Stable iron oligosaccharide compound

Abstract

The invention relates to an iron oligosaccharide compound with improved stability comprising a hydrogenated oligosaccharide in stable association with ferric oxyhydroxide, the content of dimer saccharide in said hydrogenated oligosaccharide being 2.9% by weight or less, based on the total weight of the hydrogenated oligosaccharide. In further aspects is provided a process for preparing said compound as well as the use of said compound for preparation of a composition for treatment of iron deficiency anaemia.

Claims

1. An iron oligosaccharide compound comprising a hydrogenated oligosaccharide in stable association with ferric oxyhydroxide, the hydrogenated oligosaccharide having a weight average molecular weight (Mw) of less than 3,000 Daltons, wherein the iron oligosaccharide compound has an in vitro half-life of 18.3 hours or more, and further wherein the hydrogenated oligosaccharide is derived from dextran.

2. The compound according to claim 1, wherein the in vitro half-life of the iron oligosaccharide compound is measured by the rate of hydrolysis of Fe.sup.3+ in 0.24 M HCI; 0.9% NaCl acidic solution, wherein the hydrolysis of Fe.sup.3+ is measured by optical absorbance at 287.3 nm and the half-life is the time at which the absorbance is half of the value compared to the absorbance at t=0.

3. The compound according to claim 1, wherein the apparent molecular weight (M.sub.P) of said compound is 120,000 to 180,000 Daltons, measured on an autoclaved aqueous solution prepared by dissolving in 1,000 ml water 400 g powder of hydrogenated oligosaccharide in stable association with ferric oxyhydroxide, the amount of iron (Fe) of the powder being 25% by weight.

4. The compound according to claim 3, wherein the apparent molecular weight (M.sub.P) of said compound is 130,000 to 180,000 Daltons.

5. The compound according to claim 4, wherein the apparent molecular weight (M.sub.P) of said compound is 130,000 to 160,000 Daltons.

6. The compound according to claim 1, wherein said hydrogenated oligosaccharide has a weight average molecular weight (Mw) between 500 and 3,000 Daltons, a number average molecular weight (Mn) above 500 Daltons, wherein 90% by weight of said hydrogenated oligosaccharide has molecular weights less than 3,500 Daltons, and the Mw of the 10% by weight fraction of the hydrogenated oligosaccharide having the highest molecular weights is below 4,500 Daltons.

7. The compound according to claim 6, wherein the Mw of the hydrogenated oligosaccharide is between 850 and 1,150 Daltons.

8. The compound according to claim 1, wherein 90% by weight of the hydrogenated oligosaccharide have a molecular weight of less than 2,700 Daltons.

9. The compound according to claim 1, wherein the 10% fraction of said hydrogenated oligosaccharide having the highest molecular weight has a weight average molecular weight (Mw) of less than 3,200 Daltons.

10. The compound according to claim 1, wherein the weight average molecular weight (Mw) of the hydrogenated oligosaccharide is 1,600 Daltons or less.

11. The compound according to claim 10, wherein the weight average molecular weight (Mw) of the hydrogenated oligosaccharide is approximately 1,000 Daltons.

12. The compound according to claim 1, wherein the amount of iron (Fe) in the iron oligosaccharide compound is 10-50% by weight.

13. The compound according to claim 1, wherein the content of dimer saccharide in the hydrogenated oligosaccharide is 2.9% by weight or less, based on the total weight of the hydrogenated oligosaccharide.

14. The compound according to claim 13, wherein the content of dimer saccharide in the hydrogenated oligosaccharide is 2.5% by weight or less, based on the total weight of the hydrogenated oligosaccharide.

15. The compound according to claim 14, wherein the content of dimer saccharide in the hydrogenated oligosaccharide is 2.3% by weight or less, based on the total weight of the hydrogenated oligosaccharide.

16. The compound according to claim 1, wherein the content of monomer saccharide in said hydrogenated oligosaccharide is 0.5% by weight or less, based on the total weight of the hydrogenated oligosaccharide.

17. A composition comprising a pharmacologically effective amount of a compound according to claim 1, and at least one pharmaceutically acceptable carrier.

18. The composition according to claim 17, wherein the composition has an iron content of 1-50% w/v.

19. The composition according to claim 18, wherein said composition has an iron content of 1-20% w/v.

20. The composition according to claim 19, wherein said composition has an iron content of 10% w/v.

21. The composition according to claim 20, which is an aqueous liquid comprising the iron oligosaccharide compound in dissolved or dispersed form.

22. An iron oligosaccharide compound comprising a hydrogenated oligosaccharide in stable association with ferric oxyhydroxide, the monomer units of the hydrogenated oligosaccharide being joined by 1,6-glucosidic bonds and the hydrogenated oligosaccharide having a weight average molecular weight (Mw) of between 850 and 1,150 Daltons, wherein the iron oligosaccharide compound has an in vitro half-life of 18.3 hours or more and wherein the apparent molecular weight (MP) of said compound is 130,000 to 160,000 Daltons.

23. An iron oligosaccharide compound comprising a hydrogenated oligosaccharide in stable association with ferric oxyhydroxide, the hydrogenated oligosaccharide having a weight average molecular weight (Mw) of less than 3,000 Daltons, and further wherein the iron oligosaccharide compound has an in vitro half-life of 18.3 hours or more, and the hydrogenated oligosaccharide is a hydrogenated dextran oligosaccharide.

24. The compound according to claim 1, wherein the iron oligosaccharide compound has an in vitro half-life of 20.9 hours or more, 21.6 hours or more, 21.7 hours or more, 22.5 hours or more, or 25.5 hours or more.

25. The compound according to claim 22, wherein the iron oligosaccharide compound has an in vitro half-life of 20.9 hours or more, 21.6 hours or more, 21.7 hours or more, 22.5 hours or more, or 25.5 hours or more.

26. The compound according to claim 23, wherein the iron oligosaccharide compound has an in vitro half-life of 20.9 hours or more, 21.6 hours or more, 21.7 hours or more, 22.5 hours or more, or 25.5 hours or more.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows a plot of the t.sub.1/2 vs. the dimer content of the iron oligosaccharide products.

EXAMPLES

(2) Hydrolysis and Hydrogenation of Dextran

(3) An amount of pre-hydrolysed dextran collected as permeate from a membrane having a cut-off value <5,000 Daltons is further hydrolysed at pH 1.5 at a temperature of 95 C.

(4) The hydrolysis is monitored using gel permeation chromatography (GPC) and is terminated by cooling, when the molecular weight of the material being hydrolysed is estimated to have achieved the desired value, i.e. a weight average molecular weight of 700-1,400 Daltons.

(5) In the hydrolysis, low molecular weight dextran is produced but also glucose and iso-maltose are formed. Upon hydrolysis, the disaccharide content is at 7-8% by weight.

(6) After cooling and neutralization, the amount of monomer and dimer is reduced by membrane processes having a cut-off value of 340-800 Daltons. The concentration of monosaccharide and disaccharide in the solution is monitored by gel permeation chromatography, and fractionation goes on until a dimer concentration of 2.9% by weight or less and a monomer concentration of 0.5% by weight or less is achieved.

(7) Thereafter, the content of dextran is determined by optical rotation and the amount of reducing sugar is determined by use of Somogyi's reagent. To bring down the reducing capability below 3%, sodium borohydride is added to the solution at basic pH. The applied ratio of sodium borohydride:fractionated dextran is 1:34.7.

(8) The solution is neutralized to pH <7.0 and subsequently de-ionized. The average molecular weights and the molecular weight distribution are determined chromatographically. Chromatography reveals that the desired conditions, viz. that 90% by weight of the dextran has a molecular weight less than 2,700 Daltons and that the weight average molecular weight (Mw) of the 10% by weight fraction of the dextran having the highest molecular weight is below 3,200 Daltons, are fulfilled. The final yield of dextran after de-ionization is approximately 50% relative to the initial amount of pre-hydrolysed dextran.

(9) Synthesis of Iron-Dextran

(10) 120 kg dextran as produced above is mixed as an 18% solution with 150 kg FeCl.sub.3, 6 H.sub.2O. To the agitated mixture, 93 kg Na.sub.2CO.sub.3 as a saturated aqueous solution is added, whereupon the pH is raised to 10.5 using 24 litres of concentrated aqueous NaOH (27%(w/v)).

(11) The mixture thus obtained is heated above 100 C. until it turns into a black or dark brown colloidal solution. After cooling, the solution is neutralized using 12 litres concentrated hydrochloric acid to obtain a pH of 5.8. After filtration the solution is purified using membrane processes until the chloride content in the solution is less than 0.55% calculated on basis of a solution containing 5%(w/v) iron.

(12) If the chloride content of the solution is less than desired to obtain an isotonic solution, sodium chloride is added and pH is finally adjusted to 5.6, and the solution is filtered through a 0.45 m (or alternatively a 0.2 m) membrane filter.

(13) The solution is spray dried and the iron-dextran powder is ready for marketing or for further processing.

(14) As an alternative to spray drying, the solution may be used for direct production of injection liquids having an iron content of e.g. 10% (w/v), as described above.

(15) When using the iron-dextran powder for producing injection or infusion liquids, the powder is re-dissolved in an aqueous medium, the pH is checked and, if necessary, adjusted, and the solution is filled into ampoules or vials after being sterilized by filtration. Alternatively, the sterilization can take place by autoclaving after filling into ampoules or vials.

(16) Analysis of the Stability of Iron Oligosaccharide Compounds Relative to Their Content of Dimer

(17) A range of iron oligosaccharide compounds with differing contents of disaccharide were analysed with respect to their rate of hydrolysis and apparent molecular weight, both of which are indicative of the quality of the respective compounds.

(18) The rate of hydrolysis of Fe.sup.3+ from the compound of FeOOH and oligosaccharide in acidic solution (0.24 M HCl; 0.9% NaCl) is assumed to be correlated to the rate of physiological release of iron. Therefore, the rate of hydrolysis as expressed by the half-life (t.sub.1/2) is an important parameter of the investigated compounds.

(19) The hydrolysis of Fe.sup.3+ was measured by optical absorbance at 2873 nm.

(20) Besides, it was found that the thermostability of iron oligosaccharides is a function of their apparent molecular weight (M.sub.P). Thus, such compounds are unstable to an unsatisfactory degree, if the apparent molecular weight markedly exceeds a value of 160,000 Daltons upon storage at an elevated temperature for three months as test solutions.

(21) The results are shown in Table 1.

(22) TABLE-US-00001 TABLE 1 Assessment after keeping Iron Amount of at elevated oligosaccharide dimer in t.sub.1/2/ M.sub.P/ temperature compound no. oligosaccharide hours Daltons for 3 months 1 0.5% 25.5 133,490 stable 2 0.75% 21.7 149,532 stable 3 0.75% 22.5 146,353 stable 4 1.6% 21.6 138,053 stable 6 1.6% 18.3 145,250 stable 7 2.0% 20.9 150,983 stable 8 2.0% 20.3 142,664 stable 9 3.0% 12.1 152,516 unstable 10 5.0% 12.2 185,433 unstable 11 8.0% 9.7 215,143 unstable

(23) As appears from Table 1, the apparent molecular weight is in a desirable range, viz. about 130 kD to about 160 kD, when the amount of dimer in the oligosaccharide is less than 3%. The same holds true for the rate of hydrolysis as expressed by the half-life. The Half-life (t.sub.1/2) is defined as the time at which the absorbance is the half of the value compared the absorbance at t=0.

(24) The results shown in Table 1 above may be arranged into two series. When the results are plotted into a diagram of t.sub.1/2 vs. the dimer content FIG. 1 appears. The two straight lines fitted into the two series show an interception at a dimer content of 3.5% by weight and t.sub.1/2 of 12.6 hours.