Abstract:
This invention relates to an application of riluzole or its pharmaceutically acceptable salts in the preparation of drugs having radiorestoring properties.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a novel therapeutic application of riluzole (6-trifluoro-methoxy-2-aminobenzothiazole) or the pharmaceutically acceptable salts of this compound. 
     BACKGROUND OF THE INVENTION 
     Riluzole is useful as an anticonvulsant, anxiolytic and hypnotic medicinal product (Patent EP 50,551), in the treatment of schizophrenia (EP 305,276), in the treatment of sleep disorders and depression (EP 305,277), in the treatment of cerebrovascular disorders and as an anaesthetic (EP 282,971). 
     DESCRIPTION OF THE INVENTION 
     It has now been found, surprisingly, that this compound may also be used to promote restoration following radiation. 
     Restoration following radiation is useful in X-ray therapy, in particular in the treatment of cancers, and against other sources of harmful radiation such as those encountered by persons in areas in the vicinity of nuclear explosions. 
    
    
     EXAMPLES 
     The activity of the product has been demonstrated on the rhinencephalon of young rats subjected to an overall gamma irradiation. 
     Irradiation is performed by means of a gamma ray source, cobalt-60. 
     The animals used are 15-day-old male Sprague-Dawley strain rats weighing 28 to 33 g, which are placed in an aerated Plexiglass restraining box undergoing a rotation of 180° in order to carry out homogeneous overall irradiations in a single dose of 1.5 and 2.5 Gy, the dose rate of which is 0.2 Gy per minute. The survival time between irradiation and sacrifice is 6 hours. All the animals are fixed by intra-aortic perfusion of a fixative fluid composed of 1% of paraformaldehyde, 1% of glutaraldehyde and 0.05% of calcium chloride in 0.4M phosphate buffer, pH 7.3. To prevent coagulation, 0.04 ml of heparin is injected into the ventricle, and 0.3 ml of 1% sodium nitrite to clear the vessels of red cells. 
     The animals are anaesthetized by intraperitoneal injection of 3% pentobarbitone sodium. The animals are then laid on their back and fixed to the operating table. The thoracic cage is opened and held open by means of 2 clamps. The heart is thus exposed, the tip of the left ventricle is incised and the perfusion cannula is introduced up to the beginning of the arch of the aorta and clamped. The right atrium is incised and perfusion is performed. Inflow of the perfusion fluid is effected under gravity. After perfusion, the animal&#39;s head is cut off and the brain is removed, immersed in fixative fluid and stored overnight at 4° C. 
     On the day following perfusion, frontal sections of the gyrus dentatus are cut under a binocular magnifier. The fragments collected are immersed in the washing fluid for 5 minutes. They are then dehydrated in alcohol baths of increasing concentration and thereafter included in Araldite. 1-micrometer semi-thin sections are prepared using a Reichert ultramicrotome with glass knives. They are stained in the heated state with a filtered 1% solution of toluidine blue prepared in 1% borate buffer, and then observed using an Orthoplan microscope. 
     The comparative study consists in counting on 3 non-serial sections (separated by 10 micrometers each) for each rat and on an aggregate of 1000 cells (granular and subgranular) in total. The number of pyknotic cells is counted, and then the number of surviving cells observed in this area. This enables the percentage of surviving cells relative to the number of cells in the area to be calculated (percentage survival=100×living cells/living cells+pyknotic cells). 
     The product under study is administered intraperitoneally at doses of 1, 2, 4 and 8 mg/kg, 20 minutes after irradiation (at the beginning of pyknosis). 
     The results obtained are recorded in the following tables, and show that, after treatment with the test product, neuronal degeneration is less than in irradiated controls not receiving a product. 
     
                       TEST 1______________________________________IR-      CONTROLS        RILUZOLE (2 mg/kg)RADIATION    CELLULAR SURVIVAL                    CELLULAR SURVIVAL______________________________________1.5 Gy   88.8%           91.2%2.5 Gy   87.1%           92.2%______________________________________ 
    
     
                                           TEST 2__________________________________________________________________________          RILUZOLE                 RILUZOLE                        RILUZOLE                               RILUZOLE   CONTROLS          1 mg/kg                 2 mg/kg                        4 mg/kg                               8 mg/kg   CELLULAR          CELLULAR                 CELLULAR                        CELLULAR                               CELLULARIRRADIATION   SURVIVAL          SURVIVAL                 SURVIVAL                        SURVIVAL                               SURVIVAL__________________________________________________________________________2.5 Gy  75.35 ± 2.4%          81.99 ± 2.32%                 83.54 ± 1.96%                        86.07 ± 2.78                               85.41 ± 2.14%__________________________________________________________________________ 
    
     As pharmaceutically acceptable salts, the addition salts with inorganic acids, such as hydrochloride, sulphate, nitrate or phosphate, or organic acids, such as acetate, propionate, succinate, oxalate, benzoate, fumarate, maleate, methanesulphonate, isethionate, theophyllineacetate, salicylate, phenolphthalinate or methylenebis(β-hydroxynaphthoate), or substitution derivatives of these derivatives, may be mentioned in particular. 
     The medicinal products consist at least of riluzole, in free form or in the form of an addition salt with a pharmaceutically acceptable acid, in the pure state or in the form of a composition in which it is combined with any other pharmaceutically compatible product, which may be inert or physiologically active. The medicinal products according to the invention may be employed orally or parenterally. 
     As solid compositions for oral administration, tablets, pills, powders (gelatin capsules, wafer capsules) or granules may be used. In these compositions, the active principle according to the invention is mixed with one or more inert diluents such as starch, cellulose, sucrose, lactose or silica, under a stream of argon. These compositions can also comprise substances other than diluents, for example one or more lubricants such as magnesium stearate or talc, a colouring, a coating (dragees) or a varnish. 
     As liquid compositions for oral administration, pharmaceutically acceptable solutions, suspensions, emulsions, syrups and elixirs may be used, containing inert diluents such as water, ethanol, glycerol, vegetable oils or liquid paraffin. These compositions can comprise substances other than diluents, for example wetting, sweetening, thickening, flavouring or stabilizing products. 
     The sterile compositions for parenteral administration can preferably be solutions, aqueous or non-aqueous, suspensions or emulsions. As a solvent or vehicle, water, propylene glycol, a polyethylene glycol, vegetable oils, especially olive oil, injectable organic esters, for example ethyl oleate, or other suitable organic solvents may be employed. These compositions can also contain adjuvants, especially wetting, tonicity, emulsifying, dispersing and stabilizing agents. The sterilization may be carried out in several ways, for example by aseptic filtration, by incorporation of sterilizing agents in the composition, by irradiation or by heating. They may also be prepared in the form of sterile solid compositions which can be dissolved at the time of use in sterile water or any other sterile injectable medium. 
     The doses depend on the effect sought, the treatment period and the administration route used; they are generally between 50 and 800 mg per day via the oral route for an adult, with single doses ranging from 25 to 200 mg of active substance, and between 25 and 600 mg per day via the intravenous route for an adult, with single doses ranging from 12.5 to 200 mg of active substance. 
     Generally speaking, the doctor will determine the appropriate dosage in accordance with the age, the weight and all other factors specific to the subject to be treated. 
     The examples which follow illustrate medicinal products according to the invention: 
     EXAMPLE A 
     Tablets containing a 50 mg dose of active product and having the following composition are prepared according to the usual technique: 
     
         ______________________________________Riluzole            50 mgMannitol            64 mgMicrocrystalline cellulose               50 mgPovidone excipient  12 mgSodium carboxymethylstarch               16 mgTalc                 4 mgMagnesium stearate   2 mgColloidal silica, anhydrous                2 mgMixture of methylhydroxypropyl-cellulose, polyethylene glycol6000 and titanium dioxide(72:3.5:24.5)q.s. 1 finished film-coated tabletweighing 245 mg______________________________________ 
    
     EXAMPLE B 
     Hard gelatin capsules containing a 50 mg dose of active product and having the following composition are prepared according to the usual technique: 
     
         ______________________________________Riluzole            50 mgCellulose           18 mgLactose             55 mgColloidal silica     1 mgSodium carboxymethylstarch               10 mgTalc                10 mgMagnesium stearate   1 mg______________________________________ 
    
     EXAMPLE C 
     An injection containing 10 mg of active product and having the following composition is prepared: 
     
         ______________________________________Riluzole              10     mgBenzoic acid          80     mgBenzyl alcohol        0.06   cm.sup.3Sodium benzoate       80     mgEthanol, 95%          0.4    cm.sup.3Sodium hydroxide      24     mgPropylene glycol      1.6    cm.sup.3Water                 q.s. 4 cm.sup.3______________________________________ 
    
     The invention also relates to the process for preparing medicinal products which can be used to promote restoration following radiation, consisting in mixing riluzole or the pharmaceutically acceptable salts of this compound with one or more compatible and pharmaceutically acceptable diluents and/or adjuvants. 
     The invention also relates to a method for treating a mammal, and in particular man, requiring restoration following radiation, comprising the administration of an effective amount of riluzole or the pharmaceutically acceptable salts of this compound. 
     Although the invention has been described in conjunction with specific embodiments, it is evident that many alternatives and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, the invention is intended to embrace all of the alternatives and variations that fall within the spirit and scope of the appended claims. The above references are hereby incorporated by reference.