Method for manufacturing hydroxyethyl starch derivatives

Abstract

A method for manufacturing a modified hydroxyethyl starch carrying a heptonic acid residue on at least one of its termini. Within this method, the following steps are carried out: a) dissolving hydroxyethyl starch in water, b) adjusting the pH value to a value of 8.0 to 10.0, c) adding a cyanide compound to the hydroxyethyl starch solution, heating the solution to a temperature of 80 to 99 C. and keeping it at this temperature for a first time period, and d) adjusting the pH value to a value of 2.0 to 4.0, bringing the solution to a temperature of 50 to 90 C. and keeping it at this temperature for a second time period.

Claims

1. A pharmaceutical composition containing a hydroxyethyl starch derivative, the hydroxyethyl starch derivative being obtainable by a method comprising the following steps: a) dissolving hydroxyethyl starch in water, b) adjusting the pH value to a value of 8.0 to 10.0, c) adding a cyanide compound to the hydroxyethyl starch solution, heating the solution to a temperature of 80 to 99 C. and keeping it at this temperature for a first time period, and d) adjusting the pH value to a value of 2.0 to 4.0, bringing the solution to a temperature of 50 to 90 C. and keeping it at this temperature for a second time period.

2. A pharmaceutical composition containing a complex of a hydroxyethyl starch derivative and iron ions, the complex being obtainable by a method comprising the following steps: a) dissolving hydroxyethyl starch in water, b) adjusting the pH value to a value of 8.0 to 10.0, c) adding a cyanide compound to the hydroxyethyl starch solution, heating the solution to a temperature of 80 to 99 C. and keeping it at this temperature for a first time period, d) adjusting the pH value to a value of 2.0 to 4.0, bringing the solution to a temperature of 50 to 90 C. and keeping it at this temperature for a second time period, e) cooling down the solution to a temperature of 10 to 40 C., f) adding an iron compound to the solution, g) after a third time period, adjusting the pH value of the solution to a value of 2.0 to 4.0, and h) stabilizing the formed hydroxyethyl starch complex by at least once heating it to a temperature of 80 to 99 C., cooling it down to a temperature of 10 to 40 C. and adjusting the pH value to a value of 3.0 to 7.0.

3. The pharmaceutical composition according to claim 2, wherein step h) is carried out in such a way that the pH value obtained after a heating step succeeding a previous heating step is higher than the pH value in the previous heating step.

4. The pharmaceutical composition according to claim 2, wherein step h) is carried out by the following sub-steps: h1) heating the solution to a temperature of 80 to 99 C., keeping it at this temperature for a fourth time period, cooling it down to a temperature of 10 to 40 C., adjusting the pH value to a value of 3.0 to 5.0, h2) heating the solution to a temperature of 80 to 99 C., keeping it at this temperature for a fifth time period, cooling it down to a temperature of 10 to 40 C., adjusting the pH value to a value of 4.0 to 6.0, and h3) heating the solution to a temperature of 80 to 99 C., keeping it at this temperature for a sixth time period, cooling it down to a temperature of 10 to 40 C., adjusting the pH value to a value of 5.0 to 7.0.

5. A hydroxyethyl starch derivative comprising hydroxyethyl starch carrying a heptonic acid residue on at least one of its termini.

6. The hydroxyethyl starch derivative according to claim 5, wherein it has a weight average molecular weight of less than 200 000 g/mol.

7. The hydroxyethyl starch derivative according to claim 5, wherein it has an average degree of molar substitution of 0.4 to 0.6.

8. The hydroxyethyl starch derivative according to claim 5, wherein it is made from potato starch.

9. The hydroxyethyl starch derivative according to claim 5, wherein it is complexed with iron ions.

10. The hydroxyethyl starch derivative according to claim 9, wherein the iron ions are iron(III) ions.

11. The hydroxyethyl starch derivative according to claim 9, wherein the formed complex has a radius of gyration in the range of 30 to 70 nm.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows the free iron content of iron HES in comparison to other iron-containing preparations.

DETAILED DESCRIPTION OF THE INVENTION

(2) Further details of aspects of the invention will be explained by the following examples.

Example 1

Manufacturing of HES Heptonic Acid

(3) For manufacturing heptonic-acid modified hydroxyethyl starch, HES 70/0.5 was dissolved in water for injection to reach a concentration of 14.0 to 18.0 Bx. Then, the pH value was adjusted to a value of 8.5 to 9.5 with sodium lye. For formation of the heptonic acid terminus of the hydroxyethyl starch, sodium cyanide was added and the solution was heated up to 80 to 95 C. At this reaction temperature, the solution was aerated for 5 h (alkaline heat treatment). Afterwards, the pH value was adjusted to a value of 2.5 to 3.5 using hydrochloric acid. Then, the solution was aerated at a temperature of 60 to 80 C. for 12 to 14 h (acid heat treatment). Finally, the solution was cooled down to a temperature of 20 to 30 C. and adjusted to a concentration of modified hydroxyethyl starch of 16.0 to 20.0 Bx.

Example 2

Complexation and Complex Stabilization

(4) To form an iron HES complex, iron(III) chloride was added to the modified hydroxyethyl starch of example 1 (any other heptonic-acid modified hydroxyethyl starch could also have been used). In doing so, an iron(III) chloride solution having a concentration of around 40% (w/v) iron(III) chloride was used (iron content 190 to 210 mg/ml). The ratio of iron to modified hydroxyethyl starch was approximately 1:2.7 (kg/kg). Within 24 to 36 h, a 20% sodium carbonate solution was added to this solution of iron(III) chloride and modified hydroxyethyl starch, until a pH value of 2.5 to 3.5 was again reached. Then, the complex was stabilized by a three-step temperature-time program and pH adjustment.

(5) For performing the first heat treatment, the solution was heated up to a temperature of 80 to 95 C. and stirred for 1 h. After cooling the solution down to a temperature of 20 to 30 C., the pH value was adjusted to a value of 3.5 to 4.5.

(6) For the second heat treatment, the solution was again heated up to a temperature of 80 to 95 C., stirred for 1 h and once again cooled down to a temperature of 20 to 30 C. Then, the pH value was adjusted to a value of 4.6 to 5.5.

(7) For the third heat treatment, the solution was once again heated up to a temperature of 80 to 95 C., stirred for 1 h, cooled down to a temperature of 20 to 30 C. Then, the pH value was adjusted to a value of 5.6 to 6.5.

(8) By those three subsequent heat treatments, a complex stabilization took place due to which the iron ions were very well stabilized in the modified hydroxyethyl starch, but could be released afterwards within an organism after an according uptake.

(9) The iron HES complex formed in this example had an iron content of 5.04% (w/v), i.e. the iron concentration was 5.04 g iron per 100 ml solution.

Example 3

Finishing

(10) For finishing, the solution obtained by performing example 2 was pre-filtered through a pre-filter layer. After this pre-filtration, an ultrafiltration took place. During this ultrafiltration, small molecules like dissolved salts and fragments with a low molecular weight were removed. This ultra filtration was carried out as diafiltration, using water for injection as solvent. It was stopped after the filtrate has reached a conductivity of less than 3 mS/cm. Then, the solution was concentrated until the desired iron content was reached.

(11) Finally, the iron content was once again adjusted to the desired iron concentration using water for injection as dilution medium. Furthermore, the pH value of the solution was adjusted to the target value by sodium hydroxide or hydrochloric acid. To characterize the solution formed, the viscosity, the density and the hydroxyethyl starch content were controlled.

(12) After these adjustments, the solution was filtered through a filter cascade of pre-filter layer and a secondary filter cartridge. The solution was then drawn off in labelled canisters for further use.

(13) The final solution had a dark brown colour, a viscosity 7.2 mm.sup.2/s, a density of 1.090 g/ml, a pH value of 5.1, a cyanide concentration of 0.080 ppm, a free iron content of 0.056 g/100 ml, a chloride content of 0.280 g/ml, an iron content of 5.04 g/100 ml, an HES content of 8.93 g/100 ml and a dry matter content of 12.26 g/100 ml.

Example 4

Free Iron Content

(14) Free iron has the potential to generate reactive oxygen species. Therefore, the free iron content of an iron complex to be administered to an individual should be as low as possible. Thus, the free iron content is a measure of the quality of the iron complex in terms of its suitability to be used as active ingredient for a medicinal product or medicament.

(15) The free iron content of the iron HES complex produced in examples 1 to 3 was determined and compared to the free iron content of other iron complexes present on the market. These other iron complexes are an iron dextran (marketed under the name CosmoFer) having an iron concentration of 50 g/l, an iron sucrose (marketed under the name Venofer) having an iron concentration of 20 g/l and an iron gluconate (marketed under the name Ferrlecit) having an iron concentration of 12.5 g/l.

(16) For determining the free iron content, a spectrometric analysis using a UV/VIS spectrophotometer was done. The extinction of calibration solutions and the respective sample solutions was measured at a wave length of 533 nm using a 10-mm measuring cell.

(17) The calibration solutions were in each case solutions of 5.0 ml hydroxylamine hydrochloride solution (20% (w/v)), 10.0 ml bathophenanthroline solution (33.2% (w/v)), 5.0 ml sodium acetate solution (10% (w/v)) and 10 ml iron solution (x ml 0.001% (w(v)) iron(III) nitrate in 0.005 mol nitric acid plus (10.0x) ml water, wherein x was 2.0, 3.0, 4.0, 5.0, 6.0 and 7.0). Prior to use, the solutions were extracted for three times with 10 ml chloroform each time. The chloroform extracts (lower layers) were filled up with isopropanol to 100 ml.

(18) The sample solutions were in each case solutions of 5.0 ml hydroxylamine hydrochloride solution (20% (w/v)), 10.0 ml bathophenanthroline solution (33.2% (w/v)), 5.0 ml sodium acetate solution (10% (w/v)), 2 ml sample and 498 ml water. Prior to use, the solutions were extracted for three times with 10 ml chloroform each time. The chloroform extracts (lower layers) were filled up with isopropanol to 100 ml.

(19) The extinction of the calibration solutions and the test solution were determined by using isopropanol as blank.

(20) The measured extinctions of the calibration solutions were used to calculate a regression line and the corresponding regression equation. The concentration of iron in the sample solutions was determined using the regression equation.

(21) The results are depicted in FIG. 1. The content of free iron was 1.19% (w/v) in case of the iron dextran, 2.12% (w/v) in case of the iron sucrose, 1.41% (w/v) in case of the iron gluconate and only 0.24% (w/v) in case of iron HES.

(22) Thus, iron HES produced by a method according to an aspect of the invention shows a significantly better complex stability and lower content of free iron than other iron compounds being presently on the market. Therefore, the modified hydroxyethyl starch as described herein above is a valuable basic product for an according iron HES complex. This iron HES complex in turn is a compound of particular interest for medical applications in humans or animals.

(23) The claimed manufacturing method cannot be compared with manufacturing methods disclosed in prior art relating to different starting materials. To give an example, manufacturing methods with dextrans or dextrins as starting material make use of completely different method steps since the chemistry of dextrans and dextrins on the one hand and hydroxyethyl starch on the other hand is quite different although the chemical structures of the substances appears to be similar. Technical details obtained from manufacturing methods using different starting materials cannot be transferred to the instantly claimed method.