Compounds destined for encapsulation in erythrocytes, new derivatives of naloxone and naltrexone.

0001This invention carried out in the following Laboratories: Laboratory of Bioorganic and Analytical Chemistry - University of Orleans; Transfusion Biopharmacology Laboratory-CRTS of Tours; Laboratory of Fundamental Pharmacology and Toxicology-CNRS of Tours, relates to chemical compounds useful in particular for the erythrocyte internalization of biologically active compounds and more particularly to new derivatives of naloxone and naltrexone.

0002Encapsulations of substances have already been carried out in erythrocytes (Green R. and Al, The LANCET (1980); p 327; ROPARS, NICOLAU, CHASSAIGNE - FR 82 11749)

0003However, the use of red blood cells for the transport of hydrophobic drugs still poses difficulties today when interacting with this type of drug with the erythrocyte membrane. There is either a more or less rapid leakage of the vector, or a considerable adsorption which does not allow internalization of the product.

0004One of the objects of the present invention is precisely to propose a solution to the aforementioned problem.

0005More particularly the present invention relates to a derivative intended for the encapsulation in erythrocytes of a hydrophobic biologically active compound characterized in that it consists of said biologically active compound chemically coupled to a chemical group of hydrophilic nature by an element of bond which is cleaved by lysosomal and / or plasma enzymes but which is stable in erythrocytes.

0006Such chemical compounds by their structure exhibit an accentuated hydrophilic character, a weak interaction with the erythrocyte membrane and a chemical stability with regard to the various enzymes present in this type of cells. Finally, during the destruction of erythrocytes by the phagocytic system, they can be cleaved by lysosomal or plasma enzymes and thus release the drug.

0007The hydrophilic chemical group used according to the invention can be a chain containing one or more sugars and / or one or more amino acids. It can also be a phosphate, polyphosphate or other hydrophilic function.

0008Among the chemical compounds which are the subject of the present invention, particular mention will be made of new derivatives of naloxone, naltrexone, and naltrexol.

0009Naloxone is a pure and specific antagonist of morphinomimetics without agonist effect.

0010The present invention therefore also relates to a chemical compound according to the invention characterized in that it is represented by the general formula I:<chemistry id="chem0001" num="0001"><img file="EP0442769A2_D0001.tif" /></chemistry> in which :<ul id="ul0001" list-style="dash"><li>is <b>A₁</b> represents the group OH and A₂ is the hydrogen atom, ie A₁ and A₂ together with the carbon atom to which they are attached form a carbonyl group<chemistry id="chem0002" num="0002"><img file="EP0442769A2_D0002.tif" /></chemistry></li><li><b>R₁</b> represents a group -CH₂-CH = CH₂ or<chemistry id="chem0003" num="0003"><img file="EP0442769A2_D0003.tif" /></chemistry></li><li><b>OR₂</b> represents a sulfate group or a phosphate or polyphosphate group of formula II:<chemistry id="chem0004" num="0004"><img file="EP0442769A2_D0004.tif" /></chemistry> in which :<ul id="ul0002" list-style="none"><li>. R₄ is chosen from C₁₋₃ alkoxy, OH and its alkali salts,</li><li>. X is an alkali cation and preferably Na⁺, and</li><li>. n represents an integer from 1 to 3, and</li></ul></li><li><b>OR₃</b> represents OH or a sulfate group, provided that if R₁ represents -CH₂-CH = CH₂ and <b>AT</b> a CHOH, OR₂ and / or OR₃ group are different from a sulfate group.</li></ul>

0011The derivatives of naloxone and of naltrexone are esters of naloxone and of naltrexone obtained by grafting on the hydroxyl in position 3 of a monophosphate or polyphosphate group or, on the hydroxyls in positions 3 and / or 14, of sulfate groups .

0012Among these compounds, mention will be made most particularly of the derivatives in which OR₃ represents an OH group and OR₂ a phosphate or triphosphate group of formula II.

0013These compounds of general formula I are useful as prodrugs of naloxone or naltrexone. Due to their hydrophilic nature, they can be satisfactorily internalized in red blood cells. Finally, during the destruction of said red blood cells, they are hydrolyzed in vivo and then release the molecule from the biologically active compound, that is to say naloxone or naltrexone.

0014These compounds are obtained by esterification of at least one hydroxyl of naloxone or of naltrexone.

0015While naloxone disulfate in position 3 and 14 and monosulfate in position 3 have already been described in the literature (Linder C. and Fishman J., J. Medicinal Chem. <u style="single">16</u>, 553, 1973), the various sulfates of naltrexone were still unknown today.

0016Based on the previous cited works, the inventors have therefore, after modification of the operating protocol, isolated the two naltrexone derivatives sought. Obtaining the disulfate involves direct sulfation, that of the monosulfate in position 3 a blocking and unblocking process using acetic esters.

0017In the context of the preparation of the phosphate derivatives of general formula 1, the treatment of naloxone or naltrexone with the chlorinated derivative, generated from dimethylphosphite, allows, under appropriate conditions, the selective esterification of the hydroxyl in position 3.

0018The esters thus prepared and subjected to the action of sodium iodide then give rise to the corresponding monosodium phosphates.

0019Thus, the condensation on the naloxone of cyanoethyl N, N-diisopropylchlorophosphoramidite within methylene chloride in the presence of diisopropylethylamine leads to the monoester in position 3, which by the action of cyano-2-ethanol and tetrazole then oxidation by means of tert hydroperoxide. butyl, generates the corresponding phosphate. The cyanoethyl protective groups are eliminated by ammonia within methanol, the ammonium salt is then transformed into a soda-like analog by passage over an ion exchange resin.

0020As far as naltrexone is concerned, the sequence used uses tetrabenzyl pyrophosphate. Thus, lithium or sodium phenate, obtained by treatment of naltrexone respectively with disopropylamide at low temperature or with sodium hydride at room temperature, is easily phosphorylated by means of the pyrophosphate previously mentioned.

0021The hydrogenolysis of the ester formed, followed by chromatography on an ion exchange resin, then makes it possible to isolate the desired disodium salt.

0022The same process can be used with naloxone except that due to the allylic double bond, the cleavage of the benzyl esters is carried out with trimethylsilyl bromide.

0023From the monophosphate derivatives of naloxone and naltrexone, it can then be carried out the preparation of triphosphate derivatives using 1,1 ′ carbonyldiimidazole, followed by treatment with pyrophosphate.

00246-β-naltrexol-3-phosphate is obtained by treatment of 6-β-naltrexol with tetrabenzyl pyrophosphate under the same conditions as those described above, 6-β-naltrexol itself being generated from naltrexone according to the literature (Chatterjie et al., J. Med. Chem., <u style="single">18</u>, 490, 1975).

0025As regards the compounds according to the invention of general formula I, it is also important to study their properties of interaction with the various tissues of opioid receptors: affinity and selectivity.

0026Therefore, in order to appreciate these, it was tested the ability of some derivatives of naloxone and naltrexone to bind to a specific receptor for these.

0027It is known that the multiplicity of effects generated by analgesics of the morphine type results from the simultaneous (non-selective) activation by the latter of several types -µ, δ and k- of specific central and peripheral receptors whose binding properties <u style="single">in vitro</u> and regional distributions have been clearly differentiated. At the present time, many ligands specific to opioid sites are known.

0028Thus, µ, δ and k type opioid sites coexist in the brains of mammals but in different proportions depending on the species. The percentages of µ, δ and k type opioid sites are 46, 42 and 11 respectively in the rat brain, 24, 32 and 44 in the guinea pig brain 43, 19 and 38 in the rabbit brain. Nevertheless, certain "preparations" contain a particular type of opioid site in very high proportion: the rabbit cerebellum contains 80% of sites of type µ, the hybrid cells neuroblastoma x glioma NG 108-15: 100% of sites of type δ and the guinea pig cerebellum: 85% of type k sites.

0029In addition, differential allosteric regulation of the connection has been demonstrated. <u style="single">in vitro</u> agonists and antagonists not only at the δ type site but also at the µ and k type sites: the binding of an agonist is strongly inhibited in the presence of Na⁺ ions and of 5′-guanylylimidodiphosphate (GppNHp) whereas, under these conditions, the fixation of an antagonist is not.

0030The naloxone and naltrexone derivatives which are the subject of the present invention are also characterized by a satisfactory apparent affinity for the opioid sites μ and k.

0031The present invention also relates to pharmaceutical compositions characterized in that they comprise, as active principle, at least one compound according to the invention.

0032According to a preferred embodiment of the invention, a compound of general formula I will be used.

0033The compounds of general formula I can also be used according to the invention as prodrugs of naloxone or naltrexone.

0034The present invention also relates to resealed erythrocytes containing at least one derivative according to the invention.

0035By resealed erythrocyte is intended to denote an erythrocyte which has undergone lysis and then a reconstitution of the erythrocyte membrane.

0036The examples given below without implied limitation will make it possible to demonstrate other characteristics of the present invention.

<u style="single">EXAMPLE 1</u>

:

Preparation of the disulphated derivatives of naloxone and naltrexone in positions 3 and 14

00370.30 mmol of naloxone hydrochloride (or naltrexone) are stirred in the presence of an excess of dicyclohexylcarbodiimide (3.13 mmol) in dimethylformamide (4 ml). The whole is maintained at 0 ° C. A volume of 0.5 ml of a cold solution of H₂SO₄ (0.2 ml, 3.47 mmol) is added to the mixture. After 1 hour of stirring at 0 ° C, the mixture is adjusted to pH9 with NH₄OH (10%) and the dicyclohexylurea is eliminated. After evaporation, the residue obtained is dissolved in 1 ml of DMF, then filtered to remove the inorganic salts. The 3,14-disulfate derivative precipitates with ethyl acetate. Filtration gives a white product.<chemistry id="chem0005" num="0005"><img file="EP0442769A2_D0005.tif" /></chemistry>

Description of the compounds

:

0038<chemistry id="chem0006" num="0006"><img file="EP0442769A2_D0006.tif" /></chemistry>

<u style="single">EXAMPLE 2:</u>

Preparation of the monosulfate derivative of naloxone and naltrexone in position 3

0039The diacetylation of naloxone (or naltrexone) (0.46 mmol) in the presence of 4 ml of acetic anhydride is carried out at reflux for one hour. After evaporation, the residue is dissolved in dichloromethane, and extracted several times using an aqueous solution of 5% NaOH and then with water. The organic phase is evaporated, and the product is purified by passage over a column of silica (eluent: MeOH-CH₂Cl₂: 1/9).<chemistry id="chem0007" num="0007"><img file="EP0442769A2_D0007.tif" /></chemistry>

Description of the compounds

:

0040<chemistry id="chem0008" num="0008"><img file="EP0442769A2_D0008.tif" /></chemistry>

00410.33 mmol of the 3.14-acetate compound are hydrolyzed by the action of 12 ml of an aqueous solution of H₂SO₄ at 4% for 24 hours at room temperature. The reaction mixture is adjusted to pH8 with NH₄OH (10%), and extracted with dichloromethane. After drying and evaporation of the organic phase, the 14-acetate derivative is purified on a silica column (eluent: MeOH-CH₂Cl₂: 1/9).<chemistry id="chem0009" num="0009"><img file="EP0442769A2_D0009.tif" /></chemistry>

Description of the compounds

:

0042<chemistry id="chem0010" num="0010"><img file="EP0442769A2_D0010.tif" /></chemistry><chemistry id="chem0011" num="0011"><img file="EP0442769A2_D0011.tif" /></chemistry>

0043A mixture of 14-acetate derivative (0.26 mmol) and DCCI (3.00 mmol) is stirred in 3 ml of DMF, to which is then added 1 ml of a cold solution of H₂SO₄ (0.029 ml, 0.518 mmol ) in DMF at 0 ° C. After one hour of stirring, the dicyclohexylurea is removed by simple filtration, after having basified the reaction mixture with NH₄OH (10%) at pH9. The residue obtained, dissolved in 2 ml of DMF, is again filtered to remove the inorganic salts. The product precipitates by action of ethyl acetate.<chemistry id="chem0012" num="0012"><img file="EP0442769A2_D0012.tif" /></chemistry>

Description of the compounds

:

0044<chemistry id="chem0013" num="0013"><img file="EP0442769A2_D0013.tif" /></chemistry>

0045The transition to the 3-monosulfate derivative is done by treatment of (0.10 mmol) of the 3-sulfate-14-acetate compound with a dilute solution of NH₄OH (20 ml, pH9). The hydrolysis is maintained for 2 hours at room temperature with constant stirring. After evaporation, the monosulfate dissolved in 1 ml of DMF precipitates in the presence of ethyl acetate.<chemistry id="chem0014" num="0014"><img file="EP0442769A2_D0014.tif" /></chemistry>

Description of the final compounds

0046<chemistry id="chem0015" num="0015"><img file="EP0442769A2_D0015.tif" /></chemistry>

<u style="single">EXAMPLE 3:</u>

Preparation of monosodium monophosphates of naloxone and naltrexone

0047At -10 ° C with stirring, dropwise added to a mixture of 1 eq of naloxone (or naltrexone) dissolved in dichloromethane and 5 eq of triethylamine, 3 eq of (CH₃O) ₂P (O) Cl (diluted 20 times in benzene). At the end of the addition, the mixture is brought to room temperature and then stirred for 48 hours. After concentration to dryness, the residue is taken up in dichloromethane. Then a wash is carried out with 5% bicarbonate and then quickly with water, to obtain the dimethyl phosphate derivative with yields of:<chemistry id="chem0016" num="0016"><img file="EP0442769A2_D0016.tif" /></chemistry>

0048Demethylation is carried out by means of an excess of sodium iodide (5 eq) in acetone, and leads to monosodium monophosphate.<chemistry id="chem0017" num="0017"><img file="EP0442769A2_D0017.tif" /></chemistry>

Description of the compounds

:

0049<chemistry id="chem0018" num="0018"><img file="EP0442769A2_D0018.tif" /></chemistry>

<u style="single">EXAMPLE 4:</u>

Preparation of disodium monophosphate derivatives of naloxone and naltrexone

1)

Phosphorylation by 2-cyanoethyl-N, N-diisopropylchlorophosphoramidite

I

0050Treatment of naloxone (or naltrexone) (0.55 mmol) with 2-cyanoethyl N, N-diisopropylchlorophosphoramidite (0.72 mmol) in dichloromethane in the presence of N-ethyl- N, N-diisopropylamine (1.07 mmol) , leads to the corresponding monoester with a yield of 99%. The reaction is carried out under argon at room temperature for 1 hour. Then by the action of cyano-2-ethanol (0.55 mmol) and tetrazole (0.65 mmol) for 1 hour, then oxidation with tert-hydroperoxide. butyl (0.2 ml) for 1 h 20 the phosphate derivative is obtained, the cyanoethyl protective groups of which are removed by ammonia in methanol. This derivative is then transformed into disodium phosphate by passage over an ion exchange resin. Yield: 55%.

2) Phosphorylation by tetrabenzyl pyrophosphate (TBPP)

0051Two methods are described:<ul id="ul0003" list-style="none"><li><b>AT)</b> To a solution at 0 ° C. of naloxone (or naltrexone) (0.15 mmol) in the presence of lithium diisopropylamide (0.16 mmol) in tetrahydrofuran, the following are added at -78 ° C., under argon, (0.322 mmol) TBPP. The mixture is kept for 1 hour at -78 ° C, then brought back to 0 ° C. A saturated bicarbonate solution at 0 ° C. is added. After extraction with dichloromethane, the isolated product is purified on a silica column (eluent: MEOH-CH₂Cl₂: 5/95).<chemistry id="chem0019" num="0019"><img file="EP0442769A2_D0019.tif" /></chemistry></li><li><b>B)</b> To a solution of naloxone (or naltrexone) (1.33 mmol) in THF is added (1.33 mmol) of NaH, under argon at room temperature. After 10 min, the TBPP (1.94 mmol) in solution in THF is then added. The mixture is kept at room temperature for 18 hours. The same treatment as that used in the method<b>AT</b> allows to isolate the desired products with better yields.</li></ul><chemistry id="chem0020" num="0020"><img file="EP0442769A2_D0020.tif" /></chemistry>

Description of the compounds

:

0052<chemistry id="chem0021" num="0021"><img file="EP0442769A2_D0021.tif" /></chemistry>

Protection

0053In the case of naltrexone dibenzylphosphate, hydrogenolysis, H₂ / Pd in ​​MeOH is carried out, followed by chromatography on ion exchange resin. Yield: 84%.

0054Due to the allylic double bond present in naloxone, debenzylation takes place with trimethylsilyl bromide, followed by purification by chromatography on a DEAE Trisacryl, M column. This derivative is then transformed into disodium phosphate by passage over an ion exchange resin. Yield: 68%.

Description of the compounds

:

0055<chemistry id="chem0022" num="0022"><img file="EP0442769A2_D0022.tif" /></chemistry>

<u style="single">EXAMPLE 5</u>

:

0056<b>Preparation of triphosphate derivatives of naloxone and naltrexone.</b>

0057Naloxone 3-monophosphate (or naltrexone) (0.24 mmol) is converted to the pyridinium salt by passage through a DOWEX 50X8 ion exchange column (pyridinium form). Treatment of the aqueous solution thus obtained with tributylamine (0.48 mmol), followed by several co-evaporations using dry pyridine and dimethylformamide, results in the bis-tributylammonium salt of the corresponding monophosphate.

0058This salt is then dissolved in dimethylformamide, to which is added (1.49 mmol) 1,1′-carbonyl-diimidazole (CDI). The reaction mixture is maintained at room temperature, under argon, overnight. After removing the excess CDI by adding methanol (1.98 mmol), the activated ester is obtained.

0059The tetrasodium pyrophosphate decahydrate (1.19 mmol) is transformed into the corresponding tetra-butylammonium salt in the form of a gum according to the identical protocol described above. The latter, dissolved in the DMF, is added to the starting activated ester. The reaction is kept for 45 hours at room temperature under argon. After evaporation, the product is purified by DEAE-Trisacryl M ion exchange chromatography (CH₃COO⁻) eluted with a continuous gradient (0-0.5 M of an aqueous solution of ammonium acetate). The fraction thus obtained corresponding to the pure product is lyophilized. Yield: 50%.

0060All the stages of this synthesis were checked by chromatography on a thin layer of silica (eluent: isopropyl alcohol / 27% NH₄OH solution / water: 6/3/1).

Description of the compounds

:

0061<chemistry id="chem0023" num="0023"><img file="EP0442769A2_D0023.tif" /></chemistry>

<u style="single">EXAMPLE 6 Preparation of 6-β-naltrexol-3-phosphate,</u>

1)

Reduction of naltrexone to 6-β-naltrexol

(According to Chatterjie et al., J. Med. Chem.,

18

, 490, 1975).

0062A solution of naltrexone.HCl (1mmol) in 25 ml of water is treated with a minimum of a solution of NaOH (320 mg in 25 ml of water) to an alkaline pH. The alkaline mixture is treated with formamidine sulfinic acid (4 mmol) dissolved in the rest of the NaOH solution used previously. The reaction mixture is stirred for one hour at 85 ° C., under argon. The pH is adjusted to 9.8 with a few of an HCl solution (6N) and a sodium carbonate-bicarbonate buffer. After extraction with dichloromethane, the isolated product is purified on a silica column (eluent: MeOH-CH₂Cl₂: 5/95). Yield: 73%.

Description

:

0063NMR (CDCl₃): 3.45-3.68 ppm (m, H6); 4.55 ppm (d, H5, J = 6 Hz); 6.55 and 6.70 ppm (2d, H1 and H2, J = 8 Hz).

2)

Phosphorylation by tetrabenzyl pyrophosphate.

0064To a solution of 6-β-naltrexol (0.52 mmol) in THF is added (0.52 mmol) of NaH, under argon. The TBPP (0.79 mmol) in solution in THF is then added. The reaction mixture is kept overnight at room temperature. The same treatment as that mentioned in method A makes it possible to isolate 6-β-naltrexol-3-dibenzylphosphate with a yield of 80%.

Description

:

0065NMR (CDCl₃): 3.36-3.49 ppm (m, H6); 4.50 ppm (d, H5, J = 6.20 Hz); 5.13 and 5.20 ppm (2d, PhCH₂O, J = 8.2 Hz); 6.57 ppm (d, H1, J = 8 Hz); 6.90 ppm (d, H2, J = 8 Hz) and 7.24-7.42 ppm (m, aromatic H).

3) Deprotection

0066Hydrogenolysis is carried out, H₂ / Pd in ​​MeOH, followed by chromatography on an ion exchange resin. Yield: 77%.

Description

:

0067IR (KBr): ν (P = O) 1240 cm⁻¹.

0068The biological behaviors of certain chemical compounds were then studied.

<u style="single">EXAMPLE 7</u>

:

0069First, we assessed the internalization yields of 5 compounds according to the invention, derived from naloxone or naltrexone. The results are presented in Table I.<tables id="tabl0001" num="0001"><img file="EP0442769A2_D0024.tif" /></tables>

<u style="single">EXAMPLE 8:</u>

0070These compounds have also been tested for their membrane absorption and erythrocitary and plasma stability.

0071The results are presented in Table II:<tables id="tabl0002" num="0002"><img file="EP0442769A2_D0025.tif" /></tables>

<u style="single">EXAMPLE 9</u>

:

0072In vitro screening of naloxone and naltrexone derivatives as opioid ligands of µ or k type.

Animals

0073The animals used are New Zealand rabbits of approximately 1500 g and tricolor guinea pigs of approximately 300 g.

Crude membrane fraction

0074The preparation used is a crude membrane fraction obtained from fresh tissue (rabbit cerebellum, guinea pig cerebellum) by a standard method of homogenization and differential centrifugation. The final suspension is in tris-HCl buffer (50 mM, pH 7.4) and contains approximately 5 mg of protein per ml.

Radioligand

0075[15.16 (n) -³H] diprenorphine at 25-30 CI / mmol (Amersham International plc, Amersham, England).

Competition experiences

0076Radioligand (0.3 pmol) of [³H] diprenorphine and crude membrane fraction (0.25 mg of protein) are incubated for 1 hour at 25 ° C in a final volume of 1.0 ml in Tris-HCl buffer (50 mM , pH 7.4):<ul id="ul0004" list-style="none"><li>(i) in the absence of any competing drug,</li><li>(ii) in the presence of 12 increasing concentrations of the new drug and,</li><li>(iii) in the presence of 10 µmol / l of non-radioactive diprenorphine.</li></ul>

0077The content of each tube is then quickly filtered (under vacuum) on fiberglass discs (Whatman GF / B) placed on a set of Millipore model 1225 filtration ramps. The filters are rinsed with 2 x 3 ml of cold buffer ( O-2 ° C) then dried under an IR lamp for 15 minutes. The radioactivity of each filter in 3 ml of Ready-sol MB cocktail (Beckman) is counted with a Kontron model MR 300 liquid scintillation counter.

Data analysis

0078From the measured parameters, the various constants K are then calculated_x for the sites considered.

0079Table III shows the characteristic parameters of inhibition by naloxone, naltrexone and their derivatives -3-phosphate, -3-phosphate (OMe), -3-triphosphate, -3-sulfate and -3,14- disulfate of the equilibrium binding of (³H) diprenorphine (0.3 nmol / l) in a crude membrane fraction of rabbit cerebellum (type opioid sites) and in a crude membrane fraction of guinea pig cerebellum (sites type k opioids).

0080These values ​​were calculated from the measured values ​​of the IC.50 concentrations of drug inhibiting by 50% the equilibrium binding of (3H) diprenorphine used at the fixed concentration of 0.3 nM.

0081The lower the value of K, the higher the affinity of the chemical compound for the binding site.

0082It can thus be noted that the 3-phosphate derivatives have retained an excellent apparent affinity for the opioid sites μ and k. Naloxone 3-phosphate even appears to have slightly higher activity than naloxone for both types of opioid sites.<tables id="tabl0003" num="0003"><img file="EP0442769A2_D0026.tif" /></tables>