WO2002064117A1

WO2002064117A1 - Sterile composition and its preparation

Info

Publication number: WO2002064117A1
Application number: PCT/GB2002/000647
Authority: WO
Inventors: Steven John Burton; Mark Burton
Original assignee: Prometic Biosciences Ltd
Current assignee: Prometic Bioseparations Ltd
Priority date: 2001-02-14
Filing date: 2002-02-14
Publication date: 2002-08-22
Anticipated expiration: 2003-08-14
Also published as: GB0103620D0

Abstract

A process for preparing a sterile, free-flowing powder comprising beads of a porous matrix material incorporating an active agent, comprises causing a sterile solution of the agent to flow through a sterile bed of the material, and freeze-drying the agent-containing material.

Description

STERILE COMPOSITION AND ITS PREPARATION Field of the Invention

This invention relates to a sterile composition of particles and to its preparation. Background of the Invention

It is of course well known that drugs can be administered by subcutaneous injection. There is growing interest in needleless injection, in order to avoid the hazards, inconvenience and pain associated with the use of needles. Needleless injection typically involves the delivery of a stream of particles, at high velocity, under gas pressure, through a device that directs the particles onto an area of the skin. It has been shown successfully that drugs can be administered effectively in this way, transcutaneously at various sites on the body.

Devices that can be used for needleless injection, and compositions that are suitable for delivery by needleless injection, are the subject of various publications (including patents) from PowderJect. Reference may be made in particular to WO-A-94/24263 and WO-A-96/20022.

Not all active therapeutic agents are readily amenable to the simple formulation of particles having the appropriate characteristics, including mass and density, that are generally required for needleless injection, e.g. by mixing. Mixing may involve loss of active material. Further, freeze-drying typically gives a product that has low density, and is therefore unsuitable for needleless delivery.

Alternatively, the therapeutic agent may be impregnated in a matrix material which is then subjected to freeze-drying. Such materials have a number of potential applications such as the prolonged release of the active agent, as well as transcutaneous drug delivery. A problem with this approach is the difficulty of making the product sterile; it is not possible to autoclave or filter- sterilise beads with active agent in them. Summary of the Invention

The present invention is based on the realisation that beads of a matrix material and a solution of a therapeutic agent can be sterilised independently, that the solution can be used to impregnate the beads, and that the impregnated beads can be freeze-dried, to give a product that has characteristics suitable for needleless delivery.

In particular, the invention utilises the matrix material, e.g. agarose beads, in the form of a column. This has the advantages of uniformity, reduced waste due to displacement rather than dilution, the ability to use a high concentration of actives since no dilution takes place (the process is therefore particularly suitable for drugs having low solubility), and the ability to concentrate the active, or provide a medium allowing for slow release. In addition, by suitable construction of a column with a removable part, that part can be used as the base for the impregnated matrix material, during freeze-drying. Description of the Invention

The matrix material is preferably in the form of porous spherical beads, e.g. of albumin, cellulose or agarose gel. Other suitable materials may be selected by one of ordinary skill in the art, primarily having regard to the ultimate requirement for particles intended for drug delivery applications, e.g. from a PowderJect device as described in WO-A-94/24263 or WO-A-96/20022..

The therapeutic agent that is used in this invention is not critical. Any agent that is suitable to be administered transcutaneously, or intended for controlled release, can be used. Examples include proteins such as insulin, hormones, peptides, peptide mimetics, antibiotics, anaesthetics, corticosteroids, immunomodulators, immunosuppressants, and vaccines, aswellasimmunogens such as antigens that are often together with an adjuvant.

The formulation may also include an excipient or any other component that is considered necessary or desirable. For example, the formulation may include a carbohydrate, in order to render the product stable in a dry state. Suitable carbohydrates include dextrans, sucrose and mannitol. The addition of any such material preferably does not increase the viscosity too much, in order that the active agent can adequately penetrate the beads. The column in which the matrix material is maintained, while a solution of the active agent is passed through it, may be of any conventional type. The term "column" is used herein to describe any containing apparatus in which the matrix material is maintained in a mass, and allows unidirectional flow of the formulating solution via an inlet and an outlet. Such a vessel may have a detachable lid thus allowing the formulated matrix to be lyophilised without compromising sterility. For the purposes of sterilisation, the matrix material, column housing and associated tubing can be autoclaved prior to formulation with the active compound. In practice, any suitable means of sterilising the individual components may be employed, including but not limited to gamma irradiation, vapour sterilisation and wet chemical sterilisation. The solution of the therapeutic agent is preferably sterilised by pumping it through a suitable filter in a conduit leading to the column. An advantage of this arrangement is that pumping can be discontinued as soon as breakthrough occurs; in this way, all the active material can be used, without loss. It is also preferred that a flow of sterile air should be passaged through the impregnated beads, by means of a vacuum in order to reduce the amount of any active material and associated for u\ants trapped within the interstitial spaces between beads.

Excipients such as Dextran 67 give rise to formulation solutions of increased viscosity. These solutions require increased formulation time and the extraneous formulation is more difficult to remove from within the interstitial spaces using the vacuum. The invention will now be described by way of example only with reference to the accompanying drawing, which is a schematic representation of apparatus in which the process of this invention can be conducted. The drawing shows a container 1 including a solution 2 of an active agent. This solution can be passed along a line 3 by means of a pump 4, through a sterilising filter 5 to a column 6 having an outlet 7. The column is constructed with a detachable wall 8. After filling the column, so that the active agent can impregnate the beads in the column, the wall is detached, and the open column housing can be used as the holding tray for freeze-drying the impregnated beads.

Preferably, the column design facilitates packing and impregnation with a large bed-length to cross-section area ratio and the removal of surplus formulation mixture and freeze-drying with a small bed-length to cross-section ratio. This is conveniently achieved with a column housing of elongated cuboid shape (wherein column packing and impregnation are performed with liquid flow in the direction of the longitudinal axis) with an oblong-shaped detachable side wall to facilitate the removal of surplus formulation mixture and lyophilisation. Such a column may be fitted with bed support screens at both ends and the side opposite the detached wall to retain the packed bed whilst permitting liquid flow. The following Examples illustrate the invention . Examples

Formulations of agarose particles (available as PuraBead 4, from ProMetic BioSciences Inc., Canada) were tested. For each formulation, PuraBead 4 was washed free of preservative (10 x a bed equivalent volumes of RO water) on a sintered glass funnel and packed into a chromatography column (50 mm diameter x 20 cm length) at a constant pressure of 103 kPa (15 psi). The column length and gel volume were determined.

The outlet of the packed column was connected to a UV detector. RO water was pumped through the column bed (linear flow of 30-40 cm h^"1) until a stable baseline was recorded. To give an indication of column packing, acetone (5 ml_ of a 2% v/v solution) was introduced to the column and the flow continued until elution of the acetone was complete.

The target formulation for all samples was designed to be 25% w/w agarose, 74% w/w excipient and 1% w/w insulin. These formulations were converted to an aqueous formulation solution with equivalent concentrations of excipient and active, e.g. 11.84% w/v excipient and 0.16% w/v insulin. Assuming a complete re-swell post-lyophilisation, it was calculated that 200 ml of gel would yield 22 g formulation. The excipients were Dextran 1 , sucrose, mannitol and Dextran 66. A sample of formulated agarose was prepared with each of the excipients.

Formulation solutions (x 1 ) were prepared by dissolving first the excipient in RO water (approximately 80% of the final volume). The insulin was dispersed in this solution and the pH reduced >3, using concentrated hydrochloric acid solution, to dissolve the insulin. Solutions were titrated, using sodium hydroxide solution, to pH 4.15 ± 0.2, before making up to the final volume and filtering through a SFCA membrane filter. For each formulation, the solution was pumped onto the packed column until breakthrough was observed, monitored by absorbance at 280 nm. The formulated PuraBead was transferred to a sintered glass funnel and exposed to vacuum for 10 minutes. This process removed any interstitial formulation solution and converts the agarose to the consistency of a "moist gel". The material was stored at 4°C.

Materials were lyophilised in stainless steel, sintered freeze-drying trays according to the general cycle shown in Table 1 , in conjunction with the specific excipient dependent variables detailed in Table 2.

Table 1 Lyophilisation Cycle Parameters

* parameters determined by Table 2 Table 2 Excipient-dependent lyophilisation parameters

Analysis suggested that all columns were well packed. The elution profiles provided evidence of columns free of voids or channelling. The excipients were freely soluble and a sharp breakthrough profile (UV) was observed for all formulations after approximately 1 column volume. The column approach to formulation was significantly improved by exposure of the formulated matrix to a vacuum to remove surplus formulation mixture trapped between heads in the packed bed. The formulations studied contained a 74% w/w concentration of the major excipient, which requires a formulation solution of 11.84% w/v concentration.

The moisture content of all four batches was less than 2% w/w (measured range 0.88-1.68% w/w).

The porosity of the PuraBead remained unchanged by formulation and lyophilisation with all the of the excipients studied. At the concentration used, all the excipients studied preserve the internal structure of the PuraBead material throughout the lyophilisation process.

Re-swell values are all ±15% of the predicted values. This data combined with the particle size distribution data, suggests that these materials re-swell fully on re-hydration.

Particle size analysis data suggests no significant change in particle size distribution or bead size after formulation, lyophilisation and re-hydration of the material.

Microscopy of the re-hydrated formulations revealed that the formulation and lyophilisation process did not cause a significant increase in bead damage with any of the excipients studied.

Claims

1. A process for preparing a sterile, free-flowing powder comprising beads of a porous matrix material incorporating an active agent, which comprises causing a sterile solution of the agent to flow through a sterile bed of the material, and freeze-drying the agent-containing material.

2. A process according to claim 1 , wherein the matrix material is agarose.

3. A process according to claim 1 or claim 2, which comprises stopping the flow on breakthrough.

4. A process according to any preceding claim, wherein a solution of the agent is pumped to the bed via a sterilising filter.

5. A process according to any preceding claim, which additionally comprises the application of reduced pressure to the bed after stopping the flow causing the passage of sterile air through the bed to remove extraneous liquid.

6. A process according to any preceding claim, wherein the bed is held within a column having a detachable wall, during the flow, whereby the wall can be detached and the open column housing used as a holding tray for the agent- containing material during freeze-drying.