Improved method for preparing dalteparin sodium

Abstract

To provide an improved process for the preparation of Dalteparin sodium.SOLUTION: The present invention provides an improved process for the preparation of Dalteparin sodium. The process is simple, commercially viable and industrially advantageous.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Indian Provisional Patent Application No. 201841005592, filed February 14, 2018, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to an improved method for preparing dalteparin sodium. [Background technology]

[0003] Anticoagulants, commonly referred to as "blood thinners," serve as the mainstay of therapy for the prevention and treatment of acute arterial and venous thrombotic disorders. Unfractionated heparin and low molecular weight heparins (LMWHs) are used as anticoagulants exclusively for chronic therapy because they are effective, safe, and more convenient. Each commercially available LMWH is prepared from a proprietary chemical or enzymatic depolymerization of mucosal heparin.

[0004] Dalteparin sodium is one such LMWH, a potent anticoagulant that acts through the indirect inhibition of thrombin, the major procoagulant that converts fibrinogen to fibrin. Dalteparin sodium is sold under the trade name Fragmin®.

[0005] Dalteparin sodium is produced by controlled nitrite depolymerization of heparin sodium from porcine intestinal mucosa, followed by a chromatographic purification process. 2-O-sulfo-α-L-idopyranosuronic acid at the non-reducing end of the chains and 6-O-sulfo-2,5-anhydro-D-mannitol at the reducing end Contains The mass-average relative molecular mass ranges from 5600 to 6400 Daltons (Da), with a characteristic value of approximately 6000 Da. The degree of sulfation is 2.0-2.5 per disaccharide unit. Anti-factor Xa is between 110 and 210 IU / mg. Anti-factor IIa is between 35 IU / mg and 100 IU / mg. The ratio of anti-factor Xa activity to anti-factor IIa activity is 1.9-3.2 It is.

[0006] Dalteparin sodium is structurally represented as shown below: [ka]

[0007] Dalteparin sodium was first disclosed in WO 80 / 01383 and U.S. Pat. No. 4,303,651 and is prepared by depolymerization of sodium heparin with nitrous acid or by periodate oxidation followed by sodium borohydride reduction. The use of nitrous acid and sodium borohydride results in the production of nitrite (NO 2 - ), N-nitroso (N-NO) compounds and elemental boron are produced as impurities in the final product. Although no limit is specified in the European Pharmacopoeia (Ph.Eur) for N-NO content, the Ph. requirements for the tolerance limits of nitrite and boron are very strict. The Eur monograph has a warning substructure for a potentially genotoxic impurity, so this impurity needs to be controlled. Since the production of dalteparin sodium on an industrial scale involves handling large quantities of these reagents, these impurities need to be controlled in order to maintain the quality of dalteparin sodium and at the same time meet regulatory requirements. [Table A]

[0008] Several methods are known for preparing dalteparin sodium using various depolymerization, reduction, isolation and purification procedures to meet pharmacopoeia requirements, such as depolymerization of heparin sodium with nitrous acid in aqueous medium (U.S. Pat. No. 4,500,519); controlled depolymerization of heparin followed by alcohol precipitation or purification (U.S. Pat. No. 5,019,649, EP 0 014 184 and EP 0 076 279); controlled depolymerization of heparin followed by heat or microwave treatment (EP 1 773 890); preparation of LMWH with reduced glycoserine content by oxidation of heparin using permanganate (U.S. Pat. Appl. Pub. No. 2008 / 0318328). Furthermore, methods for preparing dalteparin sodium have been disclosed, especially those with different purification techniques, such as China Patent No. 101942038; China Patent No. 102558393; China Patent No. 103232558; China Patent No. 101942038; China Patent No. 102558393; China Patent No. 104045743; China Patent No. 104045744; China There are several Chinese patents or patent applications such as Patent No. 104098716; Chinese Patent No. 105884934; Chinese Patent No. 105440160; Chinese Patent No. 106317258; Chinese Patent No. 106699929; Chinese Patent No. 106986954; Chinese Patent No. 107141373; Chinese Patent No. 107236057.

[0009] Prior art methods involve the utilization of larger amounts of sodium nitrite and sodium borohydride, which necessitates additional steps and / or chromatographic purification to remove impurities generated due to these reagents. Additionally, literature procedures utilize high temperatures during depolymerization and extended exposure to UV radiation (e.g., 20-30 minutes), or use thermal or microwave treatments to control N-NO groups, which cannot be performed during manufacturing and may affect the yield and quality of the final product.

[0010] Additionally, UV irradiation for long periods of time with high power lamps or with UV wavelengths less than 254 nanometers (nm) can generate heat, ozone gas, and result in colored products.

[0011] Applicants have found that UV reactions performed by exposing / inserting a UV lamp into the product solution for more than 10 minutes show a reduction in N-NO content on a small scale, but are not reproducible on a higher scale.

[0012] Thus, there is a need for an improved method for preparing dalteparin sodium that overcomes one or more of the shortcomings of one or more of the prior art methods. Additionally, systems and / or apparatus may be required to address product color issues and control N-NO content when practiced on a commercial scale. Summary of the Invention

[0013] The present invention provides an improved method for preparing dalteparin sodium, comprising: (a) depolymerizing sodium heparin with 2.5-3.5 wt. % sodium nitrite in the presence of an acid; (b) reducing the product obtained in step (a) with up to 2.0 molar equivalents of a reducing agent to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and exposing it to ultraviolet light irradiation at a wavelength of 254 nm and a power of 4 to 40 W for 10 seconds to 8 minutes; (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. The present invention provides a method comprising:

[0014] This improved process is efficient, cost-effective, and industrially feasible for the preparation of dalteparin sodium. Furthermore, the present invention provides nitrite (NO ) levels below the limits set by pharmacopoeial standards. 2 - ), N-NO and boron impurities. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram of a photochemical reactor used in the present method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Before describing the method of the present disclosure in more detail, it should be understood that the method is not limited to the particular embodiments described, and may, of course, vary. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present method is limited only by the appended claims.

[0017] Where a range of values ​​is provided, unless the context clearly dictates otherwise, it is understood that to the tenth of the unit of the lower limit, each intervening value between the upper and lower limits of that range, as well as any other stated value or intervening values ​​within that stated range, are encompassed within the method. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the method, subject to any specifically excluded limit in the stated range. Where a stated range includes one or both of the limits, ranges excluding either or both of the included limits are also included in the method.

[0018] Certain ranges are provided herein with the term "about" before the numerical values. The term "about" is used herein to literally support the exact number it precedes, as well as a number that is close to or approximately the number it precedes. When determining whether a number is close to or approximately a specifically recited number, the close or approximate non-recited number may be a number that provides a substantial equivalent to the specifically recited number in the context in which it is presented.

[0019] The terms "comprising" or "comprising" are used in reference to compositions, methods, and one or more components thereof, which are essential to the invention but embrace the inclusion of elements not specified, whether essential or not.

[0020] The term "reactor" is used in reference to a system, model, device or equipment.

[0021] In one embodiment, the present invention provides a method for the preparation of dalteparin sodium, more specifically, nitrite (NO ) below the limits set by the pharmacopoeia standards. 2 - ), N-NO and boron impurities.

[0022] The present invention provides an improved method for preparing dalteparin sodium, comprising: (a) depolymerizing sodium heparin with 2.5-3.5 wt. % sodium nitrite in the presence of an acid; (b) reducing the product obtained in step (a) with up to 2.0 molar equivalents of a reducing agent to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and exposing it to ultraviolet light irradiation at a wavelength of 254 nm and a power of 4 to 40 W for 10 seconds to 8 minutes; (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. The present invention provides a method comprising:

[0023] By carrying out the above process in the listed order, the thus obtained dalteparin sodium has the following molecular weight distribution, NO 2 - It was found to meet pharmacopoeial and quality requirements with regard to ion content, N-NO content and boron content.

[0024] Sodium heparin is depolymerized using nitrous acid. Nitrous acid can be added directly or can be generated in situ using a controlled amount of acid and a derivative of nitrous acid. Suitable acids can be selected from hydrochloric acid, acetic acid, sulfuric acid, and more preferably hydrochloric acid. Suitable derivatives of nitrous acid can be salts, ether salts, or more preferably alkali or alkaline earth salts. In a preferred embodiment, a salt of nitrous acid, a water-soluble salt, more preferably sodium nitrite (NaNO 2 During depolymerization, nitrite reacts with the N-sulfate groups of heparin to form an unstable N-nitroso compound as an intermediate, which then cyclizes intramolecularly to form 2,5-anhydro-D-mannose.

[0025] The depolymerization of the heparin sodium solution is carried out in the presence of sodium nitrite in an amount of 2.5% to 3.5% by weight, preferably 2.5% to 3.1% by weight, relative to the heparin sodium, at a temperature ranging from 5 to 35 °C, preferably from 5 °C to 15 °C. The depolymerization step is carried out at a pH ranging from 2.0 to 4.0 by using hydrochloric acid. It is important to use an optimal amount of sodium nitrite. If the amount of sodium nitrite is less than 2.5%, the depolymerization may be incomplete, and if the amount of sodium nitrite is more than 3.5%, the depolymerization may be excessive. The product obtained by any of these methods may not meet the official requirements for average molecular weight and distribution.

[0026] Depolymerized heparin having an aldehyde group of 2,5-anhydro-D-mannose at the reducing end is reduced to 2,5-anhydro-D-mannitol. The reduction according to the present invention is carried out using a reducing agent such as sodium, potassium or lithium borohydride. In a preferred embodiment, the reducing agent is sodium borohydride. The amount of sodium borohydride used in the reduction is 2.0 molar equivalents or less relative to the weight of sodium heparin. The reduction is carried out at room temperature for about 1.0 to 3.0 hours, more preferably about 1 hour. The optimal amount of sodium borohydride is beneficial in limiting boron impurities to a low level and helps minimize purification steps.

[0027] Then, according to step (c), isolation of crude dalteparin sodium is carried out by dissolving the product obtained in step (b) in water at a temperature ranging from 5 to 35° C., followed by the addition of sodium chloride. After this, in step (d), crude dalteparin sodium is stirred in a solvent mixture containing water and alcohol, and filtered to obtain a precipitate of dalteparin sodium. The alcohol used is selected from methanol, ethanol, isopropanol, etc.

[0028] In yet another embodiment, the present invention provides an efficient removal of N-NO content by step (e), which comprises subjecting a solution of dalteparin sodium prepared by dissolving the dalteparin sodium precipitate obtained above in water to ultraviolet irradiation. The irradiation time depends on the irradiation system used, the power of the radiation, and the amount of N-NO content to be removed from the product solution. Preferably, the ultraviolet irradiation system comprises a lamp of 4 to 40 W, and the dalteparin solution is exposed to 254 nm UV radiation for 10 seconds to 8 minutes. As a UV irradiation system, it is possible to envisage either a closed or an open device that allows the exposure of the solution of dalteparin sodium to a UV radiation source.

[0029] In certain embodiments, UV irradiation may be performed in any photochemical reactor (e.g., a UV photochemical reactor) equipped with one or more UV lamps. In certain embodiments, the photochemical reactor may be a continuous photochemical reactor incorporating one or more UV lamps. In further embodiments, any UV photochemical reactor known in the art may be used. In yet other embodiments, the photochemical reactor is comprised of a UV lamp attached with a quartz sheath. The solution containing dalteparin sodium circulates around the UV lamp protected by the quartz sheath. An illustrative example of a photochemical reactor used in the present method is shown in FIG. 1.

[0030] In another embodiment, the method according to step (f) comprises a lyophilization step. The lyophilization step comprises adding an alcohol to the solution obtained in step (e) to obtain dalteparin sodium in free powder form. The lyophilization is carried out using procedures known in the art. The alcohol is selected from the group comprising methanol, ethanol, isopropanol, and the like. In certain embodiments, the lyophilization is carried out using alcohol at a concentration of 5-15% by volume with respect to the water used in step (e). When only water is used as described in the prior art, dalteparin sodium is produced as a cake with residual moisture. The hardness of the cake varies with the change in lyophilization parameters and a powder processing step such as milling is required to obtain a free-flowing powder. On the other hand, the dalteparin sodium prepared according to the present invention has good texture, improved stability and low organic volatile impurity (OVI) content.

[0031] In a preferred embodiment, the present invention provides an improved method for preparing dalteparin sodium, comprising the steps of: (a) depolymerizing sodium heparin with 2.5-3.5 wt. % sodium nitrite in the presence of an acid; (b) reducing the product from step (a) with up to 2 molar equivalents of sodium borohydride to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; and (e) dissolving the precipitate obtained in step (d) in water and subjecting it to ultraviolet irradiation at a wavelength of 254 nm and a power of 4-40 W for 10 seconds to 8 minutes. (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. The present invention provides a method comprising:

[0032] In yet another embodiment, the present invention provides an improved method for preparing dalteparin sodium, comprising: (a) depolymerizing an aqueous solution of heparin sodium with an aqueous solution of sodium nitrite at 2.5 to 3.1% by weight based on the weight of heparin sodium in the presence of an aqueous solution of hydrochloric acid having a pH of 2 to 4 at a temperature of 5 to 10° C.; (b) reducing the product obtained in step (a) with 1.5 to 2.0 equivalents of sodium borohydride to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate of dalteparin sodium obtained in step (d) in water and exposing it to ultraviolet light irradiation at a wavelength of 254 nm and an output of 4 to 40 W for 10 seconds to 8 minutes; (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. The present invention provides a method comprising:

[0033] In yet another embodiment, the present invention provides an improved method for preparing dalteparin sodium, comprising: (a) depolymerizing an aqueous solution of heparin sodium with a 2.5-3.1% aqueous solution of sodium nitrite in the presence of an aqueous solution of hydrochloric acid having a pH of 2-4 at a temperature of 5-10° C.; (b) reducing the product obtained in step (a) with 1.5 to 2.0 equivalents of sodium borohydride to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and exposing it to ultraviolet radiation having a wavelength of 254 nm and a power of 4 to 40 W for 10 seconds to 8 minutes; (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. Including, The method does not involve any chromatographic purification steps.

[0034] In certain embodiments, the process is a continuous or batch process. In further embodiments, the process may be carried out in any photochemical reactor. Any of the photochemical reactors described above may be used in the process.

[0035] The advantages of the present invention over the prior art methods are: 1. A small amount of sodium nitrite, 2. Use of an optimal amount of sodium borohydride, thereby avoiding the need for quenching and forming less elemental boron; 3. Use of an integrated continuous flow UV reactor for reproducibility, producing 254 nm wavelength light, reducing the duration of UV exposure, and no heat to control color formation on dalteparin sodium; 4. Isolation of the product by simple alcohol precipitation rather than using time-consuming, expensive, and cumbersome chromatographic techniques; 5. The use of alcohol during lyophilization results in dalteparin sodium as a free powder, thereby avoiding an additional milling step.

[0036] example The following examples are provided to illustrate the present invention and are for illustrative purposes only and should not be construed as limiting the scope of the present invention.

[0037] Comparative Example 1: Heparin sodium (5.0 g) was dissolved in purified water and the pH of the solution was adjusted to 2-4 using aqueous hydrochloric acid at 5°C-10°C. Sodium nitrite solution (2.2%) was added to the reaction mass and stirred. The pH was then adjusted to 8-10 with sodium hydroxide followed by the addition of sodium borohydride (1.5 equivalents) and the reaction mass was kept for 16 hours. The excess of sodium borohydride was quenched with hydrochloric acid. The resulting mixture was neutralized with sodium hydroxide followed by saturation with sodium chloride. The product was stirred with methanol, precipitated, filtered and dried to obtain crude dalteparin sodium. The crude product was dissolved in purified water, saturated with sodium chloride and stirred with methanol to precipitate the product. The resulting precipitate was filtered and dried under vacuum to obtain dalteparin sodium whose molecular weight distribution profile fails to meet the pharmacopoeia requirement for weight average molecular weight (Table 1). Yield 2.84 g.

[0038] Comparative Example 2: Heparin sodium (10.0 g) was dissolved in purified water and the pH of the solution was adjusted to 2-4 using hydrochloric acid at 5°C-10°C. Sodium nitrite solution (3.5%) was added to the reaction mass and stirred. The pH was then adjusted to 8-10 with sodium hydroxide followed by the addition of sodium borohydride (1.5 equivalents) and the reaction mass was held for 16 hours. The excess sodium borohydride was quenched with hydrochloric acid. The resulting mixture was neutralized with sodium hydroxide followed by saturation with sodium chloride. The product was stirred with methanol, precipitated, filtered and dried to obtain crude dalteparin sodium. The crude product was further processed as per the procedure described in Example 1 to obtain dalteparin sodium having a molecular weight distribution profile that fails to meet the pharmacopoeia requirement for weight average molecular weight (Table 1). Yield: 3.4 g

[0039] Example 3: Heparin sodium (80 g) was dissolved in purified water and the pH of the solution was adjusted to 2-4 using hydrochloric acid at 5°C-10°C. Sodium nitrite solution (2.8%) was added to the reaction mass and stirred. The pH was then adjusted to 8-10 with sodium hydroxide followed by the addition of sodium borohydride (4.23 equivalents) and the reaction mass was kept there for 16 hours and subjected to bleaching with 30% hydrogen peroxide. The excess of sodium borohydride was quenched with hydrochloric acid. The resulting mixture was neutralized with sodium hydroxide followed by saturation with sodium chloride. The resulting mass was stirred with methanol, precipitated, filtered and dried to obtain the precipitate of dalteparin sodium. The precipitated product (29 g) was dissolved in purified water and the solution was exposed to UV light (4 W) at 254 nm for 5 minutes. The reaction mass was saturated with sodium chloride and the product was isolated by methanol precipitation followed by methanol washing. The resulting solid compound was filtered, dried under vacuum, dissolved in purified water, filtered through 0.45 μm and subsequently 0.22 μm filtration membranes, and lyophilized to obtain dalteparin sodium with a molecular weight distribution profile that meets the pharmacopoeia requirements for weight average molecular weight (Table 1). Yield: 33.4 g.

[0040] Example 4: Heparin sodium (50 g) was dissolved in purified water and the pH of the solution was adjusted to 2-4 using hydrochloric acid at 5°C-10°C. Sodium nitrite solution (2.8%) was added to the reaction mass and stirred until it was negative by starch iodine paper. The pH was then adjusted to 8-10 with sodium hydroxide followed by the addition of sodium borohydride (1.5 equivalents) and the reaction mass was kept for 16 hours. The resulting mixture was neutralized with hydrochloric acid and bleached with 30% hydrogen peroxide followed by saturating the reaction mass with sodium chloride. The resulting mass was stirred with methanol, precipitated, filtered and dried to obtain the precipitate of dalteparin sodium. The precipitated product (20 g) was dissolved in purified water and the solution was exposed to UV light (8 W) at 254 nm for 5 minutes. The reaction mass was further treated according to the procedure described in Example 3 to obtain dalteparin sodium having a molecular weight distribution profile that meets the pharmacopoeia requirements for weight average molecular weight (Table 1). Yield: 21.6g.

[0041] Example 5: Heparin sodium (250 g) was dissolved in purified water and the pH of the solution was adjusted to 2-3 using hydrochloric acid at 5°C-10°C. Sodium nitrite solution (3.0%) was added to the reaction mass and stirred. The pH of the reaction mass was adjusted to 9-10 with sodium hydroxide followed by the addition of sodium borohydride (2.0 equiv.) and stirred for 1 hour. The reaction mass was filtered through a carbon pad and washed with water. The pH of the reaction mass was adjusted to 7.0 with hydrochloric acid and then 100 mL of 30% hydrogen peroxide was added to the reaction mass and stirred for 30 minutes. Solid sodium chloride was added to the reaction mass and the product was precipitated with methanol. The resulting precipitate was filtered, washed with additional amount of methanol and dried under vacuum to obtain 138 g of crude dalteparin sodium product as a white solid.

[0042] 135 g of crude dalteparin was dissolved in purified water at 25° C.-30° C. Solid sodium chloride was added to the reaction mass and the product was precipitated with methanol. The residue was further stirred in a mixture of water and alcohol, filtered, washed with additional amount of methanol and dried under vacuum to obtain 110 g of precipitate of dalteparin product as a white solid.

[0043] 100 g of the resulting solid was dissolved in purified water and cooled below room temperature. The solution was circulated through a peristaltic pump through an integrated continuous-flow reactor equipped with a UV lamp with a wavelength of 254 nm and a power of 8 W for 40 and 60 seconds. After UV exposure, the reaction mass was treated with carbon and subjected to micron filtration. Alcohol was added to the resulting solution and stirred for 5-10 minutes. The solution was loaded into a freeze-drying tray and freeze-dried, including initial freezing (-5°C to -50°C, 3-11 hours); primary drying (-50°C to 25°C, 15-50 hours, vacuum (220-90 mTorr) and secondary drying (25-40°C, 2-5 hours, 220-90 mTorr vacuum). Yield: 90 g. [Table 1]

[0044] The molecular weight distribution is determined by gel permeation chromatography (GPC). The results in Table 1 demonstrate that the depolymerization method of the present invention using 2.5-3.1% sodium nitrite solution met the Ph.Eur molecular weight distribution profile. [Table 2]

[0045] As is apparent from Table 2, the reduction method of the present invention, i.e., the use of 1.5 to 2.0 molar equivalents, allows the preparation of dalteparin sodium (Ph.Eur) having a boron content lower than 1 ppm. [Table 3]

[0046] As noted in Table 3, preparation of dalteparin sodium according to the present invention results in a product having a lower N-NO content than that determined for Fragmin® and samples without UV irradiation. Aspects or embodiments that may be encompassed by the present invention are summarized as follows. [1]. 1. An improved method for preparing dalteparin sodium, comprising: (a) depolymerizing sodium heparin with 2.5-3.5 wt. % sodium nitrite in the presence of an acid; (b) reducing the product obtained in step (a) with up to 2.0 molar equivalents of a reducing agent to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and exposing it to ultraviolet light irradiation at a wavelength of 254 nm and a power of 4 to 40 W for 10 seconds to 8 minutes; (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. The method includes: [2]. The method according to item 1, wherein the depolymerization is carried out at a pH in the range of 2.0 to 4.0. [3]. 2. The method according to claim 1, wherein the acid is hydrochloric acid, acetic acid or sulfuric acid. [4]. 2. The method according to claim 1, wherein the reducing agent is sodium borohydride, potassium borohydride or lithium borohydride. [5]. The method according to item 1, wherein the reduction is carried out at room temperature for about 1.0 to 3.0 hours. [6]. The method according to claim 1, wherein the freeze-drying is carried out by adding alcohol to the dalteparin sodium solution obtained in step (e). [7]. The method according to item 6, wherein the alcohol has a concentration of 5 to 15% by volume relative to the water used in step (e). [8]. The method according to item 6 or 7, wherein the alcohol is ethanol. [9]. 1. An improved method for preparing dalteparin sodium, comprising: (a) depolymerizing an aqueous solution of sodium heparin with 2.5-3.5 wt. % sodium nitrite in the presence of hydrochloric acid having a pH of 2-4 at a temperature of 5-10° C.; (b) reducing the product obtained in step (a) with 1.5 to 2.0 equivalents of sodium borohydride to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and exposing it to ultraviolet light irradiation at a wavelength of 254 nm and a power of 4 to 40 W for 10 seconds to 8 minutes; (f) freeze-drying the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in pure powder form and with a bounded N-NO content; The method includes:

[10] . 1. An improved method for preparing dalteparin sodium, comprising: (a) depolymerizing an aqueous solution of heparin sodium with an aqueous solution of sodium nitrite at 2.5 to 3.1% by weight based on the weight of heparin sodium in the presence of hydrochloric acid at a pH of 2 to 4 at a temperature of 5 to 10° C.; (b) reducing the product obtained in step (a) with 1.5 to 2.0 equivalents of sodium borohydride to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and exposing it to ultraviolet light irradiation at a wavelength of 254 nm and a power of 4 to 40 W for 10 seconds to 8 minutes; (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. Including, The method does not involve any chromatographic purification steps.

[11] . 11. The method according to any one of items 1 to 10, wherein the UV irradiation is carried out in a continuous photochemical reactor incorporating one or more UV lamps.

Claims

1. 1. An improved method for preparing dalteparin sodium, comprising: (a) depolymerizing an aqueous solution of sodium heparin with an aqueous solution of sodium nitrite in the presence of an acid at a concentration of 2.5 to 3.5% by weight based on the weight of sodium heparin; (b) reducing the product of step (a) with up to 2.0 molar equivalents of a reducing agent based on the weight of the heparin sodium to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and subjecting it to ultraviolet radiation at a wavelength of 254 nm and a power of 4-40 W for 10 seconds to 60 seconds; (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. The method includes:

2. 2. The method of claim 1, wherein the depolymerization is carried out at a pH in the range of 2.0 to 4.

0.

3. 2. The method of claim 1, wherein the acid is hydrochloric acid, acetic acid or sulfuric acid.

4. 2. The method of claim 1, wherein the reducing agent is sodium borohydride, potassium borohydride or lithium borohydride.

5. 2. The method of claim 1, wherein the reduction is carried out at room temperature for 1.0 to 3.0 hours.

6. 2. The method of claim 1, wherein the lyophilization is carried out by adding alcohol to the dalteparin sodium solution obtained in step (e).

7. 7. The method of claim 6, wherein the alcohol is at a concentration of 5 to 15% by volume relative to the water used in step (e).

8. 8. The method of claim 6 or claim 7, wherein the alcohol is ethanol.

9. 1. An improved method for preparing dalteparin sodium, comprising: (a) depolymerizing an aqueous solution of sodium heparin with an aqueous solution of sodium nitrite at 2.5-3.5% by weight based on the weight of sodium heparin in the presence of hydrochloric acid at a pH of 2-4 at a temperature of 5-10° C.; (b) reducing the product obtained in step (a) with 1.5 to 2.0 molar equivalents of sodium borohydride based on the weight of heparin sodium to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and subjecting it to ultraviolet radiation at a wavelength of 254 nm and a power of 4-40 W for 10 seconds to 60 seconds; (f) freeze-drying the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in pure powder form and having an N-NO content of less than 10 ppm; The method includes:

10. 1. An improved method for preparing dalteparin sodium, comprising: (a) depolymerizing an aqueous solution of sodium heparin with an aqueous solution of sodium nitrite at 2.5-3.1% by weight based on the weight of sodium heparin in the presence of hydrochloric acid at a pH of 2-4 at a temperature of 5-10° C.; (b) reducing the product obtained in step (a) with 1.5 to 2.0 molar equivalents of sodium borohydride based on the weight of heparin sodium to obtain crude dalteparin sodium; (c) isolating the crude dalteparin sodium obtained in step (b); (d) stirring the crude product obtained in step (c) in a solvent mixture to obtain a precipitate of dalteparin sodium; (e) dissolving the precipitate obtained in step (d) in water and subjecting it to ultraviolet radiation at a wavelength of 254 nm and a power of 4-40 W for 10 seconds to 60 seconds; (f) lyophilizing the solution obtained in step (e) in the presence of alcohol to obtain dalteparin sodium in free powder form. Including, The method does not involve any chromatographic purification steps.

11. 11. The method according to any one of claims 1 to 10, wherein the UV irradiation is carried out in a continuous photochemical reactor incorporating one or more UV lamps.

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