PHARMACEUTICAL FORMULATIONS COMPRISING SAPROPTERIN DIHYDROCHLORIDE AND AT LEAST ONE ANTIOXIDANT

Field of the invention

The present invention relates to pharmaceutical formulations comprising sapropterin dihydrochloride and at least one antioxidant.

Background of the invention

Phenylketonuria (PKU) is a rare condition where babies are born unable to break down an amino acid called phenylalanine. This causes phenylalanine to build up. When phenylalanine levels get too high, it can cause damage to the brain. This can lead to intellectual and developmental disabilities.

Phenylalanine is found in foods that contain protein. PKU is manageable, mostly through your diet. The key to living with PKU successfully is finding it early. That is why all babies in the United States are screened for the disease at birth.

PKU is an inherited disease. This means it is passed down through the genes of the mother and father. It is caused by mutations in the gene that helps make an enzyme called phenylalanine hydroxylase. This enzyme helps breakdown phenylalanine. When this gene doesn’t work right, the body can’t break down phenylalanine. It starts to build up and causes damage to nerve cells in the brain.

Initially in newborns there are no symptoms. But within a few months of birth, depending on the severity of the disease, symptoms begin to show. These include:

Smaller than normal head size (called microcephaly)

Hyperactivity • A musty or mouse-like odor in urine, breath, or skin

• Lighter skin, hair, and eyes than their siblings

• Skin disorders such as eczema

• Jerking movements of the arms or legs · Tremors

• Seizures

• Delayed development

• Behavioral problems

• Psychiatric disorders ' Permanent intellectual disability

If PKU is not controlled through changes in diet, it can cause severe intellectual and developmental disability.

The U.S. Food and Drug Administration has approved the medicine sapropterin dihydrochloride (Kuvan®) for the treatment of PKU. Kuvan can help the body break down phenylalanine.

Sapropterin dihydrochloride (Kuvan® [BioMarin, CA, USA]) is the first and only registered synthetic form of the naturally occurring enzyme cofactor, BH4 (5, 6,7,8- tetrahydrobiopterin) Sapropterin is an orally active, synthetic dihydrochloride salt formulation of the Biologically active 6R-diastereoisomer of BH4 (5, 6,7,8- tetrahydrobiopterin) Although PKU is characterized by a defect in the PAH (Phenylalanine hydroxylase) enzyme, residual enzymatic activity may be present in some patients. Thus, sapropterin may act like a chemical chaperone to promote the normal metabolism of Phe(Phenylalanine) and lower its concentration in the blood in a subset of patients who are BH4 responsive. Sapropterin may be used to assist in the control of Phe concentrations. It provides the opportunity for patients who respond to BH4 to adjust their diet, thereby allowing a greater intake of Phe or even coming off of their Phe-restrictive diet. The overall frequency of BH4 responsiveness across Europe is estimated to be 55-62%, based on projections made using genetic allelic data for BH4 responsiveness, although responsiveness can only be determined by a response test.

The chemical name of sapropterin dihydrochloride is (6R)-2-amino-6-[(1 R,2S)-1 ,2- dihydroxypropyl]-5,6,7,8-tetrahydro-4(1 H)-pteridinone dihydrochloride and the molecular formula is C9H15N503-2HCI with a molecular weight of 314.17. Sapropterin dihydrochloride has the following structural formula:

The patent US7727987B2 of Merck discloses crystal forms of (6R)-L-erythro- tetrahydrobiopterin dihydrochloride and hydrates and solvates thereof. Also relates to compositions comprising selected and stable crystal forms of (6R)-L-erythro- tetrahydrobiopterin dihydrochloride or a hydrate thereof and a pharmaceutically acceptable carrier.

The patent EP1757293B1 of Daiichi Sankyo discloses an effective sapropterin hydrochloride preparation that is highly stable during storage and can administer sapropterin hydrochloride, an effective therapeutic agent for the treatment of tetrahydrobiopterin-responsive hyperphenylalaninemia, to patients of a wide range of ages, ranging from infants to adults, in a single preparation

The patent application EP1845952A2 of BioMarin Pharmaceutical discloses a stable solid formulation of tetrahydrobiopterin, or a precursor or derivative or analog thereof, that maintains its stability for an extended period of time. Compositions of the invention may comprise a stable, crystalline form of BH4 that is stable at room temperature for more than 8 hours and a pharmaceutically acceptable carrier, diluent or excipient. Exemplary stable tablets of the invention have been prepared using a dry tableting process and have been shown to have a shelf-life of at least 6 to 9 months at room temperature.

The patent application EP2680848A1 of Dipharma discloses stable pharmaceutical compositions comprising tetrahydrobiopterin and at least one stabilizing agent. Particularly the present invention relates to stable compositions of sapropterin dihydrochloride. Antioxidants that stabilize tetrahydrobiopterin; with the weight ratio of the antioxidant to active ranging from 0.2 - 1.5.

The patent application CN104257623A patent of Guangdong Zhongsheng pharmaceutical company discloses an effervescent tablet containing sapropterin dihydrochloride.

Sapropterin dihydrochloride exhibits polymorphism and many crystalline forms have been identified; among all the polymorphic forms, Form B was identified to be thermodynamically stable crystalline anhydrate form. Polymorph form B is a very stable crystalline form, that can be easily filtered off, dried and ground to particle sizes desired for pharmaceutical formulations. These outstanding properties renders polymorph form B especially feasible for pharmaceutical application.

Sapropterin dihydrochloride is currently available as oral soluble tablets of 100mg and 100mg-500mg powder packets under the brand name Kuvan™. It is marketed by BioMarin in the US and Merck Serono in Europe. Kuvan™ has been designated as an orphan medication since hyperphenylalaninemia is a rare disease. Kuvan™ is indicated to reduce blood phenylalanine levels in patients with hyperphenylalaninemia due to tetrahydrobiopterin responsive phenylketonuria. It is to be used in conjunction with phenylalanine restricted diet. In patients with phenylketonuria the role of sapropterin dihydrochloride is to enable endogenous phenylalanine hydroxylase activity and to partially restore oxidative metabolism of phenylalanine, resulting in decreased blood phenylalanine levels. In patients with BH4 deficiency, sapropterin dihydrochloride is proposed to restore endogenous phenylalanine hydroxylase activity by providing an exogenous source of the missing cofactor. Tetrahydrobiopterin is an unstable compound; at ambient temperature it is prone to autoxidation in the presence of molecular oxygen Tetrahydrobiopterin is also very hygroscopic.Therefore the development of stable oral composition comprising tetrahydrobiopterin that is prone to degradation at room temperature is a challenging task.

Thus, though researchers have developed compositions of sapropterin comprising stabilizers in variety of ratios, the stability of these compositons is low at room temperature or 40°C/75% relative humidity and need to be stored under refrigeration. Low stability of such tetrahydrobiopterin compositions is commercially undesirable and significant degradation due to improper storage could hinder therapy. Need therefore, exists for preparations of tetrahydrobiopterin that are more stable and retain desired amount of active over a longer time even when not refrigerated.

Further, the amount and type of stabilizer and other excipients present in the compositions of sapropterin determine the stability of the active and compositions thereof. Too little or too much stabilizer can affect the stability of the compositions of sapropterin and an appropriate amount of stabilizer must therefore be present in these compositions.

The stable formulations of sapropterin dihydrochloride according to the present invention thus provide desired amount of active over the entire shelf life of the product.

The solubility and dissolution rate of sapropterin dihydrochloride directly influence its bioavailability. For this reason, it is quite important to increase the solubility and dissolution rate of sapropterin dihydrochloride. A desired dissolution profile of the pharmaceutical formulation is obtained.

Detailed Description of the Invention

The main object of the present invention is to provide pharmaceutical formulations comprising sapropterin dihydrochloride and at least one antioxidant with desired stability and bioavailability. The term "sapropterin dihydrochloride" as used throughout the specification refers to not only sapropterin dihydrochloride, but also its other pharmaceutically acceptable solvates, pharmaceutically acceptable hydrates, pharmaceutically acceptable enantiomers, pharmaceutically acceptable derivatives, pharmaceutically acceptable polymorphs or pharmaceutically acceptable prodrugs thereof.

The amount of sapropterin dihydrochloride is between 20.0-30.0% preferably 25.0- 30.0% by weight of the pharmaceutical formulation.

According to another embodiment of the present invention is to provide a stable pharmaceutical formulation by appropriate ratio of sapropterin dihydrochloride to antioxidant.

Suitable antioxidants are selected from the group comprising alpha tocopherol(Vitamin E), quercetine, butylhydroxyanisole (BHA), butylhydroxytoluene (BHT), erythorbic acid, monothioglycerol, potassium metabisulfite, alpha lipoic acid, ascorbyl palmitate, propyl gallate, sodium ascorbate, sodium metabisulfite, sodium sulfite, citric acid, thymol or mixtures thereof. Preferably antioxidants are selected from quercetine, alpha tocopherol(vitamin E), butylhydroxyanisole, butylhydroxytoluene, citric acid or mixtures thereof.

The amount of antioxidant is between 5.0-7.5% preferably 5.6-6.4% by weight of the pharmaceutical formulation.

According to one embodiment of present invention, the weight ratio of sapropterin dihydrochloride to antioxidant is between 3.0-6.0(w/w), preferably 3.5-5.5(w/w), more preferably 4.0-5.4 (w/w)

In a preferred embodiment according to the present invention, said pharmaceutical formulation further comprises at least one pharmaceutically acceptable excipient which is selected from fillers, binders, disintegrants, lubricants, sweeteners, coloring agents, buffering agent or mixtures thereof. Suitable fillers are selected from the group comprising microcrystalline cellulose, mannitol, spray-dried mannitol, lactose, lactose monohydrate, lactose anhydrous, starch, dextrose, sucrose, fructose, maltose, sorbitol, xylitol, inositol, kaolin, inorganic salts, calcium salts, polysaccharides, dibasic calcium phosphate, sodium chloride, dextrates, lactitol, maltodextrin, sucrose-maltodextrin mixture, trehalose, sodium carbonate, sodium bicarbonate, calcium carbonate or mixtures thereof.

According to one embodiment of the present invention, fillers are used to achieve the desired dissolution profile, especially, when the amount of fillers is between 20.0% and 90.0%, preferably between 25.0% and 75.0%, so the pharmaceutical formulation shows desired dissolution profile.

According to one embodiment of the present invention, the amount of fillers is between 20.0% and 90.0%, 25.0% and 80.0%, 25.0% and 70.0%, 25.0% and 60.0%, 25.0% and 50.0%, 25.0% and 40.0%, 65.0% and 75.0%, 22.0% and 35.0% by weight of the pharmaceutical formulation. These ratios help to provide the desired dissolution of the formulation.

According to one embodiment of the present invention, the filler is lactose or sorbitol or microcrystalline cellulose or mixtures thereof.

Suitable binders are selected from the group comprising polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, starch, pregelatinized starch, glucose, glucose syrup, natural gums, sucrose, sodium alginate, lactose anhydrous, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, carboxy methyl cellulose, methyl cellulose, gelatin, carrageenan, guar gum, carbomer, polymethacrylates, methacrylate polymers, collagenselatin, agar, alginate, alginic acid, xanthan gum, hyaluronic acid, pectin, polysaccharides, carbomer, poloxamer, polyacrylamide, aluminium hydroxide, laponite, bentonite, polyoxyethylene-alkyl ether, polydextrose, polyethylene oxide or mixtures thereof. According to one embodiment of the present invention, the amount of binder is between 1.0% and 50.0%, 5.0% and 40.0%, preferably 10.0% and 30.0%, 15.0% and 25.0% by weight of the pharmaceutical formulation.

According to one embodiment of the present invention, the binder is lactose anhydrous.

Suitable disintegrants are selected from the group comprising polyvinyl pyrrolidone (crospovidone), crospovidone CL-Superfine (kollidon CL-Superfine), povidone, cross- linked carboxymethyl cellulose (croscarmellose sodium), low-substituted hydroxypropyl cellulose, pregelatinized starch, sodium carboxymethyl cellulose, calcium carboxymethyl cellulose, carboxymethyl cellulose, docusate sodium, guar gum, polyacryline potassium, sodium alginate, corn starch, sodium starch glycolate, alginic acid, alginates, ion-exchange resins, magnesium aluminium silica, sodium dodesyl sulphate, poloxamer, sodium glycine carbonate, sodium lauryl sulphate or mixtures thereof.

According to one embodiment of the present invention, the amount of disintegrant is between 2.0% and 15.0%, 2.0% and 10.0%, 2.0% and 8.0% by weight of the pharmaceutical formulation.

According to one embodiment of the present invention, the disintegrant is sodium starch glycolate.

Suitable lubricants are selected from the group comprising from magnesium stearate, calcium stearate, zinc stearate, talc, waxes, boric acid, hydrogenated vegetable oil, sodium chlorate, magnesium lauryl sulfate, sodium oleate, sodium acetate, sodium benzoate, polyethylene glycol, stearic acid, fatty acid, fumaric acid, glyseryl palmito sulphate, sodium stearyl fumarate, sodium lauryl sulphate or mixtures thereof.

Suitable coloring agents are selected from the group comprising curcumin, ferric oxide, titanium dioxide, Food, Drug & Cosmetic (FD&C) dyes (such as; FD&C blue, FD&C green, FD&C red, FD&C yellow, FD&C lakes), poncau, indigo Drug & Cosmetic (D&C) blue, indigotine FD&C blue, carmoisine indigotine (indigo Carmine); iron oxides (such as; iron oxide red, yellow, black), quinoline yellow, flaming red, carmine, carmoisine, sunset yellow or mixtures thereof.

Suitable sweeteners are selected from the group comprising potassium acesulfame, sodium saccharinate, neohesperidine dihydrochalcone, monoammonium glycyrrhizinate, sucralose, saccharin, sucrose, glucose, lactose, fructose, mannitol, xylitol, erythritol or mixtures thereof.

Suitable buffering agents which is selected from the group comprising glycine, sodium carbonate, alkali metal citrate, sodium citrate, tartaric acid, fumaric acid, sorbic acid, citric acid, succinic acid, adipic acid, ascorbic acid, glutaric acid, potassium hydrogen tartrate, sodium hydrogen tartrate, potassium hydrogen phthalate, sodium hydrogen phthalate, potassium dihydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, hydrochloric acid/sodium hydroxide or mixtures thereof, and preferably citric acid, fumaric acid, ascorbic acid, sodium dihydrogen phosphate, glycine , glutamic acid and mixtures thereof.

According to one embodiment of the present invention, the pharmaceutical formulation is in the form of soluble tablets, capsules, strips, powders, pastilles, sachets, effervescent compositions, pills, coated bead systems, granules, microspheres, dragees, films, orally administrable films, solids. Preferably, the pharmaceutical formulation is in the form of soluble tablets or sachets.

Example 1 : Sapropterin dihydrochloride and at least one antioxidant processed with dry granulation/direct compression (Soluble tablet production method) Process (Dry granulation/Direct compression) a. Sieving Sapropterin dihydrochloride, Sodium starch glycolate, Monoammonium glycyrrhizinate, Lactose anhydrous, Microcrystalline cellulose, Antioxidant ^* and curcumin and mixing to obtain a homogenous mixture. The mixture is granulated. b. Adding magnesium stearate to this mixture and mixing them. c. Compressing this mixture into tablets. ^* Butylhydroxyanisole, Butylhydroxytoluene, vitamin E, Quercetine or Citric acid can be used as an antioxidant.

Example 2: Sapropterin dihydrochloride and at least one antioxidant processed with dry granulation/direct compression (Soluble tablet production method) Process (Dry granulation/Direct compression) a. Sieving Sapropterin dihydrochloride, Sodium starch glycolate, Monoammonium glycyrrhizinate, Lactose anhydrous, Microcrystalline cellulose, Antioxidant ^* and curcumin and mixing to obtain a homogenous mixture. The mixture is granulated. b. Adding magnesium stearate to this mixture and mixing them. c. Compressing this mixture into tablets. ^* Butylhydroxyanisole, Butylhydroxytoluene, vitamin E, Quercetine or Citric acid can be used as an antioxidant.

Example 3: Sapropterin dihydrochloride and at least one antioxidant processed with dry granulation/direct compression (Soluble tablet production method) Process (Dry granulation/Direct compression) a. Sieving Sapropterin dihydrochloride, Sodium starch glycolate, Monoammonium glycyrrhizinate, Lactose anhydrous, Microcrystalline cellulose, Antioxidant ^* and curcumin and mixing to obtain a homogenous mixture. The mixture is granulated. b. Adding magnesium stearate to this mixture and mixing them. c. Compressing this mixture into tablets.

^* Butylhydroxyanisole, Butylhydroxytoluene, vitamin E, Quercetine or Citric acid can be used as antioxidant.

Example 4: Sapropterin dihydrochloride and at least one antioxidant processed with dry granulation/direct compression (Soluble tablet production method)

Process (Dry granulation/Direct compression) a. Sieving Sapropterin dihydrochloride, Sodium starch glycolate, Monoammonium glycyrrhizinate, Lactose anhydrous, Microcrystalline cellulose, Antioxidant ^* and curcumin and mixing to obtain a homogenous mixture. The mixture is granulated. b. Adding magnesium stearate to this mixture and mixing them. c. Compressing this mixture into tablets

^* Butylhydroxyanisole, Butylhydroxytoluene, vitamin E, Quercetine or Citric acid can be used as antioxidant.

Example 5: Sapropterin dihydrochloride and at least one antioxidant processed with mixture (Powder for oral solution / sachet)

Seiving sapropterine dihydrochloride and all excipients, then mixing to obtain homogenous powder mixture. Then the powder mixture packed in a sachet.

^* Butylhydroxyanisole, Butylhydroxytoluene, vitamin E, Quercetine or Citric acid can be used as antioxidant.

Example 6: Sapropterin dihydrochloride and at least one antioxidant processed with mixture (Powder for oral solution / sachet)

Seiving sapropterine dihydrochloride and all excipients, then mixing to obtain homogenous powder mixture. Then the powder mixture packed in a sachet.

^* Butylhydroxyanisole, Butylhydroxytoluene, vitamin E, Quercetine or Citric acid can be used as antioxidant.