3-DEAZAGUANINE SULPHONIC ACID SALTS

Abstract: Certain substituted sulphonic acid salts of 6-amino-1,5-­ dihydro-4 H -imidazo[4,5-c]pyridin-4-one (also known as 3-deaza­ guanine) are disclosed. These salts are highly water-soluble and are useful for preparing pharmaceutical dosage forms of 3-­ deazaguanine as the active ingredient.

Description: 3-DEAZAGUANINE SULPHONIC ACID SALTS This invention relates to novel watersoluble sulphonic acid salts of 3-deazaguanine. At some parts in the specification there are references to a radical R1, which is the same as the radical R1 referred to elsewhere. The abbreviations Ac, Me and Et appearing hereinbelow represent acetyl, methyl and ethyl, respectively. The abbreviation q.s. appearing hereinbelow means "as required (up to the desired total volume)". The compound 6-amino-i, 5ihydro-4H- imidazo[4,5-c]pyridin-4one (3-deazaguanine) is described and claimed in US Patent 3,896,135. The patent describes the compound as possessing antiviral and antibacterial activity. More recent reports have described the compound as also possessing antitumor activity J. Am. Chem. Soc. 98, 1492 (1976). Drug administration by the parenteral route, especially the intravenous route, for this last indication is preferred. The US Patent also discloses that 3-deazaguanine forms salts with bases such as sodium hydroxide and with acids such as hydrochloric and sulfuric. Unfortunately, investigation has shown that these salts are not suitable for preparing parenteral dosage forms. Thus, the sodium salt solution possesses a pH at which 3-deazaguanine is unstable. The hydrochloride and sulfate salts are poorly soluble so that administration of aqueous parenteral solutions of these salts is impractical. In fact, it has been found that the sulfate salt is only ca. 1/2 as soluble as the corresponding free base. This observation is quite surprising and is the reverse of the characteristic increase in solubility of acid addition salts of basic compounds. The present invention provides certain substituted sulfonic acid salts of 3eazaguanine. These salts are unexpectedly highly water soluble and may be utilized to produce convenient pharmaceutical dosage forms. In particular, the salts may be utilized to produce dosage forms which are suitable for parenteral administration. The parenteral dosage forms may be in the form of solutions, suspensions or dry solids which may be reconstituted with a suitable liquid prior to administration. The invention in its generic chemical compound aspect is a compound having the structural formula I EMI3.1 wherein R is phenyl or R1CH2 wherein R1 is hydrogen or alkyl of from one to six carbon atoms which may be substituted with one or more hydroxyl groups. The invention in a first subgeneric chemical compound aspect is a compound defined by structural formula I wherein R1 is hydrogen or unsubstituted alkyl of from one to six carbon atoms. The invention in a second subgeneric chemical compound aspect is a compound defined by structural formula I wherein R1 is alkyl of from one to six carbon atoms which is substituted with one or more hydroxyl groups. The invention as species of the compound defined by structural formula I are those species wherein R1 is hydrogen; R1 is methyl; R1 is hydroxymethyl; and R is phenyl. The invention in a pharmaceutical composition aspect is a stable, solid water soluble composition suitable for reconstitution with a pharmaceutically acceptable solvent, useful for the preparation of a stable solution containing the equivalent of a least 15 mg/ml of 3-deazaguanine free base, said composition being prepared by the steps of: 1) preparing a solution of a compound having the structural formula EMI4.1 wherein R is defined hereinabove; and 2) removing the solvent from the so prepared solution. The free base, 6-amino-1,5-dihydro-4H imidazo[4,5-c]pyridin-4-one, 3-deazaguanine, may be prepared by procedures described in US Patent 3,896,135. The teachings of this patent are incorporated herein by reference. The substituted sulfonic acids utilized to prepare the final compounds of the invention are either commercially available or they may be prepared by standard procedures known in the art. The salts of the invention may be prepared by standard procedures. Thus, approximately equal equivalent amounts of 3-deazaguanine base and the desired salt forming substituted sulfonic acid are combined in a convenient volume of a solvent such as water to obtain complete solution. The solvent may be removed, for example by lyophilization, and the residue may be purified if desired. For example the salt may be recrystallized. Alternatively, approximate equal equivalent amounts of 3eazaguanine and the desired acid may be combined in a minimum volume of solvent to produce a suspension. The suspension may be moderately heated if desired to promote complete solution. The so produced salt may be isolated and purified as described above. Solvents other than water may be utilized for the preparation of the salt. Examples of such solvents are alcohols such as methanol, ethanol, propanol, and the like; ketones such propanone, butanone, and the like; N,N-dimethylformamide; dimethylsulfoxide as well as mixtures thereof. For preparing individual sterile dosage forms, the appropriate volume of solution containing a compound of the invention may be sterile filtered into previously sterilized containers such as vials. The solvent may be removed by distillation or lyophilization and the containers may be closed as by sealing or capping. The so produced dosage forms may be reconstituted with an appropriate solvent or suspending medium prior to use. Such appropriate solvents or media are exemplified by pharmaceutically acceptable solvents or mixtures thereof such as distilled water, sterile water, sterile isotonic media such as glucose solution, ethanol, ethylene glycol, propylene glycol, and the like; as well as mixtures thereof. The reconstituted dosage form may be in the form of a solution such that would be useful for intravenous administration for example, or in the form of a suspension useful for intramuscular administration. Similar individual sterile dosage forms may also be prepared by sterile filling appropriate containers with a compound of the invention which is in dry solid form. Procedures for performing the dry sterile fill operation will be familiar to those skilled in the art. The compounds of the invention may also be utilized to prepare other dosage forms. For example tablets, capsules, powders, and suppositories may be prepared by standard methods. The alkyl groups contemplated by the invention designated by the symbol R1 may be both branched and straight chain of from one to about six carbon atoms. Examples of such groups are methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, 3methylpentyl, hexyl, and the like. The preferred alkyl groups are comprised of from one to about three carbon atoms. The alkyl groups, in addition, may be substituted with one or more hydroxyl groups. Those skilled in the art will recognize that only one hydroxyl group may be substituted on any particular carbon atom. The preferred hydroxylated alkyl groups contain up to about three carbon atoms and therefore contain no more than three hydroxyl groups, each located on different carbon atoms of the chain. Examples of the preferred hydroxylated alkyl groups are HOCH2, HOCH2CH2, EMI6.1 EMI6.2 and the like. A preferred specie of the invention is that wherein R1 is hydrogen, i.e., 3-deazaguanine methanesulfonic acid salt. Certain alkyl groups of the invention may possess an asymmetric carbon atom and therefore optical isomers may be possible. The pure isomers as well as mixtures thereof including racemic mixtures are contemplated by the invention. The compounds of the invention may exist in unsolvated as well as solvated forms, including hydrated forms. In general, the solvated forms, with pharmaceutically- acceptable solvents such as water, ethanol, and the like are equivalent to the unsolvated forms for purposes of the invention. The following procedure was utilized to determine the solubilities of various salts of 3-deazaguanine. The free base of 3-deazaguanine (250 mg) was suspended in a small volume of water and one equivalent weight of the desired acid was added with stirring. Stirring was continued and additional volumes of water were added intermittently until complete solution was obtained. Utilizing this procedure the results in the following table were obtained. Solubilities of 3-Deazaguanine Salts EMI7.1 <tb> <SEP> ml <SEP> H2O <SEP> <SEP> Solubility <SEP> <tb> <SEP> Acid <SEP> needed <SEP> to <SEP> Solubility <tb> <SEP> Dissolve <SEP> mg/ml <SEP> of <SEP> Salt <SEP> to <tb> <SEP> Free <SEP> Base* <SEP> <tb> <SEP> Free <SEP> Base <SEP> 100-125 <SEP> <SEP> 2.0-2.5 <SEP> -- <tb> <SEP> HC1 <SEP> 1 <SEP> 65-75 <SEP> I <SEP> 3.3-3.8 <SEP> 1 <SEP> 1.9 <tb> <SEP> H2S04 <SEP> 1 <SEP> 250-300 <SEP> 1 <SEP> 0.8-1.0 <SEP> 1 <SEP> 0.5 <tb> <SEP> H3P04 <SEP> 1 <SEP> 120-130 <SEP> 1.9-2.1 <SEP> 1 <SEP> 1.05 <tb> 'HOAc <SEP> 5 <SEP> 85-95 <SEP> 1 <SEP> 2.6-2.9 <SEP> 1 <SEP> 1.45 <tb> <SEP> Citric <SEP> 1 <SEP> 170-180 <SEP> 1 <SEP> <SEP> 1.4-1.5 <SEP> 1 <SEP> 0.75 <tb> <SEP> Maleic <SEP> 1 <SEP> 150-160 <SEP> 1 <SEP> 1.6-1.7 <SEP> I <SEP> 0.85 <tb> <SEP> d-Tartaric <SEP> 1 <SEP> 150-160 <SEP> 1.6-1.7 <SEP> 1 <SEP> 0.85 <tb> <SEP> MeSO3H <SEP> I <SEP> 5 <SEP> I <SEP> 50 <SEP> 1 <SEP> 25 <tb> <SEP> HO(CH2)2SO3HI <SEP> 5-10 <SEP> 1 <SEP> 25-50 <SEP> 1 <SEP> 25 <tb> <SEP> EtSO3H <SEP> I <SEP> 10 <SEP> 1 <SEP> 25 <SEP> 1 <SEP> 12.5 <tb> <SEP> C6HsSO3H <SEP> 1 <SEP> 25 <SEP> i <SEP> 10 <SEP> 1 <SEP> 5.0 <tb> *These values were obtained by dividing the higher value of the solubility range for the particular salt by the 2.0 mg/ml solubility of the free base. The results in the table demonstrate the solubility advantage for the compounds of the invention which advantage is particularly surprising in view of the decreased water solubility of the sulfate salt when compared to the free base. EXAMPLE I To a slurry of 24.5 g of 5-amino-1,5-dihydro 4H-imidazo[4,5-c]pyridin-4-one (3-deazaguanine) in 250 ml methyl alcohol was added a solution of 17.0 g of methanesulfonic acid in 50 ml of methyl alcohol. The mixture was stirred for about 10 minutes at room temperature, filtered, and the filter cake washed with methyl alcohol to give, after drying 35.5 g (88%) of 3-deazaguanine methanesulfonate salt, mp 273-2750C. This material produced a solution in water at a concentration of 41 mg/ml which remained clear for more than three days. A 1.0 g sample of this salt was recrystallized from 22 ml of 80% aqueous methyl alcohol to give material melting at 281-2830C. PHARMACEUTICAL COMPOSITIONS EXAMPLE 1 Ingredient ¯ Quantity 3-Deazaguanine methane sulfonic acid salt 300 g Lactose 974 g Corn Starch 39 g Hydroxypropyl cellulose 30 g Magnesium stearate 7 g Ethanol-water 50:50 qs The 3-Deazaguanine methanesulfonic acid salt lactose, and hydroxypropyl cellulose are blended and granulated with 50:50 ethanol water. The wet granulation is screened, dried, and rescreened. The resulting dried granulation is blended with magnesium stearate and the corn starch and the mixture is compressed into 450 mg tablets using an 11/32 inch standard concave punch. Yield equals approximately 3000 tablets each containing 100.0 mg of 3-Deazaguanine methanesulfonic acid salt. EXAMPLE 2 Ingredient Quantity 3-Deazaguanine methane sulfonic acid salt 1000 g Lactose 1900 g Corn Starch 50 g Hydroxypropyl cellulose 40 g Magnesium stearate 10 g Ethanol-water 50:50 qs The 3-Deazaguanine methanesulfonic acid salt lactose, and hydroxypropyl cellulose are blended and granulated with 50:50 ethanol water. The wet granulation is screened, dried, and rescreened. The resulting dried granulation is blended with magnesium stearate and the corn starch and the mixture is compressed into 750 mg tablets using a standard concave punch. Yield equals approximately 4000 tablets each containing 250.0 mg of 3-Deazaguanine methanesulfonic acid salt. EXAMPLE 3 Ingredient Quantity 3-Deazaguanine methane- 500 g sulfonic acid salt Lactose 1473 g Magnesium stearate 27 g The mixture is blended and filled into hard gelatin capsules, filling each capsule with 400 mg of the powder mixture. Yield equals approximately 5,000 capsules each containing 100.0 mg of 3-Deazaguanine methanesulfonic acid salt. EXAMPLE 3 Ingredient Quantity 3-Deazaguanine methane- 1000 g sulfonic acid salt Lactose 1950 g Magnesium stearate 50 g The mixture is blended and filled into hard gelatin capsules, filling each capsule with 750 mg of the powder mixture. Yield equals approximately 4,000 capsules each containing 250.0 mg of 3-Deazaguanine methanesulfonic acid salt. EXAMPLE 4 Ingredient Quantity 1. Methanesulfonic Acid, 98% Solution 18.2 g 2. 3-Deazaguanine 25.0 g 3. Water for Injection q.s. ad 1000 ml 4. Nitro en Gas High Purity Method of preparation In a suitable container, mix 1 with approximately 725 ml of 3, to yield A; Add 2 to A with mixing until 2 is dissolved; Add a sufficient amount of 3 to make 1000 ml of solution and mix well; Sterilize the solution by filtering thrcugh approprate prefilters followed by filtration through a previously sterilized membrane, using 4 for positive pressure; Aseptically fill 10.0 ml of the solution into previously sterilized vials; stopper loosely with lyophilization closures and lyophilize; Cap the lyophilized vials. When reconstituted with 10.0 ml of Sterile Water for Injection, the resultant solution will contain 25 mg/ml of 3-deazaguanine as the methanesulfonic acid salt.

Claims: CLAIMS: for the designated States: BE, CH, DE, FR, GB, IT, LI, LU, NL, SE: 1. A compound having the following structural formula EMI11.1 wherein R is phenyl or R1CH2 wherein R1 is a hydrogen atom or an alkyl radical having from one to six carbon atoms which may be substituted with one or more hydroxyl group(s). 2. A compound as claimed in Claim 1, wherein R1 is a hydrogen atom or an unsubstituted alkyl radical having from one to six carbon atoms. 3. A compound as claimed in Claim 1, wherein R1 is hydrogen, the compound being 6-amino-1,5-dihydro-4H-imidazo-[4,5-c]pyridin- 4-one methanesulphonic acid salt. 4. A compound as claimed in Claim 1, wherein R is CR3, the compound being 6-amino-1,5-dihydro-4H-imidazo[4,5-c3- pyridin-4-one ethanesulphonic acid salt. 5. A compound as claimed in Claim 1, wherein R1 is an alkyl radical having from one to three carbon atoms substituted with up to three hdyroxyl groups. 6. A compound as claimed in Claim 5, wherein Riis HOCH2. 7. A compound as claimed in Claim 1, wherein R is a phenyl radical. 8. A stable, solid, water-soluble composition suitable for reconstitution, useful for the preparation of a stable solution containing the equivalent of at least 15 mg/ml of 3 deazaguanine free base, the composition being prepared by the steps of (a) preparing a solution in a solvent of a compound as claimed in Claim 1; and (b) removing the solvent from the thus prepared solution. 9. A composition as claimed in Claim 8, which comprises 3-deazaguanine methanesulphonic acid salt. iO. A composition as claimed in Claim 8 or 9, which is reconstituted with a pharmaceutically acceptable solvent. CLAIMS: for the designated State: AT : 1. A process for producing a compound having the following structural formula I EMI13.1 wherein R is a phenyl radical of R1CH2, wherein R is a hydrogen atom or an alkyl radical having from one to six carbon atoms which may be substituted with one or more hydroxyl groups; which process comprises the steps of (a) preparing a solution of a compound of formula I by mixing in a solvent 3-deazaguanine and RS03H where R is as defined above; and (b) removing the solvent from the thus prepared solution. 2. A process according to Claim 1, wherein R1 is a hydrogen atom or an unsubstituted alkyl radical having from one to six carbon atoms. 3. A process according to Claim 1, wherein R1 is hydrogen, for producing 6-amino-1, 5-dihydro-4H-imidazor[4 ,5-c]pyridin-4-one methanesulphonic acid salt. 4. A process according to Claim 1, wherein R1 is CH3, for producing 6-amino-1,5-dihydro- 4H-imidazo[4,5-c]-pyridin-4-one ethanesulphonic acid salt. 5. A process according to Claim 1, wherein R1 is an alkyl radical having from one to three carbon atoms substituted with up to three hydroxyl groups. 6. A process according to Claim 1 wherein R is HOCH2-. 7. A process according to Claim 1, wherein R is phenyl. 8. A process according to any preceding claim, which further includes reconstituting a liquid preparation, with a pharmaceutically acceptable solvent.

Inventors: PATTISON, IAN C.
Applicants: WARNER-LAMBERT COMPANY
Application year: 1983
Main classification: C07D471
IPC codes: A61P31, A61P35, A61K31, C07D471, C07C309