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, Rp, 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. Low temperature differential scanning calorimetry (DSC) and freeze dry microscopy (FDM) experiments were conducted to estimate critical product temperature. A conservative lyophilization cycle was conducted for each formulation to collect mass flow data and individual design spaces were then established. A series of lyophilization cycles were then conducted using process conditions that resided within the individual design space and the resultant product temperature and resistance of dried product layer (Rp) values were compared between the individual cycles within each formulation. The data indicated that the Rp was component dependent with the mannitol formulation exhibiting higher Rp values than the sucrose formulation. Interestingly, when mannitol was retained amorphous, the formulation exhibited a lower Rp, similar to that of the sucrose formulation. The mixed formulation exhibited intermediate Rp values. Crystallization of mannitol is hypothesized to facilitate a decrease in the size of the ice porous structure by making the water vapor flow path tortuous, thereby increasing the Rp of mannitol formulations. Within the "acceptable" zone of the individual design space, Rp was dependent on the process condition with more aggressive shelf temperature cycles resulting in lower Rp. Specific Surface Area measurements of freeze-dried solids demonstrated that more aggressive conditions resulted in smaller surface area. Freeze-dried solids of crystalline formulations consistently exhibited higher specific surface area than the amorphous formulations.

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-, ß- and δ-forms and a hemihydrate form [mannitol hemihydrate (MHH); C6H14O6·0.5H2O]. The conditions of formation of MHH due to processing and formulation variables are well established in the literature. However, MHH's dehydration kinetics on storage and its impact on the stability of a protein has not been systematically evaluated. The overall objective was to identify conditions (temperature and humidity) at which MHH can dehydrate on storage and the consequences of the release of associated water on sucrose phase behavior and protein stability. In a mannitol-sucrose-protein lyophile, the purpose of this study was (i) to investigate the dehydration behavior of MHH (ii) to determine the influence of dehydration on sucrose crystallization and (iii) the effect of moisture released due to MHH dehydration on model protein (Bovine serum albumin, BSA or Human serum albumin, HSA) aggregation. MHH dehydration and sucrose crystallization was observed in cases where the relative humidity was ≥ 55% (open vials). A relative humidity of ≤ 33% RH prevented MHH dehydration while retaining sucrose amorphous. No protein aggregation was observed irrespective of presence of MHH or its dehydration.

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.

Stability of antibody drug conjugate formulations evaluated using solid-state hydrogen-deuterium exchange mass spectrometry.

Antibody drug conjugates (ADCs) have been at the forefront in cancer therapy due to their target specificity. All the FDA approved ADCs are developed in lyophilized form to minimize instability associated with the linker that connects the cytotoxic drug and the antibody during shipping and storage. We present here solid-state hydrogen-deuterium exchange with mass spectrometric analysis (ssHDX-MS) as a tool to analyze protein structure and matrix interactions for formulations of an ADC with and without commonly used excipients. We compared results of the ssHDX-MS with accelerated stability results using size-exclusion chromatography and determined that the former technique was able to successfully identify the destabilizing effects of mannitol and polysorbate 80. In comparison, Fourier-transform infrared spectroscopy results were inconclusive. The agreement between ssHDX-MS and stressed stability studies supports the potential of ssHDX-MS as a method of predicting relative stability of different formulations.

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. This ratio was not affected by the location of the pressure gauge on the condenser; that is, on the foreline of the vacuum pump versus on the body of the condenser itself. The total water loss due to sublimation as measured by tunable diode laser absorption spectroscopy was consistently within 5% of gravimetrically determined weight loss, regardless of whether the measurement took place during choked versus non-choked process conditions.

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. In this work, we present a computational model to generate the equipment capability curve for 2 laboratory scale freeze-dryers and compare the results to experimentally generated equipment capability curves. The average deviations of the modeling results from the experiments for the 2 lyophilizers modeled are -4.8% and -7.2%. In addition, we investigate the effect of various numerical and geometric parameters on the simulated equipment capability. Among the numerical parameters, the chamber wall thermal boundary conditions exert the largest influence with a maximum value of 12.3%. Among the geometric parameters, the inclusion of the isolation valve reduces the equipment capability by 23.7%. Larger isolation valves, required for controlled nucleation technology, choke the flow in the duct at lower sublimation rates, thereby lowering the equipment capability limit.

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. Controlled nucleation resulted in nucleation at ∼(-5°C) and uniform cake structure. Formulations containing sucrose showed better retention of protein structure by all measures than formulations without sucrose. Samples lyophilized with and without controlled nucleation were similar by most measures of protein structure. However, ssPL-MS showed the greatest photoleucine incorporation and more labeled regions for Mb-B lyophilized with controlled nucleation. The data support the use of solid-state hydrogen-deuterium exchange-mass spectrometry and ssPL-MS to study formulation and process-induced conformational changes in lyophilized proteins.

Pre-filled syringes: a review of the history, manufacturing and challenges.

Pre-filled syringes are convenient devices for the delivery of parenteral medications. They are small which makes them easy to carry and are dependable for delivering a precise dose of medication. These and many other reasons are leading to their growth in the pharmaceutical market. There are a number of review articles that describe the advantages and disadvantages of pre-filled syringes. However, there are few journal articles that present information on their manufacturing and challenges. The intent of this review article is to provide information on the history of the pre-filled syringe, methods of their manufacture, methods of filling syringes as a drug product and to examine the types of syringes available. This type of knowledge can familiarize the formulation scientist with the choices available and their possible challenges.

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. When the drug crystallizes in a frozen solution, the eutectic melting temperature is above -5°C. Crystallization in the frozen system is affected by pH in the range of pH 6-8 and buffer concentration in the range of 5-50 mM, where higher pH and lower buffer concentration favor crystallization. Physical state of the drug is critical to solid state stability, given the relative instability of amorphous drug. Stability was shown to vary considerably over the ranges of pH and buffer concentration examined, and vial-to-vial variability in degree of crystallinity is a potential concern. The formulation design space was constructed in terms of pH and drug concentration, and assuming a constant 5 mM concentration of buffer. The process design space is constructed to take into account limitations on the process imposed by the product and by equipment capability.

Practical fundamentals of glass, rubber, and plastic sterile packaging systems.

Sterile product packaging systems consist of glass, rubber, and plastic materials that are in intimate contact with the formulation. These materials can significantly affect the stability of the formulation. The interaction between the packaging materials and the formulation can also affect the appropriate delivery of the product. Therefore, a parenteral formulation actually consists of the packaging system as well as the product that it contains. However, the majority of formulation development time only considers the product that is contained in the packaging system. Little time is spent studying the interaction of the packaging materials with the contents. Interaction between the packaging and the contents only becomes a concern when problems are encountered. For this reason, there are few scientific publications that describe the available packaging materials, their advantages and disadvantages, and their important product attributes. This article was created as a reference for product development and describes some of the packaging materials and systems that are available for parenteral products.

Thermal analysis of frozen solutions: multiple glass transitions in amorphous systems.

Frozen aqueous solutions of sucrose exhibit two "glass transition-like" thermal events below the melting endotherm of ice when examined by DSC, but the physical basis of these events has been a source of some disagreement. In this study, a series of sugars, including sucrose, lactose, trehalose, maltose, fructose, galactose, fucose, mannose, and glucose were studied by modulated DSC and freeze-dry microscopy in order to better understand whether sucrose is unique in any way with respect to this behavior, as well as to explore the physical basis, and the pharmaceutical significance of these multiple transitions. Double transitions were found to be a common feature of all sugars examined. The results are consistent with both thermal events being glass transitions in that (1) both events have second-order characteristics that appear in the reversing signals, (2) annealing experiments reveal that enthalpy recovery is associated with each transition, and (3) Lissajous plots indicate that no detectable latent heat of melting is associated with either transition. The data in this study are consistent with the idea that the lower temperature transition arises from a metastable glassy mixture containing more water than that in the maximally freeze-concentrated solute. Freeze-dry microscopy observations show that for all of the sugars examined, it is the higher temperature transition that is associated with structural collapse during freeze-drying. There is no apparent pharmaceutical significance associated with the lower-temperature transition.

Rapid determination of vial heat transfer parameters using tunable diode laser absorption spectroscopy (TDLAS) in response to step-changes in pressure set-point during freeze-drying.

The purpose of this study was to perform a rapid determination of vial heat transfer parameters, that is, the contact parameter K(cs) and the separation distance l(v), using the sublimation rate profiles measured by tunable diode laser absorption spectroscopy (TDLAS). In this study, each size of vial was filled with pure water followed by a freeze-drying cycle using a LyoStar II dryer (FTS Systems) with step-changes of the chamber pressure set-point at to 25, 50, 100, 200, 300, and 400 mTorr. K(cs) was independently determined by nonlinear parameter estimation using the sublimation rates measured at the pressure set-point of 25 mTorr. After obtaining K(cs), the l(v) value for each vial size was determined by nonlinear parameter estimation using the pooled sublimation rate profiles obtained at 25 to 400 mTorr. The vial heat transfer coefficient K(v), as a function of the chamber pressure, was readily calculated, using the obtained K(cs) and l(v) values. It is interesting to note the significant difference in K(v) of two similar types of 10 mL Schott tubing vials, primary due to the geometry of the vial-bottom, as demonstrated by the images of the contact areas of the vial-bottom.

Identification of critical process variables affecting particle size following precipitation using a supercritical fluid.

The critical processing parameters affecting average particle size, particle size distribution, yield, and level of residual carrier solvent using the supercritical anti-solvent method (SAS) were identified. Carbon dioxide was used as the supercritical fluid. Methylprednisolone acetate was used as the model solute in tetrahydrofuran. Parameters examined included pressure of the supercritical fluid, agitation rate, feed solution flow rate, impeller diameter, and nozzle design. Pressure was identified as the most important process parameter affecting average particle size, either through the effect of pressure on dispersion of the feed solution into the precipitation vessel or through the effect of pressure on solubility of drug in the CO2/organic solvent mixture. Agitation rate, impeller diameter, feed solution flow rate, and nozzle design had significant effects on particle size, which suggests that dispersion of the feed solution is important. Crimped HPLC tubing was the most effective method of introducing feed solution into the precipitation vessel, largely because it resulted in the least amount of clogging during the precipitation. Yields of 82% or greater were consistently produced and were not affected by the processing variables. Similarly, the level of residual solvent was independent of the processing variables and was present at 0.0002% wt/wt THF or less.

Identification of physical-chemical variables affecting particle size following precipitation using a supercritical fluid.

The physical-chemical processing variables affecting particle size following precipitation using the supercritical antisolvent (SAS) method were investigated by varying both the composition of the feed solvent and the structure of the solute, using a series of steroids. The key factor influencing particle size in these studies appears to be the solubility of the drug in the organic solvent/supercritical fluid mixture, where relatively high solubility causes a lower degree of supersaturation in the precipitation vessel, resulting in a relatively large particle size. Higher operating pressures result in larger particle sizes, probably through the effect of pressure on solubility. Physical properties of the carrier solvent, such as vapor pressure and dielectric constant, were not effective predictors of relative particle size of the precipitated powder, nor was solubility of the model drug in the carrier solvent. In limited studies of the physical state of the precipitated solid, higher apparent crystallinity was observed for powders with larger particle size. A precipitate of a different crystal form was observed when starting with hydrocortisone hemisuccinate monohydrate and may represent the loss of water of hydration. An amorphous solid was precipitated when starting with yttrium acetate dihydrate. Broad guidelines for effective particle size reduction using this technique are presented.