EP3003273A1

EP3003273A1 - A method for stabilizing tigecycline

Info

Publication number: EP3003273A1
Application number: EP14728902.9A
Authority: EP
Inventors: Ivona JASPRICA; Sasa GRUBESIC; Anita BEVETEK MOCNIK
Original assignee: Xellia Pharmaceuticals ApS
Current assignee: Xellia Pharmaceuticals ApS
Priority date: 2013-05-31
Filing date: 2014-05-30
Publication date: 2016-04-13
Also published as: WO2014191552A1

Abstract

The present invention relates to a method for stabilizing Tigecycline using nitric acid or sulphuric acid. The present invention furthermore relates to Tigecycline compositions comprising nitric acid or sulphuric acid as the only pH adjusting agent.

Description

A method for stabilizing tigecycline

Background Tigecycline is a glycylcycline antibiotic (an analogue of minocycline) which belongs to the tetracycline family and may be illustrated by the following formula:

Formula 1

The chemical name of Tigecycline is (4S,4aS,5aR,12aS)-9-[2-(tert- buty amino)acetamido | -4,7-bis(dimefhylamino)- 1 ,4,4a, 5, 5a,6, 1 1,12a-oetahydro- 3, 10, 12, 12a-tetrahydroxy- 1 , 1 1 -dioxo-2-naphthacenecarboxamide, also known under the CAS number 220620-09-7, Tigecycline acts by inhibiting protein synthesis at the level of the bacterial ribosome. It shows higher binding affinity than tetracyclines, being active against bacterial strains with either of the two known mechanisms of tetracycline resistance: efflux and ribosomal protection. As a bacteriostatic agent, it inhibits the growth of multiple resistant gram-positive, gram-negative, anaerobic, and atypical bacteria, including methicillin-resistant Staphylococcus aureus and extended- spectrum β-lactamasc producers.

Furthermore, Tigecycline is the active ingredient of the product Tygacil®, (Tigecycline) for injection, 50 mg/vial, developed by Wyeth Pharmaceuticals and approved in US in June 2005.

The stability of Tigecycline has been discussed in several publications. Tigecycline degrades by oxidation (prevalent form of degradation in basic conditions) and cpimcrization (prevalent form of degradation in acidic environment).

According to the current Tygacil® label, each Tygacil vial contains 50 mg of Tigecycline and 100 mg of lactose monohydrate with 6% overage. The pH is adjusted with hydrochloric acid, and if necessary sodium hydroxide. The product does not contain preservatives,

CN101 167732 discloses experiments concerning Tigecycline formulations comprising hydrochloric acid, tartaric acid or lactic acid as pH-adj listing agents. In the description, a variety of inorganic and organic acids are mentioned, including sulphuric and nitric acid, but there is no disclosure of or hints to the advantages of using sulphuric or nitric acids for stabilizing Tigecycline. CN102697739 discloses the use of pH adjustment for obtaining stable Tigecycline formulations. The stability is achieved when the H is first adjusted down with TIG, II₂S0₄ or II3PO₄ and then adjusted up with KOH or NaOH.

CN1 01 919816 discloses experiments concerning of Tigecycline powders having improved dissolution properties. Several Tigecycline salts are mentioned including the sulphuric acid salt of Tigecycline. However, there is no disclosure of or hints to the advantages of using sulphuric or nitric acids for stabilizing Tigecycline.

WO2006099258 discloses Tigecycline formulations. However, there is no disclosure of or hints to the advantages of using sulphuric or nitric acids for

stabilizing Tigecycline.

WO201 2142958 discloses Tigecycline crystals and formulations comprising them. However, there is no disclosure of or hints to the advantages of using sulphuric or nitric acids for stabilizing Tigecycline.

AU2012327237 discloses Tigecycline compositions comprising one or more formulating agcnt(s) selected from a chelator, pyruvic acid, or a salt or ester thereof and ascorbic acid, and optionally one or more cxcipicnts, diluents or buffers.

Ho wever, there is no disclosure of or hints to the advantages of using sulphuric or nitric acids for stabilizing Tigecycline.

US20090275660 discloses Tigecycline compositions comprising EDTA. The pH- modifying agents that may be used includes acids and or/buffers that is required to prevent degradation from oxidation and/or epimerization of the stable parenteral formulation as described herein, and that which helps in modifying the pH of the said formulation from about 3.0 to about 5.0. Any acid/buffer which does not adversely affect the effectiveness of the drug formulations may be employed.

Acids may be exemplified as hydrochloric, succinic, L-(+)- lactic or L -tartaric acid, and the like. Buffers may be selected from citrate, acetate or phosphate buffer and the like. In one particular embodiment, 1.0N hydrochloric acid/1. ON sodium hydroxide is used. However, there is no disclosure of or hints to the advantages of using sulphuric or nitric acids for stabilizing Tigecycline,

None of the prior art citation referred above disclose or suggest that sulphuric acid or nitric acid exert a stabilizing effect when used as pH adjusting agent.

Summary of the invention

The present invention covers formulations comprising Tigecycline and sulphuric or nitric acid.

In one aspect, the present invention concerns aqueous solutions comprising Tigecycline having acidic pH obtained by addition of sulphuric acid or nitric acid as the only pH adj sting agents. In one aspect, the present invention concerns aqueous solutions comprising Tigecycline and lactose having acidic pH obtained by addition of sulphuric acid or nitric acid as the only pH adjusting agents.

According to one aspect, the pH of the basic or neutral aqueous solution containing lactose and Tigecycline is lowered by the addition of sulphuric acid or nitric acid.

According to another aspect, the pH of an aqueous solution containing lactose and Tigecycline is made acidic by the addition of sulphuric acid or nitric acid.

According to another aspect, the pH of the basic or neutral aqueous solution containing Tigecycline is adjusted to pi I 2.5 - 6.6,

According to yet another aspect, the pH of the basic or neutral aqueous solution containing Tigecycline is adjusted to pH 4-6, such as pH 4.5-5.5 or pi I 4.8-5.2 According to yet another aspect, the pll of the basic or neutral aqueous solution containing lactose and Tigecycline is adjusted to pH 4-6, such as pi I 4.5-5.5 or pH 4.8-5.2

According to yet another aspect of the present invention, a lyophilized powder is provided, which upon dissolution in pure water provides an acidic pi I. The lyophilized powder is prepared by lyophili/ation of the aqueous solutions of the present invention.

According to yet another aspect of the present invention, Tigecycline formulations are provided, which are prepared by reconstitution of the above lyophilized powder of the present invention. According to one aspect of the invention, an aqueous solution of Tigecyciine is provided comprising Tigecyciine and lactose, which is prepared by addition of sulphuric acid or nitric acid in Tigecyciine solution in an amount which is sufficient to provide an acidic pH. According to one embodiment of said aspect, an aqueous Tigecyciine solution with pH adjusted in acidic range is provided, wherein the aqueous solution of Tigecyciine comprises lactose as the only bulking agent.

The sequence of adding the ingredients of the present invention is not critical. However, according to one embodiment, an aqueous lactose solution is first provided, in which Tigecyciine is dissolved followed by adjustment of pH by the addition of sulphuric or nitric acid to the so obtained Tigecyciine solution.

According to one aspect of the invention, a method for stabilizing Tigecyciine is provided, which comprises addition of sulphuric acid or nitric acid to an aqueous solution comprising Tigecyciine and obtaining an acidic pH.

According to one embodiment of this aspect of the invention, a method for stabilizing Tigecyciine is provided comprising the steps of;

a) dissolve lactose in water;

b) add sulphuric or nitric acid in the solution obtained in step a) to obtain acidic pH;

c) dissolve Tigecyciine in the solution obtained in step a) or b) and optionally, d) add nitric acid or sulphuric acid to the solution obtained in c) in order to obtain acidic H if needed.

Based on the teaching of the present invention and the common general knowledge, the skilled artisan can calculate the amount of sulphuric or nitric acid to be added in order to achieve the targeted acidic pH according to the present invention based on the concentration of Tigecyciine in the solution and the concentration of the acid.

According to another embodiment of the above aspect, a method for stabilizing Tigecyciine is provided, further comprising lyophilization of the solution obtained in step c). According to another embodiment of this invention, a method for stabilizing Tigecyciine is provided comprising the steps of:

a) prepare an aqueous solution comprising lactose and Tigecyciine; and b) adjust the pH of the solution in step a) to preferred range or value, such as pH 4-6 by sulphuric acid or nitric acid.

According to latter embodiment, only one pH adjusting agent is used. According to another embodiment of this invention, a method for stabilizing Tigecycline is provided comprising the steps of:

a) prepare an aqueous solution comprising lactose and Tigecycline

b) adjust the pH of the solution in step a) to preferred range or value, such as pH 4-6 by sulphuric or nitric acid; and

c) lyophilization of the solution in step b).

According to another embodiment of this invention, a method for stabilizing Tigecycline is provided consisting of the steps of:

a) prepare an aqueous solution comprising lactose and Tigecycline;

c) lyophilization of the solution in step b). Finally, the present invention provides the use of sulphuric acid or nitric acid as stabilizing agents in the preparation of Tigecycline.

Detailed description

The present invention is based on the surprising finding that sulphuric acid or nitric acid provides a stabilizing effect on an aqueous solution containing Tigecycline compared to many other tested acids. The surprising findings are achieved when sulphuric acid or nitric acid is used to lower the pi I prior to lyophilization. The stabilizing effect of nitric acid and sulphuric acid is obtained when the pi I is made acidic prior to lyophilization. According to one aspect of the invention, only one pH adjusting step is needed when preparing the formulation of the present invention. According to one aspect of the invention, only one pH adjusting agent is needed when preparing the formulation of the present invention, The present aqueous solution of Tigecycline may be used as a bulk solution for the preparation of a lyophilized composition.

The lyophilized composition according to the present invention is in solid state, e.g. in form of a powder or a cake resulting from lyophilization of bulk solutions. The lyophilized composition is thus prepared by lyophilization of an aqueous solution of the present invention according to methods well known to the skilled person.

Upon dissolution of the lyophilized composition in pure water, the pH of the obtained solution is acidic. According to one embodiment, the pH of the solution obtained is within 4-6. According to one embodiment, the lyophilized composition of the present invention is dissolved in any suitable diluent to provide a formulation of Tigecycline ready for administration to a patient in need thereof. Suitable diluents include, but are not limited to 0,9% sodium chloride injection, lactated ringer's injection and 5% dextrose injection.

According to one aspect of the invention, an aqueous solution is provided, comprising Tigecycline and sulphuric acid, and further characterized by having an acidic pH.

According to one aspect of the invention, an aqueous solution is provided, comprising Tigecycline and nitric acid, and further characterized by having an acidic pH.

According to one aspect of the invention, an aqueous solution is provided, comprising Tigecycline, lactose and sulphuric acid, and further characterized by having an acidic pH.

According to one aspect of the invention, an aqueous solution is provided, comprising Tigecycline, lactose and nitric acid, and further characterized by having an acidic pH. According to one embodiment, lactose is the only bulking agent in the solution of the invention.

According to one ^"aspect of the invention, an aqueous solution is provided, comprising Tigecycline, lactose and sulphuric acid, arid further characterized by having an acidic pH of 4-6.

According to one aspect of the invention, an aqueous solution is provided, comprising Tigecycline, lactose and nitric acid, and further characterized by having an acidic pH of 4-6.

According to another aspect, a solution is provided, consisting of water, Tigecycline, lactose and sulfuric acid, characterized by having an acidic pH.

According to another aspect, a solution is provided, consisting of water, Tigecycline, lactose and sulfuric acid, characterized by having a pH of 4-6.

According to another preferred aspect, a solution is provided, consisting of water, Tigecycline, lactose and sulfuric acid, characterized by having a H of 5-6. According to another aspect, a solution is provided, consisting of water, Tigecycline, lactose and sulfuric acid, characterized by having a pH of 5. According to another aspect, a solution is provided, consisting of water, Tigec cline, lactose and nitric acid, characterized by having an acidic pH.

According to another aspect, a solution is provided, consisting of water, Tigecycline, lactose and nitric acid, characterized by having a pH of 4-6.

According to another aspect, a solution is provided, consisting of water, Tigecycline, lactose and nitric acid, characterized by having a pH of 5-6. According to another aspect, a solution is provided, consisting of water, Tigecycline, lactose and nitric acid, characterized by having a ϊ I of 5.

According to another aspect of the present invention, a lyophilized powder is provided, wherein said powder is prepared by the lyophilization of an aqueous solution having a pi I between 4 and 6 comprising Tigecycline as the active ingredient, and lactose as the bulking agent and the H adjusting agent is selected from sulphuric acid and nitric acid.

According to another aspect of the present invention, a lyophilized powder is provided, wherein said powder is prepared by the lyophilization of an aqueous solution having a pH between 4 and 6 comprising Tigecycline as the active ingredient and the pH adjusting agent is selected from sulphuric acid and nitric acid.

According to yet another aspect of the present invention, a composition is provided, wherein said composition is a lyophilized powder prepared by the lyophilization of an aqueous solution having an acidic pH comprising Tigecycline, lactose and sulphuric acid.

According to yet another aspect of the present invention, a composition is provided, wherein said composition is a lyophilized powder prepared by the lyophilization of an aqueous solution having an acidic pH consisting of Tigecycline, lactose and sulphuric acid.

According to yet another aspect of the present invention, a composition is provided, wherein said composition is a lyophilized powder prepared by the lyophilization of an aqueous solution having an acidic pH comprising Tigecycline, lactose and nitric acid.

According to yet another aspect of the present invention, a composition is provided, wherein said composition is a lyophilized powder prepared by the lyophilization of an aqueous solution having an acidic pH consisting of Tigecycline, lactose and nitric acid. "Tigecycline" is meant to embrace any compound having the structure of formula I regardless of the charge of the molecule which varies by pH. Thus, Tigecycline is present in bulk solutions, lyophilized powders arid in solutions made by dissolving the lyophilized powders in. pure water or other suitable diluents. Tigecycline is also to be understood to embrace the active ingredient in Tygacil®.

Tigecycline epimer, which inter alia is a degradation product of Tigecycline, is a com ound which may be represented by the following structure:

Tigecycline epimer is believed to be non-toxic, but it lacks the antibacterial activity of Tigecycline. "Lactose" is the well known disaccharide sugar commonly used as an excipient in pharmaceuti represented by the structure:

In present d as a bulking agent. According one embodiment of the invention, the lactose excipient is in the form of lactose monohydrate. Lactose can be anhydrous or hydrated, but lactose mono hydrate is preferred,

"Sulphuric acid" is meant to embrace the aqueous solutions of sulphuric acid. It is preferred that the sulphuric acid is diluted to a concentration of 0.5M-2M.

"Nitric acid" is meant to embrace the aqueous solutions of nitric acid. It is preferred that the nitric acid is diluted to a concentration, of 0.5M-2M. "pH" is the conventional measurement unit for hydrogen ion activity in a solution at 25°C unless other temperature is specified.

"acidic pH" as used herein is meant to cover solutions having pH below 7.

"neutral ρίΓ' as used herein is meant to cover solutions having pi I 7.

The preferred acidic pi I is 3-6 and the most preferred acidic pH is about 5. "pH adjusting agent" is any agent capable of adjusting pH in a solution comprising Tigecycline, but "pi I adjusting agent" is not meant to cover Tigecyclme, Tigecycline HC1 or Tigecycline dillCl.

"Suitable carbohydrate" as used herein is any carbohydrate or sugar alcohol which can be used as an excipient together with Tigecycline. Preferred carbohydrates include, but are not limited to, mannose, mannitol, sucrose, glucose and lactose. The most preferred carbohydrate is lactose.

"Pure water" as used herein is substantially pure and sterile water. E.g. water purified by distillation or a purification process that is equivalent or superior to distillation in the removal of chemicals and microorganisms.

"Aqueous solution" as used herein means any solution in which water is the main solvent.

"Bulk solution" is a solution comprising Tigecycline suitable for lyophili/.ation.

Experimental Example 1

The Tigecycline formulations were prepared in the following manner: lactose monohydrate was dissolved in ultrapure water and predefined quantity of diluted acid solution was added (used acids include sulphuric, phosphoric, citric, succinic, tartaric, acetic, lactic, ascorbic, and nitric acid), Tigecycline was dissolved in obtained lactose mono ydrate solution and then solution pH was adjusted to the predefined value using respective diluted acid solution (final concentration of lactose in the solution was 50 mg/mL and Tigecycline 25 mg/mL). After pH adjustment, volume of the solution was made up to predefined value.

All formulations were analyzed immediately after preparation and then subjected to stability testing for 24 hours at room temperature (23°C ± 2, protected from light) and at 2°C - 8°C. Content of impurities was analyzed at specified time points using validated reverse phase, gradient IIPLC method.

Content of main degradation impurity (Tigecycline epimer) and total impurities found in tested formulations are presented in Table 1 that follows.

Table 1:

According to above presented results, it can be concluded that among all tested acids only sulphuric acid and nitric acid have significant stabilizing effect on Tigecycline in bulk solution.

Example 2

Product solution containing 50 mg/mL of lactose monohydrate and 25 mg/ml, of Tigecycline with pH adjusted to 5.0 using sulphuric acid was prepared and lyophili ed.

Samples were analyzed immediately after lyophilization and then were subjected to stability testing at the elevated temperature (1 month at 40°C ± 2°C /75% ± 5% RH in inverted position). Validated reverse phase, gradient HPI.C method was used for impurities analysis at defined time point and obtained results are presented in Table 2 below.

Table 2:

Example 3

The Tigecycline formulations with lactose were prepared in the following manner: lactose monohydrate was dissolved in ultrapure water and a predefined quantity of a diluted acid solution was added (used acids include sulphuric and nitric acid). Tigecycline was dissolved in the obtained lactose monohydrate solution and then the pll of the solution was adjusted to the predefined value using the respective diluted acid solution (final concentration of lactose in the solution was 50 mg/mL, and Tigecycline 25 mg/mL). After pi I adjustment, volume of the solution was made up to predefined value.

Formulations containing Tigecycline and the respective acid are manufactured as follows: in ultrapure water Tigecycline was dissolved and then the solution pH. was adjusted to the predefined value using diluted sulphuric, nitric or hydrochloric acid solution (final concentration of Tigecycline in the solution was 25 mg/mL). After pll adjustment, the volume of the solution was made up to predefined value. The formulation containing Tigecycline Hydrochloride API was prepared by dissolving the API in ultrapure water with resulting concentration of Tigecycline of 25 mg/raL. After dissolution of API, the volume of the solution was made up to predefined value.

All formulations were analyzed immediately after preparation and then subjected to stability testing for 24 hours at 2°C - 8°C. Content of impurities was analyzed at specified time points using a validated reverse phase, gradient HPLC method. The content of the main degradation impurity (Tigecycline epimer) and total impurities found in tested formulations are presented in Table 3 that follows.

Table 3:

Example 4

Product solution containing 50 mg/niL of lactose monohydrate and 25 mg/niL of Tigecycline with pH adjusted to 5.0 using sulphuric acid and nitric acid were prepared and lyophilized together with formulations containing 25 mg/raL of Tigecyeline with pH adjusted to 5.0 using sulphuric acid, hydrochloric acid and nitric acid and formulation containing Tigecyeline Hydrochloride API.

Samples were analyzed immediately after lyophilization and then were subjected to stability testing at the elevated temperature (5 days at 60°C in inverted position). Validated reverse phase, gradient HPLC method was used for impurities analysis at defined time point and the obtained results are presented in Table 4 below.

Table 4:

pi T is measured in vial reconstituted with 5.3 mL of ultrapurc water

Claims

1. The use of nitric acid or sulphuric acid for stabilizing Tigecycline. 2. A method for stabilizing Tigecycline, comprising the steps of adjusting the pll of an aqueous solution of Tigecycline by the addition of sulphuric acid or nitric acid.

A method according to any of the claims 1 -2, comprising the steps of:

a) dissolving lactose in water;

b) adding sulphuric or nitric acid in the solution obtained in step a) to obtain acidic pH;

c) dissolving Tigecycline in the solution obtained in step a) or b) and optionally d) adding nitric acid or sulphuric acid to the solutio obtained in c) in order to obtain acidic pH if needed.

4. A method according to claim 3, further comprising lyophilization of the solution obtained in step c).

A method for stabilizing Tigecycline, comprising the steps of:

a) preparing an aqueous solution comprising lactose and Tigecycline; and b) adjusting the pH of the solution in step a) to preferred range or value, such pH 4-6 by sulphuric acid or nitric acid.

A method for stabilizing Tigecycline is provided comprising the steps of: a) preparing an aqueous solution comprising lactose and Tigecycline;

b) adjusting the pH of the solution of step a) to a preferred range or value, such as pH 4-6 by adding sulphuric or nitric acid; and

c) lyophilizing the solution obtained in step b).

A method for stabilizing Tigecycline is provided consisting of the steps of: a) preparing an aqueous solution comprising lactose and Tigecycline;

b) adjusting the pi I of the solution of step a) to a preferred range or value, such as pH 4-6 by adding sulphuric or nitric acid; and

c) lyophilizing the solution obtained in step b).

8. A method according to any of the claims 2-7, wherein only one pH adjusting agent is used.

9. A method according to any of the claims 2-8, wherein the pH is adjusted to pH 4-6.

10. A method according to claim 9, wherein the pH is adjusted to pH 4.5-5.5, such as pH 4.8 - 5.2.

1 1. An aqueous solution comprising Tigecycline and sulphuric acid or nitric acid as the only pH adjusting agents.

12. An aqueous solution according to claim 1 1 wherein nitric acid represents the only pH adjusting agent.

13. An aqueous solution according to claim 1 1 wherein sulphuric acid represents the only pH adjusting agent.

14. An aqueous solution according to claim 12, comprising Tigecyclme, lactose, and nitric acid,

15. An aqueous solution according to claim 11 consisting of Tigecycline, a suitable carbohydrate, and nitric acid or sulphuric acid.

16. An aqueous solution according to claim 15, wherein the carbohydrate is lactose.

17. A lyophilized powder obtained by lyophilizing the solution of any of claim 1 1 - 16, which upon dissolution in pure water provides a solution having an acidic pH.

18. A reconstituted Tigecycline formulation, prepared by reconstitution of the lyophilized powder according to claim 17.