TECHNICAL FIELD OF THE INVENTION

The present invention relates to a stable parenteral pharmaceutical composition, and in particular to a pharmaceutical composition for solution for infusion comprising a therapeutically effective quantity of tigecycline or a pharmaceutically acceptable salt or derivative thereof, as an active ingredient, and an effective quantity of trehalose in order to prevent the degradation of said active ingredient, and a process for the preparation thereof.

BACKGROUND OF THE INVENTION

Tigecycline is an analogue of minocycline, which is a semi-synthetic tetracycline. It is a t- butylglycyl substituted naphthacenecarboxamide freebase and its chemical name is (4S,4aS,5aR,12aS)-9-[2-(tertbutylamino) acetamido]-4,7-bis(dimethylamino)-l,4,4a,5,5a, 6,11, 12a -octahydro -3,10,12,12a tetrahydroxy-1,1 l-dioxo-2-naphthacenecarboxamide and its chemical structure is presented by the following Formula I.

Formula I

Tigecycline is a member of the glycy Icy cline class of antimicrobial agents and has in vivo and in vitro antibacterial activity against a broad-spectrum of pathogens. The antibacterial activity of Tigecycline is due to its ability to inhibit protein translation in bacteria by binding to the 30S ribosomal subunit and blocking entry of amino-acyl tRNA molecules into the A site of the ribosome.

Tigecycline is a yellow to orange powder. It has a poor gastrointestinal permeability and low bioavailability, thus it is provided as a lyophilized solid pharmaceutical formulation, reconstituted and diluted before intravenous administration

Tigecycline degrades under ambient conditions by oxidation and epimerization. The oxidation is the most prevalent form of degradation and relates to the chemical structure of tigecycline, as it possesses a phenol moiety, particularly prone to oxidation. When tigecycline is dissolved in water prior to lyophilization, it is mostly present as zwitterions with a resulting pH around 8, higher than the pKa of the phenolic group on tigecycline. Thus, in both water and saline solutions, the phenolic group becomes deprotonated and more susceptible to reaction with oxygen. This is why tigecycline compounding and lyophilization occur under a nitrogen blanket, while accordingly, in order to avoid unnecessary exposure to oxygen care must be taken by hospital staff during reconstitution and dilution. Consequently, an inert environment should be used during solution preparation and in the final product headspace.

When the pH of the tigecycline solution is less than the pKa of the phenolic group of tigecycline, then oxidation would occur, but to a lesser extent. Indeed, it has been observed that tigecycline oxidative degradation does decrease when the pH is lowered.

At low pH, however, another degradative process emerges, epimerization, as the most predominant degradation pathway. This epimerization occurs as a reverse of the stereochemistry of the position 4 ring atom, which is bonded to one of the dimethylamino substituents resulting in “epimer” impurity. Although the tigecycline epimer is believed to be non-toxic, it lacks the anti-bacterial efficacy of tigecycline and is, therefore, an undesirable degradation product. Tetracycline epimerization is also known to be temperature dependent, so production and storage of tetracyclines at low temperatures can also reduce the rate of epimer formation.

Both of these degradation pathways convert the pharmacologically active tigecycline molecule into a species that is inactive or with a lower antimicrobial activity.

One of the challenges in preparing and using formulations of tigecycline is that each of these two degradation pathways is favoured under a different pH range. Oxidative degradation is favoured under basic conditions, whereas epimerization is favoured under acidic conditions. Accordingly, a change to the processing or formulation of tigecycline that minimizes one of the degradation pathways typically enhances the other.

Therefore, there is a need to provide a pharmaceutical composition comprising tigecycline that is stable against tigecycline degradation over an extended period of time.

Various methods are already known for the industrial preparation of parenteral compositions comprising Tigecycline or a pharmaceutical acceptable salt or derivative thereof, as an active ingredient due to its useful therapeutical properties. However, the prior art has encountered substantial difficulties in the production of a stable parenteral tigecycline composition of an effective manufacturing process.

EP-B- 1858488 discloses a composition comprising tigecycline, a suitable carbohydrate such as lactose, and an acid or buffer. The combination of lactose and the acid or buffer resulted in lyophilized tigecycline compositions in which tigecycline was less susceptible to degradation, and namely both oxidative degradation and epimerization. Said compositions are reported to be more stable when dissolved, lyophilized, reconstituted, and/or diluted than compositions of tigecycline lyophilized with no excipients. However lyophilized powder comprising tigecycline must still be stored in controlled enviroment. In addition, the use of lactose as an excipient in lyophilized powder may cause severe allergic reactions to people with lactose intolerance and there is a big safety hazard.

EP-A- 1898884 discloses a process for the preparation of tigecycline in order to minimize the degradation tigecycline by controlling the temperature and oxygen content of environment during lyophilization process. By maintaining an aqueous liquid containing the tigecycline at a temperature of 2-8° C, before lyophilization, sparging the water used to form the liquid with an inert gas such as nitrogen, and blanketing the tigecycline with an inert gas while adding it to the water, the amount of tigecycline converted into degradants prior to lyophilization was maintained below 1% for 24 hours. Disadvantages of this approach include the difficulty of maintaining a low temperature and low oxygen content environment prior to lyophilization, and the need for hospital staff to maintain a low temperature and low oxygen content environment during reconstitution and administration of the tigecycline.

Although each of the above patents represents an attempt to overcome the stability problems of the active ingredient associated with pharmaceuticals compositions comprising tigecycline, there still exists a need for improving tigecycline’ s stability of such pharmaceutical compositions in a less complicated production approach including the difficulty of maintaining a low temperature and low oxygen content environment before lyophilization and during reconstitution and administration of tigecycline.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a stable pharmaceutical composition for parenteral administration containing tigecycline or pharmaceutically acceptable salt or derivative thereof as an active ingredient, which overcomes the deficiencies of the prior art.

It is another object of the present invention to provide a stable pharmaceutical composition for solution for infusion containing tigecycline or pharmaceutically acceptable salt or derivative thereof as an active ingredient, which is bioavailable, safe and effective with sufficient self-life and good pharmacotechnical properties.

Moreover, it is another object of the present invention to provide a suitable process for the preparation of a stable pharmaceutical composition for parenteral administration comprising a therapeutically effective quantity of tigecycline or a pharmaceutically acceptable salt or derivative thereof as an active ingredient, which is effective and reproducible.

In accordance with the above objects of the present invention, a stable pharmaceutical composition for parenteral administration is provided comprising a therapeutically effective quantity of tigecycline or a pharmaceutically acceptable salt or derivative thereof, as an active ingredient and an effective quantity of trehalose in order to prevent the degradation and improve the physicochemical stability of the active ingredient in the finished dosage form.

According to another embodiment of the present invention, a process for the preparation of a stable pharmaceutical composition for parenteral administration comprising a therapeutically effective quantity of tigecycline or a pharmaceutically acceptable salt or derivative thereof as an active ingredient, and an effective quantity of trehalose in order to prevent the degradation of said active ingredient is provided, wherein said process comprises following steps: a) Dissolving the total quantity of trehalose in water for injection and stirring for appropriate time until complete dissolution, wherein said solution preparation is performed at a temperature ranging from C to 8°C and under Nitrogen purging in the compounding vessel; b) The solution pH is adjusted to acidic pH value with suitable Hydrochloric acid solution; c) The total quantity of Tigecycline or salt or derivative thereof, is added slowly to the resulting solution of step b) and stirred for appropriate time until complete dissolved and the pH is adjusted to a pH value between 4.5 to 5.5 with suitable Hydrochloric acid or Sodium Hydroxide solution; d) The solution volume is adjusted to the predetermined volume with water for injection; e) The prepared bulk solution of step d) is aseptically filtered with suitable membrane filters; f) The filtered solution is filled in clear tubular Type I glass vials and semi-stoppered with butyl rubber stoppers for lyophilisation; and g) The filled semi-stoppered vials are lyophilized according to the following parameters: the freezing stage is carried out at a temperature ranging from about -40°C to -45°C, the primary drying stage is carried out at a temperature ranging from about -35°C to 0°C, and at pressure ranging from about O.lmbar to OJmbar and the secondary drying stage is carried out at a temperature ranging from about 25°C to 40°C, and at pressure ranging from O.lmbar to 0.3mbar.

Further preferred embodiments of the present invention are defined in dependent claims 2 to 7 and 9 to 11.

Other objects and advantages of the present invention will become apparent to those skilled in the art in view of the following detailed description.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, a pharmaceutical composition comprising tigecycline or salts or derivatives thereof is considered to be “stable” if said ingredient degradates less or more slowly than it does on its own and/or in known pharmaceutical compositions during storage.

An excipient is considered to be “incompatible” with tigecycline or salts or derivatives thereof if it promotes the degradation of said active ingredient, that is to say, if said active ingredient degrades more or faster in the presence of said excipient when compared with the degradation of said active ingredient on its own. The terms “incompatibility”, “compatible” and “compatibility” are defined accordingly.

One of the main disadvantages of tigecycline or salts or derivatives thereof is the fact that, it is very labile and consequently many limitations concerning the choice of excipients are raised.

In the study on the chemical stability of tigecycline, we have tested several stabilizing agents, including mannitol, trehalose and raffinose and also the relationship between the content of stabilizing agent and the stability of a composition comprising tigecycline.

It has been surprisingly found that the object of the present invention is achieved by employing Trehalose as stabilizing agent, in order to prevent the degradation and improve the physicochemical stability of the active ingredient both prior lyophilization and during reconstitution and administration.

Trehalose is a disaccharide, commercially available as trehalose dihydrate, that consists of two subunits of glucose bound by an a:l— >1 linkage (a-D-glucopyranosil a-D-glucopyranoside) and is thus non-reducing. This bonding makes trehalose very resistant to acid hydrolysis, and therefore is stable in solution at high temperatures, even under acidic conditions. The use of trehalose in pharmaceutical formulations is due to its characteristics such as high glass transition temperature, low rate of hydrolysis, control of osmolarity, and protein stabilization. In parenteral formulations, trehalose may be a suitable choice because it can be sterilized by autoclaving without the browning associated with conventional parenteral formulations. In addition, trehalose has a favorable critical temperature for lyophilization and thus it has been proposed as a bulking agent for parenteral products.

The pharmaceutical compositions of the present invention may also contain one or more additional formulation ingredients selected from a wide variety of excipients. According to the desired properties of the composition, any number of ingredients may be selected, alone or in combination, based upon their known uses in preparation of lyophilized form compositions.

Moreover, any excipient may optionally be added to the above composition, provided that they are compatible with the active ingredient of the composition, in order to overcome problems associated with unfavorable pharmacotechnical characteristics of these substances, and in order to increase the stability of the drug and the shelf-life of the pharmaceutical product.

The composition of the present invention may include further additives (alone or in a combination) such as stabilizing agents, pH adjusting agents, etc.. All percentages stated herein are weight percentages based on total composition weight, unless otherwise stated.

Another embodiment of the present invention is the use of a process for the preparation of powder for solution for infusion for parenteral administration containing tigecycline or salt or derivative thereof. The process steps may be as follows: a) Dissolving the total quantity of trehalose in water for injection and stirring for appropriate time until complete dissolution, wherein said solution preparation is performed at a temperature ranging from C to 8°C and under Nitrogen purging in the compounding vessel; b) The solution pH is adjusted to acidic pH value with suitable Hydrochloric acid solution; c) The total quantity of Tigecycline or salt or derivative thereof, is added slowly to the resulting solution of step b) and stirred for appropriate time until complete dissolved and the pH is adjusted to a pH value between 4.5 to 5.5 with suitable Hydrochloric acid or Sodium Hydroxide solution; d). The solution volume is adjusted to the predetermined volume with water for injection; e). The prepared bulk solution of step d) is aseptically filtered with suitable membrane filters; f). The filtered solution is filled in clear tubular Type I glass vials and semi-stoppered with butyl rubber stoppers for lyophilisation; and g) The filled semi-stoppered vials are lyophilized according to the following parameters: the freezing stage is carried out at a temperature ranging from about -40°C to -45°C, the primary drying stage is carried out at a temperature ranging from about -35°C to 0°C, and at pressure ranging from about O.lmbar to 0.3mbar and the secondary drying stage is carried out at a temperature ranging from about 25°C to 40°C, and at pressure ranging from about O.lmbar to 0.3mbar.

The parenteral pharmaceutical composition of the present invention comprising Tigecycline as an active ingredient has been compared to a parenteral reference product consisting of tigecycline with the following excipients Lactose monohydrate as bulking agent, Hydrochloric acid or Sodium Hydroxide as pH adjusting agent and water for injection. The powder was reconstituted with sodium chloride solution for injection, dextrose solution for injection, or Lactated Ringer’s solution for injection to achieve a concentration of 10 mg/mL of Tigecycline. One of the main objects of the present invention was to prepare a product with acceptable Stability. For this reason the compositions according to the present invention were exposed to accelerated and forced stability studies according to the current ICH guidelines.

Various compositions comprising Mannitol and two other bulking agents, Raffmose and Trehalose, have been tested in a 3-component mixture design, evaluating bulk solution osmolality and impurities profile of the final product immediately after lyophilisation at time t=0 and stressed at temperature of 80°C. The results are presented below (TABLE 1).

TABLE 1. Mannitol -Trehalose-Raffinose Mixture design results It is obvious that, the compositions 1, 2, 7, 8, 9, 10, 13, 14 and 15 of Table 1 comprising mannitol present increased final product impurities. The osmolality of the bulk solution appeared to be a quite discriminative response between the experimental runs, though the most restricting response appears to be the lyophilized product total impurities at temperature of 80°C for about a time period of 48hours, from where it is obvious that mannitol amount should be minimized to zero.

The following examples illustrate preferred embodiments in accordance with the present invention without limiting the scope or spirit of the invention:

EXAMPLES

Example 1: Composition of Tigecycline, Trehalose and Raffinose and Composition of

Tigecycline and Trehalose

TABLE 2: Composition I and II of Tigecycline 50mg/vial powder for solution for infusion

Preferred Tigecycline composition I and composition II according to the present invention are illustrated in Table 2.

Tigecycline composition I and composition II of the present invention were prepared according to the following manufacturing process:

Water for injection about 80% of the final volume of the vial is added in the compounding vessel and the total quantity of the excipients (trehalose and raffinose in composition I and only trehalose in composition II are added and stirred until complete dissolution. The solution preparation is performed at a temperature from 2°C to 8°C and under Nitrogen purging in the compounding vessel. The pH of the resulting solution is adjusted to acidic pH value by adding suitable quantity of Hydrochloric acid solution. Subsequently, the total amount of Tigecycline (25mg/ml) is added to the resulting solution slowly and stirred for appropriate time until complete dissolved. The pH of the resulting solution is adjusted to 5.0 with suitable Hydrochloric acid or Sodium Hydroxide solution and the solution volume is adjusted to the predetermined volume with water for injection. The prepared bulk solution is aseptically filtered with suitable membrane filters of 0.2 pm and the filtered solution is filled in clear tubular Type I glass vials 5 ml/ 13 mm with filling volume 2.12 ml/vial and semi-stoppered with butyl rubber stoppers for lyophilization. For Lyophilization, the filled semi-stoppered vials were lyophilized according to the following parameters: the freezing stage was carried out at a temperature ranging from about -40°C to -45°C, the primary drying stage was carried out at a temperature ranging from about -35°C to 20°C, more preferably from about -15°C to 0°C and at pressure ranging from about O.lmbar to 0.2mbar and the secondary drying stage was carried out at a temperature ranging from about 30°C to 40°C, and at pressure ranging from about O.lmbar to 0.2mbar.

After lyophilization, the vials were vented with partial vacuum under Nitrogen and fully stoppered. Then, they were sealed with aluminium flip-offs. The resulting cakes were stressed and analysed by HPLC (see in Table 3 and 4 below).

Another object of the present invention was to prepare a pharmaceutical composition that is stable for a long period of storage time.

Therefore, vials of Composition I and II were exposed to forced (60°C) stability studies. The stability results of Composition I and II at forced conditions, 60°C in comparison to the reference product, are shown in TABLE 3 below. Epimer is presented as the major tigecycline impurity.

TABLE 3: Comparative stability results of Composition I and II and reference product at forced conditions at 60°C. The results showed that the stability of the composition I and composition II of the present invention at forced conditions were improved compared to Reference product. Particularly, and total impurities of Composition I and II were 2.23% and 2.39%, respectively, in comparison to reference product wherein the total impurities was 2.45% and the epimer impurity of Composition I and II were 1.96% and 2.18%, respectively, in comparison to reference product, wherein the epimer impurity was 2.23%.

Moreover, vials of Composition II were exposed to accelerated (40°C±2°C/75%±5% RH) stability studies according to the current ICH guidelines. The stability results of Composition II at accelerated conditions, 40°C/75%RH in comparison to the reference product, are shown in TABLE 4 below. Epimer is presented as the major tigecycline impurity.

TABLE 4. Comparative stability results of Composition II and reference product at accelerated conditions 40°C/75%RH

The results showed that the stability of the composition II of the present invention at accelerated conditions was also good compared to Reference product.

Example 2: Composition of Tigecycline and various ratios of Thehalose

Moreover, the amount of Trehalose in Tigecycline composition is further investigated for its effect on protection of the final lyophilized product from epimerization. Thus, the following study is performed with various ratios of trehalose to tigecycline.

All compositions of example 2 were manufactured according to the same manufacturing process according to the present invention as described in example 1. The lyophilized cakes of the compositions of example 2 were stressed at temperature of 60°C and analysed by HPLC and the stability results are shown in TABLE 5 below. TABLE 5. Comparative stability results of Composition II with various ratios of Trehalose at forced conditions 60°C

The results showed that the stability of the present invention was good. Particularly total impurities and epimer impurity of Composition II of the present invention even with trehalose amount of 200mg/vial at forced conditions, (60°C) were improved compared to reference product.

Example 3: Composition of Tigecycline and various ratios of Raffinose

Furthermore, the amount of Raffinose in Tigecycline composition is further investigated for its effect on protection of the final lyophilized product from epimerization. Thus, the following study is performed with various ratios of raffinose to tigecycline. All compositions of example 3 were manufactured according to the same manufacturing process according to the present invention as described in example 1. The lyophilized cakes of the compositions of example 3 were stressed at temperature of 60°C and analysed by HPLC and the stability results are shown in TABLE 6 below.

TABLE 6. Comparative stability results of Composition of Tigecycline with various ratios of Raffinose at forced conditions 60°C

The results showed that the stability of Composition of Tigecycline with Raffinose according to the present invention was improved compared to reference product. Example 4: Composition of Tigecycline with different forms of the active ingredient

Further, the stability of Composition II of the present invention was investigated with different crystalline forms of active ingredient tigecycline. Thus, the following study is performed with various polymorphic forms of tigecycline. All compositions of example 4 were manufactured according to the same manufacturing process according to the present invention as described in example 1. The lyophilized cakes of the compositions of example 4 were tested at normal conditions (25°C±2°C/60%±5% RH), accelerated conditions (40°C±2°C/75%±5% RH) and forced conditions at temperature of 60°C and analysed by HPLC and the stability results are shown in TABLE 7 below.

TABLE 7. Comparative stability results of Composition II of Tigecycline with Trehalose lOOmg/vial and different forms of Tigecycline

Tigecycline form investigation results at accelerated conditions 40°C/75%RH

Tigecycline form investigation results at normal conditions 25°C/60%RH

The results showed that the stability of composition II with Tigecycline amorphous according to the present invention was improved compared to compositions II with other crystalline forms of Tigecycline.

Consequently, a novel improved composition of tigecycline has been achieved comprising trehalose. The use of Trehalose is able to improve the physicochemical stability of the active ingredient in the finished dosage form by protecting said active ingredient from degradation, and epimerization.

The stability of the product as well as the simple and effective manufacturing process indicates the advantages of the present invention relative to the commonly used excipients for the formulation of tigecycline.

While the present invention has been described with respect to the particular embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope thereof, as defined in the appended claims.