Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D489/00—Heterocyclic compounds containing 4aH-8, 9 c- Iminoethano-phenanthro [4, 5-b, c, d] furan ring systems, e.g. derivatives of [4, 5-epoxy]-morphinan of the formula:
  • C07D489/06—Heterocyclic compounds containing 4aH-8, 9 c- Iminoethano-phenanthro [4, 5-b, c, d] furan ring systems, e.g. derivatives of [4, 5-epoxy]-morphinan of the formula: with a hetero atom directly attached in position 14
  • C07D489/08—Oxygen atom
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P11/00—Drugs for disorders of the respiratory system
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
  • A61P25/04—Centrally acting analgesics, e.g. opioids
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P43/00—Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00

Definitions

• the present invention relates to an improved process for producing naltrexone [17- (cyclopropylmethyl)-4,5a-epoxy-3,14-dihydroxy-morphinan-6-one] from noroxymorphone [4,5- a-epoxy-3,14-dihydroxy-morphinan-6-one] by alkylation with a cyclopropylmethyl halide.
• Nalmefene is a known opioid receptor antagonist which can inhibit pharmacological effects of both administered opioid agonists and endogenous agonists derived from the opioid system.
• the clinical usefulness of nalmefene as antagonist comes from its ability to promptly (and selectively) reverse the effects of these opioid agonists, including the frequently observed depressions in the central nervous system and the respiratory system.
• Nalmefene has primarily been developed as the hydrochloride salt for use in the man- agement of alcohol dependency, where it has shown good effect in doses of 10 to 40 mg taken when the patient experiences a craving for alcohol (Karhuvaara et al., Alcohol. Clin. Exp. Res., (2007), Vol. 31 No. 7. pp 1179-1 187). Additionally, nalmefene has also been investigated for the treatment of other addictions such as pathological gambling and addiction to shopping. In testing the drug in these developmental programs, nalmefene has been used, for example, in the form of a parenteral solution (RevexTM).
• RevexTM parenteral solution
• Nalmefene is an opiate derivative quite similar in structure to the opiate antagonist naltrexone. Advantages of nalmefene compared to naltrexone include longer half-life, greater oral bioavailability and no observed liver toxicity.
• Nalmefene can be produced from naltrexone by the Wittig reaction.
• Methods for preparation of nalmefene from naltrexone by the Wittig reaction has been described by Hanh et al., (J. Med. Chem., 18, 259-262(1975), Mallinckrodt (US 4,751 ,307), Meltzner et al., (US patent No. 4,535,157) and by H. Lundbeck (WO 2010/136039).
• the free base of nalmefene is obtained, which subsequently can be converted into the hydrochloride salt by use of conventional methods.
• Naltrexone can be produced from noroxymorphone by various direct and indirect alkylation methods.
• One method is by direct alkylation of noroxymorphone with cyclopropyl- methylbromide. This process has been disclosed in general terms by Rice in WO 91/05768.
• Sanofi-Avensis (WO 2008/034973) describes a process for obtaining naltrexone in 88.6% yield by reacting noroxymorphone hydrochloride with cyclopropylmethylbromide in dimethy- lacetamide in the presence of sodium hydrogen carbonate.
• Cilag (WO 2008/138605) describes N-alkylation of noroxymorphone with cyclopropylmethylbromide in N-methyl- pyrrolidone in the presence of sodium hydrogen carbonate.
• Mallinckrodt (WO 2010/039209) describes N-alkylation of noroxymorphone with cyclopropylmethylbromide in the presence of a protic solvent.
• Specific examples in WO 2010/039209 describe the addition of water, iso- propanol or ethanol as the protic solvent.
• the present invention relates to an improved process for producing naltrexone [17- (cyclopropylmethyl)-4,5a-epoxy-3,14-dihydroxy-morphinan-6-one] from noroxymorphone [4,5- a-epoxy-3,14-dihydroxy-morphinan-6-one] by alkylation of noroxymorphone with a cyclopro- pylmethyl halide in N-ethyl-2-pyrroiidone as depicted in scheme 1 below.
• X is chosen from Br, CI and I
• naltrexone obtained from the process of the invention is further processed e.g. by the Wittig reaction to nalmefene.
• the invention relates to a process for the manufacturing of nalmefene comprising the steps, i) manufacturing of naltrexone by a process of the invention, ii) further processing of naltrexone obtained from i) to nalmefene optionally by the Wittig reaction.
• the invention relates to naltrexone directly obtained by a process of the invention.
• the invention relates to nalmefene obtained from naltrexone, wherein said naltrexone is directly obtained by the process of the invention.
• the invention relates to a pharmaceutical composition
• nalmefene obtained from naltrexone wherein said naltrexone is directly obtained by the process of the invention.
• naltrexone and “nalmefene” are intended to include any forms of the compounds, such as the free base and pharmaceutically acceptable salts.
• the free base and pharmaceutically acceptable salts include anhydrous forms and sol- vated forms such as hydrates.
• the anhydrous forms and the solvates include amorphous and crystalline forms.
• naltrexone is in the form of the free base.
• nalmefene is in the form of the hydrochloride.
• examples of "cyclopropy I methyl halides” include cyclopropyl- methyl bromide, cyclopropylmethyl chloride, cyclopropylmethyl iodide.
• the term “cyclopropylmethyl halide” refers to cyclopropylmethyl bromide.
• non-protic solvent refers to any non-protic solvent.
• non-protic solvents include hydrocarbons, ketones, esters and ethers.
• non-protic solvent refers to toluene.
• an “acid scavenger” refers to a compound selected from organic and inorganic bases, and combinations hereof. Examples include borate salts, phosphate salts, bicarbonate salts (such as KHC0 3 , NaHC0 3 , LiHC0 3 and the like), carbonate salts (such as K 2 C0 3 , Na 2 C0 3 , Li 2 C0 3 and the like), organic bases (such as pyridine, triethyl- amine, tripropylamine, tributylamine, ⁇ , ⁇ -diisopropylethylamine, N-methylmorpholine, N,N- dimethylaminopyridine), and mixtures of any of the above.
• the term “acid scavenger” refers to KHC0 3 .
• the term “acid scavenger” refers to N,N-diisopropylethylamine.
• the term "chemically pure” has its normal meaning within the art. Accordingly, an obtained compound which is at least 98% chemically pure comprises at most 2% chemical impurities.
• the chemical purity may be determined e.g. by HPLC. In the present context chemical purity is determined by % HPLC area.
• the inventors have found an improved process for producing naltrexone [17-
• noroxymorphone is mixed with cyclopropylmethyl halide in N-ethyl-2- pyrrolidone.
• the reaction is conducted in presence of an acid scavenger.
• the mixture is heated to a temperature in the range of 30 to 100°C, preferably in the range of 50-70°C, such as in the range of 50-60°C.
• Reaction time is adjusted in order to have a reasonably high conversion.
• further cyclopropyl methyl halide is added to the mixture and optionally, the mixture is further heated to increase the conversion.
• the formed naltrexone is isolated by a method comprising the following steps a) mixing the reaction mixture with an acid
• noroxymorphone prior to the reaction with cyclopropylmethyl halide; noroxymorphone is mixed with N-ethyl-2-pyrrolidone and a non-protic solvent whereupon the mixture of noroxymorphone, N-ethyl-2-pyrrolidinone and non-protic solvent is concentrated for example by distillation under vacuum.
• the process of the present invention consistently gives pure naltrexone.
• the main impurity coming from alkylation of the hydroxyl group in the phenolic moiety is controlled with the process of the invention.
• the level of the impurity 3-cyclopropylmethylnaltrexone in the isolated naltrexone is below about 0.5% (by area) as measured by HPLC.
• the process of the invention also allows efficient removal of potentially unreacted noroxymorphone in isolated naltrexone.
• Naltrexone prepared according to the method described in this invention can thus be directly used in the preparation of nalmefene e.g. by Wittig reaction. It is also envisaged in the present invention that such obtained nalmefene can be transformed into a suitable pharma- ceutically acceptable salt form such as the hydrochloride salt. In a particular embodiment nalmefene hydrochloride is obtained as dihydrate form.
• the present invention also relates to a pharmaceutical composition
• a pharmaceutical composition comprising nalmefene obtained from naltrexone obtained by the process of the invention.
• the pharmaceutical composition may further comprise at least one pharmaceutically acceptable excipient, carrier and/or diluent, and may be in a solid dosage form, such as a tablet, for oral administration.
• Solid preparations such as tablets, may be prepared by mixing the active ingredients with an ordinary carrier, such as an adjuvant and/or diluent, and subse- quently compressing the mixture in a tabletting machine.
• an adjuvant and/or diluents include: corn starch, lactose, talcum, magnesium stearate, gelatine, lactose, gums, and the like.
• compositions of the invention thus typically comprise an effective amount of nalmefene hydrochloride and one or more pharmaceutically acceptable carriers.
• Nalmefene hydrochloride obtained according to the present invention may be administered in any suitable way, e.g. orally or parenterally, and it may be presented in any suitable form for such administration, e.g. in the form of tablets, capsules, powders, syrups or solutions or dispersions for injection.
• the pharmaceutical composition will comprise nalmefene in a therapeutically effective amount.
• therapeutically effective amount refers to the amount/dose of a compound or pharmaceutical composition that is sufficient to produce an effective response (i.e., a biological or medical response of a tissue, sys- tem, animal or human sought by a researcher, veterinarian, medical doctor or other clinician) upon administration to a patient.
• the “therapeutically effective amount” will vary depending on, inter alia, the disease and its severity, and on the age, weight, physical condition and responsiveness of the patient to be treated. Furthermore, the “therapeutically effective amount” may vary if the compound of the invention is combined with one or more compounds: In such a case the amount of a given compound might be lower, such as a sub-effective amount.
• the amount of nalmefene hydrochloride in a pharmaceutical composition in unit dosage form is amount from about 10 mg to about 100 mg, such as from about 10 mg to about 60 mg, e.g. from about 10 mg to about 40 mg, or about 20 mg.
• nalmefene hydrochloride obtained according to the present invention constitutes an active ingredient in tablets, wherein said tablets further comprises lactose anhydrous, crospovidone, microcrystalline cellulose, magnesium stearate and Opadry OY-S- 28849.
• nalmefene hydrochloride obtained according to the present invention constitutes an active ingredient in tablets with the composition of Table 1.
• Table 1 nalmefene tablet composition, exemplary embodiment
• a pharmaceutical composition of the present invention may be used for reduction of alcohol consumption in patients with alcohol dependence.
• a composition comprising nalmefene HCI obtained by the present method may be used for the manufacture of a medicament for reduction of alcohol consumption in patients with alcohol dependence.
• the invention in another embodiment, relates to a method for treating alcohol dependency, comprising administering a therapeutically effective amount of nalmefene HCI obtained by the present method, or a pharmaceutical composition thereof, to a patient in the need thereof.
• alcohol dependency is a commonly known term for a skilled person.
• DSM-IVTR Diagnostic and Statistical Manual of Mental Disorders
• the term "alcohol dependency” is defined as the presence of three or more of the seven areas of life impairment related to alcohol in the same 12-month period. These impairments include tolerance, evidence of a withdrawal syndrome when alcohol is discontinued or intake is decreased, potential interference with life functioning associated with spending a great deal of time using alcohol, and returning to use despite evidence of physical or psychological problems.
• the first embodiment is denoted E1
• the second embodiment is denoted E2 and so forth.
• a process for the manufacturing of naltrexone comprising reacting noroxymorphone with cyclopropylmethyl halide in the presence of N-ethyl-2-pyrrolidone.
• reaction temperature is in the range of about 30-100°C.
• E42 Naltrexone directly obtained from the process according to any of embodiments 1 -33.
• E43 Nalmefene directly obtained from the process according to any of embodiments 34- 40.
• Buffer 1.1 g of Sodium Octanesulfonate dissolved in 1 L of water, pH adjusted to 2.3 with H 3 P0 4 .
• Noroxymorphone (51.5 g) in N-ethyl-2-pyrrolidone (168 ml) and toluene (100 ml) was concentrated under vacuum at 80-85°C. Toluene was added (200 ml) and vacuum distillation repeated. Potassium bicarbonate (24.4 g) and cyclopropyimethyl bromide (29.3 g) were added and the mixture was heated up to 60°C and maintained at that temperature for 22 hours. Further cyclopropyimethyl bromide (2.3 g) was charged and stirred at 60°C for five additional hours.
• the composition of the reaction mixture was checked by HPLC: noroxymorphone 1.5%, naltrexone 97.4% and 3-cyclopropylmethyl naltrexone 0.3%.
• the reaction mixture was treated with HCI 10% (88.9 g) and concentrated under vacuum.
• the mixture was cooled and diluted with water (1580 g).
• Ammonium hydroxide 4% in water was added over 3 hours obtaining a suspension (pH 9.3).
• the suspension was stirred and then filtered.
• the solid was washed with water and dried under vacuum at 60°C obtaining 55.9 g of naltexone.
• HPLC analysis (% by area): naltrexone 99.0%, noroxymorphone 0.1%, 3-cyclopropylmethyl naltrexone 0.3%.
• Noroxymorphone (52.7 g) in N-ethyl-2-pyrrolidone (100 ml) and toluene (100 ml) was concentrated under vacuum. Toluene was added (100 ml) and vacuum distillation repeated two more times. The mixture was diluted with N-ethyl-2-pyrrolidone. Cyclopropyimethyl bromide (30.5 g) and N,N-diisopropylethylamine (29.2 g) were added and the mixture was heated up to 60°C and maintained at that temperature for 17 hours. The composition of the reaction mix- ture was checked by HPLC (% by area): naltrexone 95.0%, noroxymorphone 3.3%, 3- cyclopropyl methyl naltrexone 0.3%.
• a mixture of noroxymorphone (60 Kg, 0.209 Kmol), N-ethyl-2-pyrrolidinone (180 kg), cyclo- propymethyl bromide (36.6 kg) and N,N-diisopropylethylamine (35.1 kg) was heated to 52- 57°C for 20 hours and 10 minutes.
• a mixture of noroxymorphone (60 Kg, 0.209 Kmol), N-ethyl-2-pyrrolidinone (180 kg), cyclo- propymethyl bromide (36.6 kg) and N,N-diisopropylethylamine (35.1 kg) was heated to 52- 57°C for 18 hours and 30 min.
• a mixture of noroxymorphone (62 Kg), N-ethyl-2-pyrrolidinone (186 kg), cyclopropymethyl bromide (37.8 kg) and N,N-diisopropylethylamine (36.2 kg) was heated to 52-57°C for 24 hours and 45 min.

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