FIELD OF THE INVENTION
The present invention relates to a process for producing a pharmaceutical formula-tion comprising insulin and zinc  the pharmaceutical formulation obtainable by the process and to the use of the formulation for the treatment of diabetes.

BACKGROUND OF THE INVENTION
Insulin is a 51 amino acid peptide hormone produced in the islets of Langerhans in the pan-creas. Its primary function  acting as a monomer  is to facilitate the transport of glucose mol-ecules across the cell membranes of adipose and muscle tissue by binding to and activating a transmembrane receptor.
Formulations of insulin are usually prepared by dissolving insulin in a small volume of water under acidic conditions. Zinc is then added to the formulation followed by a neutralisation and addition of preservatives like phenol and m-cresol.
WO 2005/012347 discloses insulin derivatives having a negatively charged side chain.
WO 2007/074133 discloses soluble pharmaceutical formulations comprising acylated insulin and more than 4 zinc atoms per 6 molecules of acylated insulin.
The present invention overcomes the problems of the prior art.

SUMMARY OF THE INVENTION
The present invention relates to a process for preparing a pharmaceutical formulation com-prising an insulin derivative  wherein the process comprises dissolving an insulin derivative in water  optionally comprising pharmaceutically acceptable excipients  to form a solution of in-sulin derivative  adjusting the pH of the solution to a pH above 7.2  adding a zinc solution while stirring continuously and adjusting the pH to the target pH of the formulation  and wherein the insulin derivative comprises and insulin molecule having a side chain attached to the e-amino group of a Lys residue present in the B chain of the parent insulin  the side chain being of the general formula:
–W–X–Y–Z.
The invention further relates to a product obtainable by the process and to the use of a prod-uct obtainable by the process.
DEFINITIONS
The term “pharmaceutical formulation” as used herein means a product compris-ing an active compound or a salt thereof together with pharmaceutical excipients such as buffer  preservative and tonicity modifier  said pharmaceutical formulation being useful for treating  preventing or reducing the severity of a disease or disorder by administration of said pharmaceutical formulation to a person. Thus a pharmaceutical formulation is also known in the art as a pharmaceutical composition.
By “target pH of the formulation” is meant the pH  which is the desired pH value in the final pharmaceutical formulation.
The term “pharmaceutically acceptable” as used herein means suited for normal pharmaceutical applications  i.e. giving rise to no adverse events in patients etc.
The term “insulin derivative” as used herein means a chemically modified parent in-sulin or an analogue thereof  wherein the modification(s) are in the form of attachment of am-ides  carbohydrates  alkyl groups  acyl groups  esters  PEGylations  and the like. One exam-ple is LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin.
The term “human insulin” as used herein means the human insulin hormone whose structure and properties are well-known. Human insulin has two polypeptide chains  named the A-chain and the B-chain. The A-chain is a 21 amino acid peptide and the B-chain is a 30 amino acid peptide  the two chains being connected by disulphide bridges: a first bridge be-tween the cysteine in position 7 of the A-chain and the cysteine in position 7 of the B-chain  and a second bridge between the cysteine in position 20 of the A-chain and the cysteine in position 19 of the B-chain. A third bridge is present between the cysteines in position 6 and 11 of the A-chain.
In the human body  the hormone is synthesized as a single-chain precursor proinsulin (preproinsulin) consisting of a prepeptide of 24 amino acids followed by proinsulin containing 86 amino acids in the configuration: prepeptide-B-Arg Arg-C-Lys Arg-A  in which C is a connecting peptide of 31 amino acids. Arg-Arg and Lys-Arg are cleavage sites for cleavage of the connecting peptide from the A and B chains.
The term “insulin peptide” as used herein means a peptide which is either human insulin or an analog or a derivative thereof with insulin activity.
The term “parent insulin” as used herein is intended to mean an insulin before any modifications of the amino acid sequence have been applied thereto.
The term “insulin analogue” as used herein means a modified insulin wherein one or more amino acid residues of the insulin have been substituted by other amino acid residues and/or wherein one or more amino acid residues have been deleted from the insulin and/or wherein one or more amino acid residues have been added and/or inserted to the insulin.
In one embodiment an insulin analogue comprises less than 8 modifications (substitu-tions  deletions  additions (including insertions) and any combination thereof) relative to the parent insulin  alternatively less than 7 modifications relative to the parent insulin  alternatively less than 6 modifications relative to the parent insulin  alternatively less than 5 modifications relative to the parent insulin  alternatively less than 4 modifications relative to the parent insu-lin  alternatively less than 3 modifications relative to the parent insulin  alternatively less than 2 modifications relative to the parent insulin. One example of an insulin analogue is AspB28 human insulin.
Modifications in the insulin molecule are denoted stating the chain (A or B)  the posi-tion  and the one or three letter code for the amino acid residue substituting the native amino acid residue.
By “desB30” or “B(1-29)” is meant a natural insulin B chain or an analogue thereof lacking the B30 amino acid and “A(1-21)” means the natural insulin A chain. Thus  e.g.  A21Gly B28Asp desB30 human insulin is an analogue of human insulin where the amino acid in position 21 in the A chain is substituted with glycine  the amino acid in position 28 in the B chain is substituted with aspartic acid  and the amino acid in position 30 in the B chain is de-leted.
Herein terms like “A1”  “A2” and “A3” etc. indicates the amino acid in position 1  2 and 3 etc.  respectively  in the A chain of insulin (counted from the N-terminal end). Similarly  terms like B1  B2 and B3 etc. indicates the amino acid in position 1  2 and 3 etc.  respectively  in the B chain of insulin (counted from the N-terminal end). Using the one letter codes for ami-no acids  terms like A21A  A21G and A21Q designates that the amino acid in the A21 position is A  G and Q  respectively. Using the three letter codes for amino acids  the corresponding expressions are A21Ala  A21Gly and A21Gln  respectively.
Herein the terms “A(0)” or “B(0)” indicate the positions of the amino acids N-terminally to A1 or B1  respectively. The terms A(-1) or B(-1) indicate the positions of the first amino acids N-terminally to A(0) or B(0)  respectively. Thus A(-2) and B(-2) indicate positions of the amino acids N-terminally to A(-1) and B(-1)  respectively  A(-3) and B(-3) indicate positions of the amino acids N-terminally to A(-2) and B(-2)  respectively  and so forth.
Herein the terms A(0) or B(0) indicate the positions of the amino acids N-terminally to A1 or B1  respectively. The terms A(-1) or B(-1) indicate the positions of the first amino acids N-terminally to A(0) or B(0)  respectively. Thus A(-2) and B(-2) indicate positions of the amino acids N-terminally to A(-1) and B(-1)  respectively  A(-3) and B(-3) indicate positions of the amino acids N-terminally to A(-2) and B(-2)  respectively  and so forth. The terms A22 or B31 indicate the positions of the amino acids C-terminally to A21 or B30  respectively. The terms A23 or B32 indicate the positions of the first amino acids C-terminally to A22 or B31  respec-tively. Thus A24 and B33 indicate positions of the amino acids C-terminally to A23 and B32  respectively  and so forth.
The term “no blunting” as used herein means that when formulated in one formulation both the rapid acting insulin and the acylated insulin has profile of action which is identical or substantially identical with the profile of action  when administering the rapid acting insulin and the acylated insulin in separate formulations.
Herein  the term “amino acid residue” is an amino acid from which  formally  a hy-droxy group has been removed from a carboxy group and/or from which  formally  a hydro-gen atom has been removed from an amino group.
hGlu is homoglutamic acid.
a-Asp is the L-form of –HNCH(CO–)CH2COOH.
ß-Asp is the L-form of –HNCH(COOH)CH2CO–.
a-Glu is the L-form of –HNCH(CO–)CH2CH2COOH.
?-Glu is the L-form of –HNCH(COOH)CH2CH2CO–.
a-hGlu is the L-form of –HNCH(CO–)CH2CH2CH2COOH.
d-hGlu is the L-form of –HNCH(COOH)CH2CH2CH2CO–.
?-Ala is –NH-CH2-CH2-COOH.
Sar is sarcosine (N-methylglycine).
The expression "an amino acid residue having a carboxylic acid group in the side chain" designates amino acid residues like Asp  Glu and hGlu. The amino acids can be in either the L- or D-configuration. If nothing is specified it is understood that the amino acid residue is in the L configuration.
The term “treatment of a disease” as used herein means the management and care of a patient having developed the disease  condition or disorder. The purpose of treatment is to combat the disease  condition or disorder. Treatment includes the administration of the active compounds to eliminate or control the disease  condition or disorder as well as to alleviate the symptoms or complications associated with the disease  condition or disorder.
The term “bolus insulin”  “meal-related insulin” or “rapid acting insulin” as used herein means an insulin peptide which has an immediately onset of action and suited to cover the need for insulin during and after the meal.
The term “diabetes” or “diabetes mellitus” includes type 1 diabetes  type 2 diabetes  gestational diabetes (during pregnancy) and other states that cause hyperglycaemia. The term is used for a metabolic disorder in which the pancreas produces insufficient amounts of insulin  or in which the cells of the body fail to respond appropriately to insulin thus preventing cells from absorbing glucose. As a result  glucose builds up in the blood.
Type 1 diabetes  also called insulin-dependent diabetes mellitus (IDDM) and juvenile-onset diabetes  is caused by B-cell destruction  usually leading to absolute insulin deficiency.
Type 2 diabetes  also known as non-insulin-dependent diabetes mellitus (NIDDM) and adult-onset diabetes  is associated with predominant insulin resistance and thus relative insulin deficiency and/or a predominantly insulin secretory defect with insulin resistance.
The term “buffer” as used herein refers to a chemical compound in a pharmaceuti-cal composition that reduces the tendency of pH of the composition to change over time as would otherwise occur due to chemical reactions. Buffers include chemicals such as sodium phosphate  TRIS  glycyl glycine  sodium acetate and sodium citrate.
The term “preservative” as used herein refers to a chemical compound which is added to a pharmaceutical formulation to prevent or delay microbial activity (growth and me-tabolism). Examples of pharmaceutically acceptable preservatives are phenol  metacresol (m-cresol) and a mixture of phenol and m-cresol.
The term “isotonicity agent” as used refers to a chemical compound in a pharma-ceutical formulation that serves to modify the osmotic pressure of the pharmaceutical formu-lation so that the osmotic pressure becomes closer to that of human plasma. Isotonicity agents include Sodium chloride  glycerol  mannitol  propylene glycol etc.
The term “stabilizer” as used herein refers to chemicals added to peptide containing pharmaceutical formulations in order to stabilize the peptide  i.e. to increase the shelf life and/or in-use time of such formulations. Examples of stabilizers used in pharmaceutical for-mulations are L-glycine  L-histidine  arginine  polyethylene glycol  and carboxymethylcellu-lose. Further phenols  zinc ions and sodium chloride can act as stabilizers.
The term “surfactant” as used herein refers to a chemical compound in a pharma-ceutical formulation that serves to modify the interface to air and hydrophobic surfaces in a way that displaces or partly displaces insulin  insulin analogues and insulin derivatives from the interfaces. Various conventional surfactants can be employed  such as polyoxyethylene fatty acid esters and alcohols  and polyoxyethylene sorbitol fatty acid esters. An example is polysorbate 20.

DESCRIPTION OF THE INVENTION
The present invention concerns a process for preparing a pharmaceutical formulation com-prising an insulin derivative  wherein the process comprises dissolving an insulin derivative in water  optionally comprising pharmaceutically acceptable excipients  to form a solution of in-sulin derivative  adjusting the pH of the solution to a pH above 7.2  adding a zinc solution while stirring continuously and adjusting the pH to the target pH of the formulation  and wherein the insulin derivative comprises and insulin molecule having a side chain attached to the e-amino group of a Lys residue present in the B chain of the parent insulin  the side chain being of the general formula:
–W–X–Y–Z
wherein W is:
an a-amino acid residue having a carboxylic acid group in the side chain which residue forms  with one of its carboxylic acid groups  an amide group together with e-amino group of a Lys residue present in the B chain of the parent insulin;
a chain composed of two  three or four a-amino acid residues linked together via amide carbonyl bonds  which chain – via an amide bond – is linked to an e-amino group of a Lys residue present in the B chain of the parent insulin  the amino acid residues of W being selected from the group of amino acid residues having a neutral side chain and amino acid residues having a carboxylic acid group in the side chain so that W has at least one amino acid residue which has a carboxylic acid group in the side chain ; or
a covalent bond from X to an e-amino group of a Lys residue present in the B chain of the parent insulin;
X is:
–CO–;
–CH(COOH)CO–;
?CO –N(CH2COOH)CH2CO–;
?CO –N(CH2COOH)CH2CON(CH2COOH)CH2CO–;
?CO –N(CH2CH2COOH)CH2CH2CO–;
?CO –N(CH2CH2COOH)CH2CH2CON(CH2CH2COOH)CH2CH2CO–;
?CO –NHCH(COOH)(CH2)4NHCO– ;
?CO –N(CH2CH2COOH)CH2CO–; or
?CO –N(CH2COOH)CH2CH2CO–.
that
when W is an amino acid residue or a chain of amino acid residues  via a bond from the underscored carbon forms an amide bond with an amino group in W  or
when W is a covalent bond  via a bond from the underscored carbonyl carbon forms an amide bond with an e-amino group of a Lys residue present in the B chain of the parent insulin;
Y is:
–(CH2)m– where m is an integer in the range of 6 to 32;
a divalent hydrocarbon chain comprising 1  2 or 3 –CH=CH– groups and a number of CH2 groups sufficient to give a total number of carbon atoms in the chain in the range of 10 to 32; and
Z is:
–COOH;
–CO–Asp;
–CO–Glu;
–CO–Gly;
–CO–Sar;
–CH(COOH)2;
–N(CH2COOH)2;
–SO3H; or
–PO3H
and any Zn2+ complexes thereof  provided that when W is a covalent bond and X is –CO–  then Z is different from –COOH.
.
The inventors have surprisingly found that by raising the pH of the solution compris-ing insulin derivative to a pH value above 7.2  there will be substantially no precipitation of the insulin derivative when the zinc solution is added meaning that no precipitate is formed or if precipitate is formed then it solubilises again at once.
Precipitation of insulin derivative in the solution can be seen by visual inspection of the solu-tion. If the insulin derivative precipitates in the solution  the precipitate renders the solution unclear. When the solution is clear and transparent no precipitation or substantially no pre-cipitation of insulin derivative is present.
In one aspect of the invention the water  wherein the insulin derivative is dissolved  comprises one or more pharmaceutically acceptable excipients when the insulin derivative is dissolved in the water. Various pharmaceutically acceptable excipients such as phenol  m-cresol  glycerol  sodium chloride and optionally TRIS or phosphate buffers can be added to the water to obtain an aqueous solution of excipients and the insulin derivative is dissolved in the aqueous solution.
In one aspect of the invention  one or more pharmaceutically acceptable excipients are added to the aqueous solution of insulin derivative before the pH of the solution is adjusted to the target pH. In one aspect of the invention  the pharmaceutically acceptable excipients are added to the formulation after target pH is adjusted.
In one aspect the pharmaceutically acceptable excipients are selected from the group con-sisting of phenol  m-cresol  glycerol and sodium chloride.
In one aspect of the invention the target pH is below the pH of the aqueous solution  whereto the zinc solution is added. In one aspect of the invention the pH of the aqueous solution is adjusted to be above 7.4 when the zinc solution is added. In one aspect of the invention the pH of the aqueous solution is adjusted to be above 7.6 when the zinc solution is added. In one aspect of the invention the pH of the aqueous solution is adjusted to be above 7.8 when the zinc solution is added. In one aspect of the invention the pH of the aqueous solution is adjusted to be above 8.0 when the zinc solution is added.
In one aspect of the invention the target pH is in the range of 7.0 to 7.8. In one aspect the target pH is in the range of 7.2 to 7.8. In one aspect the target pH is in the range of 7.4 to 7.6.
In one aspect of the invention the pH of the aqueous solution is adjusted to be above 7.4  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.0-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 7.6  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.0-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 7.8  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.0-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 8.0  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.0-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 7.2  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.2-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 7.4  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.2-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 7.6  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.2-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 7.8  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.2-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 8.0  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.2-7.8.
In one aspect the pH of the aqueous solution is adjusted to be above 7.2  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.4 to 7.6.
In one aspect the pH of the aqueous solution is adjusted to be above 7.4  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.4 to 7.6.
In one aspect the pH of the aqueous solution is adjusted to be above 7.6  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.4 to 7.6.
In one aspect the pH of the aqueous solution is adjusted to be above 7.8  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.4 to 7.6.
In one aspect the pH of the aqueous solution is adjusted to be above 8.0  the insulin solution is added and the pH is then adjusted to a target pH in the range of 7.4 to 7.6.
Various acids and bases can be used for the adjustment of pH in the aqueous solution or to reach the target pH. Examples of suitable acids are hydrochloric acid  acetic acid  sulphuric acid and phosphoric acid. Examples of suitable bases are sodium hydroxide  TRIS  car-bonates and phosphates. In one embodiment TRIS  carbonates and phosphates also act as a buffer.

In one aspect of the invention the zinc solution is added to the aqueous solution during a pe-riod longer than one minute. In one aspect of the invention the period is longer than two minutes. In one aspect of the invention the period is longer than three minutes. In one aspect of the invention the period is longer than four minutes. In one aspect of the invention the pe-riod is longer than five minutes. In one aspect of the invention the period is longer than six minutes. In one aspect of the invention the period is longer than seven minutes.
In one aspect of the invention the zinc solution comprises zinc acetate. In one aspect the zinc solution is selected from the group consisting of zinc acetate  zinc chloride  zinc sulphate and zinc gluconate. In one aspect of the invention the zinc solution is zinc acetate.
In one aspect of the invention the proportion of the zinc solution and the soluble insulin de-rivative is from 4.3 zinc atoms per 6 molecules of insulin derivative to 12 zinc atoms per 6 molecules of insulin derivative. In one aspect of the invention the proportion is between 4.5 and 12 zinc atoms per 6 molecules of insulin derivative.
In one aspect of the invention the proportion is between 4.7 and 12 zinc atoms per 6 mole-cules of insulin derivative. In one aspect of the invention the proportion is between 4.9 and 12 zinc atoms per 6 molecules of insulin derivative. In one aspect of the invention the proportion is between 5.1 and 12 zinc atoms per 6 molecules of insulin derivative. In one aspect of the invention the proportion is between 5.3 and 12 zinc atoms per 6 molecules of insulin deriva-tive. In one aspect of the invention the proportion is between 5.5 and 12 zinc atoms per 6 molecules of insulin derivative. In one aspect of the invention the proportion is between 5.7 and 12 zinc atoms per 6 molecules of insulin derivative. In one aspect of the invention the proportion is between 5.9 and 11.5 zinc atoms per 6 molecules of insulin derivative. In one aspect of the invention the proportion is between 6.1 and 11.0 zinc atoms per 6 molecules of insulin derivative. In one aspect of the invention the proportion is between 6.3 and 10.5 zinc atoms per 6 molecules of insulin derivative. In one aspect of the invention the proportion is between 6.5 and 10.0 zinc atoms per 6 molecules of insulin derivative.

In one aspect of the invention the insulin derivative is LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin.
In one aspect of the invention a rapid acting insulin is added to the formulation. The rapid acting insulin can be selected from the group consisting of AspB28 human insulin  LysB3 GluB29 human insulin and/or LysB28 ProB29 human insulin. In one aspect of the invention the rapid acting insulin is AspB28 human insulin (Insulin Aspart).
The invention further concerns a product obtainable by the process for preparing a pharma-ceutical formulation comprising an insulin derivative. The product obtainable by the process of the invention can comprise a rapid acting insulin  such as insulin aspart and no blunting occurs.
In one aspect of the invention the use of a product obtainable by the process for preparing a pharmaceutical formulation comprising an insulin derivative for the treatment of diabetes is provided.
In a further aspect of the invention the formulation further comprises a pharmaceutically acceptable preservative which may be selected from the group consisting of phenol  o-cresol  m-cresol  p-cresol  methyl p-hydroxybenzoate  propyl p-hydroxybenzoate  2-phenoxyethanol  butyl p-hydroxybenzoate  2-phenylethanol  benzyl alcohol  chlorobutanol  and thiomerosal  bronopol  benzoic acid  imidurea  chlorohexidine  sodium dehydroacetate  chlorocresol  ethyl p-hydroxybenzoate  benzethonium chloride  chlorphenesine (3p-chlorphenoxypropane-1 2-diol) or mixtures thereof. In a further aspect of the invention the preservative is present in a concentration from 0.1 mg/ml to 20 mg/ml. In a further aspect of the invention the preservative is present in a concentration from 0.1 mg/ml to 5 mg/ml. In a further aspect of the invention the preservative is present in a concentration from 5 mg/ml to 10 mg/ml. In a further aspect of the invention the preservative is present in a concentration from 10 mg/ml to 20 mg/ml. Each one of these specific preservatives constitutes an alternative aspect of the invention. The use of a preservative in pharmaceutical compositions is well-known to the skilled person. For convenience reference is made to Remington: The Science and Practice of Pharmacy  19th edition  1995.
In a further aspect of the invention the formulation further comprises an isotonic agent which may be selected from the group consisting of a salt (e.g. sodium chloride)  a sugar or sugar alcohol  an amino acid (e.g. glycine  L-histidine  arginine  lysine  isoleucine  aspartic acid  tryptophan  threonine)  an alditol (e.g. glycerol (glycerine)  1 2-propanediol (propyleneglycol)  1 3-propanediol  1 3-butanediol) polyethyleneglycol (e.g. PEG400)  or mixtures thereof. Any sugar such as mono-  di-  or polysaccharides  or water-soluble glucans  including for example fructose  glucose  mannose  sorbose  xylose  maltose  lactose  sucrose  trehalose  dextran  pullulan  dextrin  cyclodextrin  soluble starch  hydroxyethyl starch and carboxymethylcellulose-Na may be used. In one aspect the sugar additive is sucrose. Sugar alcohol is defined as a C4-C8 hydrocarbon having at least one --OH group and includes  for example  mannitol  sorbitol  inositol  galactitol  dulcitol  xylitol  and arabitol. In one aspect the sugar alcohol additive is mannitol. The sugars or sugar alcohols mentioned above may be used individually or in combination. There is no fixed limit to the amount used  as long as the sugar or sugar alcohol is soluble in the liquid preparation and does not adversely effect the stabilizing effects achieved using the methods of the invention. In one aspect  the sugar or sugar alcohol concentration is between about 1 mg/ml and about 150 mg/ml. In a further aspect of the invention the isotonic agent is present in a concentration from 1 mg/ml to 50 mg/ml. In a further aspect of the invention the isotonic agent is present in a concentration from 1 mg/ml to 7 mg/ml. In a further aspect of the invention the isotonic agent is present in a concentration from 8 mg/ml to 24 mg/ml. In a further aspect of the invention the isotonic agent is present in a concentration from 25 mg/ml to 50 mg/ml. Each one of these specific isotonic agents constitutes an alternative aspect of the invention. The use of an isotonic agent in pharmaceutical compositions is well-known to the skilled person. For convenience reference is made to Remington: The Science and Practice of Pharmacy  19th edition  1995.
Typical isotonic agents are sodium chloride  mannitol  dimethyl sulfone and glycerol and typical preservatives are phenol  m-cresol  methyl p-hydroxybenzoate and benzyl alcohol.
Examples of suitable buffers are sodium acetate  glycylglycine  HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) and sodium phosphate.
Formulations of this invention can be used in the treatment of states which are sensitive to insulin. Thus  they can be used in the treatment of type 1 diabetes  type 2 diabetes and hyperglycaemia for example as sometimes seen in seriously injured persons and persons who have undergone major surgery. The optimal dose level for any patient will depend on a variety of factors including the efficacy of the specific insulin derivative employed  the age  body weight  physical activity  and diet of the patient  on a possible combination with other drugs  and on the severity of the state to be treated. It is recommended that the daily dosage of the formulation of this invention be determined for each individual patient by those skilled in the art in a similar way as for known insulin formulations.
Where expedient  the insulin derivatives of this invention may be used in mixture with other types of insulin  e.g. insulin analogues with a more rapid onset of action. Examples of such insulin analogues are described e.g. in the European patent applications having the publication Nos. EP 214826 (Novo Nordisk A/S)  EP 375437 (Novo Nordisk A/S) and EP 383472 (Eli Lilly & Co.).
The present invention is further illustrated by the following examples which  however  are not to be construed as limiting the scope of protection.
The invention will be summarized in the following paragraphs:
1. A process for preparing a pharmaceutical formulation comprising an insulin derivative  wherein the process comprises dissolving an insulin derivative in water  adjusting the pH of the solution to a pH above 7.2  adding a zinc solution while stirring continuously and adjusting the pH to the target pH of the formulation.
2. A process according to paragraph 1  wherein the water comprises one or more pharma-ceutically acceptable excipients.
3. A process according to paragraph 1  wherein one or more pharmaceutically acceptable excipients is added to the formulation after target pH is adjusted.
4. A process according to paragraphs 1-3  wherein the pharmaceutically acceptable excipi-ents are selected from the group consisting of phenol  m-cresol  glycerol and sodium chloride.
5. A process according to paragraphs 1-4  wherein the target pH is below the pH of the wa-ter.
6. A process according to paragraph 1-5  wherein the pH of the aqueous solution is adjusted to be above 7.4 when the zinc solution is added.
7. A process according to paragraph 1-6  wherein the pH of the aqueous solution is adjusted to be above 7.6 when the zinc solution is added.
8. A process according to paragraph 1-7  wherein the pH of the aqueous solution is adjusted to be above 7.8 when the zinc solution is added.
9. A process according to paragraph 1-8  wherein the pH of the aqueous solution is adjusted to be above 8.0 when the zinc solution is added.
10. A process according to paragraphs 1-9  wherein the zinc solution is added during a period longer than one minute.
11. A process according to paragraphs 1-10  wherein the period is longer than two minutes  longer than three minutes  longer than four minutes  longer than five minutes  longer than six minutes or longer than seven minutes.
12. A process according to paragraphs 1-11  wherein the target pH is in the range of 7.0 to 7.8.
13. A process according to paragraphs 1-12  wherein the target pH is in the range of 7.2 to 7.8.
14. A process according to paragraphs 1-13  wherein the target pH is in the range of 7.4 to 7.6.
15. A process according to paragraphs 1-14  wherein the zinc solution comprises zinc ace-tate.
16. A process according to paragraphs 1-15  wherein the proportion of the zinc solution and the soluble insulin derivative is from 4.3 zinc atoms per 6 molecules of insulin derivative to 12 zinc atoms per 6 molecules of insulin derivative  from 4.5 to 12 zinc atoms per 6 molecules of insulin derivative  from 4.7 and 12 zinc atoms per 6 molecules of insulin de-rivative  from 4.9 and 12 zinc atoms per 6 molecules of insulin derivative  from 5.1 and 12 zinc atoms per 6 molecules of insulin derivative  from 5.3 and 12 zinc atoms per 6 mole-cules of insulin derivative  from 5.5 and 12 zinc atoms per 6 molecules of insulin deriva-tive  from 5.7 and 12 zinc atoms per 6 molecules of insulin derivative  from 5.9 and 11.5 zinc atoms per 6 molecules of insulin derivative  from 6.1 and 11.0 zinc atoms per 6 mol-ecules of insulin derivative  from 6.3 and 10.5 zinc atoms per 6 molecules of insulin de-rivative or from 6.5 and 10.0 zinc atoms per 6 molecules of insulin derivative.
17. A process according to paragraphs 1-16  wherein the insulin derivative comprises an in-sulin molecule having a side chain attached to the e-amino group of a Lys residue present in the B chain of human insulin or an analogue thereof  the side chain being of the general formula:
–W–X–Y–Z
wherein W is:
• an a-amino acid residue having a carboxylic acid group in the side chain which resi-due forms  with one of its carboxylic acid groups  an amide group together with e-amino group of a Lys residue present in the B chain of the parent insulin;
• a chain composed of two  three or four a-amino acid residues linked together via amide carbonyl bonds  which chain – via an amide bond – is linked to an e-amino group of a Lys residue present in the B chain of the parent insulin  the amino acid resi-dues of W being selected from the group of amino acid residues having a neutral side chain and amino acid residues having a carboxylic acid group in the side chain so that W has at least one amino acid residue which has a carboxylic acid group in the side chain ; or
• a covalent bond from X to an e-amino group of a Lys residue present in the B chain of the parent insulin;
X is:
• –CO–;
• –CH(COOH)CO–;
• ?CO –N(CH2COOH)CH2CO–;
• ?CO –N(CH2COOH)CH2CON(CH2COOH)CH2CO–;
• ?CO –N(CH2CH2COOH)CH2CH2CO–;
• ?CO –N(CH2CH2COOH)CH2CH2CON(CH2CH2COOH)CH2CH2CO–;
• ?CO –NHCH(COOH)(CH2)4NHCO– ;
• ?CO –N(CH2CH2COOH)CH2CO–; or
• ?CO –N(CH2COOH)CH2CH2CO–.
that
a) when W is an amino acid residue or a chain of amino acid residues  via a bond from the underscored carbon forms an amide bond with an amino group in W  or
b) when W is a covalent bond  via a bond from the underscored carbonyl carbon forms an amide bond with an e-amino group of a Lys residue present in the B chain of the parent insu-lin;
Y is:
• –(CH2)m– where m is an integer in the range of 6 to 32;
• a divalent hydrocarbon chain comprising 1  2 or 3 –CH=CH– groups and a number of CH2 groups sufficient to give a total number of carbon atoms in the chain in the range of 10 to 32; and
Z is:
• –COOH;
• –CO–Asp;
• –CO–Glu;
• –CO–Gly;
• –CO–Sar;
• –CH(COOH)2;
• –N(CH2COOH)2;
• –SO3H; or
• –PO3H
and any Zn2+ complexes thereof  provided that when W is a covalent bond and X is –CO–  then Z is different from –COOH.
18. A process according to paragraph 17  wherein W is selected from the group consisting of a-Asp  ß-Asp  a-Glu  ?-Glu  a-hGlu and d-hGlu.
19. A process according to paragraph 17  wherein W is selected from the group consisting of a-Asp-Gly; Gly-a-Asp; ß-Asp-Gly; Gly-ß-Asp; a-Glu-Gly; Gly-a-Glu; ?-Glu-Gly; Gly-?-Glu; a-hGlu-Gly; Gly-a-hGlu; d-hGlu-Gly; and Gly-d-hGlu  a-Asp–a-Asp; a-Asp–a-Glu; a-Asp–a-hGlu; a-Asp–ß-Asp; a-Asp–?-Glu; a-Asp–d-hGlu; ß-Asp–a-Asp; ß-Asp–a-Glu; ß-Asp–a-hGlu; ß-Asp–ß-Asp; ß-Asp–?-Glu; ß-Asp–d-hGlu; a-Glu–a-Asp; a-Glu–a-Glu; a-Glu–a-hGlu; a-Glu–ß-Asp; a-Glu–?-Glu; a-Glu–d-hGlu; ?-Glu–a-Asp; ?-Glu–a-Glu; ?-Glu–a-hGlu; ?-Glu–ß-Asp; ?-Glu–?-Glu; ?-Glu–d-hGlu; a-hGlu–a-Asp; a-hGlu–a-Glu; a-hGlu–a-hGlu; a-hGlu–ß-Asp; a-hGlu–?-Glu; a-hGlu–d-hGlu; d-hGlu–a-Asp; d-hGlu–a-Glu; d-hGlu–a-hGlu; d-hGlu–ß-Asp; d-hGlu–?-Glu; and d-hGlu–d-hGlu.
20. A process according to paragraphs 17-19  wherein X is –CO– or –CH(COOH)CO–.
21. A process according to paragraphs 17-20  wherein Y is –(CH2)m– where m is an integer in the range of from 6 to 32  from 8 to 20  from 12 to 20 or from 12-16.
22. A process according to paragraphs 17-21  wherein Z is –COOH.
23. A process according to paragraphs 17  18  20  21 and 22  wherein the insulin derivative is LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin.
24. A process according to paragraphs 1-23  wherein rapid acting insulin is added to the for-mulation.
25. A process according to paragraphs 1-24  wherein the rapid acting insulin is selected from the group consisting of AspB28 human insulin  LysB3 GluB29 human insulin and/or LysB28 ProB29 human insulin.
26. A process according to paragraph 25  wherein the rapid acting insulin is AspB28 human insulin.
27. A product obtainable by the process of paragraphs 1-27.
28. Use of a product obtainable by the process of paragraphs 1-27 for the treatment of diabe-tes.
In one aspect the invention is summarized in the following paragraphs:
1) A process for preparing a pharmaceutical formulation comprising an insulin derivative  wherein the process comprises dissolving an insulin derivative in water  adjusting the pH of the solution to a pH above 7.2  adding a zinc solution while stirring continuously and adjusting the pH to the target pH of the formulation.
2) A process according to paragraph 1  wherein the water comprises one or more phar-maceutically acceptable excipients.
3) A process according to paragraph 1  wherein one or more pharmaceutically accepta-ble excipients is added to the formulation after target pH is adjusted.
4) A process according to paragraphs 1-3  wherein the pharmaceutically acceptable ex-cipients are selected from the group consisting of phenol  m-cresol  glycerol and so-dium chloride.
5) A process according to paragraphs 1-4  wherein the target pH is below the pH of the water.
6) A process according to paragraph 1-5  wherein the pH of the aqueous solution is ad-justed to be above 7.4 when the zinc solution is added.
7) A process according to paragraph 1-6  wherein the pH of the aqueous solution is ad-justed to be above 7.6 when the zinc solution is added.
8) A process according to paragraph 1-7  wherein the pH of the aqueous solution is ad-justed to be above 7.8 when the zinc solution is added.
9) A process according to paragraph 1-8  wherein the pH of the aqueous solution is ad-justed to be above 8.0 when the zinc solution is added.
10) A process according to paragraphs 1-9  wherein the zinc solution is added during a period longer than one minute.
11) A process according to paragraphs 1-10  wherein the period is longer than two minutes  longer than three minutes  longer than four minutes  longer than five minutes  longer than six minutes or longer than seven minutes.
12) A process according to paragraphs 1-11  wherein the target pH is in the range of 7.0 to 7.8.
13) A process according to paragraphs 1-12  wherein the target pH is in the range of 7.2 to 7.8.
14) A process according to paragraphs 1-13  wherein the target pH is in the range of 7.4 to 7.6.
15) A process according to paragraphs 1-14  wherein the zinc solution comprises zinc acetate.
16) A process according to paragraphs 1-15  wherein the proportion between the zinc so-lution and the soluble insulin derivative is from 4.3 zinc atoms per 6 molecules of in-sulin derivative to 12 zinc atoms per 6 molecules of insulin derivative.
17) A process according to paragraphs 1-16  wherein the insulin derivative comprises an insulin molecule having a side chain attached to the e-amino group of a Lys residue present in the B chain of human insulin or an analogue thereof  the side chain being of the general formula:
–W–X–Y–Z
wherein W is:
• an a-amino acid residue having a carboxylic acid group in the side chain which resi-due forms  with one of its carboxylic acid groups  an amide group together with e-amino group of a Lys residue present in the B chain of the parent insulin;
• a chain composed of two  three or four a-amino acid residues linked together via amide carbonyl bonds  which chain – via an amide bond – is linked to an e-amino group of a Lys residue present in the B chain of the parent insulin  the amino acid resi-dues of W being selected from the group of amino acid residues having a neutral side chain and amino acid residues having a carboxylic acid group in the side chain so that W has at least one amino acid residue which has a carboxylic acid group in the side chain ; or
• a covalent bond from X to an e-amino group of a Lys residue present in the B chain of the parent insulin;
X is:
• –CO–;
• –CH(COOH)CO–;
• ?CO –N(CH2COOH)CH2CO–;
• ?CO –N(CH2COOH)CH2CON(CH2COOH)CH2CO–;
• ?CO –N(CH2CH2COOH)CH2CH2CO–;
• ?CO –N(CH2CH2COOH)CH2CH2CON(CH2CH2COOH)CH2CH2CO–;
• ?CO –NHCH(COOH)(CH2)4NHCO– ;
• ?CO –N(CH2CH2COOH)CH2CO–; or
• ?CO –N(CH2COOH)CH2CH2CO–.
that
a) when W is an amino acid residue or a chain of amino acid residues  via a bond from the underscored carbon forms an amide bond with an amino group in W  or
b) when W is a covalent bond  via a bond from the underscored carbonyl carbon forms an amide bond with an e-amino group of a Lys residue present in the B chain of the parent insu-lin;
Y is:
• –(CH2)m– where m is an integer in the range of 6 to 32;
• a divalent hydrocarbon chain comprising 1  2 or 3 –CH=CH– groups and a number of CH2 groups sufficient to give a total number of carbon atoms in the chain in the range of 10 to 32; and
Z is:
• –COOH;
• –CO–Asp;
• –CO–Glu;
• –CO–Gly;
• –CO–Sar;
• –CH(COOH)2;
• –N(CH2COOH)2;
• –SO3H; or
• –PO3H
and any Zn2+ complexes thereof  provided that when W is a covalent bond and X is –CO–  then Z is different from –COOH.
18) A process according to paragraph 17  wherein the insulin derivative is LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin.
19) A process according to paragraphs 1-18  wherein a rapid acting insulin is added to the formulation .
20) A process according to paragraphs 1-19  wherein the rapid acting insulin is selected from the group consisting of AspB28 human insulin  LysB3 GluB29 human insulin and/or LysB28 ProB29 human insulin.
21) A product obtainable by the process of paragraphs 1-20.
22) Use of a product obtainable by the process of paragraphs 1-20 for the treatment of diabetes.

All references  including publications  patent applications  and patents  cited herein are hereby incorporated by reference in their entirety and to the same extent as if each refer-ence were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein (to the maximum extent permitted by law).
All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.
The use of any and all examples  or exemplary language (e.g.  “such as”) provided herein  is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the inven-tion.
The citation and incorporation of patent documents herein is done for convenience only and does not reflect any view of the validity  patentability  and/or enforceability of such patent documents.
This invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law.

EXAMPLES
Example 1
Process for preparing a formulation comprising LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin  600 nmol/ml (100U/ml):
0.6 mmol LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin was dissolved in 300 ml water and mixed with 500 ml of an aqueous solution containing 16 mmol phenol  16 mmol m-cresol and 213 mmol glycerol. pH was adjusted to 7.40 and 50 ml 0.01 M zinc acetate was added continuously by use of a peristaltic pump while stirring at moderate speed. The addition was done over approximately 30 minutes. After addition of zinc acetate  water for injection was added to 950 ml  pH was adjusted to 7.60 and finally water was added to final volume of 1 litre.
Example 2
Process for preparing a formulation comprising LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin  1200 nmol/ml (200U/ml):
1.2 mmol LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin was dissolved in 300 ml water and mixed with 500 ml of an aqueous solution containing 16 mmol phenol  16 mmol m-cresol and 213 mmol glycerol. pH was adjusted to 7.50 and 110 ml 0.01 M zinc acetate was added continuously by use of a peristaltic pump while stirring at moderate speed. The addition was done over approximately 40 minutes. After addition of zinc acetate  water for injection was added to 950 ml  pH was adjusted to 7.60 and finally water was added to final volume of 1 litre.
Example 3
Process for preparing a formulation comprising LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin and insulin aspart 600 nmol/ml (U100/ml):

LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin solution: 0.42 mmol LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin was dissolved in 210 ml water and mixed with 350 ml of an aqueous solution containing 11.2 mmol phenol  11.2 mmol m-cresol  7 mmol NaCl and 144 mmol glycerol. pH was adjusted to 7.40 and 32.9 ml 0.01 M zinc acetate was added continuously by use of a peristaltic pump while stirring at moderate speed. The addition was done over approximately 30 minutes. After addition of zinc acetate  water for injection was added to 630 ml and pH was adjusted to 7.40.

Insulin aspart solution: 0.18 mmol insulin aspart was suspended in 15 ml water and mixed with a solution containing 9 ml 0.01 M zinc acetate and 4.8 ml 0.2 N hydrochloric acid to ob-tain a clear solution. The volume was adjusted to 35 ml by adding water. 180 ml of a solution containing 4.8 mmol phenol  4.8 mmol m-cresol  3 mmol NaCl and 62 mmol glycerol was then added. Finally pH was adjusted to 7.40 and the volume was adjusted to 270 ml by adding water.

Mixing of LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin solution and insulin aspart solution: 630 ml of LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin solution and 270 ml of insulin aspart solution were mixed. pH was adjusted to 7.40 and finally the vol-ume was adjusted to 1 litre by adding water
Example 4
Process for preparing a formulation comprising LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin and insulin aspart  1200 nmol/ml (200 U/ml):
LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin solution: 0.84 mmol LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin was dissolved in 210 ml water and mixed with 350 ml of an aqueous solution containing 11.2 mmol phenol  11.2 mmol m-cresol  7 mmol NaCl and 144 mmol glycerol. pH was adjusted to 7.40 and 60.1 ml 0.01 M zinc acetate was added continuously by use of a peristaltic pump while stirring at moderate speed. The addition was done over approximately 30 minutes. After addition of zinc acetate  water for injection was added to 630 ml and pH was adjusted to 7.40.

Insulin aspart solution: 0.36 mmol insulin aspart was suspended in 15 ml water and mixed with a solution containing 18 ml 0.01 M zinc acetate and 4.8 ml 0.2 N hydrochloric acid to obtain a clear solution. The volume was adjusted to 35 ml by adding water. 180 ml of a solu-tion containing 4.8 mmol phenol  4.8 mmol m-cresol  3 mmol NaCl and 62 mmol glycerol was then added. Finally pH was adjusted to 7.40 and the volume was adjusted to 270 ml by adding water.

Mixing of LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin solution and insulin aspart solution: 630 ml of LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin solution and 270 ml of insulin aspart solution were mixed. pH was adjusted to 7.40 and finally the vol-ume was adjusted to 1 litre by adding water.

CLAIMS

1. A process for preparing a pharmaceutical formulation comprising an insulin derivative  wherein the process comprises dissolving an insulin derivative in water  adjusting the pH of the solution to a pH above 7.2  adding a zinc solution while stirring continuously and adjusting the pH to the target pH of the formulation  and wherein the insulin derivative comprises an insulin molecule having a side chain attached to the e-amino group of a Lys residue present in the B chain of human insulin or an analogue thereof  the side chain be-ing of the general formula:
–W–X–Y–Z
wherein W is:
• an a-amino acid residue having a carboxylic acid group in the side chain which resi-due forms  with one of its carboxylic acid groups  an amide group together with e-amino group of a Lys residue present in the B chain of the parent insulin;
• a chain composed of two  three or four a-amino acid residues linked together via amide carbonyl bonds  which chain – via an amide bond – is linked to an e-amino group of a Lys residue present in the B chain of the parent insulin  the amino acid resi-dues of W being selected from the group of amino acid residues having a neutral side chain and amino acid residues having a carboxylic acid group in the side chain so that W has at least one amino acid residue which has a carboxylic acid group in the side chain ; or
• a covalent bond from X to an e-amino group of a Lys residue present in the B chain of the parent insulin;
X is:
• –CO–;
• –CH(COOH)CO–;
• ?CO –N(CH2COOH)CH2CO–;
• ?CO –N(CH2COOH)CH2CON(CH2COOH)CH2CO–;
• ?CO –N(CH2CH2COOH)CH2CH2CO–;
• ?CO –N(CH2CH2COOH)CH2CH2CON(CH2CH2COOH)CH2CH2CO–;
• ?CO –NHCH(COOH)(CH2)4NHCO– ;
• ?CO –N(CH2CH2COOH)CH2CO–; or
• ?CO –N(CH2COOH)CH2CH2CO–.
that
a) when W is an amino acid residue or a chain of amino acid residues  via a bond from the underscored carbon forms an amide bond with an amino group in W  or
b) when W is a covalent bond  via a bond from the underscored carbonyl carbon forms an amide bond with an e-amino group of a Lys residue present in the B chain of the parent insu-lin;
Y is:
• –(CH2)m– where m is an integer in the range of 6 to 32;
• a divalent hydrocarbon chain comprising 1  2 or 3 –CH=CH– groups and a number of CH2 groups sufficient to give a total number of carbon atoms in the chain in the range of 10 to 32; and
Z is:
• –COOH;
• –CO–Asp;
• –CO–Glu;
• –CO–Gly;
• –CO–Sar;
• –CH(COOH)2;
• –N(CH2COOH)2;
• –SO3H; or
• –PO3H.
2. A process according to claim 1  wherein the water comprises one or more pharmaceuti-cally acceptable excipients.
3. A process according to claim 1  wherein one or more pharmaceutically acceptable excip-ients is added to the formulation after target pH is adjusted.
4. A process according to claims 1-3  wherein the pharmaceutically acceptable excipients are selected from the group consisting of phenol  m-cresol  glycerol and sodium chloride.
5. A process according to claims 1-4  wherein the target pH is below the pH of the water.
6. A process according to claims 1-5  wherein the zinc solution is added during a period longer than one minute.
7. A process according to claims 1-6  wherein the period is longer than two minutes  longer than three minutes  longer than four minutes  longer than five minutes  longer than six minutes or longer than seven minutes.
8. A process according to claims 1-7  wherein the target pH is in the range of 7.0 to 7.8.
9. A process according to claims 1-8  wherein the zinc solution comprises zinc acetate.
10. A process according to claim 9  wherein the insulin derivative is LysB29Ne-hexadecandioyl-?-Glu desB30 human insulin.
11. A process according to claims 1-10  wherein a rapid acting insulin is added to the formu-lation.
12. A process according to claims 1-11  wherein the rapid acting insulin is selected from the group consisting of AspB28 human insulin  LysB3 GluB29 human insulin and/or LysB28 ProB29 human insulin.
13. A product obtainable by the process of claims 1-12.
14. Use of a product obtainable by the process of claims 1-12 for the treatment of diabetes.