Recent advances and persistent challenges in the design of freeze-drying process for monoclonal antibodies.

Monoclonal antibodies constitute nowadays an important therapeutic class and the number of approved molecules for clinical uses continues to increase, achieving considerable part of the therapeutic market. Yet, the stability in solution of these biopharmaceuticals is often low. That is why freeze-drying has been and remains the method of choice to obtain monoclonal antibodies in the solid state and to improve their stability. The design of freeze-drying process and its optimization are still topical subjects of interest and the pharmaceutical industry is regularly challenged by the requirements of quality, safety and efficiency set by the regulatory authorities. These requirements imply a deep understanding of each step of the freeze-drying process, developing techniques to control the critical parameters and to monitor the quality of the intermediate and the final product. In addition to quality issues, the optimization of the freeze-drying process in order to reduce the cycle length is of great interest since freeze-drying is known to be an energy-expensive and time-consuming process. In this review, we will present the recent literature dealing with the freeze-drying of monoclonal antibodies and focus on the process parameters and strategies used to improve the stability of these molecules and to optimize the FD process.

Compression of Vectors for Small Interfering RNAs Delivery: Toward Oral Administration of siRNA Lipoplexes in Tablet Forms.

Currently, most nonviral nucleic acid vectors are in the form of colloidal suspensions administered primarily parenterally. This type of formulation and the mode of administration impose strong constraints such as the size of the administered vectors or the production of sterile preparations. The tablet form provides access to easy oral administration, well accepted by patients; As regards nucleic acid vectors, a dry form represents an advance in terms of stability. Using an optimized lipid-based small interfering RNA-delivery system, we studied the tabletability of a liquid suspension of these vectors. We optimized the conditions of freeze-drying by choosing excipients and process, allowing for the conservation of both the gene-silencing efficacy of the formulated siRNAs and the supramolecular structure of the lipid particulate system. Gene-silencing efficacy was assayed on luciferase-expressing cells and the structure of the siRNA vector in freeze-dried and tablet forms was examined using small-angle X-ray scattering (SAXS) synchrotron radiation. The freeze-dried powders were then mixed with excipients necessary for the good progress of the compression by allowing for a regular supply of the matrix and the reduction of friction. The compression was carried out using a rotary press simulator that allows for complete monitoring of the compression conditions. After compression, formulated siRNAs retained more than 60% of their gene-silencing efficacy. Within the tablets, a specific SAXS signal was detectable and the lamellar and cubic phases of the initial liquid suspension were restored after resuspension of siRNA vectors by disintegration of the tablets. These results show that the bilayer lipid structures of the particles were preserved despite the mechanical constraints imposed by the compression. If such a result could be expected after the freeze-drying step, it was never shown, to our knowledge, that siRNA-delivery systems could retain their efficacy and structure after mechanical stress such as compression. This opens promising perspectives to oral administration of siRNA as an alternative to parenteral administration.

An overview on dosage forms and formulation strategies for vaccines and antibodies oral delivery.

Most of biopharmaceuticals in clinical use today are available in a solution or suspension form and delivered by invasive routes (i.e. injection). However, several attempts have been made in order to develop effective oral formulations of 'biomolecules' characterized by a fragile structure and a low bioavailability. To achieve an efficient delivery of such molecules by non-parenteral route, in particular, via the oral route, novel concepts are needed not only to overcome significant enzymatic and diffusion barriers but also to ensure stability and biological activity. Vaccines and antibodies have a special interest as biomolecules because of their high therapeutic efficacy both in prevention and treatment of several chronic diseases. In this review, we would like to highlight the trends made in the development of pharmaceutical forms to deliver these molecules by the oral route. Hence, we will focus on the description of the different forms (solutions, suspensions, powders, tablets, micro and nanocarriers …) available today or under research study, in which product stability and efficacy are maintained. A special attention will be paid to the formulation strategies that may include the addition of several functional excipients and/or adjuvants, aiming to protect, to functionalize or to modulate their release in the body.

Tableting behavior of freeze and spray-dried excipients in pharmaceutical formulations.

Most of biopharmaceuticals, in their liquid form, are prone to instabilities during storage. In order to improve their stability, lyophilization is the most commonly used drying technique in the pharmaceutical industry. In addition, certain applications of biopharmaceutical products can be considered by oral administration and tablets are the most frequent solid pharmaceutical dosage form used for oral route. Thus, the tableting properties of freeze-dried products used as cryo and lyoprotectant could be a key element for future pharmaceutical developments and applications. In this study, we investigated the properties that might play a particular role in the specific compaction behavior of freeze-dried excipients. The tableting properties of freeze-dried trehalose, lactose and mannitol were investigated and compared to other forms of these excipients (spray-dried, commercial crystalline and commercial crystalline milled powders). The obtained results showed a specific behavior in terms of compressibility, tabletability and brittleness for the amorphous powders obtained after freeze-drying. The comparison with the other powders showed that this specific tableting behavior is linked to both the specific texture and the physical state (amorphization) of these freeze-dried powders.

Development of monoclonal antibodies in tablet form: A new approach for local delivery.

Among the various pharmaceutical forms, tablets offer numerous advantages, like ease of administration, cost-effectiveness in production, and better stability of biomolecules. Beyond these benefits, the tablet form opens up possibilities for alternative routes for the local delivery of biopharmaceuticals such as oral or vaginal administration, thereby expanding the therapeutic applications of these biomolecules and overcoming the inconvenients associated with parenteral administration. However, to date there is limited information on the feasibility of developing biomolecules in the tablet form. In this study, we have evaluated the feasibility of developing monoclonal antibodies in the tablet form while preserving their biological properties. Different excipients and process parameters were studied to assess their impact on the antibody's integrity during tableting. ELISA results show that applying compression pressure up to 100 MPa is not detrimental to the antibody's binding properties when formulated from a lyophilized powder containing trehalose or sucrose as the major excipient. This observation was confirmed with SPR and ultracentrifugation experiments, which demonstrated that neither the binding affinity for both Fc and Fab antibody fragments nor its aggregation rate are affected by the tableting process. After compression, the tablets containing the antibodies have been shown to be stable for 6 months at room temperature.

Image analysis quantification of sticking and picking events of pharmaceutical powders compressed on a rotary tablet press simulator.

PURPOSE: The aim of this work was to develop a quantification method based on image analysis, able to characterize sticking during pharmaceutical tableting. Relationship between image analysis features and relevant mechanical parameters recorded on an instrumented tablet press simulator were investigated. METHODS: Image analysis, based on gray levels co-occurrence matrices (GLCM), generated textural features of the tablet surface. The tableting simulator (Stylcam® 200R, Medelpharm), instrumented with force and displacement transducers, provided accurate records. The tablet defects and compaction process parameters were studied using three pharmaceutical powders (Fast-Flo® lactose, anhydrous Emcompress® and Avicel® PH200 microcrystalline cellulose), five compression pressures (60 to 250 MPa), five lubricating levels, and three types of punches (standard steel, amorphous hard carbon and anti-sticking punches). RESULTS: Texture parameters made it possible to quantify with precision tablets' aspect. The selected parameter IC2 (Information on Correlation 2) plotted versus the ratio between the ejection shear stress (Esh) and the compression pressure (Cp) let appear a relevant knowledge space where it was possible to identify a normal and a degraded tableting mode. A positive link between those two parameters was shown. CONCLUSION: Since the Esh/Cp ratio was related to image analysis results, it proved to be an interesting defect tag.

Indices for the brittleness of pharmaceutical tablets: A reassessment.

Brittleness is an important mechanical property. In the classical sense, a material is considered brittle if, during loading, it behaves elastically until failure. Nevertheless, it is also sometimes understood as the fact to be resistant to breakage. In the case of pharmaceutical tablets, three different indices have been defined to measure brittleness: the brittle fracture index (BFI), the brittle/ductile index (BDI) and the tablet brittleness index (TBI). The aim of this work was to reassess the meaning of the different indices that are known to give contradictory results. Using theoretical considerations, numerical modelling and experiments, it was possible to show that the only index that unequivocally measures the brittleness of the tablet understood as elastic until failure is the BFI. If the other two indices can be useful, for example to assess the friability of the tablet in the case of the TBI, they do not make it possible to measure tablet brittleness in the classical sense, i.e. as opposed to ductility.

Effect of geometrical features on the capping behavior of biconvex tablets.

Capping is a common industrial issue during the manufacturing of pharmaceutical tablets. It is influenced by both process and formulation parameters. In this work, a systematic study of the influence of the geometrical features of biconvex tablets on capping occurrence was performed on a model formulation, using a design of experiment. Capping was characterized by the pressure at which half of the produced tablets were capped. The influence of the tablet geometry was assessed by varying three parameters: the diameter (D), the band thickness (W) and the ratio between the radius of curvature (R) and the diameter, i.e. R/D. Results showed that having a large diameter, a low band thickness and a high curvature (i.e. a low R/D) favored capping occurrence. Moreover, the effects are not independent as cross-effect were detected. Finally, even for homothetic tablets (i.e. same R/D and W/D) it is shown that a large diameter increases capping occurrence. These results could be used in the future as a guideline for punch selection during tablet development.

Tableting properties of freeze-dried trehalose: Physico-chemical and mechanical investigation.

Freeze-drying of biopharmaceutical products is the method of choice in order to improve their stability and storage conditions. Such freeze-dried products are usually intended for parenteral route administration. However, many biopharmaceutical materials administered by parenteral route are used to treat local diseases particularly in the gastro-intestinal tract. Therefore, many studies concentrate nowadays their effort on developing alternative dosage forms to deliver biopharmaceutical molecules by the oral route. Tablets are the most popular solid pharmaceutical dosage form used for oral administration since they present many advantages, but poor informations are available on the possibility of tableting freeze-dried powders. In this study, we evaluate the compaction behavior of freeze-dried trehalose powder since trehalose is one of the most used cryo and lyoprotectant for the lyophilisation of biopharmaceutical entities. Results show that freeze-dried trehalose powder can be tableted while remaining amorphous and the obtained compacts present very specific properties in terms of compressibility, tabletability, brittleness and viscoelasticity compared to the crystalline trehalose and compared to classical pharmaceutical excipients.

Comparing failure tests on pharmaceutical tablets: Interpretation using experimental results and a numerical approach with cohesive zone models.

The mechanical strength is an important quality attribute of pharmaceutical tablets. It can be determined using different failure tests like the Brazilian test or the three-point bending test. Nevertheless, literature shows that different failure tests often give conflicting values of tensile strengths (TS), which are generally calculated using the maximum stress criterion as a failure criterion. This work started from the hypothesis that these discrepancies are in fact due to the application of this criterion which is not suited to study pharmaceutical tablets, first due to heterogeneity of the stress distributions during the tests and second due to the quasi-brittle nature of pharmaceutical tablets. As an alternative, a numerical fracture criterion which is known to be well-suited for quasi-brittle solids (cohesive zone model, CZM) was used and calibrated using experiments. Using this approach, the breaking forces obtained numerically were shown to be in fair agreement with the experimental ones. Above all, the numerical results made it possible to catch the trends when comparing the different failure tests one to another. Especially, the model made it possible to retrieve the factor 2 between the TS obtained by three-point bending and by diametral compression found in the literature.

Breaking patterns of press-coated tablets during the diametral compression test: Influence of the product, geometry and process parameters.

Press-coated tablets are a high-interest technology in chronopharmaceutics, for modified release applications. As for any kind of tablet, the test of the mechanical resistance is of primary importance at the industrial level during both the development and production steps. For this purpose, the diametral compression test is commonly used in the industry for press-coated tablets. Nevertheless, the result of this test can be much more complex compared to the case of single layer tablets. This work aims to study the applicability of this test to press-coated tablets. Diametral compression tests were performed on press-coated tablets obtained with different products (shell/core), shell sizes and compaction pressures. Four types of breaking profiles were found: total diametral, shell diametral, around the core and laminated depending on the process parameters/products used to obtain the tablet. Digital image correlation was used in order to understand the breaking patterns especially in terms of failure initiation and propagation. The kind of breaking pattern obtained is dependent on the final structure of the tablet in terms of density distribution and thus of elastic properties. To confirm the findings, numerical simulations by the finite element method was used to visualize the stress distribution inside the tablet and confirm the influence of the process parameters. The multiple failure profiles obtained imply that the output value of the diametral compression test applied to press-coated tablets should be taken with caution.

Controlling the lag-time and release kinetics of press-coated tablets using process parameters and tablet geometry.

Press-coated tablets are an advantageous technology to achieve delayed releases of active ingredients. They are characterized by a core-shell structure, that makes it possible to tune the lag-time and release kinetics in order to meet the chronotherapeutical goals. Thus, these features are the most important quality attributes to be controlled when designing a press-coated tablet. Many studies have focused on the influence of the formulation on the release attributes. This work aims to study the influence of geometrical and process parameters on the release attributes of press-coated tablets, while keeping a constant formulation. In particular, the variation of compression pressure, layer thickness and band thickness made it possible to vary the lag-time from 1 h to 10 h. These parameters also have an influence on the release kinetics after the lag-time. Indeed, two main opening modes were observed during the dissolution test that correspond to fast or slow release rates. The opening mode obtained depends on the density distribution in the shell, which is directly influenced by the process parameters.

Influence of the punch shape on the core and shell structure of press-coated tablets.

Press-coated tablets are a key technology to achieve delayed releases in chronotherapeutics. The drug release properties of this kind of tablets are linked to its unique core-shell structure. It is thus important to understand the influence of the process parameters on this structure. As different shapes can be used in the industry, we focused, in this study, on understanding the influence of punch shape on the final structure of a press-coated tablet. Experiments were performed using flat, bevel-edged and concave punches for the coating-compression to study the effect of the punch shape on the final properties of the core but also on the density distribution in the shell. The experiments were supported by numerical simulation to understand the mechanical effects in the powder compression process. It was found that the radial and axial stress state in the shell and in the core during compression is very dependent on the punch shape. The use of concave punches results in a more hydrostatic stress state compared to flat punches. The consequences on the structure are a more homogenous shell and less deformation of the core, which confirms that the tooling shape is a critical parameter to consider for the production of press-coated tablets.

Changes in the specific surface area of tablets composed of pharmaceutical materials with various deformation behaviors.

OBJECTIVE: The aim of this work is to study the effect of compaction on the specific surface area of tablets composed of various pharmaceutical materials (microcrystalline cellulose, lactose, and anhydrous calcium phosphate) compacted under seven degrees of compaction pressure. METHODS: In a first part, the influence of the deformation behavior of the compacted materials on the evolution of the specific surface area is observed. In a second part, the brittle and ductile abilities of the materials are calculated using the specific surface area values. The experimental results are used to calculate the number and the force of interparticulate bonds inside the tablet. RESULTS AND DISCUSSION: Tablets made of microcrystalline cellulose, which deform plastically, have specific surface areas that fall under pressure. In the case of lactose, the tablet specific surface area first increases to reach a maximum value at a pressure of 150 MPa. At higher pressure, however, the specific surface area decreases. The specific surface area of tablets composed of anhydrous calcium phosphate consistently increases, whatever the compaction pressure applied. Moreover, the evolution of the specific surface area is correlated with the tensile strength of the corresponding tablets. The number and the force of interparticulate bonds make it possible to classify the materials according to their deformation behavior and to quantify their ability to form cohesive tablets.

Polymorphic transformation of anhydrous caffeine under compression and grinding: a re-evaluation.

Polymorphic transformations that may occur during mechanical treatment are of great interest for the production of pharmaceutical solids. Anhydrous caffeine is a well-known example of such transformations but a careful reading of the already existing literature shows that published results are contradictory. In this study, both forms of caffeine, form I and form II, respectively metastable and stable at ambient pressure and temperature, were submitted to compression in an instrumented alternative press and to grinding, and were studied before and after treatment by X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC). Compression experiments showed no changes of form II during compression, whereas form I was partially transformed into form II. Nevertheless, this transformation did not happen immediately. Form II appeared after a kinetically slow transformation and was clearly detectable only after a few days, fact that was never mentioned by previous authors. Same phenomenon was observed after the grinding of form I but also after an extensive grinding of form II. DSC and XRPD measurements indicated that polymorphic transformation did not happen directly, but that a new intermediate form was obtained after mechanical treatment, which slowly turned into form II within a few days.

Effect of the compaction parameters on the final structure and properties of a press-coated tablet (Tab-in-Tab): Experimental and numerical study of the influence of core and shell dimensions.

With increasing interest in chronopharmaceutics, press-coated tablets have become a key technology in the field of modified release drug delivery systems. Although their benefits in terms of drug release have been largely studied, the comprehension of the compaction process of press-coated tablets is yet to complete. Particularly, the effects of geometrical parameters like the ratios between the thickness/diameter of the core and the thickness/diameter of the whole tablet were so far not much considered. Moreover, there is only few studies in the literature about the effect of the press-coating compression on the final structure and properties of the core. The present work consists in a joint experimental and numerical study that aims to assess these points. The study revealed high stress concentrations on the core during compression, causing high permanent deformations of the core, especially when the ratio between the core thickness and the total tablet thickness was high. The mechanical properties of the core tablet were also shown to be impacted: its density and strength were found to decrease before increasing again along the coating-compression. This effect was highlighted to be dependent on the triaxiality of the stress state (i.e. the ratio between the stresses in the different directions), itself depending on the two studied geometrical parameters. As the properties of the core affect the release attributes, ratios between the dimensions of the core and the dimensions of the whole tablet (thickness, diameter) should be taken into account as critical parameters for the manufacture of press-coated tablets.

Fate of Tableted Freeze-Dried siRNA Lipoplexes in Gastrointestinal Environment.

The incorporation of siRNA into nanocarriers is mandatory to facilitate its intracellular delivery, as siRNA itself cannot enter cells. However, the incorporation of these nanocarriers into oral, solid dosage forms and their fate in the gastrointestinal environment is yet to be explored. In the present work, the fate of, (i) naked siRNA, (ii) freshly prepared siRNA lipoplexes, and (iii) tableted siRNA lipoplexes, in simulated gastric and intestinal fluids was studied. The siRNA, either released from or protected within the lipoplexes, was quantified by gel electrophoresis and siRNA efficacy was assessed in cell transfection. The freshly prepared lipoplexes kept their siRNA load and transfection efficiency totally preserved during 1 h of incubation in simulated gastric fluid at 37 °C. However, in simulated intestinal fluid, despite no release of siRNA from lipoplexes after 6 h of incubation, gene silencing efficacy was dramatically decreased even after 1 h of exposure. The lipoplexes obtained from tablets efficiently protected siRNA in simulated gastric fluid, thus preserving the gene silencing efficacy, whereas their incubation in simulated intestinal fluid resulted in a marked siRNA release and decreased gene silencing efficacy. These results provided a detailed explanation for understanding the fate of siRNA in gastrointestinal conditions, when simply loaded in lipoplexes or formulated in the form of tablets.

Anisotropic porous structure of pharmaceutical compacts evaluated by PGSTE-NMR in relation to mechanical property anisotropy.

PURPOSE: The pore space anisotropy of pharmaceutical compacts was evaluated in relation to the mechanical property anisotropy. METHODS: The topology and the pore space anisotropy were characterized by PGSTE-NMR measurements. Parallelepipedical compacts of anhydrous calcium phosphate (aCP) and microcrystalline cellulose (MCC) were tested on top, bottom and side faces. A microindentation and three-point single beam tests were used to measure Brinell hardness, tensile strength and Young's modulus. All the data were submitted to a statistical analysis to test for significance. RESULTS: The porous structure of MCC compacts was anisotropic, contrary to those of aCP. The analysis of the pore space by PGSTE-NMR method showed that its structural anisotropy was controlled by the behaviour under compaction of the excipients. At the same time, the Young's modulus and the tensile strength were the same whatever the direction of testing. For the aCP compacts, all the faces had the same Brinell hardness. With MCC compacts, only the bottom face showed a lower Brinell hardness. CONCLUSIONS: Except for Brinell hardness measured on MCC compacts, the tested samples were characterized by anisotropic mechanical properties when its porous structures were sometimes anisotropic. Then, there is not a straight link between porosity anisotropy and mechanical properties.

Applicability of impulse excitation technique as a tool to characterize the elastic properties of pharmaceutical tablets: Experimental and numerical study.

Elastic properties are of particular interest during the development of tablets especially for the definition of the formulation and of the process parameters. Impulse excitation, which is used in several industrial fields to determine elastic properties of materials, is presented in this article as a new fast and relatively cheap technology for the determination of elastic constants of pharmaceutical tablets. This technique is based on the detection of the natural resonance frequencies of solids. It was found in the present work that, for tablets obtained using different products under different compaction pressures, it was possible to detect clearly at least 3 resonance frequencies. Moreover, the shape of the resonance peaks obtained in the spectrum could be a sign of the viscoelastic nature of the tablet. With the two first resonance frequencies, it was possible, under the assumption of isotropy, to calculate Young's modulus and Poisson's ratio for each tablet using the methodology presented in the norm ASTM E1876-01. The values obtained were found independent of the tablet size as expected, and were consistent with those presented in the literature using other methodologies. Moreover, using FEM simulation, it was found that the difference between the experimental value of the third resonance frequency and the value obtained numerically was well correlated with the expected anisotropy of the tablet. Impulse excitation could thus be an interesting methodology to study tablet anisotropy.

Role of Precompression in the Mitigation of Capping: A Case Study.

Capping is an important industrial problem that can arise during the manufacturing of pharmaceutical tablets. It corresponds, for biconvex tablets, to the detachment of one of the cups of the tablet during the ejection from the press or after relaxation. Solutions to this problem remain mainly empirical. Among them, precompression is widely used. One of the most popular explanation of the role of precompression in the mitigation of capping is that it increases the total time under compression. Following this interpretation, press manufacturers developped devices or machines that make it possible to maintain the pressure between precompression and main compression. In this note, we present a case study of capping. For the formulation proposed, a precompression that was maintained until the compression gave similar results as no precompression at all, i.e. capping of all the tablets. On the contrary, if the precompression was released before compression, capping stops completely. In this case, the effect of precompression is thus due to the separation of two compression events. Moreover, results prove that this separation must last long enough for the precompression to be efficient. This example shows that effect of precompression is more complex than often described in the literature.