Effects of temperature ramp rate during the primary drying process on the properties of amorphous-based lyophilized cake, Part 1: Cake characterization, collapse temperature and drying behavior

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Abstract

In the lyophilization process for injectable pharmaceuticals, the shelf of the lyophilizer is heated to the target temperature at a constant ramp rate during the primary drying process. Although the shelf temperature (Ts) and chamber pressure (Pc) have mainly been investigated to optimize the primary drying process, the impact of the ramp rate on the lyophilized cake properties is poorly understood. We evaluated the relationship between the ramp rate and cake properties using a model formulation containing 10% trehalose as a bulking agent. Elegant lyophilized cakes were obtained when lyophilization was conducted at a fast ramp rate. In contrast, the lyophilized cakes collapsed at slow ramp rate cycles. To identify the cause of collapse, the impact of the ramp rate on the collapse temperature (Tc) was evaluated by light transmission freeze-dry microscopy. The Tc decreased with the decrease in the ramp rate. Lower Tc and higher resistance of the dried matrix in the low sublimation state were hypothesized as the cause of the collapse. Numerous lyophilization runs were executed at different Ts and ramp rates. We confirmed that an increased ramp rate led to successful lyophilization at a higher Ts and that the drying time was significantly reduced.

Introduction

Lyophilization has long been used to stabilize drug products in the pharmaceutical industry. In particular, lyophilization has been used in the development of injectable pharmaceuticals and has allowed for the stabilization of various materials, including small molecules, large molecules and nanoparticles. Furthermore, in recent formulation technology, lyophilization has been applied to orally disintegrating tablets, nasal formulations for vaccines and powders for pulmonary administration [16]. Thus, lyophilization is an essential technology in the pharmaceutical industry, and its use is expected to be expanded to various applications.

Lyophilization is generally known to be a time- and cost-consuming process. Thus, an optimization study has been conducted to minimize the process time. Lyophilization consists of three main processes: freezing, primary drying and secondary drying. In primary drying, ice crystals are sublimed from a frozen solution, and a great deal of time is required to reach the drying endpoint. Although the time required for primary drying can be shortened by the addition of heat to the vial, lyophilization may fail due to collapse or meltback when the product temperature (Tp) exceeds the critical temperature. Collapse or meltback during the primary drying process causes an increase in the residual moisture of the lyophilizate, potentially causing the product to become unstable. Several studies have reported that collapse during the lyophilization process has no significant impact on the stability of proteins [33], [40]. However, formulation researchers and engineers generally recognize that collapse should be avoided because of the impact of collapse on product values, such as the elegance of the cake and the reconstitution time [4]. Thus, the primary drying process is the most important of the three processes, and product quality and manufacturing efficiency should be considered when determining the drying conditions.

The optimization of the lyophilization cycle has mainly focused on the primary drying process [20], [32]. To avoid collapse or meltback, the Tp must be kept lower than the critical temperature (the collapse temperature or the eutectic point). However, maintaining a higher Tp is desirable to shorten the process time. Thus, Ts and Pc, which are related to the Tp, have been optimized in numerous trial experiments that have been performed to date [3], [37]. It is also known that Tp and the sublimation rate during the primary drying process depend on the microstructure of the frozen product, and several studies have reported the impact of the freezing rate, annealing and ice nucleation kinetics [6], [15], [36]. Thus, the Ts, Pc and freezing conditions have been investigated with regard to the optimization of the primary drying process. Furthermore, the primary drying behavior can be theoretically predicted using a heat and mass transfer model, and simulation programs for cycle optimization have been proposed by a number of researchers [17], [19], [30]. For example, the Tp or the primary drying time is predicted as a function of the Ts and Pc, and the obtained values are plotted on a graph. The design space of the primary drying process can be determined based on the contour map that is prepared [17], [19], [26], [28].

To promote ice sublimation, the Ts is increased to target temperature at a constant ramp rate in the beginning of the primary drying process. Although the above-mentioned process parameters have previously been the focus in efforts to optimize the primary drying process, the impact of the temperature ramp rate is poorly understood. In previous studies, a wide range of ramp rates have been applied to prepare lyophilizate samples (0.03 °C/min, [8]; 0.07 °C/min, [12]; 0.1 °C/min, [25]; 0.2 °C/min, [14]; 0.3–0.4 °C/min, [13]; 0.5 °C/min, [2]; 1.0 °C/min [9], and there is no common ramp rate that ensures a successful lyophilization process. In the mathematical model, other than Ts and Pc, both the heat transfer coefficient [1], [5], [10], [11] and the resistance of the dry layer of the sublimed water vapor [18], [21] have been reported to potentially affect Tp. However, the ramp rate is not an important parameter in the model equation, and the impact of the ramp rate on the drying behavior, such as the Tp and drying time, cannot be predicted theoretically. Thus, it will be of interest to learn whether the properties of the actual lyophilized cakes are changed by the ramp rate.

The aim of the present study was to investigate the impact of the ramp rate on the properties of lyophilized cakes and drying behavior. A sample solution containing 10% trehalose was used as a model formulation and was lyophilized at different ramp rates. The obtained lyophilized cakes were subjected to several evaluations, and the impact of the ramp rate on the properties of the cakes was investigated. Furthermore, the differences in the drying behaviors of the lyophilized cycles was discussed, focusing on the relationship between Tc obtained by light transmission freeze-dry microscopy (LT-FDM) and the recorded Tp data.

Section snippets

Materials

All of the chemicals used in this study were obtained from the following commercial venders: D-(+)-trehalose dihydrate (Hayashibara, Okayama, Japan), l-arginine, l-arginine hydrochloride and citric acid monohydrate (EMD Millipore, Billerica, MA), Tween 80 (Croda, Edison, NJ), Hydranal® Coulomat AG (Sigma Aldrich, St. Louis, MO) and Hydranal® Coulomat CG (Sigma Aldrich).

All of the packaging materials used in this study were obtained from the following commercial venders: 5 mL type 1 glass vial

Effect of ramp rate on the appearance and residual moisture of the product

Lyophilized vials were collected from the edge and center of the tray, and the appearance of the cakes was evaluated. In Fig. 1, photographs show the appearance of the lyophilized cakes that were prepared at different ramp rates and shelf temperatures in the primary drying process. Regardless of the ramp rate, no significant shrinkage was observed in the top layer of the cakes. However, the bottom layer of the cake shrank when lyophilization was conducted at a slow ramp rate (0.06 °C/min). At

Impact of ramp rate on the properties of the lyophilized cakes

When lyophilization was conducted at fast ramp rate cycles, elegant cakes were formed and a uniform porous microstructure was observed. However, cake shrinkage, increased residual moisture and microstructural changes were confirmed at slow ramp rate cycles. These features were generally observed when a collapse occurred during the primary drying process [34], [35], and it is hypothesized that a decrease in the ramp rate led to the collapse of the lyophilized cake. With regards to the timing of

Conclusion

We investigated the impact of the ramp rate during the primary drying process on the properties and drying behavior of lyophilized cakes. The lyophilized cakes were found to collapse as the ramp rate decreased.

To identify the cause of collapse at slow ramp cycles, Tc was evaluated by LT-FDM. Although the ramp rate itself would not have an effect on the Tc, it is thought that the drying situation formed by the decrease of the ramp rate decreases Tc. In the vial lyophilization and the results of

References (41)

  • W.Y. Kuu et al.

    Rapid determination of dry layer mass transfer resistance for various pharmaceutical formulations during primary drying using product temperature profiles

    Int. J. Pharm.

    (2006)
  • E.V.A. Meister et al.

    Freeze-dry microscopy of protein/sugar mixtures: drying behavior, interpretation of collapse temperatures and a comparison to corresponding glass transition data

    J. Am. Pharm. Assoc.

    (2009)
  • J.D. Meyer et al.

    Impact of bulking agents on the stability of a lyophilized monoclonal antibody

    Eur. J. Pharm. Sci.

    (2009)
  • D.E. Overcashier et al.

    Lyophilization of protein formulations in vials: investigation of the relationship between resistance to vapor flow during primary drying and small-scale product collapse

    J. Pharm. Sci.

    (1999)
  • S.M. Patel et al.

    Lyophilization process design space

    J. Pharm. Sci.

    (2013)
  • M.J. Pikal et al.

    Physical chemistry of freeze-drying: measurement of sublimation rates for frozen aqueous solutions by a microbalance technique

    J. Pharm. Sci.

    (1983)
  • M.J. Pikal et al.

    The collapse temperature in freeze-drying: dependence on measurement methodology and rate of water removal from the glassy phase

    Int. J. Pharm.

    (1990)
  • K. Schersch et al.

    Systematic investigation of the effect of lyophilizate collapse on pharmaceutically relevant proteins III: collapse during storage at elevated temperatures

    Eur. J. Pharm. Biopharm.

    (2013)
  • J.A. Searles et al.

    Annealing to optimize the primary drying rate, reduce freezing-induced drying rate heterogeneity, and determine T'g pharmaceutical lyophilization

    J. Pharm. Sci.

    (2001)
  • N.W. Warne

    Development of high concentration protein biopharmaceuticals: the use of platform approaches in formulation development

    Eur. J. Pharm. Biopharm.

    (2011)
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