of key heat transfer modes in lyophilization. Measurements of vial heat transfer rates in a laboratory-scale freeze-dryer were performed using pure water, which was partially sublimed under various conditions. The separation distance between the shelf and the vial was systematically varied, and sublimation rates were determined gravimetrically.

Quality by design in formulation and process development for a freeze-dried, small molecule parenteral product: a case study.

A case study has been developed to illustrate one way of incorporating a Quality by Design approach into formulation and process development for a small molecule, freeze-dried parenteral product. Sodium ethacrynate was chosen as the model compound. Principal degradation products of sodium ethacrynate result from hydrolysis of the unsaturated ketone in aqueous solution, and dimer formation from a Diels-Alder condensation in the freeze-dried solid state.

Controlled nucleation in freeze-drying: effects on pore size in the dried product layer, mass transfer resistance, and primary drying rate.

A novel and scalable method has been developed to enable control of the ice nucleation step for the freezing process during lyophilization. This method manipulates the chamber pressure of the freeze dryer to simultaneously induce nucleation in all product vials at a desired temperature. The effects of controlled nucleation on the drying rate of various formulations including 5% (w/w) mannitol, 5% (w/w) sucrose, and a mixture of 3% (w/w) mannitol and 2% (w/w) sucrose were studied.

Computational analysis of fluid dynamics in pharmaceutical freeze-drying.

Analysis of water vapor flows encountered in pharmaceutical freeze-drying systems, laboratory-scale and industrial, is presented based on the computational fluid dynamics (CFD) techniques. The flows under continuum gas conditions are analyzed using the solution of the Navier-Stokes equations whereas the rarefied flow solutions are obtained by the direct simulation Monte Carlo (DSMC) method for the Boltzmann equation. Examples of application of CFD techniques to laboratory-scale and industrial scale freeze-drying processes are discussed with an emphasis on the utility of CFD for improvement of design and experimental characterization of pharmaceutical freeze-drying hardware and processes.

Evidence of partial unfolding of proteins at the ice/freeze-concentrate interface by infrared microscopy.

The goal of this research was to use infrared spectroscopy in combination with a freeze drying stage to gain a better understanding of the mechanism of loss of protein integrity due to the stresses associated with freezing. Infrared spectra were collected in triplicate for the interstitial space between ice crystals and through ice crystals in a partially frozen system. Spectra were collected for lactate dehydrogenase (LDH) and human immune globulin (IgG) both in the presence and absence of an added surfactant (polysorbate 80).

Rapid freeze-drying cycle optimization using computer programs developed based on heat and mass transfer models and facilitated by tunable diode laser absorption spectroscopy (TDLAS).

Computer programs in FORTRAN were developed to rapidly determine the optimal shelf temperature, T(f), and chamber pressure, P(c), to achieve the shortest primary drying time. The constraint for the optimization is to ensure that the product temperature profile, T(b), is below the target temperature, T(target). Five percent mannitol was chosen as the model formulation.