EP1206670A1

EP1206670A1 - Lyophilization method

Info

Publication number: EP1206670A1
Application number: EP00954556A
Authority: EP
Inventors: Bernd Sennhenn; Martin Kramer
Original assignee: Bayer AG; Bayer Healthcare AG
Current assignee: Bayer AG
Priority date: 1999-08-02
Filing date: 2000-07-21
Publication date: 2002-05-22
Anticipated expiration: 2020-07-21
Also published as: DE19936281A1; ES2237445T3; US6684524B1; WO2001009559A1; DE19936281C2; EP1206670B1; DE50009496D1; CA2380949A1; AU6697200A; JP2003506654A

Abstract

The invention relates to a lyophilization method which comprises the following steps: In a first step, the pressure in the drying chamber is reduced at a temperature in the drying chamber that is above the solidification point of the preparation until a visible crystallization of the solvent is observed. In a second step, the temperature in the drying chamber is reduced to a temperature that is below or equal the solidification point of the preparation until the crystallization of the solvent is terminated. In a third step, the frozen solvent is sublimed by applying reduced pressure.

Description

Freeze-drying process

The present invention relates to a new method for freeze drying (lyophilization).

Freeze drying is an important process for stabilizing hydrolysis-sensitive and thermolabile preparations, as well as materials of biological origin that are to be dried under gentle conditions. With the help of freeze drying materials can be made without major

Changes and losses in biological activity are dried. A positive aspect of freeze drying is that the dried, "lyophilic" products can be reconstituted very quickly owing to their porous structure and very large specific surface area and assume their original properties again in solution. Therefore, freeze drying is preferably used for therapeutic sera, blood products, biologically active substances (hormones, vitamins, enzymes, medicinal substances), food preparations and flavors Liquid and semi-solid water-containing preparations, eg solutions, emulsions and suspensions, are suitable for freeze drying.

Drying from the frozen state combines the advantages of freezing and dehydration at low temperature and is generally carried out as follows:

• Cooling and crystallization of the solvent in the preparation

Atmospheric pressure.

Main drying, i.e. Sublimation of the crystallized solvent.

• Post-drying, ie evaporation of non-installed solvent components. The two drying steps differ fundamentally: In the main drying (primary drying) the sublimation of the frozen solvent takes place under reduced pressure. In the optional post-drying (secondary drying), the evaporation of unfrozen solvent takes place at reduced pressure and at an elevated temperature.

In the processes known from the prior art, the preparations to be dried are placed in vessels, e.g. So-called vials, frozen at atmospheric pressure and the temperature of the product is set to a value suitable for starting the main drying.

Freezing (crystallization) is followed by main drying, during which the frozen solvent is converted from the solid to the gaseous state under reduced pressure, i.e. is sublimated. The energy used in sublimation is e.g. supplied via heated shelves.

During the main drying process, the frozen preparation must not warm up above its melting point. After-drying can follow the main drying, in which unfrozen solvent is removed at elevated temperature and reduced pressure. These are solvents that e.g. can be adsorbed on the solid matrix or enclosed in amorphous areas.

In the present application, crystallization means the freezing (solidification) of the solvent content in the preparation. In the present application, preparation is understood to mean any type of material that is suitable for freeze-drying.

The temperature profile during freeze drying can be controlled by suitable devices. Temperature-adjustable setting plates are known to the person skilled in the art. With this method, the setting plates can be used both after loading (cooling variant A) and before loading

Freezing temperature (cooling variant B). One is also possible Pre-heating of the plates and / or the preparation on the plates to a temperature above the actual freezing temperature in order to ensure that the individual vials are at the same temperature or to minimize the cooling time before freezing. This is followed by the actual freezing with a further reduction in the plate temperature (cooling variant C).

Variants A-C describe freezing on shelves. Other known processes are freezing processes in cold baths and rotating vessels (shell freezing, spin freezing) or by spraying devices; they differ in principle from the methods described above. The preparations to be dried are usually aqueous

Systems. In principle, other solvents or their mixtures with aqueous systems can also be used, e.g. Carboxylic acids (e.g. glacial acetic acid), dimethyl sulfoxide (DMSO), ethers (e.g. dioxane), dimethylformamide or alcohols (e.g. t-butanol).

The various conventional types of freezing and freeze drying are e.g. adequately described in relevant textbooks, e.g. Lyophilization, Essig, Oschmann, Wissenschaftliche Verlagsgesellschaft Stuttgart mbH, 1993; Pages 15-29, Freeze-drying, Georg-Wilhelm Oetjen, VCH Verlag, 1997; Page 3-58 and Freeze Drying, Athanasios I. Liapis, in: Handbook of

Industrial Drying, ed. By A.S. Mujumdar, Montreal, pages 295-326.

All freezing processes have in common that if the preparation is suitable, a tempering step (thermal treatment or annealing) can take place after freezing. This tempering step serves to promote the crystallization of amorphously solidified solids and unfrozen solvent and thus to achieve increased crystallinity and reduced residual moisture. To carry out the frozen preparation is heated to a temperature which is above the glass transition temperature (Tg ') of the amorphously solidified solution and below the melting point of the solution. The amorphous phase, which usually contains high proportions of non-crystallized solvent, changes from the glass state to the rubbery state and the mobility of molecules is increased. The consequence is Formation of nucleoli that grow into crystals (so-called eruptive recrystallization) and the attachment of solvent molecules to already existing solvent crystals.

The annealing process is also known from the literature. Descriptions of the

Annealing processes can be found in The Lyophilization of Pharmaceuticals: A Literature Review, N.A. Williams and G. P. Polli, Journal of Parenteral Science and Technology, (1984 Mar-Apr) 38 (2) 48-59, Basic Aspects and Future Trends in the Freeze-Drying of Pharmaceuticals, L. Rey, Develop. biol. Standart., Vol. 74, (Karger, Basel, 1991), pp. 3-8 and Fundamental Aspects of Lyophilization, L. Rey,

Researches and Development in Freeze-Drying, ed. By L. Rey, Paris, 1964, 24-47.

The lyophilisates produced with the freeze-drying processes according to the prior art usually have a high flow resistance, which hinders the escape of the gaseous solvent. It can also

Crystallization of the dissolved ingredients partly to completely omitted, so that products are obtained which are partly to completely amorphous. The consequences that can result from this are mechanical damage to the product cake due to the escaping solvent vapor flow and thereby potential product loss, as well as collapse and thawing phenomena during drying.

In addition, the end user places particular demands on pharmaceutical and food preparations, so that severe damage is not desired.

It was therefore an object of the present invention to find a method for freeze-drying with which lyophilisates can be produced which do not have the problematic properties mentioned above and are therefore easier to handle. Surprisingly, it has now been found that mechanically more stable lyophilisates are obtained if the freeze-drying process is carried out as follows:

Phase 1: Lower the pressure in the drying chamber until

Onset of visible crystallization of the solvent at a temperature in the drying chamber that is above the fixed point of the preparation. Phase 2: Lowering the temperature in the drying chamber to a temperature which is below or identical to the fixed point of the preparation until the crystallization of the solvent has ended. Phase 3: sublimation of the frozen solvent using reduced pressure.

In the present application, the fixed point of the preparation is understood to be the temperature at which the solvent in the preparation changes to the solid state.

According to the invention, the pressure in the drying chamber is initially at one

Temperature in the drying chamber, which is above the fixed point of the preparation, is reduced to a pressure value below atmospheric pressure (according to FIG. 1). This results in superficial cooling of the preparation by evaporation and partial crystallization of the solvent on the surface (phase 1). In a preferred embodiment, the pressure in the case of aqueous solutions is 0.1 to 6 mbar, in particular 0.2 to 3 mbar. For various preparations, this pressure p is plotted in the drying chamber (measured with a capacity manometer) as a function of the concentration c (in mol / L) in FIG. 1. The values for various aqueous preparations were shown as follows: solid line, squares = mannitol solid line, circles = sucrose solid line, diamonds = sodium chloride broken line, circles = glycine broken line, triangles = maltose - square on the ordinate = solvent water

This pressure reduction can e.g. be carried out at room temperature. In a further embodiment, the preparations are preheated to a temperature which is between room temperature and the fixed point of the preparation before or during the reduction in pressure. This pre-tempering (e.g. on

Shelves) also ensures that the cooling devices, some of which have low cooling rates, in a short time to the desired crystallization temperature, i.e. can be brought into the area of the fixed point of the preparation. It is crucial that this pre-tempering does not lead to crystallization of the solvent.

Have crystals now, e.g. formed in the form of a water / ice mixture or an ice layer floating on the surface, the pressure in the drying chamber can be raised again to ambient pressure and the temperature in the drying chamber for crystallization at or below the fixed point of the

Preparation to be brought (phase 2). It is also possible to keep the pressure reduced during crystallization; this has no relevant effects on the crystallization of the solvent. In principle, any temperature that is below the fixed point of the preparation or is identical to it is suitable for crystallization. In a preferred embodiment, the temperature is

Crystallization in aqueous solutions between -60 ° C and 0 ° C.

After crystallization, the preparation may be final

Temperature brought to the start of drying. This temperature is from the present product and from the vapor pressure curve of the solvent

Pressure to be used in the main drying depends. In a In a preferred embodiment, this temperature is -60 ° C. to 0 ° C. in aqueous solutions.

Then the main drying follows. In principle, this is the same as for the methods according to the prior art. In a further embodiment, the method additionally has a post-drying phase (phase 4) after the main drying. However, this is not necessary in some cases if there is an annealing phase (phase 2a).

According to a further embodiment, an annealing process as described above is connected to phase 2. This tempering process is referred to below as phase 2a. Annealing provides products with higher crystallinity and lower residual moisture after the main drying and shortens the post-drying or makes them unnecessary.

The method according to the invention is to be explained in more detail by FIGS. 2 to 7: Here, the temperature (T) and the pressure (p) are plotted in millibars (mbar) in the drying chamber against the time t, the temperature being the solid, the pressure the broken line is shown. For better clarification of the methods, the figures always show embodiments

Main and final drying.

Fig. 2 shows a conventional manufacturing method according to the prior art.

Fig. 3 shows a conventional manufacturing process with tempering after

State of the art.

4 shows the process according to the invention with pressure reduction (phase 1), crystallization (phase 2), tempering step (phase 2a) and subsequent main and secondary drying (phases 3 and 4). 5 shows the method according to the invention with pre-temperature control and pressure reduction (phase 1), crystallization (phase 2) and subsequent main and secondary drying (phases 3 and 4).

6 shows the method according to the invention with pre-tempering and

Pressure reduction (phase 1), crystallization (phase 2), tempering step (phase 2a) and subsequent main and final drying (phases 3 and 4).

7 shows the process according to the invention with pressure reduction (phase 1), crystallization (phase 2), and subsequent main and subsequent drying (phases 3 and 4).

The lyophilisates which can be produced by the process according to the invention have improved structural cohesion and are less mechanically damaged by the escaping steam flow, even at increased sublimation rates, than lyophilisates which are produced by processes according to the prior art. They show less pronounced collapse phenomena.

The residual moisture contents which can be achieved by the process according to the invention are in principle comparable to those which are achieved by freeze-drying according to the prior art (see Table 3).

Preparations with or without so-called scaffolders are suitable for use in the process according to the invention. With such scaffolders, a porous scaffold or a matrix can be generated during freeze drying. Freeze-drying products which are produced using scaffolders or other substances which are suitable as scaffolders on account of their physicochemical properties are preferred. Freeze-drying products which are selected from the compound classes amino acids, carbohydrates (mono-, disaccharides, sugar alcohols, oligo-, polysaccharides), peptides, polymeric compounds and salts are particularly preferred. be put. Most preferred are those which are produced using scaffolders selected from the group consisting of mannitol, sucrose, maltose, glycine and sodium chloride.

Tab. 1: List of the preferred scaffold builders A large number of solvents are suitable for the process according to the invention. For the sake of better understanding, the description mainly deals with aqueous systems. However, the invention expressly also relates to non-aqueous systems. Aqueous solutions are preferably used.

embodiments

Implementation scheme of freeze-drying with the "vacuum-induced" freezing according to the invention and methods according to the prior art

Input materials, materials and devices

• A 5% aqueous solution of mannitol was prepared and sterile filtered through a 0.2μm membrane filter.

• The solution was filled to 3 ml in 10-liter tubular glass vials and freeze-drying stoppers were attached.

• For freeze drying, the filled vials were placed in a freeze dryer from Kniese (floor space 0.6 m ² ).

Execution:

• The solution was preheated on the shelves at + 10 ° C.

• The chamber pressure was then reduced to 0.65 mbar (for parameter selection see Fig. 1).

• After the pressure value of 0.65 mbar was reached and partial freezing on the product surface began, the system was vented to ambient pressure and at the same time brought the setting plates to a temperature that e.g. for mannitol can be -7.5 ° C. • The products were kept at the respective temperature for 1 hour and then cooled to -40 ° C (freezing option III).

• Freezing was followed by main drying for 8 hours at + 40 ° C and 1.6 mbar without subsequent drying. The observed abnormalities were given in Table 2. • Appropriate solutions were used as a reference, which are not the

“Vacuum-induced freezing according to the invention (freezing variant III) were thrown, but frozen at 2K / min to - 0 ° C (freezing variant I) and hypothermia, or quickly frozen in the cold bath to -60 ° C (freezing variant II) and then freeze-dried under the same conditions.

Tab. 2: Unwanted changes and damage to the product cake in various freezing processes and main drying with plate temperature (+ 40 ° C). A weighting of the strength and frequency of the damage occurred was given with (-), i.e. none, (+) weak, (++) strong and (+++) very strong.

Implementation schemes of freeze-drying with the "vacuum-induced" freezing according to the invention (variant III) and with the "vacuum-induced" freezing according to the invention with subsequent tempering process (variant IV)

Input materials, materials and devices

• An aqueous, 2% solution of mannitol was prepared and sterile filtered through a 0.2 μm membrane filter. • The solution was filled to 3 ml in 10R tube glass vials and freeze-drying stoppers were attached.

• For freeze drying, the vials were placed in a freeze dryer from Kniese (floor space 0.6 m ² ).

Execution:

• The solutions were preheated on the shelves at + 10 ° C. • The chamber pressure was then reduced to 0.65 mbar (for parameter selection see

Fig. 1).

• After the pressure value of 0.65 mbar was reached and partial freezing on the product surface began, the system was vented to ambient pressure and at the same time brought the setting plates to a temperature that e.g. for mannitol can be -7.5 ° C.

• The products were kept at the respective temperature for 1 hour and then cooled to ^ -0 ° C (variant III).

• For variant IV, the samples were warmed to -3 ° C following the procedure of variant III, annealed for 4 hours at this temperature and then cooled to -40 ° C.

• As a reference, samples were frozen at a cooling rate of 2 K / min to -40. The samples were hypothermic. (Variant I).

• Freezing according to variant I, III or IV was followed by main drying for 20 hours at -10 ° C and 0.2 mbar and post-drying at + 40 ° C and 0.2 mbar for 2 hours.

After freeze-drying, the residual moisture of the lyophilisates was also determined by a Karl Fischer titration:

Tab. 3: Dependency of residual moisture and drying time on the freezing process.

Claims

claims

1. A method for freeze-drying preparations in a drying chamber, comprising the steps of cooling the preparation and crystallization of the solvent and sublimation of the frozen

Solvent by means of reduced pressure, the process being carried out as follows:

Phase 1: Lower the pressure in the drying chamber until visible crystallization of the solvent begins at a temperature in the drying chamber that is above the fixed point of the preparation. Phase 2: Lowering the temperature in the drying chamber to a temperature which is below or is identical to the fixed point of the preparation until the end of the

Crystallization of the solvent. Phase 3: sublimation of the frozen solvent using reduced pressure.

2. The method according to claim 1, characterized in that an aqueous solution is present.

3. The method according to claim 1, characterized in that the pressure in phase 1 is reduced to 0.1 to 6 mbar in aqueous preparations.

4. The method according to claim 3, characterized in that the pressure in phase 1 is reduced to 0.2 to 3 mbar.

5. The method according to claim 1, characterized in that the temperature in

Phase 2 is set to -60 to 0 ° C for aqueous preparations.

6. The method according to claim 1, characterized in that a tempering step (phase 2a) is carried out, wherein a temperature is set which is above the glass transition temperature (Tg ') of the amorphous solidified solution and below the fixed point of the preparation.

7. The method according to claim 1, characterized in that the temperature is set to -60 to 0 ° C in the start of the main drying in aqueous preparations.

8. The method according to claim 1, characterized in that a scaffold is used.

9. The method according to claim 1, characterized in that mannitol, sucrose, maltose, glycine or sodium chloride is used as the scaffolding agent.