CA2078601A1 - Production of crystalline penem - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Disclosed is a method of crystallizing (1R,5S,6S)-2-[(6,7-dihydro-5H-pyrazolo[1,2-a][1,2,4]triazolium-6-yl)]thio-6-[(R)-1-hydroxyethyl]-1-methyl-carbapenem-3-carboxylate (herein-after simply referred to as L-627), by maintaining an aqueous solution of L-627 at a temperature in the range from the eutectic temperature of the solution to a temperature lower than 0°C. The method provides such advantages that loss of L-627 accompanied by crystallization is reduced, the number of steps in the preparation of vial formulations is small and maintenance of these steps under sterile and dust-free conditions can be per-formed easily, dispensing of the drug can be conducted with quantitative accuracy, and the crystals promptly dissolve in a solvent at the time of use.

Description

2~8~1 - l - 24205-944 This invention relates to a method of providing crystalline (lR,5S,6S)-2-l(6,7-dihydro-5H-pyrazolo[1,2-a][1,2,4]
triazolium-6-yl]thio-6-[(R)-l-hydroxyethyl]-l-methyl-carbapenem-3-carboxylate (hereinafter simply referred to as L-627), a carbapenem antibiotic substance, excellent in solubility and also providing a vial containing the said crystalline compound.
Conventionally, crystalline L-627 filled in a vial has been provided by, for example, a method (disclosed in EP
289801, among others) which comprises dissolving L-627 by heating, subjecting the solution to filtration and sterilization, cooling the filtrate to cause crystallization, collecting the crystals by filtration, drying the crystals, then filling the crystals in the vial.
However, such conventional methods as above are accompanied by, among others, the following drawbacks, namely, (1) since L-627 decomposes when dissolved by heating or L-627 dissolved in the mother liquor does not completely precipitate as crystals when conducting crystallization, the amount of crystal-line L-627 is smaller than that of L-627 actually dissolved, (2) since the number of steps is relatively large, it is difficult to maintain of these steps under sterile and dust-free conditions, (3) since the filling of the drug into vials must be conducted after the drug is converted to crystalline powder, quantitatively accurate distribution is difficult as compared with the case of conducting the distribution in the state of a solution, and (4) dissolution of the crystals in the solvent at the time of use takes a relatively long time.

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Circurnstances being such as above, a method has been sought for providing crystals of L-627, involving reduced loss of L-627 in crystallization, reduced number of steps for providing vials containing L-627 thus easily maintaining, sterility and dust-free conditions during the steps, easé of quantitatively accurate distribution of the drug and realization of prompt dis-solution of crystals in a solvent at the time of use.
In view of the above-mentioned drawbacks in conven-tional methods, the present inventors have studied diligently and found unexpectedly that, when an aqueous solution of ~-627 is maintained at temperatures ranging from eutectic temperatures to temperatures lower than 0C, crystals of excellent solubility can be obtained, loss of L-627 accompanied by crystallization is reduced, and that, when this method of crystallization is performed in a vial, a vial containing crystalline L-627 having high solu-bility in a solvent at the time of use can be obtained, the process can be conducted simply and conveniently with reduced number of steps to be carried out under sterile and dust-free conditions, and the drug can be readily distributed with quantita-tive accuracy, thus the present invention has been accomplished.
Namely, the present invention relates to a method of crystallizing L-627, which is characterized by maintaining an aqueous solution of L-627 at temperatures ranging from the eutectic temperature of the solution to temperatures lower than OC.
The present invention.can be conducted by maintaining : , ~ - . .

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- 2a - 24205-944 an aqueous solution of L-627 at temperatures ranging from the eutectic temperatures to temperatures lower than 0C.
The concentration of L-627 in its aqueous solution ranges usually from 0.5% (w/w) to 10% (w/w), preferably from 1% (w/w) to 5% (w/w), more preferably from 1.5~ (w/w) to 2.5%
(w/w). The aqueous solution is made by dissolving L-627 to distilled water at the concentration as mentioned above.

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.- :, : . -3 2~78601 The aqueous solution of L-627 may contain for example alkaline metal halide such as sodium chloride potassium chloride, preferably sodium chloride, for increasing solbility of L-627 to water. The concentration of the alkaline metal chloride in its aqueous solution ranges usually from 0.1% tw/w) to 10%
(w/w), preferably from 0.5% (w/w) to 5% (w/w)/ more preferably from 1% (w/w) to 3% (w/w).
The aqueous solution of L-627 may also contain an organic solvent which does not-inhibit the crystallization nor exert undesirable effects on L-627.
Examples of the organic solvent include water-soluble organic solvents such as Cl6 alcohol e.g. methyl alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol, and C3 7 ketone e.g. acetone. Preferable examples of the organic solvents which may be contained include Cl_3 alcohol such as methyl alcohol and ethyl alcohol, and C3 5 ketone such as acetone, and more preferable examples include methyl alcohol, ethyl alcohol and acetone. While the concentration of these organic solvents in an aqueous solution of L-627 varies with kinds of such solvents, it usually ranges from 0.1% (v/v) to 10% (v/v), preferably from 0.5% (v/v) to 6% (v/v), more preferably, for example, from 1% (v/v) to 3% (v/v). Practically, when ethyl alcohol is employed, it is added to an aqueous solution of L-627 so that the concentration becomes preferably 0.5% (v/v) to 6% (v/v), more preferably, 1% (v/v) to 3% (v/v).
These solvents are mixed preferably after L-627 is dissolved in water.
In the present invention, eutectic temperatures include eutectic point and temperatures lower than those at which eutectic crystal can be formed.
Practically, in the case of using 2% aqueous solution of L-627, the eutectic temperatures mean those whose electric resistance ranges from about lO KQ to lower 2~786~1 than lO KQ , more specifically -10C to -2C.
The eutectic temperatures are influenced by the concentration of L-627 or a water-soluble organic solvent contained in the aqueous solution of L-627, and they are, generally, in the range of -10C to -0.5C, preferably -6C to -1C, more preferably -4C to -2C.
The temperatures ranging from the eutectic temperatures to those lower than 0C, at which the present invention is carried out, usually ranges from -10C to temperatures lower than 0C, preferablly -6C
to -1C, more preferablly -4C to -2C. The eutectic temperatures are usually lowered by dissolving alkaline metal halide to the aqueous solution of L-627.
Concretely, in the case of using a 2% ethanolic aqueous solution of L-627, the present invention can be conducted by maintaining the solution at temperatures ranging from -10C to -0.2C, preferably -6C to -0.5C, more preferably -4C to -1C.
While the time during which the aqueous solution of L-627 is maintained at temperatures ranging from the eutectic temperatures to those lower than 0C is influenced by the concentration of L-627 or a water-soluble organic solvent contained in the aqueous solution of L-627, it ranges generally from 0.5 hour to 48 hours, preferably from 5 hours to 30 hours, more preferably from 10 hours to 20 hours.
In the crystallization method of the present invention, for performing the crystallization with higher efficiency, it is preferable to freeze the aqueous solution of L-627 prior to maintaining the solution at temperatures ranging from the eutectic temperatures to those lower than 0C.
The frozen state means, in the measurement of conductivity, that the electric resistance of the aqueous solution of L-627 exceeds 104-6KQ. While the temperature for freezing the aqueous solution varies 2 ~

with, for example, the concentration of L-627 or the concentration of a water-soluble organic solvent contained in the aqueous solution, it ranges usually from -40C to -10C, preferably from -30C to -10C, more preferably from -25C to -15C. Practically, for example, in the case of using a solvent consisting of water alone, the temperature for freezing the aqueous solution ranges from -40C to -10C, preferably from -30C to -10C, more pre-ferably from -25C to -15C. And, in the case of, for example, using a 2% (v/v) ethanolic aqueous solution of L-627, tempera-tures for freezing the aqueous solution ranges from -40C to -10C, preferably from -30C to -10C, more preferably from -25C
to -15C.
The freezing may be conducted rapidly or over a period of time. The time required for the freezing varies with the concentration of L-627, the concentration of a water-soluble organic solvent contained in the aqueous solution or temperatures at the time of conducting the freezing, and it ranges generally from 0.5 hour to 48 hours, preferably from one hour to 30 hours, more preferably from one hour to 10 hours.
In the crystallization method of this invention, for performing the crystallization with higher efficiency, it is preferable to freeze an aqueous solution of L-627 after maintain-ing the aqueous solution at temperatures ranging from the eutectic temperatures to those lower than 0C. The temperatures in this freezing process are influenced by the concentration of L-627 or the concentration of a water-soluble aqueous solvent contained 2$7$~1 in the aqueous solution, and they are yenerally within the range from -40C to -10C, preferably from -30C to -15C, more preferably from -25C to -15C. Practically, for example, in the case of using a solvent consisting of water alone, the tempera-ture for freezing the aqueous solution ranges from -40C to -10C, preferably from -30C to -10C, more preferably from -25C to -15C. And, in the case of, for example, using a 2~ (v/v) ethanolic aqueous solution, the aqueous solution is cooled to temperatures ranging from -40C to -10C, preferably from -30C
L0 to -10C, more preferably -25C to -15C.
The freezing may be conducted rapidly or over a period of time. The time required for the freezing varies with the concentration of L-627, the concentration of a water-soluble organic solvent contained in the aqueous solution or temperatures at the time of conducting the freezing, and it ranges generally from 0.5 hour to 48 hours, preferably from one hour to 30 hours, more preferably from one hour to iO hours.
In the crystallization method of this invention, for performing the crystallization with a higher efficiency, it is preferable to repeat the above-mentioned series of steps includ-ing freezing, maintaining the temperatures ranging from eutectic temperatures to those lower than 0C and cooling. The frequency of the repetition varies with the concentration of L-627, the concentration of a water-soluble organic solvent contained in the aqueous solution, the temperatures when conducting freezing, those when raising temperatures and those for cooling. It ranges 2~7~01 _ 7 _ 24205-944 preferably from once to 15 times, more preferably, for example, from twice to ten times.
And, in the present invention, by conducting the above-mentioned crystallization of L-627 in a vial, drying the crystals under reduced pressure and closing the vial tightly, vials containing crystalline powder of L-627 can be provided.
Crystals obtained by conducting the above-mentioned method of this invention in vials are dried under reduced pres-sure in vials. The pressure employed in this process is generally 5 mmHg or less, preferably ranges from l mmHg to 0.1 mmHg, more preferably 0.1 mmHg to 0.5 mmHg.
The temperatures in the process of conducting the drying under reduced pressure vary with the heat of sublimation of the solvent, the concentration of L-627, the concentration of a water-soluble organic solvent contained in the aqueous solution or the pressure when drying the crystals under reduced pressure.
And, for avoiding melting of the crystals, by adjusting the environmental temperatures at the initial stage at about 50C at the highest, the drying under reduced pressure is conducted at the preparation témperatures not exceeding the melting point of crystals of L-627, and then, after the water-content in the crystals is decreased to 6% to 8% (w/w), is conducted until the moisture in the crystals of L-627 becomes about 2% (w/w) or less while maintaining the environmental temperature at temperatures ranging from 25C to 50C, preferably from 30C to 45C. In the drying stage, the temperature of the preparation does not exceed 2 ~ a ~

the melting point of L-627j which can hardly be specified,!be-cause the melting point rises when the moisture in crystals of L-627 decreases by sublimation, but it is lower than 0C at the initial stage of the drying under reduced pressure, and, at the time when the moisture in the crystals is reduced to 8% or less, it can be raised up to about 20C to 40C.
The time required in the process of drying under reduced pressure varies with, among others, the concentration of L-627, the concentration of a water-soluble organic solvent in the aqueous solution and the pressure or the temperature when drying the crystals under reduced pressure, it usually ranges from 4 hours to 40 hours, preferably from 7 hours to 30 hours, more preferably from 10 hours to 20 hours.
In the case of conducting crystallization of the present invention in vials, it is preferable to carry out all the steps under sterile and dust-free conditions. In this case, sterilization of the aqueous solution of L-627 is conducted by sterilizing filtration. For instance, the sterilization can be performed by using, for example, a membrane filter of about 0.2 um of capability of removing minute particles. Practical examples of such membrane filters as above include nylon membrane (NR
type: manufactured by Nihon Pall Ltd.) and polyvinylidene membrane (GV type: manufactured by Japan Millipore Corp.). Sterilization of containers such as vials can be conducted by, for example, steam sterilization under pressure or dry heat sterilization, preferably steam sterilization under pressure (e.g. for 15 min.

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2~78~1 _ 9 _ 24205-944 to 120 min. at 100C to 150C). While dispensing of L-627 into vials is conducted preferably after dissolving L-627 into water, it can also be conducted after drying the crystals of L-627 into a powdery state. The amount to be dispensed ranges from 50 mg to 1000 mg per vial.
To state a preferred embodiment of the invention in greater detail, preparation of the crystalline cmpound of the present invention in vials can be conducted as follows;
(a) L-627 is dissolved in water, (b) the aqueous solution of L-627 is subjected to steriliz-ing filtration, which is dispensed into sterilized vials, (c) the aqueous solution of L-627 is maintained at tem-peratures ranging from the eutectic temperature of the solution to temperatures lower than 0C, (d) the aqueous solution is dried under reduced pressure, and (e) the vials are closed tightly.
In the above process also, it is preferable to (c') freeze the aqueous solution of L-627, before the step (c) or to (c") cool the solution, after the step (c), or to repeat a series of steps (c'), (c) and(c"). And, if desired, it is also possible to add a sterilized water-soluble organic solvent to the aqueous solution of L-627.
The vials referred to in the present invention are any vessels capable of containing a drug sealed tightly under sterile conditions, for example, vials, ampoules, etc.

.' ~ , The tight closure can be performed, in the case of vials, by applying a rubber stopper and by fastening with an aluminum cap, and, in the case of ampoules, by melt-sealing, etc.
L-627 and starting materials thereof can be synthe-sized by, for example, the method disclosed in EP 289801 or methods analogous thereto.
The crystals of L-627 obtained by the method of this invention can be used as an antibacterial agent in accordance with a conventional method, and can be safely administered, in the form of for example a vial containing its antibacterially effec-tive amount, to mammals including man for the therapy of infec-tious diseases. The dosage varies widely with the agent, body ~ weight and symptoms of the patient, dosage forms, doctor's - diagnosis, etc. It ranges normally from about 200 to about 8,000 mg per day for the therapy of infectious diseases of adults (for example, infectious diseases of urinary passages, suppurative diseases, infectious diseases of respiratory organs or infectious diseases of bile duct, etc.). In general, the antibacterial agent can be administered intravenously as injection by dissolving in, for example, distilled water.
The present invention in a preferred embodiment pro-vides a method of preparing crystals of L-627, which is character-ized by reduced loss of L-627 accompanying crystallization, fewer processing steps and easy maintenance of these steps under sterile and dust-free conditions, easy dispensation of the drug with quantitative accuracy, and quick dissolution of crystals in a .
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Reference Example 1 In 18 ml of distilled water was dissolved 200 mg of L-627, and the solution was subjected to filtration with the membrane filter (manufactured by Japan Millipore Corp.: SLGV
025 LS). The filtrate was freeze-dried to give powdery L-627, to which was added 1.8 ml of sterilized distilled water, followed by heating up to 40C to dissolve L-627 completely. The aqueous solution of L-627 was left standing for 3 hours at 5C in a refrigerator, then resulting crystalline precipitates were collec-ted by filtration. The crystals were washed with a small volume of a sterilized 50% (V/V) ethanolic aqueous solution. The cry-stals washed as above were subjected to lyophilization for 12 hours under reduced pressure not exceeding l mmHg while adjusting environmental temperatures to a range from 20C to 25C, followed by continuing the lyophilization for 3 hours under the same inner pressure of the lyophilizer while adjusting environmental temperatures to a range of 35C to 40C. After completion of the lyophilization, inner pressure of the lyophilizer was restored to normal pressure to give 152 mg (yield: 78%) of L-627 as crystals.
The crystallinity of thus-obtained L-627 was confirmed under observation with a polarizing microscope.
Working Example l In 10 ml of distilled water was dissolved 200 mg :

2~7~6~1 of L-627, and the solution was subjected to filtration with the membrane filter (manufactured by Japan Millipore Corp.: SLGV 025 LS). The filtrate was filled in a sterilized vial, and the vial was put in a thermostat (manufactured by NESLAB Inc.: RTE-9). The temperature of the solution was cooled to -18C taking one hour to have the solution frozen. Then, the temperature was raised up to those ranging from -2C to -0.5C and this temperature range was maintained for about 2 hours, then the temperature was lowered to -20C taking one hour. The process of this-raising and lowering the temperature was repeated twice, then the inner pressure of the lyophilizer was reduced to 1 mmHg or lower. Lyophilization was conducted for 12 hours while adjusting the environmental temperatures to a range of 20C to 25C. Lyophilization was further conducted for 3 hours under the same inner pressure of the lyophilizer while adjusting the environmental temperatures to a range of 35C to 40C. After completion of the lyophilization, the inner pressure of the lyophilizer was restored to normal pressure to give 199 mg (yield: 99.5%) of L-627 as crystals. The crystallinity of L-627 thus obtained was confirmed under observation with a polarizing microscope.
Working Example 2 In 10 ml of 2% (v/v) ethanolic aqueous solution was dissolved 200 mg of L-627, and the solution was subjected to filtration with the membrane filter (manufactured by Japan Millipore Corp.: SLGV 025 LS).
The filtrate was filled in a sterilized vial, and the vial was put in a thermostat (manufactured by NESLAB
Inc.: RTE-9), and the temperature of the solution was cooled to -20C taking one hour to have the solution frozen. The temperature was raised up to those ranging from -3C to -0.5C, and the temperature of this range was maintained for about 2 hours, then the temperature was lowered to -18C taking one hour. The process of this raising and lowering the temperature was repeated twice, then the inner pressure of the lyophilizer was reduced to 1 mmHg or lower. Lyophilization was conducted for 12 hours while adjusting the environmental temperatures to a range of 20C to 25C.
Lyophilization was further conducted for 3 hours under the same inner pressure of the lyophilizer while adjusting the environmental temperatures to a range of 35C to 40C. After completion of the lyophilization, the inner pressure of the lyophilizer was restored to normal pressure to give 199.2 mg (yield: 99.6%) of L-627 as crystals. The crystallinity of L-627 thus obtained was confirmed under observation with a polarizing microscope.

Claims (27)

1. A method of crystallizing (1R,5S,6S)-2-[(6,7-dihydro-5H-pyrazolo[1,2-a][1,2,4]triazolium-6-yl)]thio-6-[(R)-1-hydroxy-ethyl]-1-methyl-carbapenem-3-carboxylate, which comprises main-taining an aqueous solution of the said compound at a temperature in the range from the eutectic temperature of the solution to a temperature lower than 0°C.

2. A method according to Claim 1, which further comprises freezing the aqueous solution prior to the step of maintaining the solution at a temperature within the said range.

3. A method according to Claim 1, wherein the eutectic temperature is from -10°C to -2°C.

4. A method according to Claim 1, which further comprises freezing the aqueous solution after the step of maintaining the aqueous solution at a temperature in the said range.

5. A method according to Claim 2 or 4, wherein the freezing is conducted at -40°C to -10°C for 0.5 hour to 48 hours.

6. A method according to Claim 1, 2, 3 or 4 wherein the said temperature range is from -6°C to -1°C.

7. A method according to Claim 6, wherein the said temperature range is from -4°C to -2°C.

8. A method according to Claim 1, 2, 3 or 4 wherein the aqueous solution is maintained at a temperature in the said range for from 0.5 hour to 48 hours.

9. A method according to Claim 1, 2, 3 or 4 wherein the aqueous solution is maintained at a temperature in the said range for from 5 hours to 30 hours.

10. A method according to claim 1, 2, 3 or 4 wherein the aqueous solution is maintained at a temperature in the said range for from 10 hours to 20 hours.

11. A method according to Claim 1, 2, 3 or 4, wherein the aqueous solution also contains an alkaline metal halide.

12. A method according to Claim 11, wherein the alkaline metal halide is sodium chloride.

13. A method according to Claim 11, wherein the alkaline metal halide is contained in the aqueous solution at a concen-tration of 0.1% (w/w) to 10% (w/w).

14. A method according to Claim 1, 2, 3 or 4 wherein the aqueous solution is supplemented with an organic solvent.

15. A method according to Claim 14, wherein the organic solvent is a C1-6 alcohol or C3-7 ketone.

16. A method according to Claim 14, wherein the organic solvent is ethanol.

17. A method according to Claim 14, wherein the organic solvent is contained in the aqueous solution at a concentration of from 1% (v/v) to 10% (v/v).

- 14a -

18. A method according to Claim 1, 2, 3 or 4, wherein the carbapenemcarboxylate is contained in the aqueous solution at a concentration of from 0.5% (w/w) to 10% (w/w).

19. A method according to Claim 18, wherein the concen-tration is 1.5% (w/w) to 2.5% (w/w).

20. A method according to Claim 1, 2, 3 or 4, which comprises repeating from once to 15 times a series of steps in-cluding freezing the aqueous solution, maintaining it at a temperature in the said range from the eutectic temperature of the solution to a temperature lower than 0°C and then freezing it.

21. A method of providing a vial containing (1R,5S,6S)-2-[(6,7-dihydro-5H-pyrazolo[1,2-a][1,2,4]triazolium-6-yl)]thio-6-[(R)-1-hydroxyethyl]-1-methyl-carbapenem-3-carboxylate, which comprises crystallizing the said compound in a vial in accor-dance with the method according to Claim 1, 2, 3 or 4, drying the crystals under reduced pressure and closing the vial tightly.

22. A vial produced by the method according to Claim 21.

23. A method according to Claim 21, wherein the drying is conducted at the initial stage at temperatures not exceeding the melting point of crystals of (1R,5S,5S)-2-[(6,7-dihydro-5H-pyrazolo[1,2-a][1,2,4]triazolium-6-yl)]thio-6-[(R)-1-hydroxyethyl]-1-methyl-carbapenem-3-carboxylate, and then, after the water content in the crystals is decreased to 6% to 8% (w/w), is con-ducted until the moisture in the crystals of the said compound becomes about 2% (w/w) or less while maintaining the environmental temperature at temperatures ranging from 25°C to 50°C, under reduced pressure of 5mmHg or less for 4 to 40 hours.

24. A method of producing a vial containing an anti-bacterial active compound (1R,5S,6S)-2-[(6,7-dihydro-5H-pyrazolo [1,2-a][1,2,4]-triazolium-6-yl)]thio-6-[(R)-1-hydroxyethyl]-1-methyl-carbapenem-3-carboxylate, which method comprises:
[A] dispensing into the vial, a predetermined amount of an aqueous solution which contains the active compound at a concentration of 0.5 to 10% (w/w) and which may optionally further contain an alkali metal halide at a concentration of up to 10%
(w/w) or an organic solvent at a concentration of up to 10% (v/v) or both, the organic solvent being water soluble and not inhibiting a crystallization of the active compound and not exerting undesirable effects on the active compound;
[B] maintaining the aqueous solution at a temperature lower than 0°C and at or higher than the eutectic temperature which is in the range of from -10°C to -0.5°C for a period of time sufficient for the active compound to crystallize, thereby obtain-ing crystals of the active compound contained in an aqueous medium; and [C] drying the crystals under reduced pressure and tightly closing the vial, wherein all the steps are conducted under sterile and dust-free conditions.

25. A method according to claim 24, which further comprises freezing the aqueous solution between the steps [A]
and [B].

26. A method according to claim 24, which further com-prises:
freezing the aqueous solution between the steps [B]
and [C].

27. A method according to claim 24, 25 or 26, wherein the steps except for the steps [A] and [C] are repeated more than once.