EE05864B1 - Composition of a compound containing a 3-hydroxycyclopentone ring and a method of stabilizing the same - Google Patents

Abstract

The invention relates to a composition comprising a compound having a 3-hydroxycyclopentanone moiety in its structure, an organic solvent comprising an alcohol or an ester or a mixture thereof, and a salt capable of dissociating in the solvent, or its constitutive ions. The invention further relates to a kit comprising such composition, to a method of preparing the composition, and to a method of stabilizing a compound having a 3-hydroxycyclopentanone moiety in the solvent using the salt.

Description

Technical field

The invention relates to the field of chemistry and medicine, and more particularly to compositions containing compounds having a 3-hydroxycyclopentanone ring in their structure, such as prostaglandins, and methods for stabilizing such compounds.

State of the art

A significant number of compounds, including those used as pharmaceuticals, contain a 3-hydroxycyclopentanone ring and have the structure shown below, in which -R is variable

Such compounds, hereinafter referred to as active ingredients (or active components), are usually unstable due to their tendency to release a water molecule through the following reaction:

=> Examples of such compounds are prostaglandins, especially the lipophilic prostaglandins of the E group (e.g. alprostadil (PGE1) and dinoprostone (PGE2)) and the D group (e.g. PGD2).

PGE1 and PGE2 are described in the European Pharmacopoeia as members of the group of prostaglandin analogues used to treat a variety of physiological conditions. PGE1 and PGE2-based pharmaceutical preparations are among the most effective and safest medicines required by the health system on the World Health Organization's List of Essential Medicines. They are mainly administered parenterally, although topical and intravaginal preparations are also available on the market. Due to the instability of the 3-hydroxycyclopentanone ring, PGE1 and PGE2 can be degraded to prostaglandin A1 (PGA1) and prostaglandin A2 (PGA2), respectively, which are the main degradation products in PGE1 and PGE2 preparations and the main cause of deterioration in the quality of the preparations. The formation and accumulation of PGA1 and PGA2 leads to rapid degradation and deterioration in the quality of PGE1 and PGE2-based medicines.

Due to the unstable nature of PGE1 and PGE2, medicinal products containing these compounds are only available as concentrates, which must be diluted or reconstituted immediately before use by reconstitution in a suitable solvent or solution (e.g. ready-to-use saline solution for infusion). The concentrates available are either solid (e.g. lyophilized preparations containing hydroxypropyl-beta-cyclodextrin as a stabilizer) or non-aqueous solutions (e.g. ethanol-based).

Ethanol-based solutions are easy to prepare due to their simple composition, manufacturing process and quality control. But most importantly, ethanol-based preparations have the advantage of being easy to administer when used as a medicine. The solution can be injected directly into an infusion solution and does not require reconstitution. Simplified handling leads to fewer errors and reduced risks (e.g. microbial contamination of the infusion solution due to difficult handling). An additional advantage is that the simple preparation of ethanol-based solutions contains at least one active ingredient and a solvent. The simplicity of the preparation results from the simple and cost-effective production of such medicines compared to the production of a lyophilized form. Shelf life of ethanol-based concentrates of medicines containing PGE1 and PGE2 on the market

is 2 years when stored at 2°C to 8°C. The concentration of active ingredients (PGE1 and PGE2) in pharmaceutical preparations is usually specified in μg/ml and mg/ml scales for most concentrations (e.g. 20 μg/ml and 1000 mg/ml).

PGD2 is an important endogenous prostaglandin that has recently been identified as a compound for use as or in human pharmaceuticals. The wider use of the compound in human pharmaceutical formulations is primarily due to its chemical instability in pharmaceutical formulations.

In contrast, ethanol-based solutions containing at least one active ingredient exhibit insufficient stability of the active ingredient due to the tendency of the water molecule to dissociate from the 3-hydroxycyclopentanone ring structure, as previously described, which poses several risks to obtaining a high-quality preparation. The instability of the active ingredient is mainly temperature dependent, so the preparation, handling and storage steps must be approached with the utmost care in terms of temperature control.

Thus, the object of this invention is to provide selected chemical stability in relation to preventing or reducing the degradation of the active ingredient in a human pharmaceutical formulation containing components with a 3-hydroxycyclopentanone ring in their chemical structure.

The closest technical nature to the invention is stabilized E-group prostaglandins (US3851052, Pfizer, published 26.11.1974), which comprises a stabilized pharmaceutical composition comprising a biologically active E-group prostaglandin together with a storage stabilizing amount of an alkali or alkaline earth metal sulfite salt. A composition comprising a pharmaceutically acceptable liquid medium, for example an aliphatic alcohol such as ethanol, is particularly preferred. The disadvantage of this solution is that the invention uses only an alkali or alkaline earth metal sulfite salt for stabilization.

The essence of the invention

The inventors' objective is to identify stabilizers for use in concentrated and dilute solutions of compounds containing the 3-hydroxycyclopentanone ring, in order to provide extended shelf life formulations that are stable, easy to use, and can be prepared and analyzed simply and cost-effectively. Furthermore, the inventors' objective is to overcome the limitations of PGD2 as a drug and open up the possibility of using the molecule for health benefits.

The aim of the invention is to determine conditions under which substances containing a 3-hydroxycyclopentanone ring have reduced release of water from the ring in non-aqueous solution and thus improved stability and thus quality (as defined by stable levels of active ingredients and degradation products in solution) throughout their shelf life. This is achieved by using a small amount of a salt in the solution that is capable of dissociating in the solvent and/or salt-forming ions. The use of a salt in a non-aqueous solution of a compound containing a 3-hydroxycyclopentanone ring makes it possible to prevent the release of water from the ring.

One specific object of the invention is to provide a composition comprising a compound containing a 3-hydroxycyclopentanone ring in an organic solvent, wherein the composition is stable, i.e. characterized by a low (minimal) level of degradation products due to the release of water from the 3-hydroxycyclopentanone ring during storage, and a stable level of active ingredient, resulting in an extended shelf life of such a product. In addition, such a composition can be easily administered as a ready-to-use preparation by injection into an infusion solution without being reconstituted, which eliminates (or causes minimal errors) in the preparation of the composition for administration to an individual and involves minimal risks of contamination (e.g. biological (e.g. microbial), chemical) for the composition and ready-to-use preparations during administration.

Another specific object of the invention is to provide a kit comprising said composition, the kit being characterized by ease of handling and composition.

The composition is easy to prepare for administration to an individual as a ready-to-use preparation and can be stored for a long time without any or significant deterioration in the quality of the active ingredient.

Another specific object of the invention is to provide a simple and cost-effective method for preparing said composition, which is easy to carry out and which contains a minimum number of necessary components.

Another specific object of the invention is to provide a method for stabilizing a compound containing a 3-hydroxycyclopentanone ring in an organic solvent.

The embodiments of the present invention will be described below together with the presentation of the technical effects achieved by implementing the invention. In addition, other technical effects achieved and other problems to be solved will be apparent to those skilled in the art upon reading the present disclosure.

A first aspect of the present invention relates to a composition comprising a compound containing a 3-hydroxycyclopentanone ring, a solvent containing an alcohol or an ester or a mixture thereof, and a salt capable of dissociating in the solvent, or the ions forming it.

The composition of the present invention provides stability of the active ingredient, which is expressed in a stable content of the active ingredient. The present composition contains a minimum number of necessary components and is therefore characterized by a simple and cost-effective manufacturing process and quality control. In addition, the composition can be easily administered as a ready-to-use preparation for use as a medicine, for example for injection immediately into an infusion solution, and therefore does not require reconstitution. Such simplified handling results in minimal or no risk of contamination, as well as errors that may occur during the preparation of the preparation.

In a particular embodiment, the solvent further comprises water. In a still more particular embodiment, the solvent comprises water in an amount of 0.05 wt% to 10 wt%, more particularly 0.5 wt% to 4 wt%, preferably 2 wt%.

up to 4% by weight. A water content in this range further improves the stability of the active ingredient compared to the same formulation not containing this amount of water.

In another specific embodiment, the alcohol is selected from a monohydric alcohol, a polyhydric alcohol, or mixtures thereof, and/or the ester is ethyl acetate. In a still more specific embodiment, the monohydric alcohol is ethanol and/or the polyhydric alcohol is selected from propylene glycol, 1,3-butanediol, and mixtures thereof.

In another specific embodiment, the salt is added to the composition as a compound or the salt is formed in situ by adding precursors to the composition.

In another specific embodiment, the salt is an alkali metal or alkaline earth metal salt.

In another specific embodiment, the salt is a halogen salt, especially a chloride salt.

In another specific embodiment, the salt is sodium chloride, calcium chloride, or magnesium chloride.

In another specific embodiment, the salt is magnesium chloride, specifically magnesium chloride hexahydrate.

In another specific embodiment, the salt stabilizes a compound containing a 3-hydroxycyclopentanone ring. Stabilization of the compound is achieved by preventing the release of water from the compound containing a 3-hydroxycyclopentanone ring.

In another specific embodiment, the composition comprises a salt at a concentration of 0.05 μg/ml to 5000 μg/ml, preferably 0.5 μg/ml to 1000 μg/ml, more preferably 0.5 μg/ml to 500 μg/ml, especially 1 μg/ml to 30 μg/ml.

In another specific embodiment, the composition comprises a compound containing a 3-hydroxycyclopentanone ring at a concentration of 1 μg/ml to 10,000 μg/ml, preferably 5 μg/ml to 5,000 μg/ml, especially 10 μg/ml to 1,000 μ pg/ml.

In another specific embodiment, the weight ratio of compound to salt is 1:5000 to 200000:1, preferably 1:200 to 10000:1, more preferably 1:50 to 2000:1, especially 1:50 to 20:1.

In another specific embodiment, the weight (μg) to volume (ml) ratio of salt to solvent is 0.05:1 to 5000:1, more preferably 0.5:1 to 1000:1, more preferably 0.5:1 to 500:1, especially 1:1 to 30:1.

In another specific embodiment, the compound containing a 3-hydroxycyclopentanone ring is a prostaglandin, particularly prostaglandin E or prostaglandin D.

In another specific embodiment, the prostaglandin is prostaglandin E1 (PGE1, alprostadil), prostaglandin E2 (PGE2, dinoprostone), or prostaglandin D2 (PGD2).

In another specific embodiment, the composition is contained in an ampoule, vial, syringe, bottle, or container.

Another aspect of the present invention relates to a kit of parts comprising a composition according to the invention contained in an ampoule, vial, plunger, syringe, bottle or container.

The stability of the 3-hydroxycyclopentanone ring-containing compound in the composition of the present invention allows the composition to be packaged and stored in solution form, eliminating the need to reconstitute it prior to administration to an individual. The kit according to another aspect provides for easy handling, easy administration and long-term shelf life of the composition of the invention.

A third aspect of the present invention relates to a method for preparing a composition according to the invention, the method comprising mixing a solution containing a compound containing a 3-hydroxycyclopentanone ring, an alcohol or an ester or a mixture thereof, and a salt capable of dissociating in a solvent, or salt precursors.

The method according to the third aspect allows the preparation of a composition comprising a compound containing a 3-hydroxycyclopentanone ring in a solvent, wherein

the composition is characterized by a stable content of the compound during storage and thus a minimal amount of impurities, which are degradation products of the compound, or their absence. The method according to the third aspect allows the preparation of a composition containing a compound containing a 3-hydroxycyclopentanone ring, from which a stable composition has not been prepared so far. In addition, the method according to the third aspect allows the preparation of stable compositions of the compound containing a 3-hydroxycyclopentanone ring in a solvent over a wide range of concentrations of the compound, i.e. both diluted and concentrated compositions.

A fourth aspect of the present invention relates to a method for stabilizing a compound containing a 3-hydroxycyclopentanone ring, the method comprising bringing together a solution containing the compound, an alcohol or ester or a mixture thereof, and a salt capable of dissociating in the solvent, or the ions formed therefrom.

The method according to the fourth aspect provides for the effective stabilization of a compound containing a 3-hydroxycyclopentanone ring by using a salt which acts as a ring stabilizer, preventing the separation of a water molecule.

A fifth aspect of the present invention relates to a method for increasing the chemical stability of a composition comprising a compound containing a 3-hydroxycyclopentanone ring and a solvent, the method comprising adding to the composition at least one salt capable of dissociating in a solvent, or ions forming the same, wherein the solvent comprises an alcohol or an ester, or a mixture thereof.

A sixth aspect of the present invention relates to the use of a salt capable of dissociating in a solvent, or the ions forming it, for stabilizing at least one compound containing a 3-hydroxycyclopentanone ring in a solvent, wherein the solvent comprises an alcohol or an ester or a mixture thereof.

The third to sixth aspects of the present invention may be characterized by specific embodiments similar to the specific embodiments of the first aspect of the present invention.

The essence of the present invention is explained by the following embodiments.

Examples of carrying out the invention

The following description provides means and methods that can be used to carry out the present invention, as well as examples of embodiments of the present invention. It should be noted that the singular forms in the description and claims include the plural forms unless clearly indicated otherwise.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as is commonly understood by one skilled in the art to which the disclosure pertains, unless the contrary is clearly indicated. For the purposes of this disclosure, the following terms are used.

The term “approximately” is used to characterize certain quantitative characteristics. This term refers to the uncertainty inherent in the measurement of any quantitative characteristic and refers to the range that is “quantitative characteristic ± measurement error.” The measurement error may be 10%, more preferably 5%.

The terms "comprise", "comprises", "which includes" and "included" are not intended to limit the list of features that follow such terms and are characterized by, for example, elements, components, numbers, i.e., such terms do not imply exhaustive lists, but rather imply the presence of any other additional features characterized by, for example, additional elements, components, numbers.

All percentages herein that characterize content, amount, or concentration are expressed in weight percent (wt%) unless otherwise indicated or the context otherwise requires.

The term "3-hydroxycyclopentanone ring-containing compound" means a compound containing a 3-hydroxycyclopentanone ring in its structure, especially a compound that is usually unstable due to the tendency for a water molecule to be removed from the ring. In the context of the present invention, the stability of such a compound is improved by the addition of a salt, which

stabilizes the 3-hydroxycyclopentanone ring of the compound, preventing the release of water. The general structure of such compounds can be represented by the following formula:

wherein R can be any substituent. Typical examples of such compounds are prostaglandins, for example from the E group (e.g. alprostadil (PGE1) and dinoprostone (PGE2)) and from the D group (e.g. PGD2):

Prostaglandin E1 (PGE1)

Prostaglandin E2 (PGE2)

Prostaglandin D2 (PGD2)

The terms “salt” and “salt component” in the context of the present invention mean compounds that meet the definition of “salt” in the following reference: IUPAC, Compendium of Chemical Terminology, 2nd ed. “Gold Book” (1997), i.e. a chemical compound consisting of a collection of cations and anions (including salts/substances with a melting point below room temperature or the storage temperature of the product and substances that may dissociate under given conditions within the product, providing sources of ions).

The terms "stability", "stable", "stabilize" and "stabilized" in the context of the present invention mean maintaining the concentration of the active ingredient in the composition of the invention at or slightly below the initial concentration (i.e. immediately after preparation), especially compared to compositions not containing a stabilizer. In one embodiment, the concentration of the active ingredient decreases by no more than 6% over 36 months and/or no more than 10% over 60 months when stored at 5°C ± 3°C. For example, the concentration of the active ingredient decreases by no more than 5% over 36 months, preferably no more than 4% over 36 months, preferably no more than 3.5% over 36 months, more preferably no more than 3% over 36 months, and most preferably no more than 2.5% over 36 months, and/or no more than 8% over 60 months, more preferably no more than 6% over 60 months, even more preferably no more than 5.5% over 60 months, even more preferably no more than 5.0% over 60 months, and most preferably no more than 4% over 60 months.

Non-limiting embodiments of the claimed invention are set forth below.

The applicant has been preparing PGE1 and PGE2-based concentrates as solutions in anhydrous ethanol for 20 years as pharmaceutical preparations which are widely used as medicines in hospitals. The solutions according to the invention are much more stable and have a longer shelf life compared to the prior art products. In particular, the rate of formation of degradation products in the solution according to the invention is significantly reduced compared to the prior art. The extent of the effect and the manner in which the stabilization is achieved meet all the objectives of the invention.

The formulations of the present invention containing active ingredients containing a 3-hydroxycyclopentanone ring (e.g. PGE1 and PGE2) together with a salt have a shelf life that is significantly extended (e.g. from 24 months to at least more than 36 months, in particular 60 months and up to 7-8 years when stored at 5°C ± 3°C), which is advantageous for the use of the formulations as pharmaceutical formulations. For example, prior art formulations exhibit a 10-15% decrease in active ingredient content after 24 months of storage at 5°C ± 3°C, whereas the formulations of the present invention show a similar decrease, e.g. after storage under the same conditions for more than 60 months. The handling and storage time at room temperature without the risk of significant formation of degradation products is extended (e.g. from less than 3 months to 15-18 months at 25°C ± 2°C). The improved stability of pharmaceutical products based on the composition of the present invention did not have a negative impact on the manufacturing process and quality control of the products, nor on the use or safety of the drug by the user or patient.

It is known that the active ingredients are very sensitive to bases, acids and oxidizing agents over a wide range of concentrations. In particular, bases and acids accelerate the elimination of water from the 3-hydroxycyclopentanone ring, for example, PGE1 and PGE2 are formed from PGE1 and PGE2, respectively. Degradation products are considered to be major impurities in pharmaceutical preparations containing PGE1 and PGE2, and therefore the levels of degradation products must be strictly controlled.

In one embodiment of the invention, the composition comprises a salt capable of dissociating in a solvent, or ions forming it. The salt ions may be either monovalent or polyvalent and may be added as a neutral salt or may be formed in situ in the solution (e.g., by mixing acids and alkalis or bases or by any other means that increases the concentration of ions in the solution). Without wishing to be bound by a particular theory, the inventors of the present invention believe that the salt used in the composition of the invention acts as a source of ions, increasing the ionic strength, and as a stabilizer for the active ingredient. In one embodiment of the invention, the salt is used at a concentration of about 0.05 μg/ml to 5000 μg/ml, for example about 0.5 μg/ml to 1000 μg/ml, preferably

about 0.5 μg/ml to 500 μg/ml, more preferably about 1 μg/ml to 100 μg/ml, especially about 1 μg/ml to 30 μg/ml. When used on the μg/ml and mg/ml scale, the salts have a very important effect on stabilizing the active ingredient in solution, i.e. the salts prevent the degradation of the active ingredient due to the elimination of water from the 3-hydroxycyclopentanone ring.

In one embodiment of the invention, the salt is an alkali metal or alkaline earth metal salt, for example, a sodium, potassium, lithium, magnesium, calcium salt. In one embodiment of the invention, the salt is a halogen salt, for example, a bromide salt, a chloride salt, a fluoride salt, and an iodide salt. In one particular embodiment of the invention, the salt is sodium chloride, potassium chloride, lithium chloride, magnesium chloride, calcium chloride. In a more particular embodiment of the invention, the salt is magnesium chloride MgCl2. In one most particular embodiment, the salt is magnesium chloride hexahydrate (MgCl2 x 6H2O).

In one specific embodiment, the salt used to stabilize an ethanolic solution containing a compound containing a 3-hydroxycyclopentanone ring at a concentration of 10 μg/ml to 1000 μg/ml is magnesium chloride hexahydrate and is added at a concentration of 30 μg/ml. Without wishing to be bound by a particular theory, the inventors of the present invention believe that the stability of the composition is improved due to the stabilization of the 3-hydroxycyclopentanone structure of the molecules by preventing the release of water from the ring of the structure.

Stability studies have shown that improved stability (indicated by a slow decrease in the active ingredient and/or a slow accumulation of degradation products) can be achieved with essentially all salts that meet the following conditions: the salt compound consists of a cation and an anion and is capable of dissociating into ions in the solvent and thus increasing the ionic strength of the solution. The stabilizing effect of the salt can be observed by the slow rate of decrease in the content of PGE1, PGE2 and PGD2 in the preparations according to the invention, as well as by the slow rate of increase in the amount of additives.

In one embodiment of the invention, the solvent is a non-aqueous or organic solvent. In one particular embodiment, the solvent comprises an alcohol or an ester or a mixture thereof. In one particular embodiment, the alcohol is selected from a monohydric alcohol, a polyhydric

alcohol or mixtures thereof. In another more specific embodiment, the ester is ethyl acetate. In a most specific embodiment, the monohydric alcohol is ethanol, and/or the polyhydric alcohol is selected from propylene glycol, 1,3-butanediol, and mixtures thereof. In one embodiment of the present invention, where the composition of the invention is intended for use as a pharmaceutical product, the solvent is a physiologically and/or pharmaceutically acceptable solvent that is approved for use in pharmaceutical formulations for humans.

The solvent of the present invention does not consist predominantly of water. However, water may be present in small amounts or residual amounts of up to a few percent. In a particular embodiment of the present invention, the solvent of the present invention further comprises water in an amount of up to 10%, for example 7.4%, in particular 0.5% to 4%, preferably 2% to 4%. The inventors have found that the presence of water in the solvent in an amount of up to 10% can further improve the stability of the 3-hydroxycyclopentanone ring-containing compound in an organic solvent compared to the same formulation not containing water.

In one embodiment of the present invention, ethanol is 96% ethanol Ph. Eur. (95.1-96.9% by volume), anhydrous ethanol Ph. Eur. (at least 99.5% by volume), absolute ethanol or any mixture thereof according to the definitions and requirements of the European Pharmacopoeia. Anhydrous ethanol Ph. Eur. (at least 99.5% by volume) and absolute ethanol are synonymous, often referred to as 100% ethanol or anhydrous ethanol, which in this case are also synonymous.

In one embodiment of the invention, the compound containing a 3-hydroxycyclopentanone ring is a prostaglandin, more particularly prostaglandin E or prostaglandin D. In one particular embodiment of the invention, the compound is prostaglandin E1 (PGE1, alprostadil), prostaglandin E2 (PGE2, dinoprostone) or prostaglandin D2 (PGD2). PGE1, PGE2 and PGD2 are soluble in all of the above solvents in sufficient concentration and can be used in pharmaceutical formulations due to their beneficial effects and suitable toxicological profile. In one embodiment of the invention, the compound containing a 3-hydroxycyclopentanone ring is present in the composition at a concentration of 1 μg/ml to 10,000 μg/ml, preferably 5 μg/ml to 5,000 μg/ml, especially 10 μg/ml to 1,000 μg/ml.

In one embodiment, the composition according to the present invention is in the form of a concentrate (concentrated composition, concentrated solution), containing, for example, a 3-hydroxycyclopentanone ring-containing compound in a concentration of 50 μg/ml to 10,000 μg/ml, or in the form of ready-to-use compositions containing, for example, an active ingredient in a concentration of 1 μg/ml to 50 μg/ml.

In one embodiment of the invention, the composition of the invention is prepared by dissolving one active ingredient in at least one of the above-described solvents, adding at least one salt or other ion source that acts as a stabilizer for the active ingredient. Thus, in one particular embodiment, the composition of the invention comprises at least one active ingredient in at least one organic solvent and at least one ion source. The ion source may be added to the composition as a neutral salt or may be added separately, for example by mixing with an acid and an alkali or base or any other. In one embodiment, the stabilizer of the active ingredient and thus the composition with the ion source are provided in a solution that does not contain water or contains little of it.

In one embodiment of the invention, the salt is added to the solvent during the preparation of the liquid formulation prior to packaging into a ready-to-distribute or marketable sales package (including, but not limited to, ampoules, vials, cartridges, syringes, especially pre-filled syringes, bottles, containers). Active ingredients are characterized by a reduced rate of water release in the absence of oxygen and therefore it is desirable to purge the formulation and the void space with an inert gas.

The stabilized preparation can be used in the same manner as a conventional pharmaceutical preparation that does not contain a stabilizer, for example by dilution with an infusion solution, intravaginal or intracervical or topical administration. The composition can be prepared as a concentrated injection solution for direct administration.

In addition, the stabilized preparation may be used as an intermediate step for distribution or storage prior to any other use (including, but not limited to, chemical modification of active ingredients in the chemical industry or direct/indirect administration to patients, repackaging as a whole product).

All values published are descriptive of the preparations intended for administration by any route (including, but not limited to, concentrates for infusion solutions). The preparation should not be used directly on patients or in any other application without due consideration of safety and following correct procedures.

Examples

The invention will be explained below with some non-limiting exemplary embodiments.

The demonstration of the stabilizing effect of the salts on the test substances was carried out in accelerated stability tests at specified storage temperatures of 25 °C and 30 °C with uncontrolled relative humidity, as the samples were packaged in type I glass ampoules.

The samples used in the accelerated stability studies were prepared by combining different substances with different solvents, with or without different stabilization components. The stability study was performed under accelerated storage conditions with different storage periods. The sales packaging used was a 1 ml type I glass ampoule.

High-performance liquid chromatography (HPLC) was used to analyze the samples prepared for accelerated stability studies to determine the concentration of substances used in the sample preparation, as well as to determine the degradation products formed during the degradation of substances. All results are the average values of samples tested in triplicate at all time points under all conditions.

Examples 1-3 demonstrate the testing of compositions containing a compound containing a 3-hydroxycyclopentanone ring under GMP conditions for human pharmaceuticals prior to the preparation of validation batches.

Example 1

Preparation of a composition containing anhydrous ethanol (as solvent) and 20 μg/ml alprostadil (PGE-1) (reference solution)

Composition batches: E10021615, E10021715, E10021815.

Anhydrous ethanol was measured directly into the mixing vessel under an inert gas atmosphere. The corresponding amount of alprostadil was added and the composition was mixed until complete dissolution. The concentration of alprostadil in the solution was 20 μg/ml. The prepared solution was aseptically (under an argon atmosphere) transferred into 1 ml type I glass ampoules and sealed by flame melting. The components used to prepare the reference composition are presented in Table 1.

Example 2

Preparation of a composition containing 97% by volume ethanol (as solvent), 20 μg/ml alprostadil and 30 μg/ml MgCl2 x 6H2O

Composition batch: E102K0118.

Anhydrous ethanol was measured directly into the mixing vessel under an inert gas atmosphere. Appropriate amounts of MgCl2 x 6H2O and water for injection were added and the resulting solutions were mixed to dissolve the salt. Appropriate amounts of alprostadil were added and the compositions were mixed until the components were completely dissolved. The concentrations of alprostadil and MgCl2 x 6H2O in the solution were 20 μg/ml and 30 μg/ml, respectively. The prepared solution was aseptically (under an argon atmosphere) transferred into 1 ml type I glass ampoules and sealed by flame melting. The amounts of components used to prepare the composition of Example 2 are given in Table 2.

Example 3

Preparation of a composition containing 97% v/v ethanol (as solvent), 20 μg/ml alprostadil and 100 μg/ml MgCl2 x 6H2O

Composition batch: batch E102K0218.

Anhydrous ethanol was measured directly into the mixing vessel under an inert gas atmosphere. Appropriate amounts of MgCl2 x 6H2O and water for injection were added and the resulting solutions were mixed to dissolve the salt. Appropriate amounts of alprostadil were added and the compositions were mixed until complete dissolution. The concentrations of alprostadil and MgCl2 x 6H2O in the solution were 20 μg/ml and 100 μg/ml, respectively. The prepared solution was aseptically (under an argon atmosphere) transferred into 1 ml type I glass ampoules and sealed by flame melting. The amounts of components used to prepare the composition of Example 3 are presented in Table 3.

The results of the accelerated stability tests of Examples 1-3 are presented in Tables 4 and 5. The stability tests were performed at 25°C ± 2°C.

Table 4 shows the concentration of alprostadil (μg/ml) in the compositions of Examples 1-3 immediately after preparation and after the compositions were stored for 1, 2, 3, 4, 6 and 10 months.

Table 5 shows the PGA1 (alprostadil degradation product) content (%) in the compositions of Examples 1-3 immediately after preparation and after the compositions were stored for 1, 2, 3, 4, 6 and 10 months under accelerated conditions (25 °C ± 2 °C).

As can be seen from the results of the stability tests of the compositions of Examples 1-3, the use of a salt in a composition containing a compound containing a 3-hydroxycyclopentanone ring provides improved chemical stability of the compound (alprostadil in Examples 1-3), i.e.

stable content of the compound (reduction from the initial concentration to only about 93% to 94%) and low accumulation of the degradation product of alprostadil (only up to 6%) after storage under accelerated conditions for 10 months compared to reference compositions (containing no salt), in which after storage for 6 months the concentration of alprostadil was only 72% to 77% of the initial concentration and the accumulation of PGA1 was up to 22% to 25%.

Examples 4-14

Examples 4-14 were performed to determine the optimal water content for two different salts under laboratory conditions.

Example 4

Preparation of a composition containing anhydrous ethanol (as solvent), 20 μg/ml alprostadil and 1000 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 1⁄2 volume of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 1⁄2 volume of solvent. The two starting solutions were mixed in a ratio of 1 : 1 and the prepared composition was transferred to glass ampoules and sealed by flame melting. The concentration of alprostadil and MgCl2 x 6H2O in the solution was 20 μg/ml and 1000 μg/ml, respectively. The amounts of components used to prepare the composition of Example 4 are presented in Table 6.

Example 5

Preparation of a composition containing 98% v/v ethanol (as solvent), 20 μg/ml alprostadil and 1000 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of anhydrous ethanol and the corresponding amount of MgCl2 x 6H2O was dissolved in 14 volumes of 96% ethanol. The two stock solutions were mixed in a 1:1 ratio and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentrations of alprostadil and MgCl2 x 6H2O in the solution were 20 μg/ml and 1000 μg/ml, respectively. The amounts of the components used to prepare the composition of Example 5 are given in Table 7.

Example 6

Preparation of a composition containing 98% v/v ethanol (as solvent), 20 μg/ml alprostadil and 100 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of anhydrous ethanol and the corresponding amount of MgCl2 x 6H2O was dissolved in 14 volumes of 96% ethanol. The two stock solutions were mixed in a 1:1 ratio and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentrations of alprostadil and MgCl2 x 6H2O in the solution were 20 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 6 are given in Table 8.

Example 7

Preparation of a composition containing 96% v/v ethanol (as solvent), 20 μg/ml alprostadil and 1000 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 1⁄2 volume of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 1⁄2 volume of solvent. The two starting solutions were mixed in a 1:1 ratio and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentration of alprostadil and MgCl2 x 6H2O in the solution was 20 μg/ml and 1000 μg/ml, respectively. The amounts of components used to prepare the composition of Example 7 are presented in Table 9.

Example 8

Preparation of a composition containing 96% v/v ethanol (as solvent), 20 μg/ml alprostadil and 100 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 14 volumes of solvent. The two starting solutions were mixed in a ratio of 1:1 and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentration of alprostadil and MgCl2 x 6H2O in the solution was 20 μg/ml and 100 μg/ml, respectively. The amounts of the components used to prepare the composition of Example 8 are given in Table 10.

Example 9

Preparation of a composition containing anhydrous ethanol (as solvent), 20 μg/ml alprostadil and 1000 μg/ml CaCl2 x 2H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of solvent and the corresponding amount of CaCl2 x 2H2O was dissolved in 14 volumes of solvent. The two starting solutions were mixed in a ratio of 1:1 and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentration of alprostadil and CaCl2 x 2H2O in the solution was 20 μg/ml and 1000 μg/ml, respectively. The amounts of components used to prepare the composition of Example 9 are presented in Table 11.

Example 10

Preparation of a composition containing 98% v/v ethanol (as solvent), 20 μg/ml alprostadil and 1000 μg/ml CaCl2 x 2H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of anhydrous ethanol and the corresponding amount of CaCl2 x 2H2O was dissolved in 14 volumes of 96% ethanol. The two stock solutions were mixed in a 1:1 ratio and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentrations of alprostadil and CaCl2 x 2H2O in the solution were 20 μg/ml and 1000 μg/ml, respectively. The amounts of components used to prepare the composition of Example 10 are given in Table 12.

Example 11

Preparation of a composition containing 98% v/v ethanol (as solvent), 20 μg/ml alprostadil and 100 μg/ml CaCl2 x 2H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of anhydrous ethanol and the corresponding amount of CaCl2 x 2H2O was dissolved in 14 volumes of 96% ethanol. The two stock solutions were mixed in a 1:1 ratio and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentrations of alprostadil and CaCl2 x 2H2O in the solution were 20 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 11 are given in Table 13.

Example 12

Preparation of a composition containing 96% v/v ethanol (as solvent), 20 μg/ml alprostadil and 1000 μg/ml CaCl2 x 2H2O

The corresponding amount of alprostadil was dissolved in one part by volume of solvent and the corresponding amount of CaCl2 x 2H2O was dissolved in 1⁄2 parts by volume of solvent. The two starting solutions were mixed in a ratio of 1 : 1 and the prepared composition was transferred to glass ampoules and sealed by flame melting. The concentration of alprostadil and CaCl2 x 2H2O in the solution was 20 μg/ml and 1000 μg/ml, respectively. The amounts of components used to prepare the composition of Example 12 are presented in Table 14.

Example 13

Preparation of a composition containing 96% v/v ethanol (as solvent), 20 μg/ml alprostadil and 100 μg/ml CaCl2 x 2H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of solvent and the corresponding amount of CaCl2 x 2H2O was dissolved in 14 volumes of solvent. The two starting solutions were mixed in a ratio of 1:1 and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentration of alprostadil and CaCl2 x 2H2O in the solution was 20 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 13 are presented in Table 15.

Example 14

Preparation of a composition containing anhydrous ethanol (as solvent) and 20 μg/ml alprostadil (reference solution)

The corresponding amount of alprostadil was dissolved in the corresponding amount of solvent. The solution was transferred into glass ampoules and sealed by flame melting. The concentration of alprostadil in the solution was 20 μg/ml. The amounts of components used to prepare the composition of Example 14 are given in Table 16.

The results of accelerated stability tests of the compositions of Examples 4-14 are presented in Table 17. The stability tests were conducted at 30°C ±1°C.

Table 17 shows the PGA1 (alprostadil degradation product) content (%) in the compositions of Examples 4-14 after the compositions were stored for 8 and 20 days under accelerated conditions.

The results of the stability tests of the compositions of Examples 4-14, as shown in Table 17, show that the use of a salt in a composition containing a compound containing a 3-hydroxycyclopentanone ring provides improved chemical stability of the compound (alprostadil in Examples 4-14) when stored for 8 and 20 days under accelerated conditions, i.e., a low accumulation of the degradation product of alprostadil (PGA1) of only 4.7% compared to the reference composition (containing no salt), in which the accumulation of PGA1 was up to 7.5% after storage for 20 days.

At the same time, the results in Table 17 show that the accumulation of PGA1 in alprostadil compositions in ethanol containing a small amount of water (up to 4% in Examples 5-8 and 10-11 and 13) is generally lower than in similar compositions that do not contain water (i.e., in anhydrous ethanol: Examples 9 and 14). Thus, the results in Table 17 show that the addition of a small amount of water to a composition containing a compound containing a 3-hydroxycyclopentanone ring in an organic solvent further improves the chemical stability of the compound compared to a composition of the compound in an anhydrous solvent.

Furthermore, the data in Table 17 show that two different salts provide effective stabilization of the 3-hydroxycyclopentanone ring-containing compound in an organic solvent.

Examples 15-17

Examples 15-17 demonstrate the use of a single salt (NaCl) as a stabilizer for a compound containing a 3-hydroxycyclopentanone ring in an organic solvent.

Example 15

Preparation of a composition containing 96% v/v ethanol (as solvent) and 20 μg/ml alprostadil (reference solution)

The appropriate amount of alprostadil was dissolved in the appropriate amount of solvent. The solution was transferred into 1 ml type I glass ampoules (under nitrogen atmosphere) and sealed in a flame until melted.

The concentration of alprostadil in the solution was 20 μg/ml. The amounts of components used to prepare the composition of Example 15 are given in Table 18.

Example 16

Preparation of a composition containing 96% v/v ethanol (as solvent), 20 μg/ml alprostadil and 100 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in one part by volume of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 1⁄2 parts by volume of solvent. The two stock solutions were mixed in a ratio of 1:1 and the prepared composition was transferred into 1 ml glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentration of alprostadil and MgCl2 x 6H2O in the solution was 20 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 16 are presented in Table 19.

Example 17

Preparation of a composition containing 96% v/v ethanol (as solvent), 20 μg/ml alprostadil and 100 μg/ml NaCl

The corresponding amount of alprostadil was dissolved in 1⁄2 volume of solvent and the corresponding amount of NaCl was dissolved in 1 volume of solvent. The two stock solutions were mixed in a ratio of 1:1 and transferred to 1 ml glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentration of alprostadil and NaCl in the solution was 20 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 17 are given in Table 20.

The results of accelerated stability tests of the compositions of Examples 15-17 are presented in Table 21. The stability tests were performed at 30°C ± 1°C.

Table 21 shows the content (%) of PGA1 (alprostadil degradation product) in the compositions of Examples 15-17 immediately after preparation of the compositions and after storage for 7 and 14 days under accelerated conditions.

The results of the stability tests of the compositions of Examples 15-17 presented in Table 21 show that the use of salt in the composition containing a compound containing a 3-hydroxycyclopentanone ring provides better chemical stability of the compound alprostadil when stored for 7 and 14 days under accelerated conditions, i.e., the accumulation of the degradation product of alprostadil (PGA1) was only 12.2% compared to the reference composition (not containing salt), in which the accumulation of PGA1 was up to 17% after storage for 14 days.

Furthermore, the results in Table 21 show that in addition to the addition of MgCl2 x 6H2O and CaCl2 x 2H2O, the addition of another salt, i.e. NaCl, provides effective stabilization of alprostadil in ethanol.

Thus, the results of the presented Examples 1-17 clearly demonstrate that different types of salts are capable of stabilizing a compound containing a 3-hydroxycyclopentanone ring in an organic solvent.

Examples 18-20

Examples 18-20 demonstrate the use of salt at various concentrations to stabilize a 3-hydroxycyclopentanone ring-containing compound (PGE1) in an organic solvent.

Example 18

Preparation of a composition containing 96% v/v ethanol (as solvent), 60 μg/ml alprostadil and 100 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 34 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 34 volumes of solvent. The two stock solutions were mixed in a 1:1 ratio and transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentrations of alprostadil and MgCl2 x 6H2O in the solution were 60 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 18 are given in Table 22.

Example 19

Preparation of a composition containing 96% ethanol (vol/vol) (as solvent), 60 μg/ml alprostadil and 30 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 14 volumes of solvent. The two starting solutions were mixed in a ratio of 1:1 and the prepared composition was transferred into glass ampoules and sealed by flame melting. The concentration of alprostadil and MgCl2 x 6H2O in the solution was 60 μg/ml and 30 μg/ml, respectively. The amounts of components used to prepare the composition of Example 19 are presented in Table 23.

Example 20

Preparation of a composition containing 96% v/v ethanol (as solvent) and 60 μg/ml alprostadil (reference solution)

The corresponding amount of alprostadil was dissolved in the corresponding amount of solvent. The solution was transferred into glass ampoules and sealed by heating in a flame. The concentration of alprostadil in the solution was 60 μg/ml. The amounts of components used to prepare the composition of Example 20 are given in Table 24.

The results of accelerated stability tests of the compositions of Examples 18-20 are presented in Table 21. The stability tests were carried out at 30°C ± 1°C.

Table 25 shows the content (%) of PGA1 (alprostadil degradation product) in the compositions of Examples 18-20 immediately after preparation of the compositions and after storage for 7 and 14 days under accelerated conditions.

The results of stability tests of the compositions of Examples 18-20 presented in Table 25 show that both concentrations of MgCl2 x 6H2O, i.e. low 30 μg/ml and high 100 μg/ml, ensured effective stabilization of alprostadil in the organic solvent.

Examples 21-24

Examples 21-24 demonstrate the use of salt at various concentrations to stabilize a concentrated solution of a 3-hydroxycyclopentanone ring-containing compound (PGE1) in an organic solvent.

Example 21

Preparation of a composition containing 96% v/v ethanol (as solvent), 500 μg/ml alprostadil and 100 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 14 volumes of solvent. The two stock solutions were mixed in a 1:1 ratio and transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentrations of alprostadil and MgCl2 x 6H2O in the solution were 500 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 21 are given in Table 26.

Example 22

Preparation of a composition containing 96% v/v ethanol (as solvent), 500 μg/ml alprostadil and 30 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 1⁄2 volume of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in % volume of solvent. The two stock solutions were mixed in a ratio of 1 : 1 and transferred into glass ampoules, which were sealed by flame melting. The concentrations of alprostadil and MgCl2 x 6H2O in the solution were 500 μg/ml and 30 μg/ml, respectively. Example 22

The amounts of components used to prepare the composition are presented in Table 27.

Example 23

Preparation of a composition containing 96% v/v ethanol (as solvent) and 500 μg/ml alprostadil (reference solution)

The corresponding amount of alprostadil was dissolved in the corresponding amount of solvent. The solution was transferred into glass ampoules and sealed by heating in a flame. The concentration of alprostadil in the solution was 500 μg/ml. The amounts of components used to prepare the composition of Example 23 are given in Table 28.

Example 24

Preparation of a composition containing 96% v/v ethanol (as solvent), 500 μg/ml alprostadil and 1000 μg/ml MgCl2 x 6H2O

The corresponding amount of alprostadil was dissolved in 14 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 1 volume of solvent. The two stock solutions were mixed in a ratio of 1:1 and transferred into glass ampoules and sealed by flame melting. The concentrations of alprostadil and MgCl2 x 6H2O in the solution were 500 μg/ml and 1000 μg/ml, respectively. The amounts of components used to prepare the composition of Example 24 are given in Table 29.

The results of the accelerated stability tests of the compositions of Examples 21-24 are presented in Table 30. The stability tests were performed at 30°C ± 1°C.

Table 30 shows the content (%) of PGA1 (alprostadil degradation product) in the compositions of Examples 21-24 immediately after preparation of the compositions and after storage for 7 and 14 days under accelerated conditions.

The results of the stability tests of the compositions of Examples 21-24 presented in Table 30 show that both concentrations of MgCl2 x 6H2O, i.e. low 30 μg/ml and high 1000 μg/ml, provide effective stabilization of the concentrated solution of alprostadil in organic solvent.

Examples 25-27

Examples 25-27 demonstrate the use of salt at various concentrations to stabilize a concentrated solution of a 3-hydroxycyclopentanone ring-containing compound (PGE2) in an organic solvent.

Example 25

Preparation of a composition containing 96% v/v ethanol (as solvent), 1000 μg/ml dinoprostone (PGE2) and 1000 μg/ml MgCl2 x 6H2O

The corresponding amount of dinoprostone was dissolved in 14 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 14 volumes of solvent. The two stock solutions were mixed in a 1:1 ratio and transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentration of both dinoprostone and MgCl2 x 6H2O in the solution was 1000 μg/ml. The amounts of components used to prepare the composition of Example 25 are given in Table 31.

Example 26

Preparation of a composition containing 96% v/v ethanol (as solvent), 1000 μg/ml dinoprostone and 100 μg/ml MgCl2 x 6H2O

The corresponding amount of dinoprostone was dissolved in 14 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 1⁄2 volumes of solvent. The two stock solutions were mixed in a 1:1 ratio and transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentrations of dinoprostone and MgCl2 x 6H2O in the solution were 1000 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 26 are given in Table 32.

Example 27

Preparation of a composition containing 96% v/v ethanol (as solvent) and 1000 μg/ml dinoprostone (reference solution)

The corresponding amount of dinoprostone was dissolved in the corresponding amount of solvent. The solution was transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentration of dinoprostone in the solution was 1000 μg/ml. The amounts of components used to prepare the composition of Example 27 are given in Table 33.

The results of accelerated stability tests of the compositions of Examples 25-27 are presented in Tables 34 and 35. The stability tests were conducted at 30°C ± 1°C.

Table 34 shows the concentration of dinoprostone (μg/ml) in the compositions of Examples 25-27 immediately after preparation and after the compositions were stored for 7 and 14 days under accelerated conditions.

Table 35 shows the PGA2 (dinoprostone degradation product) content (%) in the compositions of Examples 25-27 immediately after preparation of the compositions and after storage for 7 and 14 days under accelerated conditions.

The results of stability tests of the compositions of Examples 25-27 presented in Table 34 show that both concentrations of MgCl2 x 6H2O, i.e. low 100 μg/ml and high 1000 μg/ml, provide effective stabilization of a concentrated solution of dinoprostone (PGE2) in an organic solvent.

Examples 28-29

Examples 28-29 demonstrate the use of salt at various concentrations to stabilize a dilute solution of a 3-hydroxycyclopentanone ring-containing compound (PGD2) in an organic solvent.

Example 28

Preparation of a composition containing 96% v/v ethanol (as solvent) and 10 μg/ml PGD2 (reference solution)

The corresponding amount of PGD2 was dissolved in the corresponding amount of solvent. The solution was transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentration of PGD2 in the solution was 10 μg/ml. The amounts of components used to prepare the composition of Example 28 are given in Table 36.

Example 29

Preparation of a composition containing 96% v/v ethanol (as solvent), 10 μg/ml PGD2 and 100 μg/ml MgCl2 x 6H2O

The corresponding amount of PGD2 was dissolved in 14 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 14 volumes of solvent. The two stock solutions were mixed in a 1:1 ratio and transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentrations of PGD2 and MgCl2 x 6H2O in the solution were 10 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 29 are given in Table 37.

The results of accelerated stability tests of the compositions of Examples 28-29 are presented in Table 38. The stability tests were performed at 30°C ± 1°C.

Unlike the results obtained with Examples 1-27, the results for Examples 28-29 are presented in relative values (%) based on the area under the curve obtained from the detector.

Table 38 shows the concentration of PGD2 (μg/ml) in the compositions of Examples 28-29 immediately after preparation and after the compositions were stored for 7 and 14 days under accelerated conditions.

The results of stability tests of the compositions of Examples 28-29 presented in Table 38 show that the use of the salt MgCl2 x 6H2O provides effective stabilization of a dilute solution of a compound containing a 3-hydroxycyclopentanone ring, i.e. PGD2, in an organic solvent, while a similar solution not containing the salt is very unstable due to the decomposition of PGD2.

Examples 30-31

Examples 30-31 demonstrate the use of salt at various concentrations to stabilize a dilute solution of a 3-hydroxycyclopentanone ring-containing compound (PGD2) in an organic solvent.

Example 30

Preparation of a composition containing 96% v/v ethanol (as solvent) and 20 μg/ml PGD2 (reference solution)

The corresponding amount of PGD2 was dissolved in the corresponding amount of solvent. The solution was transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentration of PGD2 in the solution was 20 μg/ml. The amounts of components used to prepare the composition of Example 30 are given in Table 39.

Example 31

Preparation of a composition containing 96% v/v ethanol (as solvent), 16 μg/ml PGD2 and 100 μg/ml MgCl2 x 6H2O

The corresponding amount of PGD2 was dissolved in 14 volumes of solvent and the corresponding amount of MgCl2 x 6H2O was dissolved in 14 volumes of solvent. The two stock solutions were mixed in a 1:1 ratio and transferred to glass ampoules (under nitrogen atmosphere) and sealed by flame melting. The concentrations of PGD2 and MgCl2 x H2O in the solution were 16 μg/ml and 100 μg/ml, respectively. The amounts of components used to prepare the composition of Example 31 are given in Table 40.

The results of accelerated stability tests of the compositions of Examples 30-31 are presented in Table 41. The stability tests were performed at 30°C ± 1°C.

Unlike the results of Examples 1-27, the results of Examples 30-31 are presented as relative values (%) based on the area under the curve obtained from the detector.

Table 41 shows the concentration of PGD2 (μg/ml) in the compositions of Examples 30-31 immediately after preparation and after the compositions were stored for 7 and 14 days under accelerated conditions.

The results of stability tests of the compositions of Examples 30-31 presented in Table 41 show that the use of the salt MgCl2 x 6H2O provides effective stabilization of a dilute solution of a compound containing a 3-hydroxycyclopentanone ring, i.e. PGD2, in an organic solvent, while a similar solution not containing the salt is very unstable due to the decomposition of PGD2.

Example 32

Long-term stability study of compositions according to the invention

3 batches of the formulation of the present invention in a sales package (1 ml glass ampoules) were prepared according to the procedure described above in Example 2. The results of their long-term stability study (storage at 5°C ± 3°C, 18 months) are shown in the table below. Table 42 shows the PGA1 (alprostadil degradation product) content (%) in the compositions of the invention immediately after preparation of the compositions and after storage for 3, 6, 9, 12 and 18 months.

The results of the stability tests of the compositions according to the invention, presented in Table 42, show that the compositions according to the invention have very good long-term stability when stored at a temperature of 5°C ± 3°C, i.e. when the compositions are stored for a long time, especially 18 months and longer, small amounts of alprostadil degradation product are present.

The publication describes only selected results from the tests, which represent the main evidence and trends that are also reproducible in the other combinations tested. Some of the combinations tested are part of a commercially important formulation used in human medicine with a well-documented stability profile and correlation between stabilities at different temperatures tested.

Stability studies have shown that improved stability (assessed by low loss of active ingredient and/or slow accumulation of degradation products) can be achieved with essentially all salts that meet the following conditions specified above, i.e. the compound must consist of a cation and an anion and must dissociate into ions in the solvent and thus increase the ionic strength of the solution. The stabilizing effect can be observed both in the slow increase in the content of the active ingredients (PGE1, PGE2 and PGD2)

by the rate of decrease in the preparations according to the invention, as well as by the slow rate of increase in the amount of impurities, which are degradation products of the active ingredients.

All tested concentrations had a positive stabilizing effect for all tested active ingredients at all concentrations, meaning that a beneficial stabilizing effect is likely to occur outside of the combinations of concentrations tested.

Claims (30)

1. A composition comprising a compound containing a 3-hydroxycyclopentanone ring, an alcohol or an ester, or a solvent containing a mixture thereof, and a salt capable of dissociating in the solvent, or ions forming it, characterized in that the salt is a halogen salt. 2. The composition according to claim 1, characterized in that the solvent further comprises water. 3. The composition according to claim 2, characterized in that the solvent contains water in an amount of 0.05 wt% to 10 wt%, more particularly 0.5 wt% to 4 wt%, preferably 2 wt% to 4 wt%. 4. A composition according to any one of claims 1 to 3, characterized in that the alcohol is selected from a monohydric alcohol, a polyhydric alcohol or mixtures thereof, and/or the ester is ethyl acetate. 5. The composition according to claim 4, characterized in that the monohydric alcohol is ethanol and/or the polyhydric alcohol is selected from propylene glycol, 1,3-butanediol and mixtures thereof. 6. A composition according to any one of claims 1 to 5, wherein the salt is added to the composition as a compound or the salt is obtained in situ by adding its precursors to the composition. 7. A composition according to any one of claims 1 to 6, wherein the salt is an alkali metal or alkaline earth metal salt. 8. A composition according to any one of claims 1 to 7, wherein the salt is a chloride salt. 9. A composition according to any one of claims 1 to 8, wherein the salt is sodium chloride, calcium chloride or magnesium chloride. 10. A composition according to any one of claims 1 to 9, characterized in that the salt is magnesium chloride, in particular magnesium chloride hexahydrate. 11. A composition according to any one of claims 1 to 10, characterized in that the salt concentration is from 0.05 μg/ml to 5000 μg/ml, preferably from 0.5 μg/ml to 1000 μg/ml, more preferably from 0.5 μg/ml to 500 μg/ml, especially from 1 μg/ml to 30 μg/ml. 12. A composition according to any one of claims 1 to 11, characterized in that the concentration of the compound containing the 3-hydroxycyclopentanone ring is from 1 μg/ml to 10,000 μg/ml, preferably from 5 μg/ml to 5,000 μg/ml, especially from 10 μg/ml to 1,000 μg/ml. 13. A composition according to any one of claims 1 to 12, characterized in that the compound containing a 3-hydroxycyclopentanone ring is a prostaglandin, in particular prostaglandin E or prostaglandin D. 14. The composition of claim 13, wherein the prostaglandin is prostaglandin E1, prostaglandin E2 or prostaglandin D2. 15. The composition according to any one of claims 1 to 14, characterized in that it is packaged in an ampoule, vial, cartridge, syringe, bottle or container. 16. A kit of parts comprising a composition according to any one of claims 1 to 14, provided in an ampoule, vial, cartridge, syringe, bottle or container. 17. A method for preparing a composition according to any one of claims 1 to 15, comprising mixing a compound containing a 3-hydroxycyclopentanone ring, a solvent containing an alcohol or ester or a mixture thereof, and a salt capable of dissociating in the solvent, or salt precursors, wherein the salt is a halogen salt. 18. A method for stabilizing a compound containing a 3-hydroxycyclopentanone ring, the method comprising bringing together a solvent containing the compound, an alcohol or an ester, or a mixture thereof, and a salt capable of dissociating in the solvent, or forming ions thereof, characterized in that the salt is a halogen salt. 19. The method according to claim 17 or 18, characterized in that the solvent further comprises water. 20. The method according to claim 19, characterized in that the solvent contains water in an amount of 0.05 wt% to 10 wt%, more particularly 0.5 wt% to 4 wt%, preferably 2 wt% to 4 wt%. 21. The method according to any one of claims 17 to 20, wherein the alcohol is selected from a monohydric alcohol, a polyhydric alcohol or mixtures thereof, and/or the ester is ethyl acetate. 22. The method according to any one of claims 17 to 21, characterized in that the monohydric alcohol is ethanol and/or the polyhydric alcohol is selected from propylene glycol, 1,3-butanediol and mixtures thereof. 23. The method according to any one of claims 17 to 22, wherein the salt is an alkali metal or alkaline earth metal salt. 24. The method according to any one of claims 17 to 23, wherein the salt is a chloride salt. 25. The method according to any one of claims 17 to 24, wherein the salt is sodium chloride, calcium chloride or magnesium chloride. 26. A method according to any one of claims 17 to 25, characterized in that the salt is magnesium chloride, in particular magnesium chloride hexahydrate. 27. The method according to any one of claims 17 to 26, characterized in that the mass ratio of the compound to the salt or ions forming it is 1:5000 to 200000:1, preferably 1:200 to 10000:1, more preferably 1:50 to 2000:1, especially 1:50 to 20:1. 28. The method according to any one of claims 17 to 27, characterized in that the ratio of mass (μg) to volume (ml) of the salt or its constituent ions and the solvent is 0.05:1 to 5000:1, more preferably 0.5:1 to 1000:1, more preferably 0.5:1 to 500:1, especially 1:1 to 30:1. 29. A method according to any one of claims 17 to 28, characterized in that the compound containing a 3-hydroxycyclopentanone ring is a prostaglandin, in particular prostaglandin E or prostaglandin D. 30. The method of claim 29, wherein the prostaglandin is prostaglandin E1, prostaglandin E2 or prostaglandin D2.