FIELD OF THE INVENTION
The present invention relates to a process for synthesis of water soluble Ferric
Derisomaltose, which is stable and has reduced toxicity and is useful in the treatment
of iron deficiency anaemia. In particular, the present invention relates to a solvent
free and eco-friendly improved process for synthesis of water soluble Ferric
Derisomaltose.
BACKGROUND OF THE INVENTION
Patients with iron deficiency anaemia (IDA)are prescribed iron supplementation in
order to treat and manage anaemia and to replenish the body stores. Significant
proportions of patients are found to benefit by supplementing iron intravenously
(IV).
Treatment and management of IDA typically involve dietary changes by
incorporating food groups rich in iron. Dietary supplementation with oral iron is a
first line of treatment which apart from being safe is cost effective and convenient.
However, where supplementation with oral iron fails to provide the desired result,
parenteral therapy is employed as a second line of treatment. Intravenous iron
preparations areusually available as ferric gluconate, iron sucrose, iron dextran, and
ferric carboxymaltose preparations in the market,which are delivered to patients in a
single administration for treatment of anaemia.
Ferric Derisomaltose (also known as Iron isomaltoside) is an iron replacement
product for intravenous infusion. Ferric derisomaltose is an iron carbohydrate
complex with a matrix structure composed of interchanging layers of ferric
hydroxide and the carbohydrate derisomaltose. Derisomaltose consists of linear,
hydrogenated isomaltooligosaccharides with an average molecular weight of 1000
Da and a narrow molecular weight distribution that is almost devoid of mono- and

disaccharides. Ferric derisomaltose has an average molecular weight of 155,000 Da
and has the following empirical formula: {FeO(1-3X) (OH)(1+3X) (C6H5O73-)X}, (H20)T,
(C6H10O6)R(-C6H10O5-)Z(C6H13O5)R, (NaCl)Y X= 0.0311; T = 0.25; R = 0.14; Z =
0.49; Y = 0.14
It is a helical inclusion complex in which individual D glucose units are linked to
form a Dextran moiety. These Dextran units, in turn, self-repeat themselves in a
polymeric chain forming Ferric derisomaltose. It is a non-branched, non-anaphylactic
carbohydrate [W. Richter, Hapten inhibition of passive antidextran dextran
anaphylaxis in guinea pigs. Role of molecular size in anaphylactogenicity and
perceptibility of dextran fractions, International Archives of Allergy and Immunology
41(1971) 826–844; K.-G. Ljungström, Invited commentary: retreatment with dextran
1 makes dextran 40 therapy safer, Journal of Vascular Surgery 43 (2006) 1070–
1072], and is structurally different from branched polysaccharides used in iron
dextran.
Ferric derisomaltose contains a polynuclear Fe(III)oxyhydroxide core which is
stabilized by a hydrogenated (reduced) Dextran 1000 and a low amount of hydroxyl
acid, which promotes the stability and solubility of compound. Synthesis of such
iron-carbohydrate complexes are known and described in the art. Said synthesis
processes involve use of solvents like methanol or ethanol, which makes the
processes cumbersome Handling of such solvents increases the capital costs as it
requires equipment and protective clothing.
However, the major challenges during the synthesis include maintaining the physico-
chemical stability of trivalent iron ions/salts with low molecular weights of the
saccharides/polysaccharides. The carbohydrate shell is unique for each preparation
since the carbohydrate shell determines the metabolic pathway of the complexes,
affectingtheir pharmacokinetics and pharmacodynamics, as well as their interaction
with the innate immunesystem and, thus, side effects [Koskenkorva-Frank, T.S; et.al
The complex interplay of ironmetabolism, reactive oxygen and reactive nitrogen
species: Insights into the potential of different iron therapies to induce oxidative and
nitrosative stress. Free Radica. Biol. Med. 2013, 65, 1174–1194]. Depending on the

carbohydrate shell the preparations can be classified as (a) non-dextran based and (b)
dextran/dextran based complexes. Further, low and higher molecular weight dextran
complexes are not much stable as compared to modified molecular weight dextran
complex (as oligosaccharide). Higher molecular weight dextran is associated with
solubility problems in formulation as well as Injection grade formulations while
lower molecular weight dextran is associated with toxicity issues.
Therefore, there remains a need for an improved process for manufacture of ferric
derisomaltose with good stability and reduced toxicity and which does not require
solvents like methanol and ethanol.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to provide a solvent free process
for the synthesis of Ferric derisomaltose which provides a stable and less toxic ferric
derisomaltose.
It is another object of the present invention to provide a process for the synthesis of
Ferric derisomaltose which is industrially feasible and economic.
It is yet another object of the present invention to provide a ferric derisomaltose
which is stable and non-toxic.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a simple and solvent free and an
economic process for synthesis of ferric derisomaltose complex with high iron
content, good stability and reduced toxicity.
In an aspect, the present invention provides a solvent free process for synthesis of
ferric derisomaltose complex comprises the steps of:

i. preparation of modified dextran comprising in-situ reduction of
dextran ;
ii. oxidizing electrolytic iron with 10.0% hydrogen peroxide to make
nascent ferric iron which is highly feasible for coupling with reduced
dextran of step (i) to obtain a ferric iron-dextran;
iii. heating the nascent ferric iron of step (ii) with reduced dextran of step
(i) in presence of an alkali, followed by cooling;
iv. adjusting the pH in the range of 5.50-6.50 using mineral acid; and
v. filtering, drying the filtrate in a spray dryer to obtain the product.
In a second aspect, the present invention provides a ferric derisomaltose complex so
obtainable that has improved stability, yield and reduced toxicity.
DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided
to assist in a comprehensive understanding of various embodiments of the present
disclosure as defined by the claims and their equivalents. It includes various specific
details to assist in that understanding but these are to be regarded as merely
exemplary. Accordingly, those of skilled in the art will recognize that various
changes and modifications of the various embodiments described herein can be made
without departing from the scope and spirit of the present disclosure. In addition,
descriptions of well-known functions and constructions may be omitted for clarity
and conciseness. Further it is to be understood that the singular forms "a," "an," and
"the" include plural referents unless the context clearly indicates otherwise.
Described herein is an improved process for synthesis of ferric derisomaltose
complex, which does not use any solvent. In other words, the synthesis process
described herein is solvent free.

The present invention provides a process for synthesis of ferric derisomaltose
complex comprises the steps of:
i. preparation of modified dextran comprising in-situ reduction of
dextran ;
ii. oxidizing electrolytic iron with 10.0% hydrogen peroxide to make
nascent ferric iron which is highly feasible for coupling with reduced
dextran of step (i) to obtain a ferric iron-dextran;
iii. heating the nascent ferric iron of step (ii) with reduced dextran of step
(i) in presence of an alkali, followed by cooling;
iv. adjusting the pH in the range of 5.50-6.50 using mineral acid; and
v. filtering, drying the filtrate in a spray dryer to obtain the product.
In particular, the process for synthesis of said ferric derisomaltose complex
comprises the step of selecting a suitable Dextran. As already discussed, low
molecular weight and high molecular weight Dextran complexes are not suitable; the
inventors of the present invention have provided selection of suitable dextran as a
key step to control the toxicity and stability of the compound. In a preferred
embodiment, Dextran-5 is selected as starting material for the process of synthesis of
ferric derisomaltose, Said Dextran -5 is converted to dextran – 1 by controlled
hydrolysis which can be performed according to standard methods. Thereafter, the
dextran undergoes in situ reduction yield Dextran -1 having molecular weight of
between 850 and 1100 Dalton, preferably between 800 and 1100 Dalton and most
preferably it has a molecular weight of 1000 Dalton.
Surprisingly, the present inventors found that the ‘in situ’ synthesis of dextran-1
under controlled condition of a residual reducing agent in the reacting solution,
results in production of modified dextran which is substantially free from low
molecular weight carbohydrate. Dextran-1 so produced is substantially free of any
low molecular weight carbohydrate that is it comprises less than equal to 2%.
‘In-situ’ synthesized dextran avoids the need for costly purification steps to obtain
reduced/hydrogenated dextran of molecular weight in the range of 850 to 1100 Da.
The step of reduction also reduces the concentration of unreduced dextran in the

solution resulting in a low concentration of unreduced dextran which further
diminishes the chances of reduction of ferric ions to undesired ferrous ions, thereby
reducing impurity formation. Thus, the present process avoids the use commercial
variety of Dextran -1 that is used by existing processes and subsequently obviates use
of a costly separation process typically carried out by membrane filtration or solvent
isolation to remove lower molecular weight dextran from the modified dextran
compound.
The step of reduction of the dextran into modified dextran is carried out in presence
of a mild reducing agent under controlled conditions. Mild reducing agents can be
selected from sodium cyanoborohydride, lithium borohydride, sodium borohydride,
preferably the mild reducing agent is sodium borohydride . Further the ratio of the
amount of the mild reducing agent and that of dextran is preferably is in the range of
0.010 to 0.25: 1. In a preferred embodiment, the ratio of sodium borohydride to
dextran-1 is maintained at 0.019:1. Typically the reduction of dextran-5 is carried out
for a period of about 120 minutes.
In an embodiment, the step of reduction is performed at a controlled condition. The
dextran is subjected to reduction in presence of a residual reducing agent at a
temperature of 25°C to 35°C.
In a preferred embodiment, Dextran-1 undergoes reduction under controlled
condition in presence of a sodium borohydride at room temperature followed by
quenching to reduce the affinity of oxidizing agent that may hinder the nascent ferric
ion in further complexation reaction. The process continues until the unreduced
dextran-1 concentration in the solution was in the range of 0.05 to 0.1%. Samples are
tested by standard methods such as NELSON method for monitoring the
carbohydrate content.
In an embodiment of the present invention, the reduced hydrolysed dextran is passed
through celite bed to improve the stability of modified dextran.

In the step of oxidizing electrolytic iron as recited under step (ii) with an oxidizing
agent to make nascent ferric ion, the electrolytic iron is oxidized by 10% of hydrogen
peroxide.
In the step of heating the nascent ferric iron of step (ii) with reduced dextran of step
(i) in presence of an alkali, followed by cooling, wherein the alkali is hydroxide
alkali and is free from chloride. In said step water is added to the nascent ferric ions
of step (ii) with continuous stirring. Reduced dextran of step (i) is added followed by
alkali solution for about 25 to 35 minutes.
The electrolytic iron is oxidized in the presence of 10 % hydrogen peroxide in
aqueous medium at specific pHof range 4.0-4.5, and is monitored until the free iron
and ferrous content is less than about 0.5% level in reaction mass at specific pH 4.0-
4.5. Said step produces the nascent ferric ion in solution. Consequently, it reduces the
impurities and obviates the need for further steps of purification thereby decrease the
cost of manufacturing the ferric derisomaltose.
The process also comprises steps of (iv) adjusting the pH in the range of 5.50-6.50
using mineral acid; and(v) filtering, drying the filtrate in a spray dryer to obtain the
ferric derisomaltose complex.
The ferric derisomaltose complex so obtained is heated at a temperature of about
80°C to about 85°C for a period of 1 hour to 7 hours. Preferably, heating is carried
out for a period of 2 to 3 hours. The reaction mass is cooled to temperature of about
40°C and the pH is adjusted in the range of 7.0 to 8.0 by addition of mineral acid.
In an embodiment the solution is filtered through 20µm, 2.5µm, 0.45µm and 0.2µm
filter paper. In a preferred embodiment, the solution is filtered over diatomaceous
earth (Celite bed) to remove any undissolved residue from reaction mass followed by
filtration through 1.2 micron membrane. The solution is then transferred to the spray
dryer for drying the reaction mass.

In a preferred embodiment, the ferric derisomaltose complex so produced is further
reduced to reduce the content of the dimer saccharide of ferric derisomaltose to less
than 1.8% which results in an iron complex having more stable and increased the half
life of the initial products like iron Isomaltoside. This reduction in dimer content also
resulted in improved stability as well as toxicity based on accelerated stability
testing. The dimer content of Ferric Derisomaltose is less than 1.8%. Table 1
provides the stability data of the Ferric Derisomaltose produced by the method of the
present invention.
The ferric derisomaltose obtained can be spray dried according to standard
procedure. Preferably the inlet temperature of the dryer is maintained at about 140°C
and the outlet temperature is at about 115°C-140°C to obtain a brown red powder
with iron content in the complex in the range of 25-30%w/w and molecular weight of
the complex in the range of 100kDa to 160kDa.
Ferric derisomaltose complex, in the spray dried form can be obtained is dark brown,
non-transparent powder aqueous solution with pH 5.0-7.0, readily soluble in water
and was used for preparation of parenteral compositions. Ferric derisomaltose has an
average molecular weight of 155,000 Da and has the following empirical formula:
{FeO(1-3X) (OH)(1+3X) (C6H5O7 3-)X}, (H20)T, (C6H10O6)R(-C6H10O5-
)Z(C6H13O5)R, (NaCl)Y X= 0.0311; T = 0.25; R = 0.14; Z = 0.49; Y = 0.14
The ferric derisomaltose so obtained in the present invention consists of linear,
hydrogenated isomalto-oligosaccharides with an average molecular weight of 1000
Da and a narrow molecular weight distribution that is almost devoid of mono- and
disaccharides.
Ferric derisomaltose so obtained by the process of the present invention is stable and
has an iron content of 25-30%w/w with reduced toxicity.
In a further embodiment the present invention also provides a parenteral composition
comprising 100 mg of elemental iron as ferric derisomaltose in 1mL in water for
injection. Further, the aqueous solution of ferric derisomaltose can be suitably used
for preparation of injections by adjusting the concentration of iron and by adding

suitable amount of sodium chloride in order to make the solution isotonic using
standard technique.
Among other advantages of the present invention, the inventors found that said
process offers high dosing flexibility with optimized administration convenience to
treat patients with iron deficiency. Further the ferric derisomaltose obtainable by the
present process is stable and has good yield. It can be used to prepare parenteral
administration to the patients suffering from iron deficiency anaemia.
Further embodiments will be explained by some illustrative examples.
Example 1: Preparation of reduced dextran
100g Dextran-1 was passed through a Celite bed to improve the quality of it.
Dextran-1 was mixed with sodium borohydride at room temperature followed by
quenching by using dil. HCl (10%) to reduces the affinity of reducing agent which
may hindered the nascent Ferric ion in further complexation reaction. The
concentration of sodium borohydride was maintained between 0.3 to 0.7mg/ml;
preferably at 0.5mg/ml and the temperature below 35°C. The reduction was carried
using a ventilated reactor to exhaust the inflammable hydrogen gas produced during
the reduction reaction. The process was continued until the unreduced Dextran-1
concentration in the solution was in the range of 0.05 to 0.1%.The ratio of sodium
borohydride to dextran-1 was maintained at 0.019:1.
Example 2: Preparation of nascent ferric ions
Electrolytic iron was oxidized by 10% of hydrogen peroxide in aqueous medium by
electrolysis method at specific pH and was monitored by titration method until the
free iron and ferrous content is less than about 0.5% level in reaction mass at specific
pH 4.50- pH 5.5.
Example 3: Formation of Ferric Derisomaltose complex:
The nascent ferric ions (Freshly prepare) as obtained in Example 2 was added to
water with continuous stirring. Reduced dextran of example 1 was later added
followed by alkali solution and for about 25 to 35 minutes. Ferric Derisomaltose
complex so obtained was heated and the temperature was maintained at 80°C-85°C

for 1-7 hours preferably 2-3 hrs. The reaction mass was cooled to temperature of
about 40°C and the pH was adjusted in the range of 7.0-8.0 by addition of mineral
acid.
The ferric derisomaltose complex so produced was further reduced to reduce the
content of the dimer saccharide of ferric derisomaltose to less than 1.8% which
results in an iron complex having more stable and increased the half life of the initial
products like iron Isomaltoside. This reduction in dimer content also resulted in
improved stability as well as toxicity based on accelerated stability testing. The
dimer content of Ferric Derisomaltose is less than 1.8%. Table 1 provides the
stability data of the Ferric Derisomaltose produced by the method of the present
invention.
The solution was filtered over Celite bed to remove any undissolved residue from
reaction mass followed by filtration through 1.2 micron and the solution was
transferred to the spray dryer for drying the reaction mass. The inlet temperature of
the dryer was maintained at about 140ᵒC and the outlet temperature at about 115°C to
obtain brown red powder with iron content in the complex in the range of 25-
30%w/w and molecular weight of the complex in the range of 100kDa to 160kDa.
The ferric derisomaltose complex so obtained was readily soluble in water and was
dark brown, non-transparent aqueous solution with pH 5.0-7.0, containing ferric
derisomaltose which was used for preparation of parenteral compositions.
Stability studies were carried out to observe the shelf life of the ferric derisomaltose
complex at a storage temperature of 30 ± 2°C and humidity of 40% ± 5%.
Table 1: Stability Data of the Ferric Derisomaltose

Period Description Loss on pH Carbohydrate Iron Filtration Endotoxin
completed Drying (5% (on dried Basis) Content Test
[In Month] solution) (on dried
Basis) (100 mg/
ml solution)

Brown or NMT 5.50-8.5 NLT 30.0% w/w NLT a. Should 0.5 Eu/mg
dark brown 6.0% 20%w/w pass of Iron

free flowing
powder w/w 0.45 µ
b. Should
pass
0.20 µ
Initial Complies 3.22% 6.7 33.32% 26.22% Complies Complies
(0 Month)
1 Month Complies 3.59% 6.8 33.16% 26.55% Complies Complies
3 Month Complies 3.66% 6.7 33.67% 26.82% Complies Complies
6 Month Complies 3.92% 6.7 33.56% 26.02% Complies Complies
9 month Complies 4.12% 6.7 33.86% 26.52% Complies Complies
12 month Complies 4.22% 6.7 33.92% 26.31% Complies Complies
As observed, the ferric derisomaltose complex was found to have long term stability.
Further, table 2 provides the toxicity data for the Ferric derisomaltose produced by
the present invention.

Description Iron
Content (on
dried Basis) Abnormal Toxicity Test
10 Times 20 Times 50 Times
Brown free 26.22% Concentration Weight of Procedure Concentration Weight of Procedure Concentration Weight of Procedure
flowing sample sample sample
powder injected injected injected

0.333 mg Fe/ 254.00 mg 254.00 mg 0.666 mg Fe/ 508.00 mg 508.00 mg 1.665 mg Fe/ 1270.02 mg 1270.02 mg
0.5 ml per of sample 0.5 ml per of sample 0.5 ml per of sample
mouse IV dissolved in
100 ml of
sterile
water for
injection by
heating in a
water bath mouse IV dissolved in
100 ml of
sterile
water for
injection by
heating in a
water bath mouse IV dissolved in
100 ml of
sterile
water for
injection by
heating in a
water bath
Results No Mortality Observ ed No Mortality Observed No Mortality Observ ed
As observed, the ferric derisomaltose obtained is safe and not toxic.
By dissolving in water for injections and filled into glass vials. Each 1 mL of
solution contains 100 mg of elemental iron as ferric derisomaltose in water for
injection.

WE CLAIM:

1. A process for synthesis of ferric derisomaltose complex comprises the steps
of:
i. preparation of modified dextran comprising in-situ reduction of
dextran ;
ii. oxidizing electrolytic iron with 10.0% hydrogen peroxide to make
nascent ferric iron which is highly feasible for coupling with reduced
dextran of step (i) to obtain a ferric iron-dextran;
iii. heating the nascent ferric iron of step (ii) with reduced dextran of step
(i) in presence of an alkali, followed by cooling;
iv. adjusting the pH in the range of 5.50-6.50 using mineral acid; and
v. filtering, drying the filtrate in a spray dryer to obtain the product.
2. The process as claimed in claim 1, wherein step (i) comprises in situ reduction of
dextran in presence of a reducing agent and wherein the dextran is present in ratio of
0.010 to 0.25: 1 with the reducing agent.
3. The process as claimed in claims 1 and 2, wherein step (I) comprises a step of
hyrdolysis prior to in situ reduction of the dextran.
4. The process as claimed in claims 1 and 2, wherein the reducing agents are selected
from sodium cyanoborohydride, lithium borohydride, sodium borohydride.
5. The process as claimed in claims 1 to 4 wherein in step (iii) the nascent ferric iron
of step (ii) with reduced dextran of step (i) is heated at a temperature of about 80°C
to about 85°C for a period of 1 hour to 7 hours.
6. The process as claimed in claims 1 to 5 wherein step (iii) further comprises the
step of cooling the ferric derisomaltose complex solution to temperature of about
40°C and the pH is adjusted in the range of 7.0 to 8.0 by addition of mineral acid.
7. The process as claimed in claim 1 to claim 6 wherein ferric derisomaltose complex
solution is filtered by passing the solution through diatomaceous earth.

8. The process as claimed in claim 1 to claim 7 wherein ferric derisomaltose complex
solution is filtered through 20µm, 2.5µm, 0.45µm and 0.2µm filter paper.
9. A ferric derisomaltose complex as obtained by the process of claims 1 to 8 having
improved stability, yield and reduced toxicity.
10. The ferric derisomaltose as claimed in claim 9 is stable and has an iron content of
25-30%w/w with reduced toxicity.