USE OF L-CARNITINE DERIVATIVES FOR THE MANUFACTURE OF A MEDICAMENT FOR THE THERAPEUTICAL TREATMENT OF PERIPHERAL NEUROPATHIES

Abstract: The use is disclosed of compounds of general formula wherein: Y is hydrogen, methyl or amino, and R is an unsubstituted or substituted alkyl group selected from methyl, ethyl, 1-methylpropyl, isobutyl, isopropyl, mercaptomethyl and 3-guanidinopropyl and the pharmacologically acceptable salts thereof, for treating degenerative alterations of the nervous system. The compounds can be administered orally or parenterally.

Description: The present invention relates to the use of the acyl derivatives of L-carnitine of formula (I) and of their pharmacologically acceptable salts of formula (I') and (I'') for treating peripheral neuropathies. The acyl derivatives of L-carnitine according to the invention are represented by the following formula (I) wherein: Y is hydrogen, methyl or amino, and R is an unsubstituted or substituted alkyl group selected from methyl, ethyl, 1-methylpropyl, isobutyl, isopropyl, mercaptomethyl and 3-guanidinopropyl. Formula (I) represents the compounds of the present invention as inner salts. The compounds of the present invention also encompass the pharmacologically acceptable salts of the compounds of formula (I) that have formula (I') wherein X⁻ is the anion of a pharmacologically acceptable acid selected from chloride, bromide, orotate, acid aspartate, acid citrate, acid phosphate, acid fumarate, lactate, acid maleate, acid oxalate and acid sulphate. If Y is amino, the pharmacologically acceptable salts of the compounds of formula (I) have general formula (I'') wherein X⁻ has the previously indicated meaning. For the sake of simplicity, reference shall be made hereinbelow to the inner salts of formula (I). However, it should be understood that every disclosure equally applies to the pharmacologically acceptable salts of formula (I') and (I''). Among the compounds of formula (I) the following are preferred: (a) L-isoleucyl L-carnitine: (b) L-leucyl L-carnitine: (c) L-valyl L-carnitine: (d) L-cysteinyl L-carnitine: (e) L-arginyl L-carnitine: (f) isovaleryl L-carnitine: (g) isobutyryl L-carnitine: (h) alpha-methylbutyryl L-carnitine: Among the compounds (a) - (h), isovaleryl L-carnitine is particularly preferred. The compounds of formula (I) are all known compounds. Thus, for instance, the L-amino acylcarnitines (a) - (e) and processes for their preparation are disclosed in the European patent application 87830245.4 (publication n° 0252030). These compounds are useful as hepatoprotecting agents. Isovaleryl L-carnitine is a natural product: it forms by catabolic conversion of L-leucina, one of the essential aminoacids. Patent application GB-A-2 013 496 discloses the use of isovaleryl L-carnitine for the treatment of hipolipoproteinaemias and associated diseases. Isovaleryl L-carnitine can be synthesized by reacting a solution of L-carnitine chloride in trifluoroacetic acid with isovaleryl chloride at room temperature. Upon termination of the reaction, isovaleryl L-carnitine is precipitated by adding ethyl ether to the reaction mixture (m.p. 173-175°C; rotatory optical power - 23 (ç = 1, H₂O) ). Also isobutyryl carnitine and alpha-methylbutyryl carnitine are natural products (see e.g. L.L. Bieber e Y.R. Choi, Isolation and identification of aliphatic short-chain acylcarnitines from beef heart: Possible role for carnitine in branched-chain aminoacid metabolism, in Proc. Natl. Acad. Sci USA, 74 , n. 7, pp 2795-2798, 1977). Methods for synthesizing these acyl derivatives of carnitine are e.g. disclosed by E. Strack and D. Müller, Darstellung von O-acyl-carnitinen, in Hoppe-Seyler's Z. Physiol. Chem. 351 , pp 95-98, 1970 and by T. Bohmer e J. Bremer, Propionylcarnitine, physiological variations in vivo, in Biochim. Biophys. Acta, 152 , pp 559-567, 1968. For these compounds, no previous therapeutical applications are known. The use of an acyl derivative of carnitine, viz. acetyl L-carnitine, for treating a particular class of degenerative alterations of the nervous system, i.e. peripheral neuropathies, has been disclosed already (US patent 4,751,242; European patent application 87830298.3, publication n. 0256999) wherein the definition of peripheral neuropathies is applied to a group of persistent disturbances of the motor neurons of the brain stem and spinal cord and/or the primary sensory neurons and/or the peripheral autonomic neurons, with involvement of the peripheral axons and their attendant supporting structures. The present invention provides, for the use of an acyl L-carnitine (I) or the pharmacologically acceptable salts thereof (I') and (I'') for producing a pharmaceutical composition for the therapeutical treatment of neuronal degenerations i.e. peripheral neuropathies. In practice, from about 1000 to 2000 mg/day of an acyl L-carnitine (I) or an equivalent amount of a pharmacologically acceptable salt thereof (I') and (I'') are administered orally or parenterally. The treatment generally lasts for at least 30 to 60 days and can be prolonged several months. It is apparent that the pharmaceutical compositions that are most suitable having regard to the therapeutical application of the present invention are compositions that, in unit dosage form, comprise from about 500 to about 1000 mg of acyl L-carnitine of formula (I) or an equivalent amount of a pharmacologically acceptable salt thereof of formula (I') or (I'') and a pharmacologically acceptable excipient therefor. Examples of suitable compositions in unit dosage forms are for instance disclosed in the US patent 4,464,393. It will suffice to substitute one of the compounds of the present invention for acetyl carnitine in the compositions of the above-identified patent. The efficacy of the compounds (I), (I') and (I'') in the treatment of the degenerative alterations of the nervous system i.e, peripheral neuropathies was assessed by both pharmacological tests in experimental animals models and in clinical trials. Hereinbelow, some of these experiments are illustrated. PHARMACOLOGICAL TESTS CLINICAL EVALUATION OF FUNCTIONAL RESTORATION FOLLOWING CUTTING AND IMMEDIATE MICROSURGICAL RECONSTRUCTION OF THE SCIATIC NERVE IN RATS. In this test male Wistar rats weighing 200-250 grams were used. Following general anesthesia (Nembutal, 4 mg/100 g e.p.) the sciatic nerve was aseptically isolated at the thigh bilaterally. The nerve was incised just distally to the branch to the gluteus maximus and immediately reconstructed via microsurgical peri-perineural anastomosis. Following surgery the rats were randomly subdivided into six groups and subcutaneously injected according to the following scheme: The treatment began on the first day one minute following surgery and was continued for eight weeks. After this time period, the degree of functional restoration was evalueted according to the following scale proposed by Richardson et al , "Percussive injury to peripheral nerve in rats", J. Neurosurg. 51 , 178-187 (1979), and Zalewsk et al, "An evaluation of nerve repair with nerve allografts in normal and immunologically tolerant rats", J. Neurosurg. 52 , 557-563 (1980): 0 atrophy of the anterior tibial muscle (AT) and toe long extensor TLE), foot drop 1 No atrophy of AT and TLE, foot drop 2 No atrophy of AT and TLE, no foot drop 3 No atrophy of AT and TLE, restoration of foot dorsal flexion 4 No atrophy of AT and TLE, spreading out of toes. RESULTS The degree of functional restorations is reported in the following table: The clinical rating is significantly higher in the rats of groups V and VI treated with isovaleryl L-carnitine and alpha methylbutyryl L-carnitine than in the placebo-treated controls (P ≦ 0.05).

Claims: Claims for the following Contracting States : AT, BE, CH, DE, FR, GB, LI, LU, NL, SE Use of an acyl derivative of L-carnitine, having general formula (I) wherein: Y is hydrogen, methyl or amino, and R is an unsubstituted or substituted alkyl group selected from methyl, ethyl, 1-methylpropyl, isobutyl, isopropyl, mercaptomethyl and 3-guanidinopropyl or a pharmacologically acceptable salt thereof, for producing a medicament for treating peripheral neuropathies. The use of claim 1, wherein the pharmacologically acceptable salt has formula (I') wherein X⁻ is the anion of a pharmacologically acceptable acid selected from chloride, bromide, orotate, acid aspartate, acid citrate, acid phosphate, acid fumarate, lactate, acid maleate, acid oxalate and acid sulphate, and R and Y have the previously defined meanings. The use of claim 1, wherein the pharmacologically acceptable salt has formula (I'') wherein X⁻ is the anion of a pharmacologically acceptable acid selected from chloride, bromide, orotate, acid aspartate, acid citrate, acid phosphate, acid fumarate, lactate, acid maleate, acid oxalate and acid sulphate, and R and Y have the previously defined meanings. The use of claim 1, wherein the compound of formula (I) is selected from L-isoleucyl L-carnitine, L-leucyl L-carnitine, L-valyl L-carnitine, L-cysteinyl L-carnitine, L-arginyl L-carnitine, isovaleryl L-carnitine, isobutyryl L-carnitine and alpha-methylbutyryl L-carnitine. An orally or parenterally administrable pharmaceutical composition comprising isobutyryl- or alpha-methylbutyryl L-carnitine or a pharmacologically acceptable salt thereof as active principle, and a pharmacologically acceptable excipient therefor. An orally or parenterally administrable pharmaceutical composition for the treatment of peripheral neuropathies, comprising isobutyryl- or alpha-methylbutyryl L-carnitine as active principle, and a pharmacologically acceptable excipient therefor. Claims for the following Contracting States: GR, ES A process for producing a pharmaceutical composition for treating peripheral neuropathies. which comprises mixing an acyl derivative of L-carnitine, having general formula (I) wherein: Y is hydrogen, methyl or amino, and R is an unsubstituted or substituted alkyl group selected from methyl, ethyl, 1-methylpropyl, isobutyl, isopropyl, mercaptomethyl and 3-guanidinopropyl or a pharmacologically acceptable salt thereof, with a pharmacologically acceptable excipient therefor. The process of claim 1, wherein the pharmacologically acceptable salt has formula (I') wherein X⁻ is the anion of a pharmacologically acceptable acid selected from chloride, bromide, orotate, acid aspartate, acid citrate, acid phosphate, acid fumarate, lactate, acid maleate, acid oxalate and acid sulphate, and R sand Y have the previously defined meanings. The process of claim 1, wherein the pharmacologically acceptable salt has formula (I'') wherein X⁻ is the anion of a pharmacologically acceptable acid selected from chloride, bromide, orotate, acid aspartate, acid citrate, acid phosphate, acid fumarate, lactate, acid maleate, acid oxalate and acid sulphate, and R and Y have the previously defined meanings.

Inventors: CAVAZZA, CLAUDIO
Applicants: SIGMA-TAU INDUSTRIE FARMACEUTICHE RIUNITE S.P.A.
Application year: 1989
Main classification: A61K31
IPC codes: C07C323, A61P25, C07C279, A61K31, C07C229