WO2007049296A2

WO2007049296A2 - Amorphous form of telithromycin

Info

Publication number: WO2007049296A2
Application number: PCT/IN2006/000243
Authority: WO
Inventors: Pandurang Balwant Deshpande; Parven Kumar Luthra; Manish Kanchanbhai Patel; Mahesh Pravinchandra Davadra
Original assignee: Alembic Limited
Priority date: 2005-10-28
Filing date: 2006-07-10
Publication date: 2007-05-03
Also published as: WO2007049296A3

Abstract

The present invention relates to novel substantially amorphous Telithromycin and its process of preparation.

Description

NOVEL FORM OF TELITHROMYCIN

Field of invention

The present invention provides novel substantially amorphous form of Telithromycin of formula (I) and its process of preparation.

Background of the invention

Telithromycin is chemically known as 11 ,12-dideoxy-3-de[(2,6-dideoxy-3-C- methyl-3-O-methyl-α-L-ribohexopyranosyl)oxy]-6-O-methyl-3-oxo-12,11- (oxycarbonyl[4-[4-(3-pyridinyl)-1 H-imidazol-1-yl]butyl]imino)-erythromycin. It is marketed under brand name "Ketek" and is indicated for the treatment of bacterial infections. Telithromycin of formula (I) is a ketolide which differs chemically from the macrolide group of antibacterials by the lack of α-L-cladinose at position 3 of the erythronolide A ring, resulting in a 3-keto function. It is further characterized by a Cn-Ci₂ carbamate substituted by an imidazolyl and pyridyl ring through a butyl chain. Telithromycin exhibits antibacterial activity and is used for treatment of community acquired pneumonia, acute exacerbation of chronic bronchitis, acute sinusitis, tonsillitis/pharyngitis.

Polymorphism is the occurrence of different crystalline forms of a single compound and it is a property of some compounds and complexes in solid state. The polymorphic and pseudo polymorphic solids display different physical properties, including those due to packing, and various thermodynamic, spectroscopic, interfacial and mechanical properties (See H. Brittain, Polymorphism in Pharmaceutical Solids, Marcel Dekker, New York, N.Y., 1999, pp. 1-2). Polymorphic and pseudopolymorphic forms of the drug substance (also known as the "active pharmaceutical ingredient" (API)), as administered by itself or formulated as a drug product (also known as the final or finished dosage form, or as the pharmaceutical composition) are well known and may affect, for example, the solubility, stability, flowability, fractability, and compressibility of drug substances and the safety and efficacy of drug products, (see, e.g., Knapman, K Modem Drug Discoveries, March 2000: 53). Polymorphs of a compound can be characterized by x-ray diffraction pattern, infrared spectrum, DSC etc.

Telithromycin was first reported in US Patent No. 5,635,485, which also disclose its process for preparation. Surprisingly inventors of present invention have found that Telithromycin also exists in substantially amorphous form.

One important physical property that can vary between two polymorphic forms is solubility, which can affect the bioavailability of the drug. Therefore there is a need to develop new polymorphic forms of a drug since it provides new opportunity to improve the performance characteristics of a pharmaceutical product.

The latest trend in the pharmaceutical industry is to study polymorphism in drugs as well as the difference in the activity of different polymorphic forms of a given drug. The term polymorphism includes different physical forms, crystal forms, crystalline/liquid crystalline/non-crystalline (amorphous) forms. This has become very interesting especially after observing that many antibiotics, antibacterials, tranquilizers etc., exhibit polymorphism and one or more of the polymorphic forms of a given drug exhibit superior bio-availability and consequently show much higher activity compared to other polymorphs. It has also been disclosed that the amorphous forms in a number of drugs exhibit different dissolution characteristics and in some cases different bioavailability patterns compared to the crystalline form [Konne T., Chem. Pharm. Bull., 38, 2003 (1990)]. For some therapeutic indications one bioavailability pattern may be favored over another. Further, it has been found that the crystalline forms are less readily soluble than the amorphous form which may cause problems in the bioavailability of drug product in the body.

It is therefore there exists a need for the development of different polymorphs which advantageously alters the physical characteristics which helps in formulation a drug substance.

Object of the invention

The primary object of the present invention is to provide the novel substantially amorphous form of Telithromycin of formula (I) and its process of preparation.

Summary of the invention

Accordingly present invention provides novel substantially amorphous form of Telithromycin and its process of preparation.

Brief description of the drawings

FIGURE-1 represents PXRD of substantially amorphous form Telithromycin.

Detailed description of the invention The term "substantially amorphous" as mentioned hereinabove refers to a condition in which greater than 90% of compound of formula (I) is in amorphous form. It indicates presence of small amounts of crystalline material in amorphous Telithromycin. The presence of crystalline material does not allow for a good halo shape pattern in powder x-ray diffraction spectrum which typical of amorphous form that is substantially free of crystalline material.

Telithromycin used for the present invention can be prepared by methods known perse or by any methods known to person skilled in art, particularly by process disclosed in the co-pending PCT application of present inventors, published as WO2005105821. The term "treating" as used hereinabove refers to simple dictionary meaning: "To subject to a process, action, or change, especially to a chemical or physical process or application". It is also indented to include chemical processes such as leaching, slurring, contacting and the like.

The preferred embodiment of present invention provides substantially amorphous Telithromycin which is characterized by powder x-ray diffraction spectrum which is substantially the same as shown in Figure 1.

The process for preparing substantially amorphous Telithromycin comprises steps of,

(a) treating Telithromycin with an acid

(b) optionally degassing the reaction mass

(c) treating above reaction mass with a base

Telithromycin is treated with aqueous solution of an acid at temperature of about 5⁰C to about 4O⁰C. The reaction mass can be optionally degassed for about 1 hour to about 10 hours. Further it is treated with a suitable base at temperature of about 5°C to about 40⁰C and the stirring can be continued for about 10 hours to about 30 hours at temperature of about 5⁰C to about 30⁰C, preferably room temperature to obtain substantially amorphous Telithromycin. It can be further isolated by conventional methods such as filtration or centrifugation and dried.

The examples of an acid include but are not limited to hydrochloric acid, sulphuric acid, acetic acid, formic acid and the like or mixtures thereof, preferably hydrochloric acid. The base can be selected from group comprising of alkali or alkaline earth metal hydroxides, carbonates, bicarbonate and the like or mixtures thereof. The examples of a base includes but are not limited to sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, cesium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate and the like or mixtures thereof, preferably sodium carbonate. Degassing can be conveniently performed by application of vacuum or by purging nitrogen in the reaction mass, or by any method known to person skilled in art.

Another aspect of the present invention provides Telithromycin having particle size wherein (do_.9) is less than or equal to about 400 μm.

The process of the present invention is illustrated in more detail by the following examples, but not limited in any way and should not be construed so as to limit the scope of the invention in any manner.

Examples Example 1:

40 ml HCI solution (2 ml HCI in 38 ml water) was added to 5 g of Telithromycin. Vacuum was applied to the solution for about 4 to 5 hours. After releasing the vacuum the pH of the solution was adjusted to about 7 by using saturated sodium bicarbonate solution. The reaction mixture was stirred overnight and filtered to obtain amorphous Telithromycin (yield: 4.4 g).

PXRD: As characterized in Figure-1.

While the present invention has been described in terms of its specific . embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.

Claims

1. Substantially amorphous Telithromycin.

2. Substantially amorphous Telithromycin characterized by powder x-ray diffraction spectrum which is substantially the same as shown in Figure 1.

3. A process for the preparation of substantially amorphous Telithromycin comprises steps of,

(a) treating Telithromycin with an acid

(b) optionally degassing the reaction mass

(c) treating above reaction mass with a base

4. A process as claimed in claim 3, wherein said acid is selected from group comprising of hydrochloric acid, sulphuric acid, acetic acid and.formic acid.

5. A process as claimed in claim 8, wherein said acid is hydrochloric acid.

6. A process as claimed in claim 3, wherein said base is selected from group comprising of alkali or alkaline earth metal hydroxides, carbonates and bicarbonate.

7. A process as claimed in claim 6, wherein said base is selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, cesium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate and like, preferably sodium carbonate.

8. Telithromycin having particles size wherein (do.9) is less than or equal to about 400 μm.